D22.11 - Meteorology

SIGNIFICANCE AND USE
5.1 This test method provides a standard for comparison of rotating type anemometers, specifically cup anemometers and propeller anemometers, of different types. Specifications by regulatory agencies (4-7) and industrial societies have specified performance values. This standard provides an unambiguous method for measuring starting threshold, distance constant, transfer function, and off-axis response.
SCOPE
1.1 This test method covers the determination of the starting threshold, distance constant, transfer function, and off-axis response of a cup anemometer or propeller anemometer from direct measurement in a wind tunnel.  
1.2 This test method provides for a measurement of cup anemometer or propeller anemometer performance in the environment of wind tunnel airflow. Transference of values determined by these methods to atmospheric flow must be done with an understanding that there is a difference between the two flow systems.  
1.3 The values stated in SI units are to be regarded as standard. The values given in parentheses after SI units are provided for information only and are not considered standard.  
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

SIGNIFICANCE AND USE
5.1 Guidance is provided on designing model evaluation performance procedures and on the difficulties that arise in statistical evaluation of model performance caused by the stochastic nature of dispersion in the atmosphere. It is recognized there are examples in the literature where, knowingly or unknowingly, models were evaluated on their ability to describe something which they were never intended to characterize. This guide is attempting to heighten awareness, and thereby, to reduce the number of “unknowing” comparisons. A goal of this guide is to stimulate development and testing of evaluation procedures that accommodate the effects of natural variability. A technique is illustrated to provide information from which subsequent evaluation and standardization can be derived.
SCOPE
1.1 This guide provides techniques that are useful for the comparison of modeled air concentrations with observed field data. Such comparisons provide a means for assessing a model's performance, for example, bias and precision or uncertainty, relative to other candidate models. Methodologies for such comparisons are yet evolving; hence, modifications will occur in the statistical tests and procedures and data analysis as work progresses in this area. Until the interested parties agree upon standard testing protocols, differences in approach will occur. This guide describes a framework, or philosophical context, within which one determines whether a model's performance is significantly different from other candidate models. It is suggested that the first step should be to determine which model's estimates are closest on average to the observations, and the second step would then test whether the differences seen in the performance of the other models are significantly different from the model chosen in the first step. An example procedure is provided in Appendix X1 to illustrate an existing approach for a particular evaluation goal. This example is not intended to inhibit alternative approaches or techniques that will produce equivalent or superior results. As discussed in Section 6, statistical evaluation of model performance is viewed as part of a larger process that collectively is referred to as model evaluation.  
1.2 This guide has been designed with flexibility to allow expansion to address various characterizations of atmospheric dispersion, which might involve dose or concentration fluctuations, to allow development of application-specific evaluation schemes, and to allow use of various statistical comparison metrics. No assumptions are made regarding the manner in which the models characterize the dispersion.  
1.3 The focus of this guide is on end results, that is, the accuracy of model predictions and the discernment of whether differences seen between models are significant, rather than operational details such as the ease of model implementation or the time required for model calculations to be performed.  
1.4 This guide offers an organized collection of information or a series of options and does not recommend a specific course of action. This guide cannot replace education or experience and should be used in conjunction with professional judgment. Not all aspects of this guide may be applicable in all circumstances. This guide is not intended to represent or replace the standard of care by which the adequacy of a given professional service must be judged, nor should it be applied without consideration of a project's many unique aspects. The word “Standard” in the title of this guide means only that the document has been approved through the ASTM consensus process.  
1.5 This standard applies to gaussian plume models; it may not be applicable to non-point sources, heavy gas models from evaporation from pool (for example, liquid spills), as well as near-field receptors.  
1.6 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this guide...

SIGNIFICANCE AND USE
5.1 This practice will characterize the distribution of wind with a maximum of utility and a minimum of archive space. Applications of wind data to the fields of air quality, wind engineering, wind energy, agriculture, oceanography, forecasting, aviation, climatology, severe storms, turbulence and diffusion, military, and electrical utilities are satisfied with this practice. When this practice is employed, archive data will be of value to any of these fields of application. The consensus reached for this practice includes representatives of instrument manufacturers which provides a practical acceptance of these theoretical principles used to characterize the wind.
SCOPE
1.1 This practice covers a method for characterizing surface wind speed, wind direction, peak one-minute speeds, peak three-second and peak one-minute speeds, and standard deviations of fluctuation about the means of speed and direction.  
1.2 This practice may be used with other kinds of sensors if the response characteristics of the sensors, including their signal conditioners, are equivalent or faster and the measurement uncertainty of the system is equivalent or better than those specified below.  
1.3 The characterization prescribed in this practice will provide information on wind acceptable for a wide variety of applications.  
Note 1: This practice builds on a consensus reached by the attendees at a workshop sponsored by the Office of the Federal Coordinator for Meteorological Services and Supporting Research in Rockville, MD on Oct. 29–30, 1992.  
1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

SIGNIFICANCE AND USE
5.1 Sonic anemometer/thermometers are used to measure turbulent components of the atmosphere except in confined areas and very close to the ground. These practices apply to the use of these instruments for field measurement of the wind, sonic temperature, and atmospheric turbulence components. The quasi-instantaneous velocity component measurements are averaged over user-selected sampling times to define mean along-axis wind components, mean wind speed and direction, and the variances or covariances, or both, of individual components or component combinations. Covariances are used for eddy correlation studies and for computation of boundary layer heat and momentum fluxes. The sonic anemometer/thermometer provides the data required to characterize the state of the turbulent atmospheric boundary layer.  
5.2 The sonic anemometer/thermometer array shall have a sufficiently high structural rigidity and a sufficiently low coefficient of thermal expansion to maintain an internal alignment to within ±0.1°. System electronics must remain stable over its operating temperature range; the time counter oscillator instability must not exceed 0.01 % of frequency. Consult with the sensor manufacturer for an internal alignment verification procedure.  
5.3 The calculations and transformations provided in these practices apply to orthogonal arrays. References are also provided for common types of non-orthogonal arrays.
SCOPE
1.1 These practices cover procedures for measuring one-, two-, or three-dimensional vector wind components and sonic temperature by means of commercially available sonic anemometer/thermometers that employ the inverse time measurement technique. These practices apply to the measurement of wind velocity components over horizontal terrain using instruments mounted on stationary towers. These practices also apply to speed of sound measurements that are converted to sonic temperatures but do not apply to the measurement of temperature using ancillary temperature devices.  
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

SIGNIFICANCE AND USE
5.1 This test method provides a standard for comparison of wind vanes of different types. Specifications by regulatory agencies and industrial societies (3-5) have stipulated performance values. This test method provides an unambiguous method for measuring starting threshold, delay distance, and overshoot ratio.
SCOPE
1.1 This test method covers the determination of the starting threshold, delay distance, and overshoot ratio of a wind vane from direct measurements in a wind tunnel. This test method is applicable only to wind vanes having measurable overshoot.  
1.2 This test method provides for determination of the performance of a system consisting of a wind vane and its associated position-to-output transducer in wind tunnel flow. Use of values determined by this test method to describe performance in atmospheric flow of a wind direction measuring system incorporating the vane must be done with an understanding of the differences between the two systems and the two environments.  
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

SIGNIFICANCE AND USE
5.1 The object of this test method is to provide guidelines for the construction of a psychrometer and the techniques required for accurately measuring the humidity in the atmosphere. Only the essential features of the psychrometer are specified.
SCOPE
1.1 General:  
1.1.1 This test method covers the determination of the humidity of atmospheric air by means of wet- and dry-bulb temperature readings.  
1.1.2 This test method is applicable for meteorological measurements at the earth's surface, for the purpose of the testing of materials, and for the determination of the relative humidity of most standard atmospheres and test atmospheres.  
1.1.3 This test method is also applicable when the temperature of the wet bulb only is required. In this case, the instrument comprises a wet-bulb thermometer only.  
1.1.4 Relative humidity (RH) does not denote a unit. Uncertainties in the relative humidity are expressed in the form RH ± rh %, which means that the relative humidity is expected to lie in the range (RH − rh) % to (RH  + rh) %, where RH is the observed relative humidity. All uncertainties are at the 95 % confidence level.  
1.2 Method A—Psychrometer Ventilated by Aspiration:  
1.2.1 This method incorporates the psychrometer ventilated by aspiration. The aspirated psychrometer is more accurate than the sling (whirling) psychrometer (see Method B), and it offers advantages in regard to the space which it requires, the possibility of using alternative types of thermometers (for example, electrical), easier shielding of thermometer bulbs from extraneous radiation, accidental breakage, and convenience.  
1.2.2 This method is applicable within the ambient temperature range 5 °C to 80 °C, wet-bulb temperatures not lower than 1 °C, and restricted to ambient pressures not differing from standard atmospheric pressure by more than 30 %.  
1.3 Method B—Psychrometer Ventilated by Whirling (Sling Psychrometer):  
1.3.1 This method incorporates the psychrometer ventilated by whirling (sling psychrometer).  
1.3.2 This method is applicable within the ambient temperature range 5 °C to 50 °C, wet-bulb temperatures not lower than 1 °C and restricted to ambient pressures not differing from standard atmospheric pressure by more than 30 %.  
1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.5 Warning—Mercury has been designated by many regulatory agencies as a hazardous material that can cause serious medical issues. Mercury, or its vapor, has been demonstrated to be hazardous to health and corrosive to materials. Caution should be taken when handling mercury and mercury containing products. See the applicable product Safety Data Sheet (SDS) for additional information. Users should be aware that selling mercury and/or mercury containing products into your state or country may be prohibited by law.  
1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. (For more specific safety precautionary statements, see 8.1 and 15.1.)  
1.7 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

SIGNIFICANCE AND USE
5.1 This practice provides data needed for selection of instrument systems to measure meteorological quantities and to provide an estimate of the precision of measurements made by such systems.  
5.2 This practice is based on the assumption that the repeated measurement of a meteorological quantity by a sensor system will vary randomly about the true value plus an unknowable systematic difference. Given infinite resolution, these measurements will have a Gaussian distribution about the systematic difference as defined by the Central Limit Theorem. If it is known or demonstrated that this assumption is invalid for a particular quantity, conclusions based on the characteristics of a normal distribution must be avoided.
SCOPE
1.1 Sensor systems used for making meteorological measurements may be tested for laboratory accuracy in environmental chambers or wind tunnels, but natural exposure cannot be fully simulated. Atmospheric quantities are continuously variable in time and space; therefore, repeated measurements of the same quantities as required by Practice E177 to determine precision are not possible. This practice provides standard procedures for exposure, data sampling, and processing to be used with two measuring systems in determining their operational comparability (1,2).2  
1.2 The procedures provided produce measurement samples that can be used for statistical analysis. Comparability is defined in terms of specified statistical parameters. Other statistical parameters may be computed by methods described in other ASTM standards or statistics handbooks (3).  
1.3 Where the two measuring systems are identical, that is, same make, model, and manufacturer, the operational comparability is called functional precision.  
1.4 Meteorological determinations frequently require simultaneous measurements to establish the spatial distribution of atmospheric quantities or periodically repeated measurement to determine the time distribution, or both. In some cases, a number of identical systems may be used, but in others a mixture of instrument systems may be employed. The procedures described herein are used to determine the variability of like or unlike systems for making the same measurement.  
1.5 This standard does not purport to address the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. (See 8.1 for more specific safety precautionary information.)  
1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

SIGNIFICANCE AND USE
4.1 Applications—Ambient atmospheric temperature measurements can be made using resistance thermometers for many purposes. The application determines the most appropriate type of resistance thermometer and data recording method to be used. Examples of three typical meteorological applications for temperature measurements follow.  
4.1.1 Single-level, near-surface measurements for weather observations (1)3, thermodynamic computations for industrial applications, or environmental studies (2).  
4.1.2 Temperature differential or vertical gradient measurements to characterize atmospheric stability for atmospheric dispersion analyses studies (2).  
4.1.3 Temperature fluctuations for heat flux or temperature, or variance computations, or both. Measurements of heat flux and temperature variance require high precision measurements with a fast response to changes in the ambient atmosphere.  
4.2 Purpose—This practice is designed to assist the user in selecting an appropriate temperature measurement system for the intended atmospheric application, and properly installing and operating the system. The manufacturer's recommendations and the U.S. Environmental Protection Agency handbook on quality assurance in meteorological measurements (3) should be consulted for calibration and performance audit procedures.
SCOPE
1.1 This practice provides procedures to measure representative near-surface atmospheric (outdoor air) temperature for meteorological purposes using commonly available electrical thermometers housed in radiation shields mounted on stationary or portable masts or towers.  
1.2 This practice is applicable for measurements over the temperature range normally encountered in the ambient atmosphere, –50 to +50 °C.  
1.3 Air temperature measurement systems include a radiation shield, resistance thermometer, signal cables, and associated electronics.  
1.4 Measurements can be made at a single level for various meteorological purposes, at two or more levels for vertical temperature differences, and using special equipment (at one or more levels) for fluctuations of temperature with time applied to flux or variance measurements.  
1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.7 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

SIGNIFICANCE AND USE
5.1 This test method provides a standard method for evaluating the performance of sonic anemometer/thermometers that use inverse time solutions to measure wind velocity components and the speed of sound. It provides an unambiguous determination of instrument performance criteria. The test method is applicable to manufacturers for the purpose of describing the performance of their products, to instrumentation test facilities for the purpose of verifying instrument performance, and to users for specifying performance requirements. The acoustic pathlength procedure is also applicable for calibration purposes prior to data collection. Procedures for operating a sonic anemometer/thermometer are described in Practices D5527.  
5.2 The sonic anemometer/thermometer array is assumed to have a sufficiently high structural rigidity and a sufficiently low coefficient of thermal expansion to maintain an internal alignment to within the manufacturer's specifications over its designed operating range. Consult with the manufacturer for an internal alignment verification procedure and verify the alignment before proceeding with this test method.  
5.3 This test method is designed to characterize the performance of an array model or probe design. Transducer shadow data obtained from a single array is applicable for all instruments having the same array model or probe design. Some non-orthogonal arrays may not require specification of transducer shadow corrections or the velocity calibration range.
SCOPE
1.1 This test method covers the determination of the dynamic performance of a sonic anemometer/thermometer which employs the inverse time measurement technique for velocity or speed of sound, or both. Performance criteria include: (a) acceptance angle, (b) acoustic pathlength, (c) system delay, (d) system delay mismatch, (e) thermal stability range, (f) shadow correction, (g) velocity calibration range, and (h) velocity resolution.  
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

SIGNIFICANCE AND USE
5.1 Sodars have found wide applications for the remote measurement of wind and turbulence profiles in the atmosphere, particularly in the gap between meteorological towers and the lower range gates of wind profiling radars. The sodar’s far field acoustic power is also used for refractive index calculations and to estimate atmospheric stability, heat flux, and mixed layer depth (1-5).3 Sodars are useful for these purposes because of strong interaction between sound waves and the atmosphere’s thermal and velocity micro-structure that produce acoustic returns with substantial signal-to-noise ratios (SNR). The returned echoes are Doppler-shifted in frequency. This frequency shift, proportional to the radial velocity of the scattering surface, provides the basis for wind measurement. Advantages offered by sodar wind sounding technology include reasonably low procurement, operating, and maintenance costs, no emissions of eye-damaging light beams or electromagnetic radiation requiring frequency clearances, and adjustable frequencies and pulse lengths that can be used to optimize data quality at desired ranges and range resolutions. When properly sited and used with adequate sampling methods, sodars can provide continuous wind and turbulence profile information at height ranges from a few tens of meters to over a kilometer for typical averaging periods of 1 to 60 minutes.
SCOPE
1.1 This guide describes the application of acoustic remote sensing for measuring atmospheric wind and turbulence profiles. It includes a summary of the fundamentals of atmospheric sound detection and ranging (sodar), a description of the methodology and equipment used for sodar applications, factors to consider during site selection and equipment installation, and recommended procedures for acquiring valid and relevant data.  
1.2 This guide applies principally to pulsed monostatic sodar techniques as applied to wind and turbulence measurement in the open atmosphere, although many of the definitions and principles are also applicable to bistatic configurations. This guide is not directly applicable to radio-acoustic sounding systems (RASS), or tomographic methods.  
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this guide.  
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

SIGNIFICANCE AND USE
5.1 Standard value relative humidity environments are important for conditioning materials in shelf-life studies or in the testing of mechanical properties such as dimensional stability and strength. Relative humidity is also an important operating variable for the calibration of many species of measuring instruments.
SCOPE
1.1 This practice describes one method for generating constant relative humidity (rh) environments in relatively small containers.  
1.2 This practice is applicable for obtaining constant relative humidities ranging from dryness to near saturation at temperatures spanning from 0 °C to 50 °C.  
1.3 This practice is applicable for closed systems such as environmental conditioning containers and for the calibration of hygrometers.  
1.4 This practice is not recommended for the generation of continuous (flowing) streams of constant humidity unless precautionary criteria are followed to ensure source stability. (See Section 9.)  
1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.6 Warning—Saturated salt solutions are extremely corrosive, and care should be taken in their preparation and handling. There is also the possibility of corrosive vapors in the atmospheres over the saturated salt solutions.2  
1.7 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. For more specific safety precautionary information see 1.6 and 10.1.  
1.8 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

SIGNIFICANCE AND USE
5.1 Humidity information is important for the understanding of atmospheric phenomena and industrial processes. Measurements of the dew-point and calculations of related vapor pressures are important to quantify the humidity information.
SCOPE
1.1 This test method covers the determination of the thermodynamic dew- or frost-point temperature of ambient air by the condensation of water vapor on a cooled surface. For brevity, this is referred to in this test method as the condensation temperature.  
1.2 This test method is applicable for the range of condensation temperatures from 60°C to −70°C.  
1.3 This test method includes a general description of the instrumentation and operational procedures, including site selection, to be used for obtaining the measurements and a description of the procedures to be used for calculating the results.  
1.4 This test method is applicable for the continuous measurement of ambient humidity in the natural atmosphere on a stationary platform.  
1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. For specific precautionary statements, see Section 8.  
1.7 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

SIGNIFICANCE AND USE
5.1 Atmospheric pressure is one of the basic variables used by meteorologists to describe the state of the atmosphere.  
5.2 The measurement of atmospheric pressure is needed when differences from “standard” pressure conditions must be accounted for in some scientific and engineering applications involving pressure dependent variables.  
5.3 These test methods provide a means of measuring atmospheric pressure with the accuracy and precision comparable to the accuracy and precision of measurements made by governmental meteorological agencies.
SCOPE
1.1 These test methods cover the measurement of atmospheric pressure with two types of barometers: the Fortin-type mercurial barometer and the aneroid barometer.  
1.2 In the absence of abnormal perturbations, atmospheric pressure measured by these test methods at a point is valid everywhere within a horizontal distance of 100 m and a vertical distance of 0.5 m of the point.  
1.3 Atmospheric pressure decreases with increasing height and varies with horizontal distance by 1 Pa/100 m or less except in the event of catastrophic phenomena (for example, tornadoes). Therefore, extension of a known barometric pressure to another site beyond the spatial limits stated in 1.2 can be accomplished by correction for height difference if the following criteria are met:  
1.3.1 The new site is within 2000 m laterally and 500 m vertically.  
1.3.2 The change of pressure during the previous 10 min has been less than 20 Pa.
The pressure, P2 at Site 2 is a function of the known pressure P1 at Site 1, the algebraic difference in height above sea level,  h1 −  h2, and the average absolute temperature in the space between. The functional relationship between P1 and  P2 is shown in 10.2. The difference between P1 and P2 for each 1 m of difference between h1 and h2 is given in Table 1 and 10.4 for selected values of P1 and average temperature.  
1.4 Atmospheric pressure varies with time. These test methods provide instantaneous values only.  
1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. Specific safety precautionary statements are given in Section 7.

SIGNIFICANCE AND USE
5.1 This test method provides a standard for comparison of rotating type anemometers, specifically cup anemometers and propeller anemometers, of different types. Specifications by regulatory agencies (4-7) and industrial societies have specified performance values. This standard provides an unambiguous method for measuring starting threshold, distance constant, transfer function, and off-axis response.
SCOPE
1.1 This test method covers the determination of the starting threshold, distance constant, transfer function, and off-axis response of a cup anemometer or propeller anemometer from direct measurement in a wind tunnel.  
1.2 This test method provides for a measurement of cup anemometer or propeller anemometer performance in the environment of wind tunnel air flow. Transference of values determined by these methods to atmospheric flow must be done with an understanding that there is a difference between the two flow systems.  
1.3 The values stated in SI units are to be regarded as standard. The values given in parentheses after SI units are provided for information only and are not considered standard.  
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

SIGNIFICANCE AND USE
5.1 Standard value relative humidity environments are important for conditioning materials in shelf-life studies or in the testing of mechanical properties such as dimensional stability and strength. Relative humidity is also an important operating variable for the calibration of many species of measuring instruments.
SCOPE
1.1 This practice describes one method for generating constant relative humidity (rh) environments in relatively small containers.  
1.2 This practice is applicable for obtaining constant relative humidities ranging from dryness to near saturation at temperatures spanning from 0 to 50°C.  
1.3 This practice is applicable for closed systems such as environmental conditioning containers and for the calibration of hygrometers.  
1.4 This practice is not recommended for the generation of continuous (flowing) streams of constant humidity unless precautionary criteria are followed to ensure source stability. (See Section 9.)  
1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.6 Warning—Saturated salt solutions are extremely corrosive, and care should be taken in their preparation and handling. There is also the possibility of corrosive vapors in the atmospheres over the saturated salt solutions.2  
1.7 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. For more specific safety precautionary information see 1.6 and 10.1.  
1.8 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

SIGNIFICANCE AND USE
5.1 This test method will provide a standard for comparison of wind vanes of different types. Specifications by regulatory agencies and industrial societies (3-5) have stipulated performance values. This test method provides an unambiguous method for measuring starting threshold, delay distance, and overshoot ratio.
SCOPE
1.1 This test method covers the determination of the starting threshold, delay distance, and overshoot ratio of a wind vane from direct measurements in a wind tunnel. This test method is applicable only to wind vanes having measurable overshoot.  
1.2 This test method provides for determination of the performance of a system consisting of a wind vane and its associated position-to-output transducer in wind tunnel flow. Use of values determined by this test method to describe performance in atmospheric flow of a wind direction measuring system incorporating the vane must be done with an understanding of the differences between the two systems and the two environments.  
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.  
1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

SIGNIFICANCE AND USE
5.1 This practice will characterize the distribution of wind with a maximum of utility and a minimum of archive space. Applications of wind data to the fields of air quality, wind engineering, wind energy, agriculture, oceanography, forecasting, aviation, climatology, severe storms, turbulence and diffusion, military, and electrical utilities are satisfied with this practice. When this practice is employed, archive data will be of value to any of these fields of application. The consensus reached for this practice includes representatives of instrument manufacturers which provides a practical acceptance of these theoretical principles used to characterize the wind.
SCOPE
1.1 This practice covers a method for characterizing surface wind speed, wind direction, peak one-minute speeds, peak three-second and peak one-minute speeds, and standard deviations of fluctuation about the means of speed and direction.  
1.2 This practice may be used with other kinds of sensors if the response characteristics of the sensors, including their signal conditioners, are equivalent or faster and the measurement uncertainty of the system is equivalent or better than those specified below.  
1.3 The characterization prescribed in this practice will provide information on wind acceptable for a wide variety of applications.  
Note 1: This practice builds on a consensus reached by the attendees at a workshop sponsored by the Office of the Federal Coordinator for Meteorological Services and Supporting Research in Rockville, MD on Oct. 29–30, 1992.  
1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.  
1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

SIGNIFICANCE AND USE
5.1 This test method will provide a standard for comparison of rotating type anemometers, specifically cup anemometers and propeller anemometers, of different types. Specifications by regulatory agencies (4-7) and industrial societies have specified performance values. This standard provides an unambiguous method for measuring Starting Threshold, Distance Constant, Transfer Function, and Off-Axis Response.
SCOPE
1.1 This test method covers the determination of the Starting Threshold, Distance Constant, Transfer Function, and Off-Axis Response of a cup anemometer or propeller anemometer from direct measurement in a wind tunnel.  
1.2 This test method provides for a measurement of cup anemometer or propeller anemometer performance in the environment of wind tunnel flow. Transference of values determined by these methods to atmospheric flow must be done with an understanding that there is a difference between the two flow systems.  
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

SIGNIFICANCE AND USE
5.1 Sonic anemometer/thermometers are used to measure turbulent components of the atmosphere except for confined areas and very close to the ground. These practices apply to the use of these instruments for field measurement of the wind, sonic temperature, and atmospheric turbulence components. The quasi-instantaneous velocity component measurements are averaged over user-selected sampling times to define mean along-axis wind components, mean wind speed and direction, and the variances or covariances, or both, of individual components or component combinations. Covariances are used for eddy correlation studies and for computation of boundary layer heat and momentum fluxes. The sonic anemometer/thermometer provides the data required to characterize the state of the turbulent atmospheric boundary layer.  
5.2 The sonic anemometer/thermometer array shall have a sufficiently high structural rigidity and a sufficiently low coefficient of thermal expansion to maintain an internal alignment to within ±0.1°. System electronics must remain stable over its operating temperature range; the time counter oscillator instability must not exceed 0.01 % of frequency. Consult with the manufacturer for an internal alignment verification procedure.  
5.3 The calculations and transformations provided in these practices apply to orthogonal arrays. References are also provided for common types of non-orthogonal arrays.
SCOPE
1.1 These practices cover procedures for measuring one-, two-, or three-dimensional vector wind components and sonic temperature by means of commercially available sonic anemometer/thermometers that employ the inverse time measurement technique. These practices apply to the measurement of wind velocity components over horizontal terrain using instruments mounted on stationary towers. These practices also apply to speed of sound measurements that are converted to sonic temperatures but do not apply to the measurement of temperature by the use of ancillary temperature devices.  
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.  
1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

SIGNIFICANCE AND USE
5.1 The object of this test method is to provide guidelines for the construction of a psychrometer and the techniques required for accurately measuring the humidity in the atmosphere. Only the essential features of the psychrometer are specified.
SCOPE
1.1 General:  
1.1.1 This test method covers the determination of the humidity of atmospheric air by means of wet- and dry-bulb temperature readings.  
1.1.2 This test method is applicable for meteorological measurements at the earth's surface, for the purpose of the testing of materials, and for the determination of the relative humidity of most standard atmospheres and test atmospheres.  
1.1.3 This test method is also applicable when the temperature of the wet bulb only is required. In this case, the instrument comprises a wet-bulb thermometer only.  
1.1.4 Relative humidity (RH) does not denote a unit. Uncertainties in the relative humidity are expressed in the form RH ± rh %, which means that the relative humidity is expected to lie in the range (RH − rh) % to (RH  + rh ) %, where RH is the observed relative humidity. All uncertainties are at the 95 % confidence level.  
1.2 Method A—Psychrometer Ventilated by Aspiration:  
1.2.1 This method incorporates the psychrometer ventilated by aspiration. The aspirated psychrometer is more accurate than the sling (whirling) psychrometer (see Method B), and it offers advantages in regard to the space which it requires, the possibility of using alternative types of thermometers (for example, electrical), easier shielding of thermometer bulbs from extraneous radiation, accidental breakage, and convenience.  
1.2.2 This method is applicable within the ambient temperature range 5 to 80°C, wet-bulb temperatures not lower than 1°C, and restricted to ambient pressures not differing from standard atmospheric pressure by more than 30 %.  
1.3 Method B—Psychrometer Ventilated by Whirling (Sling Psychrometer):  
1.3.1 This method incorporates the psychrometer ventilated by whirling (sling psychrometer).  
1.3.2 This method is applicable within the ambient temperature range 5 to 50°C, wet-bulb temperatures not lower than 1°C and restricted to ambient pressures not differing from standard atmospheric pressure by more than 30 %.  
1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.5 Warning—Mercury has been designated by many regulatory agencies as a hazardous material that can cause serious medical issues. Mercury, or its vapor, has been demonstrated to be hazardous to health and corrosive to materials. Caution should be taken when handling mercury and mercury containing products. See the applicable product Safety Data Sheet (SDS) for additional information. Users should be aware that selling mercury and/or mercury containing products into your state or country may be prohibited by law.  
1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. (For more specific safety precautionary statements, see 8.1 and 15.1.)

SIGNIFICANCE AND USE
5.1 This test method provides a standard method for evaluating the performance of sonic anemometer/thermometers that use inverse time solutions to measure wind velocity components and the speed of sound. It provides an unambiguous determination of instrument performance criteria. The test method is applicable to manufacturers for the purpose of describing the performance of their products, to instrumentation test facilities for the purpose of verifying instrument performance, and to users for specifying performance requirements. The acoustic pathlength procedure is also applicable for calibration purposes prior to data collection. Procedures for operating a sonic anemometer/thermometer are described in Practice D5527.  
5.2 The sonic anemometer/thermometer array is assumed to have a sufficiently high structural rigidity and a sufficiently low coefficient of thermal expansion to maintain an internal alignment to within the manufacturer's specifications over its designed operating range. Consult with the manufacturer for an internal alignment verification procedure and verify the alignment before proceeding with this test method.  
5.3 This test method is designed to characterize the performance of an array model or probe design. Transducer shadow data obtained from a single array is applicable for all instruments having the same array model or probe design. Some non-orthogonal arrays may not require specification of transducer shadow corrections or the velocity calibration range.
SCOPE
1.1 This test method covers the determination of the dynamic performance of a sonic anemometer/thermometer which employs the inverse time measurement technique for velocity or speed of sound, or both. Performance criteria include: (a) acceptance angle, (b) acoustic pathlength, (c) system delay, (d) system delay mismatch, (e) thermal stability range, (f) shadow correction, (g) velocity calibration range, and (h) velocity resolution.  
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

SIGNIFICANCE AND USE
4.1 Applications—Ambient atmospheric temperature measurements can be made using resistance thermometers for many purposes. The application determines the most appropriate type of resistance thermometer and data recording method to be used. Examples of three typical meteorological applications for temperature measurements follow.  
4.1.1 Single-level, near-surface measurements for weather observations (1)3, thermodynamic computations for industrial applications, or environmental studies (2).  
4.1.2 Temperature differential or vertical gradient measurements to characterize atmospheric stability for atmospheric dispersion analyses studies (2).  
4.1.3 Temperature fluctuations for heat flux or temperature, or variance computations, or both. Measurements of heat flux and temperature variance require high precision measurements with a fast response to changes in the ambient atmosphere.  
4.2 Purpose—This practice is designed to assist the user in selecting an appropriate temperature measurement system for the intended atmospheric application, and properly installing and operating the system. The manufacturer's recommendations and the U.S. Environmental Protection Agency handbook on quality assurance in meteorological measurements (3) should be consulted for calibration and performance audit procedures.
SCOPE
1.1 This practice provides procedures to measure representative near-surface atmospheric (outdoor air) temperature for meteorological purposes using commonly available electrical thermometers housed in radiation shields mounted on stationary or portable masts or towers.  
1.2 This practice is applicable for measurements over the temperature range normally encountered in the ambient atmosphere, –50 to +50°C.  
1.3 Air temperature measurement systems include a radiation shield, resistance thermometer, signal cables, and associated electronics.  
1.4 Measurements can be made at a single level for various meteorological purposes, at two or more levels for vertical temperature differences, and using special equipment (at one or more levels) for fluctuations of temperature with time applied to flux or variance measurements.  
1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

SIGNIFICANCE AND USE
5.1 This practice provides data needed for selection of instrument systems to measure meteorological quantities and to provide an estimate of the precision of measurements made by such systems.  
5.2 This practice is based on the assumption that the repeated measurement of a meteorological quantity by a sensor system will vary randomly about the true value plus an unknowable systematic difference. Given infinite resolution, these measurements will have a Gaussian distribution about the systematic difference as defined by the Central Limit Theorem. If it is known or demonstrated that this assumption is invalid for a particular quantity, conclusions based on the characteristics of a normal distribution must be avoided.
SCOPE
1.1 Sensor systems used for making meteorological measurements may be tested for laboratory accuracy in environmental chambers or wind tunnels, but natural exposure cannot be fully simulated. Atmospheric quantities are continuously variable in time and space; therefore, repeated measurements of the same quantities as required by Practice E177 to determine precision are not possible. This practice provides standard procedures for exposure, data sampling, and processing to be used with two measuring systems in determining their operational comparability (1,2).2  
1.2 The procedures provided produce measurement samples that can be used for statistical analysis. Comparability is defined in terms of specified statistical parameters. Other statistical parameters may be computed by methods described in other ASTM standards or statistics handbooks (3).  
1.3 Where the two measuring systems are identical, that is, same make, model, and manufacturer, the operational comparability is called functional precision.  
1.4 Meteorological determinations frequently require simultaneous measurements to establish the spatial distribution of atmospheric quantities or periodically repeated measurement to determine the time distribution, or both. In some cases, a number of identical systems may be used, but in others a mixture of instrument systems may be employed. The procedures described herein are used to determine the variability of like or unlike systems for making the same measurement.  
1.5 This standard does not purport to address the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. (See 8.1 for more specific safety precautionary information.)

SIGNIFICANCE AND USE
5.1 Guidance is provided on designing model evaluation performance procedures and on the difficulties that arise in statistical evaluation of model performance caused by the stochastic nature of dispersion in the atmosphere. It is recognized there are examples in the literature where, knowingly or unknowingly, models were evaluated on their ability to describe something which they were never intended to characterize. This guide is attempting to heighten awareness, and thereby, to reduce the number of “unknowing” comparisons. A goal of this guide is to stimulate development and testing of evaluation procedures that accommodate the effects of natural variability. A technique is illustrated to provide information from which subsequent evaluation and standardization can be derived.
SCOPE
1.1 This guide provides techniques that are useful for the comparison of modeled air concentrations with observed field data. Such comparisons provide a means for assessing a model's performance, for example, bias and precision or uncertainty, relative to other candidate models. Methodologies for such comparisons are yet evolving; hence, modifications will occur in the statistical tests and procedures and data analysis as work progresses in this area. Until the interested parties agree upon standard testing protocols, differences in approach will occur. This guide describes a framework, or philosophical context, within which one determines whether a model's performance is significantly different from other candidate models. It is suggested that the first step should be to determine which model's estimates are closest on average to the observations, and the second step would then test whether the differences seen in the performance of the other models are significantly different from the model chosen in the first step. An example procedure is provided in Appendix X1 to illustrate an existing approach for a particular evaluation goal. This example is not intended to inhibit alternative approaches or techniques that will produce equivalent or superior results. As discussed in Section 6, statistical evaluation of model performance is viewed as part of a larger process that collectively is referred to as model evaluation.  
1.2 This guide has been designed with flexibility to allow expansion to address various characterizations of atmospheric dispersion, which might involve dose or concentration fluctuations, to allow development of application-specific evaluation schemes, and to allow use of various statistical comparison metrics. No assumptions are made regarding the manner in which the models characterize the dispersion.  
1.3 The focus of this guide is on end results, that is, the accuracy of model predictions and the discernment of whether differences seen between models are significant, rather than operational details such as the ease of model implementation or the time required for model calculations to be performed.  
1.4 This guide offers an organized collection of information or a series of options and does not recommend a specific course of action. This guide cannot replace education or experience and should be used in conjunction with professional judgment. Not all aspects of this guide may be applicable in all circumstances. This guide is not intended to represent or replace the standard of care by which the adequacy of a given professional service must be judged, nor should it be applied without consideration of a project's many unique aspects. The word “Standard” in the title of this guide means only that the document has been approved through the ASTM consensus process.  
1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this guide.  
1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health ...

SIGNIFICANCE AND USE
5.1 Sodars have found wide applications for the remote measurement of wind and turbulence profiles in the atmosphere, particularly in the gap between meteorological towers and the lower range gates of wind profiling radars. The sodar’s far field acoustic power is also used for refractive index calculations and to estimate atmospheric stability, heat flux, and mixed layer depth (1-5).3 Sodars are useful for these purposes because of strong interaction between sound waves and the atmosphere’s thermal and velocity micro-structure that produce acoustic returns with substantial signal-to-noise ratios (SNR). The returned echoes are Doppler-shifted in frequency. This frequency shift, proportional to the radial velocity of the scattering surface, provides the basis for wind measurement. Advantages offered by sodar wind sounding technology include reasonably low procurement, operating, and maintenance costs, no emissions of eye-damaging light beams or electromagnetic radiation requiring frequency clearances, and adjustable frequencies and pulse lengths that can be used to optimize data quality at desired ranges and range resolutions. When properly sited and used with adequate sampling methods, sodars can provide continuous wind and turbulence profile information at height ranges from a few tens of meters to over a kilometre for typical averaging periods of 1 to 60 minutes.
SCOPE
1.1 This guide describes the application of acoustic remote sensing for measuring atmospheric wind and turbulence profiles. It includes a summary of the fundamentals of atmospheric sound detection and ranging (sodar), a description of the methodology and equipment used for sodar applications, factors to consider during site selection and equipment installation, and recommended procedures for acquiring valid and relevant data.  
1.2 This guide applies principally to pulsed monostatic sodar techniques as applied to wind and turbulence measurement in the open atmosphere, although many of the definitions and principles are also applicable to bistatic configurations. This guide is not directly applicable to radio-acoustic sounding systems (RASS), or tomographic methods.  
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this guide.

SIGNIFICANCE AND USE
Humidity information is important for the understanding of atmospheric phenomena and industrial processes. Measurements of the dew-point and calculations of related vapor pressures are important to quantify the humidity information.
SCOPE
1.1 This test method covers the determination of the thermodynamic dew- or frost-point temperature of ambient air by the condensation of water vapor on a cooled surface. For brevity this is referred to in this method as the condensation temperature.
1.2 This test method is applicable for the range of condensation temperatures from 60°C to − 70°C.  
1.3 This test method includes a general description of the instrumentation and operational procedures, including site selection, to be used for obtaining the measurements and a description of the procedures to be used for calculating the results.
1.4 This test method is applicable for the continuous measurement of ambient humidity in the natural atmosphere on a stationary platform.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. For specific precautionary statements, see Section 8.

SIGNIFICANCE AND USE
Standard value relative humidity environments are important for conditioning materials in shelf-life studies or in the testing of mechanical properties such as dimensional stability and strength. Relative humidity is also an important operating variable for the calibration of many species of measuring instruments.e and rate of degradation and the performance rankings produced by exposures to unfiltered open-flame carbon-arcs can be much different from that produced by exposures to other types of laboratory light sources. Typically, exposures conducted according to this practice will produce degradation faster than similar exposures conducted according to Practice D822 or D5031 and may cause different types of degradation.  
4.2.2 Interlaboratory comparisons are valid only when all laboratories use the same type of carbon-arc and exposure conditions.  
4.3 Reproducibility of test results between laboratories has been shown to be good when the stability of materials is evaluated in terms of performance ranking compared to other materials or to a control.4,5 Therefore, exposure of a similar material of known performance (a control) at the same time as the test materials is strongly recommended. It is recommended that at least three replicates of each material be exposed to allow for statistical evaluation of results.  
4.4 Test results will depend upon the care that is taken to operate the equipment. Significant factors include regulation of line voltage, freedom from salt or other deposits from water, temperature and humidity control, and conditions of the electrodes.  
4.5 All references to exposures in accordance with this practice must include a complete description of the test cycle used.
SCOPE
1.1 This practice describes one method for generating constant relative humidity (rh) environments in relatively small containers.  
1.2 This practice is applicable for obtaining constant relative humidities ranging from dryness to near saturation at temperatures spanning from 0 to 50°C.
1.3 This practice is applicable for closed systems such as environmental conditioning containers and for the calibration of hygrometers.  
1.4 This practice is not recommended for the generation of continuous (flowing) streams of constant humidity unless precautionary criteria are followed to ensure source stability. (See Section 9.)  
1.5 CautionSaturated salt solutions are extremely corrosive, and care should be taken in their preparation and handling. There is also the possibility of corrosive vapors in the atmospheres over the saturated salt solutions.  
1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. For more specific safety precautionary information see 1.5 and 10.1.

SIGNIFICANCE AND USE
This test method will provide a standard for comparison of rotating type anemometers, specifically cup anemometers and propeller anemometers, of different types. Specifications by regulatory agencies (4-7) and industrial societies have specified performance values. This standard provides an unambiguous method for measuring Starting Threshold, Distance Constant, Transfer Function, and Off-Axis Response.
SCOPE
1.1 This test method covers the determination of the Starting Threshold, Distance Constant, Transfer Function, and Off-Axis Response of a cup anemometer or propeller anemometer from direct measurement in a wind tunnel.
1.2 This test method provides for a measurement of cup anemometer or propeller anemometer performance in the environment of wind tunnel flow. Transference of values determined by these methods to atmospheric flow must be done with an understanding that there is a difference between the two flow systems.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

SIGNIFICANCE AND USE
Atmospheric pressure is one of the basic variables used by meteorologists to describe the state of the atmosphere.
The measurement of atmospheric pressure is needed when differences from “standard” pressure conditions must be accounted for in some scientific and engineering applications involving pressure dependent variables.
These methods provide a means of measuring atmospheric pressure with the accuracy and precision comparable to the accuracy and precision of measurements made by governmental meteorological agencies.
SCOPE
1.1 These methods cover the measurement of atmospheric pressure with two types of barometers: the Fortin-type mercurial barometer and the aneroid barometer.
1.2 In the absence of abnormal perturbations, atmospheric pressure measured by these methods at a point is valid everywhere within a horizontal distance of 100 m and a vertical distance of 0.5 m of the point.  
1.3 Atmospheric pressure decreases with increasing height and varies with horizontal distance by 1 Pa/100 m or less except in the event of catastrophic phenomena (for example, tornadoes). Therefore, extension of a known barometric pressure to another site beyond the spatial limits stated in 1.2 can be accomplished by correction for height difference if the following criteria are met:
1.3.1 The new site is within 2000 m laterally and 500 m vertically.
1.3.2 The change of pressure during the previous 10 min has been less than 20 Pa.
The pressure, P2 at Site 2 is a function of the known pressure P1 at Site 1, the algebraic difference in height above sea level,  h1 − h 2, and the average absolute temperature in the space between. The functional relationship between P1 and  P2 is shown in 10.2. The difference between P1 and P2 for each 1 m of difference between h1 and h2 is given in Table 1 and 10.4 for selected values of P1 and average temperature.
1.4 Atmospheric pressure varies with time. These methods provide instantaneous values only.
1.5 The values stated in SI units are to be regarded as the standard.
1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. Specific safety precautionary statements are given in Section 7.
TABLE 1 Selected Values   Average
Tempera-
ture,
Pressure P1, Pa 110 000100 00090 00080 00070 000 Correction to P1, Pa/m, positive if  h1 > h, negative if h1   h2 230 1615131210 240 1614131110 250 1514121110 260 14131211 9 270 14131110 9 280 13121110 9 290 131211 9 8 300 131110 9 8 310 121110 9 8

SIGNIFICANCE AND USE
This test method will provide a standard for comparison of wind vanes of different types. Specifications by regulatory agencies and industrial societies (3-5)  have stipulated performance values. This test method provides an unambiguous method for measuring starting threshold, delay distance, and overshoot ratio.
SCOPE
1.1 This test method covers the determination of the starting threshold, delay distance, and overshoot ratio of a wind vane from direct measurements in a wind tunnel. This test method is applicable only to wind vanes having measurable overshoot.
1.2 This test method provides for determination of the performance of a system consisting of a wind vane and its associated position-to-output transducer in wind tunnel flow. Use of values determined by this test method to describe performance in atmospheric flow of a wind direction measuring system incorporating the vane must be done with an understanding of the differences between the two systems and the two environments.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

SIGNIFICANCE AND USE
Sonic anemometer/thermometers are used to measure turbulent components of the atmosphere except for confined areas and very close to the ground. These practices apply to the use of these instruments for field measurement of the wind, sonic temperature, and atmospheric turbulence components. The quasi-instantaneous velocity component measurements are averaged over user-selected sampling times to define mean along-axis wind components, mean wind speed and direction, and the variances or covariances, or both, of individual components or component combinations. Covariances are used for eddy correlation studies and for computation of boundary layer heat and momentum fluxes. The sonic anemometer/thermometer provides the data required to characterize the state of the turbulent atmospheric boundary layer.
The sonic anemometer/thermometer array shall have a sufficiently high structural rigidity and a sufficiently low coefficient of thermal expansion to maintain an internal alignment to within ±0.1°. System electronics must remain stable over its operating temperature range; the time counter oscillator instability must not exceed 0.01 % of frequency. Consult with the manufacturer for an internal alignment verification procedure.  
The calculations and transformations provided in these practices apply to orthogonal arrays. References are also provided for common types of non-orthogonal arrays.
SCOPE
1.1 These practices cover procedures for measuring one-, two-, or three-dimensional vector wind components and sonic temperature by means of commercially available sonic anemometer/thermometers that employ the inverse time measurement technique. These practices apply to the measurement of wind velocity components over horizontal terrain using instruments mounted on stationary towers. These practices also apply to speed of sound measurements that are converted to sonic temperatures but do not apply to the measurement of temperature by the use of ancillary temperature devices.
1.2 The values stated in SI units are to be regarded as the standard.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

SIGNIFICANCE AND USE
This practice will characterize the distribution of wind with a maximum of utility and a minimum of archive space. Applications of wind data to the fields of air quality, wind engineering, wind energy, agriculture, oceanography, forecasting, aviation, climatology, severe storms, turbulence and diffusion, military, and electrical utilities are satisfied with this practice. When this practice is employed, archive data will be of value to any of these fields of application. The consensus reached for this practice includes representatives of instrument manufacturers which provides a practical acceptance of these theoretical principles used to characterize the wind.
SCOPE
1.1 This practice covers a method for characterizing surface wind speed, wind direction, peak one-minute speeds, peak three-second and peak one-minute speeds, and standard deviations of fluctuation about the means of speed and direction.
1.2 This practice may be used with other kinds of sensors if the response characteristics of the sensors, including their signal conditioners, are equivalent or faster and the measurement uncertainty of the system is equivalent or better than those specified below.
1.3 The characterization prescribed in this practice will provide information on wind acceptable for a wide variety of applications.
Note 1—This practice builds on a consensus reached by the attendees at a workshop sponsored by the Office of the Federal Coordinator for Meteorological Services and Supporting Research in Rockville, MD on Oct. 29–30, 1992.  
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

SIGNIFICANCE AND USE
This practice provides data needed for selection of instrument systems to measure meteorological quantities and to provide an estimate of the precision of measurements made by such systems.
This practice is based on the assumption that the repeated measurement of a meteorological quantity by a sensor system will vary randomly about the true value plus an unknowable systematic difference. Given infinite resolution, these measurements will have a Gaussian distribution about the systematic difference as defined by the Central Limit Theorem. If it is known or demonstrated that this assumption is invalid for a particular quantity, conclusions based on the characteristics of a normal distribution must be avoided.
SCOPE
1.1 Sensor systems used for making meteorological measurements may be tested for laboratory accuracy in environmental chambers or wind tunnels, but natural exposure cannot be fully simulated. Atmospheric quantities are continuously variable in time and space; therefore, repeated measurements of the same quantities as required by Practice E177 to determine precision are not possible. This practice provides standard procedures for exposure, data sampling, and processing to be used with two measuring systems in determining their operational comparability (1,2).  
1.2 The procedures provided produce measurement samples that can be used for statistical analysis. Comparability is defined in terms of specified statistical parameters. Other statistical parameters may be computed by methods described in other ASTM standards or statistics handbooks (3).
1.3 Where the two measuring systems are identical, that is, same make, model, and manufacturer, the operational comparability is called functional precision.
1.4 Meteorological determinations frequently require simultaneous measurements to establish the spatial distribution of atmospheric quantities or periodically repeated measurement to determine the time distribution, or both. In some cases, a number of identical systems may be used, but in others a mixture of instrument systems may be employed. The procedures described herein are used to determine the variability of like or unlike systems for making the same measurement.
1.5 This standard does not purport to address the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. (See 8.1 for more specific safety precautionary information.)

SIGNIFICANCE AND USE
Guidance is provided on designing model evaluation performance procedures and on the difficulties that arise in statistical evaluation of model performance caused by the stochastic nature of dispersion in the atmosphere. It is recognized there are examples in the literature where, knowingly or unknowingly, models were evaluated on their ability to describe something which they were never intended to characterize. This guide is attempting to heighten awareness, and thereby, to reduce the number of “unknowing” comparisons. A goal of this guide is to stimulate development and testing of evaluation procedures that accommodate the effects of natural variability. A technique is illustrated to provide information from which subsequent evaluation and standardization can be derived.
SCOPE
1.1 This guide provides techniques that are useful for the comparison of modeled air concentrations with observed field data. Such comparisons provide a means for assessing a model's performance, for example, bias and precision or uncertainty, relative to other candidate models. Methodologies for such comparisons are yet evolving; hence, modifications will occur in the statistical tests and procedures and data analysis as work progresses in this area. Until the interested parties agree upon standard testing protocols, differences in approach will occur. This guide describes a framework, or philosophical context, within which one determines whether a model's performance is significantly different from other candidate models. It is suggested that the first step should be to determine which model's estimates are closest on average to the observations, and the second step would then test whether the differences seen in the performance of the other models are significantly different from the model chosen in the first step. An example procedure is provided in Appendix X1 to illustrate an existing approach for a particular evaluation goal. This example is not intended to inhibit alternative approaches or techniques that will produce equivalent or superior results. As discussed in Section 6, statistical evaluation of model performance is viewed as part of a larger process that collectively is referred to as model evaluation.
1.2 This guide has been designed with flexibility to allow expansion to address various characterizations of atmospheric dispersion, which might involve dose or concentration fluctuations, to allow development of application-specific evaluation schemes, and to allow use of various statistical comparison metrics. No assumptions are made regarding the manner in which the models characterize the dispersion.
1.3 The focus of this guide is on end results, that is, the accuracy of model predictions and the discernment of whether differences seen between models are significant, rather than operational details such as the ease of model implementation or the time required for model calculations to be performed.
1.4 This guide offers an organized collection of information or a series of options and does not recommend a specific course of action. This guide cannot replace education or experience and should be used in conjunction with professional judgment. Not all aspects of this guide may be applicable in all circumstances. This guide is not intended to represent or replace the standard of care by which the adequacy of a given professional service must be judged, nor should it be applied without consideration of a project's many unique aspects. The word “Standard” in the title of this guide means only that the document has been approved through the ASTM consensus process.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and to determine the applicability of regulatory limitations prior to use.

SIGNIFICANCE AND USE
Sodars have found wide applications for the remote measurement of wind and turbulence profiles in the atmosphere, particularly in the gap between meteorological towers and the lower range gates of wind profiling radars. The sodar’s far field acoustic power is also used for refractive index calculations and to estimate atmospheric stability, heat flux, and mixed layer depth (1-5) . Sodars are useful for these purposes because of strong interaction between sound waves and the atmosphere’s thermal and velocity micro-structure that produce acoustic returns with substantial signal-to-noise ratios (SNR). The returned echoes are Doppler-shifted in frequency. This frequency shift, proportional to the radial velocity of the scattering surface, provides the basis for wind measurement. Advantages offered by sodar wind sounding technology include reasonably low procurement, operating, and maintenance costs, no emissions of eye-damaging light beams or electromagnetic radiation requiring frequency clearances, and adjustable frequencies and pulse lengths that can be used to optimize data quality at desired ranges and range resolutions. When properly sited and used with adequate sampling methods, sodars can provide continuous wind and turbulence profile information at height ranges from a few tens of meters to over a kilometre for typical averaging periods of 1 to 60 minutes.
SCOPE
1.1 This guide describes the application of acoustic remote sensing for measuring atmospheric wind and turbulence profiles. It includes a summary of the fundamentals of atmospheric sound detection and ranging (sodar), a description of the methodology and equipment used for sodar applications, factors to consider during site selection and equipment installation, and recommended procedures for acquiring valid and relevant data.
1.2 This guide applies principally to pulsed monostatic sodar techniques as applied to wind and turbulence measurement in the open atmosphere, although many of the definitions and principles are also applicable to bistatic configurations. This guide is not directly applicable to radio-acoustic sounding systems (RASS), or tomographic methods.

SIGNIFICANCE AND USE
This test method provides a standard method for evaluating the performance of sonic anemometer/thermometers that use inverse time solutions to measure wind velocity components and the speed of sound. It provides an unambiguous determination of instrument performance criteria. The test method is applicable to manufacturers for the purpose of describing the performance of their products, to instrumentation test facilities for the purpose of verifying instrument performance, and to users for specifying performance requirements. The acoustic pathlength procedure is also applicable for calibration purposes prior to data collection. Procedures for operating a sonic anemometer/thermometer are described in Practice D 5527.
The sonic anemometer/thermometer array is assumed to have a sufficiently high structural rigidity and a sufficiently low coefficient of thermal expansion to maintain an internal alignment to within the manufacturer's specifications over its designed operating range. Consult with the manufacturer for an internal alignment verification procedure and verify the alignment before proceeding with this test method.
This test method is designed to characterize the performance of an array model or probe design. Transducer shadow data obtained from a single array is applicable for all instruments having the same array model or probe design. Some non-orthogonal arrays may not require specification of transducer shadow corrections or the velocity calibration range.
SCOPE
1.1 This test method covers the determination of the dynamic performance of a sonic anemometer/thermometer which employs the inverse time measurement technique for velocity or speed of sound, or both. Performance criteria include: (a) acceptance angle, (b) acoustic pathlength, (c) system delay, (d) system delay mismatch, (e) thermal stability range, (f) shadow correction, (g) velocity calibration range, and (h) velocity resolution.
1.2 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

SIGNIFICANCE AND USE
Applications—Ambient atmospheric temperature measurements can be made using resistance thermometers for many purposes. The application determines the most appropriate type of resistance thermometer and data recording method to be used. Examples of three typical meteorological applications for temperature measurements follow.
Single-level, near-surface measurements for weather observations (1) , thermodynamic computations for industrial applications, or environmental studies (2).
Temperature differential or vertical gradient measurements to characterize atmospheric stability for atmospheric dispersion analyses studies (2).
Temperature fluctuations for heat flux or temperature, or variance computations, or both. Measurements of heat flux and temperature variance require high precision measurements with a fast response to changes in the ambient atmosphere.
Purpose—This practice is designed to assist the user in selecting an appropriate temperature measurement system for the intended atmospheric application, and properly installing and operating the system. The manufacturer's recommendations and the U.S. Environmental Protection Agency handbook on quality assurance in meteorological measurements (3) should be consulted for calibration and performance audit procedures.
SCOPE
1.1 This practice provides procedures to measure representative near-surface atmospheric (outdoor air) temperature for meteorological purposes using commonly available electrical thermometers housed in radiation shields mounted on stationary or portable masts or towers.
1.2 This practice is applicable for measurements over the temperature range normally encountered in the ambient atmosphere, –50 to +50°C.
1.3 Air temperature measurement systems include a radiation shield, resistance thermometer, signal cables, and associated electronics.
1.4 Measurements can be made at a single level for various meteorological purposes, at two or more levels for vertical temperature differences, and using special equipment (at one or more levels) for fluctuations of temperature with time applied to flux or variance measurements.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

SCOPE
1.1 These practices cover procedures for measuring one-, two-, or three-dimensional vector wind components and sonic temperature by means of commercially available sonic anemometer/thermometers that employ the inverse time measurement technique. These practices apply to the measurement of wind velocity components over horizontal terrain using instruments mounted on stationary towers. These practices also apply to speed of sound measurements that are converted to sonic temperatures but do not apply to the measurement of temperature by the use of ancillary temperature devices.
1.2 The values stated in SI units are to be regarded as the standard.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

SCOPE
1.1 This practice describes one method for generating constant relative humidity (rh) environments in relatively small containers.
1.2 This practice is applicable for obtaining constant relative humidities ranging from dryness to near saturation at temperatures spanning from 0 to 50C.
1.3 This practice is applicable for closed systems such as environmental conditioning containers and for the calibration of hygrometers.
1.4 This practice is not recommended for the generation of continuous (flowing) streams of constant humidity unless precautionary criteria are followed to ensure source stability. (See Section 9 .)
1.5 Caution-Saturated salt solutions are extremely corrosive, and care should be taken in their preparation and handling. There is also the possibility of corrosive vapors in the atmospheres over the saturated salt solutions.
1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. For more specific safety precautionary information see 1.5 and 10.1 .

SCOPE
1.1 This test method covers the determination of the thermodynamic dew- or frost-point temperature of ambient air by the condensation of water vapor on a cooled surface. For brevity this is referred to in this method as the condensation temperature.
1.2 This test method is applicable for the range of condensation temperatures from 60C to 70C.
1.3 This test method includes a general description of the instrumentation and operational procedures, including site selection, to be used for obtaining the measurements and a description of the procedures to be used for calculating the results.
1.4 This test method is applicable for the continuous measurement of ambient humidity in the natural atmosphere on a stationary platform.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. For specific precautionary statements, see Section 8 .

SCOPE
1.1 This test method covers the determination of the Starting Threshold, Distance Constant, Transfer Function, and  Off-Axis Response of a cup anemometer or propeller anemometer from direct measurement in a wind tunnel.
1.2 This test method provides for a measurement of cup anemometer or propeller anemometer performance in the environment of wind tunnel flow. Transference of values determined by these methods to atmospheric flow must be done with an understanding that there is a difference between the two flow systems.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

SCOPE
1.1 This practice covers a method for characterizing surface wind speed, wind direction, peak one-minute speeds, peak three-second and peak one-minute speeds, and standard deviations of fluctuation about the means of speed and direction.
1.2 This practice may be used with other kinds of sensors if the response characteristics of the sensors, including their signal conditioners, are equivalent or faster and the measurement uncertainty of the system is equivalent or better than those specified below.
1.3 The characterization prescribed in this practice will provide information on wind acceptable for a wide variety of applications. This practice builds on a consensus reached by the attendees at a workshop sponsored by the Office of the Federal Coordinator for Meteorological Services and Supporting Research in Rockville, MD on Oct. 29-30, 1992.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

SCOPE
1.1 This test method covers the determination of the starting threshold, delay distance, and overshoot ratio of a wind vane from direct measurements in a wind tunnel. This test method is applicable only to wind vanes having measurable overshoot.
1.2 This test method provides for determination of the performance of a system consisting of a wind vane and its associated position-to-output transducer in wind tunnel flow. Use of values determined by this test method to describe performance in atmospheric flow of a wind direction measuring system incorporating the vane must be done with an understanding of the differences between the two systems and the two environments.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

SCOPE
1.1 General
1.1.1 This test method covers the determination of the humidity of atmospheric air by means of wet- and dry-bulb temperature readings.
1.1.2 This test method is applicable for meteorological measurements at the earth's surface, for the purpose of the testing of materials, and for the determination of the relative humidity of most standard atmospheres and test atmospheres.
1.1.3 This test method is also applicable when the temperature of the wet bulb only is required. In this case, the instrument comprises a wet-bulb thermometer only.
1.1.4 Relative humidity (RH) does not denote a unit. Uncertainties in the relative humidity are expressed in the form  RH  rh %, which means that the relative humidity is expected to lie in the range (RH  rh) % to (RH  + rh ) %, where RH is the observed relative humidity. All uncertainties are at the 95 % confidence level.
1.2 Method A- Psychrometer Ventilated by Aspiration:
1.2.1 This method incorporates the psychrometer ventilated by aspiration. The aspirated psychrometer is more accurate than the sling (whirling) psychrometer (see Method B), and it offers advantages in regard to the space which it requires, the possibility of using alternative types of thermometers (for example, electrical), easier shielding of thermometer bulbs from extraneous radiation, accidental breakage, and convenience.
1.2.2 This method is applicable within the ambient temperature range 5 to 80C, wet-bulb temperatures not lower than 1C, and restricted to ambient pressures not differing from standard atmospheric pressure by more than 30 %.
1.3  Method B- Psychrometer Ventilated by Whirling (Sling Psychrometer):
1.3.1 This method incorporates the psychrometer ventilated by whirling (sling psychrometer).
1.3.2 This method is applicable within the ambient temperature range 5 to 50C, wet-bulb temperatures not lower than 1C and restricted to ambient pressures not differing from standard atmospheric pressure by more than 30 %.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. (For more specific safety precautionary statements, see 8.1 and 15.1 .)

SCOPE
1.1 These methods cover the measurement of atmospheric pressure with two types of barometers: the Fortin-type mercurial barometer and the aneroid barometer.
1.2 In the absence of abnormal perturbations, atmospheric pressure measured by these methods at a point is valid everywhere within a horizontal distance of 100 m and a vertical distance of 0.5 m of the point.
1.3 Atmospheric pressure decreases with increasing height and varies with horizontal distance by 1 Pa/100 m or less except in the event of catastrophic phenomena (for example, tornadoes). Therefore, extension of a known barometric pressure to another site beyond the spatial limits stated in can be accomplished by correction for height difference if the following criteria are met:
1.3.1 The new site is within 2000 m laterally and 500 m vertically.
1.3.2 The change of pressure during the previous 10 min has been less than 20 Pa.
The pressure, P2 at Site 2 is a function of the known pressure P1 at Site 1, the algebraic difference in height above sea level,  h1 h 2, and the average absolute temperature in the space between. The functional relationship between P1 and  P2 is shown in 10.2 . The difference between P1 and P2 for each 1 m of difference between h1 and h2 is given in Table 1 and 10.4 for selected values of P1 and average temperature.
1.4 Atmospheric pressure varies with time. These methods provide instantaneous values only.
1.5 The values stated in SI units are to be regarded as the standard.
1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.  Specific safety precautionary statements are given in Section 7.

SIGNIFICANCE AND USE
This practice provides data needed for selection of instrument systems to measure meteorological quantities and to provide an estimate of the precision of measurements made by such systems.
This practice is based on the assumption that the repeated measurement of a meteorological quantity by a sensor system will vary randomly about the true value plus an unknowable systematic difference. Given infinite resolution, these measurements will have a Gaussian distribution about the systematic difference as defined by the Central Limit Theorem. If it is known or demonstrated that this assumption is invalid for a particular quantity, conclusions based on the characteristics of a normal distribution must be avoided.
SCOPE
1.1 Sensor systems used for making meteorological measurements may be tested for laboratory accuracy in environmental chambers or wind tunnels, but natural exposure cannot be fully simulated. Atmospheric quantities are continuously variable in time and space; therefore, repeated measurements of the same quantities as required by Practice E 177 to determine precision are not possible. This practice provides standard procedures for exposure, data sampling, and processing to be used with two measuring systems in determining their operational comparability  (,).
1.2 The procedures provided produce measurement samples that can be used for statistical analysis. Comparability is defined in terms of specified statistical parameters. Other statistical parameters may be computed by methods described in other ASTM standards or statistics handbooks ().
1.3 Where the two measuring systems are identical, that is, same make, model, and manufacturer, the operational comparability is called functional precision.
1.4 Meteorological determinations frequently require simultaneous measurements to establish the spatial distribution of atmospheric quantities or periodically repeated measurement to determine the time distribution, or both. In some cases, a number of identical systems may be used, but in others a mixture of instrument systems may be employed. The procedures described herein are used to determine the variability of like or unlike systems for making the same measurement.
This standard does not purport to address the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. (See for more specific safety precautionary information.)

SIGNIFICANCE AND USE
Guidance is provided on designing model evaluation performance procedures and on the difficulties that arise in statistical evaluation of model performance caused by the stochastic nature of dispersion in the atmosphere. It is recognized there are examples in the literature where, knowingly or unknowingly, models were evaluated on their ability to describe something which they were never intended to characterize. This guide is attempting to heighten awareness, and thereby, to reduce the number of “unknowing” comparisons. A goal of this guide is to stimulate development and testing of evaluation procedures that accommodate the effects of natural variability. A technique is illustrated to provide information from which subsequent evaluation and standardization can be derived.
SCOPE
1.1 This guide provides techniques that are useful for the comparison of modeled air concentrations with observed field data. Such comparisons provide a means for assessing a model's performance, for example, bias and precision or uncertainty, relative to other candidate models. Methodologies for such comparisons are yet evolving; hence, modifications will occur in the statistical tests and procedures and data analysis as work progresses in this area. Until the interested parties agree upon standard testing protocols, differences in approach will occur. This guide describes a framework, or philosophical context, within which one determines whether a model's performance is significantly different from other candidate models. It is suggested that the first step should be to determine which model's estimates are closest on average to the observations, and the second step would then test whether the differences seen in the performance of the other models are significantly different from the model chosen in the first step. An example procedure is provided in to illustrate an existing approach for a particular evaluation goal. This example is not intended to inhibit alternative approaches or techniques that will produce equivalent or superior results. As discussed in Section , statistical evaluation of model performance is viewed as part of a larger process that collectively is referred to as model evaluation.
1.2 This guide has been designed with flexibility to allow expansion to address various characterizations of atmospheric dispersion, which might involve dose or concentration fluctuations, to allow development of application-specific evaluation schemes, and to allow use of various statistical comparison metrics. No assumptions are made regarding the manner in which the models characterize the dispersion.
1.3 The focus of this guide is on end results, that is, the accuracy of model predictions and the discernment of whether differences seen between models are significant, rather than operational details such as the ease of model implementation or the time required for model calculations to be performed.
1.4 This guide offers an organized collection of information or a series of options and does not recommend a specific course of action. This guide cannot replace education or experience and should be used in conjunction with professional judgment. Not all aspects of this guide may be applicable in all circumstances. This guide is not intended to represent or replace the standard of care by which the adequacy of a given professional service must be judged, nor should it be applied without consideration of a project's many unique aspects. The word "Standard" in the title of this guide means only that the document has been approved through the ASTM consensus process.
This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and to determine the applicability of regulatory limitations prior to use.

SCOPE
1.1 This guide describes the application of acoustic remote sensing for measuring atmospheric wind and turbulence profiles. It includes a summary of the fundamentals of atmospheric sound detection and ranging (sodar), a description of the methodology and equipment used for sodar applications, factors to consider during site selection and equipment installation, and recommended procedures for acquiring valid and relevant data.
1.2 This guide applies principally to pulsed monostatic sodar techniques as applied to wind and turbulence measurement in the open atmosphere, although many of the definitions and principles are also applicable to bistatic configurations. This guide is not directly applicable to radio-acoustic sounding systems (RASS), or tomographic methods.

SIGNIFICANCE AND USE
Atmospheric pressure is one of the basic variables used by meteorologists to describe the state of the atmosphere.
The measurement of atmospheric pressure is needed when differences from “standard” pressure conditions must be accounted for in some scientific and engineering applications involving pressure dependent variables.
These methods provide a means of measuring atmospheric pressure with the accuracy and precision comparable to the accuracy and precision of measurements made by governmental meteorological agencies.
SCOPE
1.1 These methods cover the measurement of atmospheric pressure with two types of barometers: the Fortin-type mercurial barometer and the aneroid barometer.
1.2 In the absence of abnormal perturbations, atmospheric pressure measured by these methods at a point is valid everywhere within a horizontal distance of 100 m and a vertical distance of 0.5 m of the point.
1.3 Atmospheric pressure decreases with increasing height and varies with horizontal distance by 1 Pa/100 m or less except in the event of catastrophic phenomena (for example, tornadoes). Therefore, extension of a known barometric pressure to another site beyond the spatial limits stated in 1.2 can be accomplished by correction for height difference if the following criteria are met:
1.3.1 The new site is within 2000 m laterally and 500 m vertically.
1.3.2 The change of pressure during the previous 10 min has been less than 20 Pa.
The pressure, P2 at Site 2 is a function of the known pressure P1 at Site 1, the algebraic difference in height above sea level, h1 - h2, and the average absolute temperature in the space between. The functional relationship between P1 and P2 is shown in 10.2. The difference between P1 and P2 for each 1 m of difference between h1 and h2 is given in Table 1 and 10.4 for selected values of P1 and average temperature.
1.4 Atmospheric pressure varies with time. These methods provide instantaneous values only.
1.5 The values stated in SI units are to be regarded as the standard.
1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. Specific safety precautionary statements are given in Section 7.

SIGNIFICANCE AND USE
Applications—Ambient atmospheric temperature measurements can be made using resistance thermometers for many purposes. The application determines the most appropriate type of resistance thermometer and data recording method to be used. Examples of three typical meteorological applications for temperature measurements follow.
4.1.1 Single-level, near-surface measurements for weather observations (1)3 , thermodynamic computations for industrial applications, or environmental studies (2).
4.1.2 Temperature differential or vertical gradient measurements to characterize atmospheric stability for atmospheric dispersion analyses studies (2).
4.1.3 Temperature fluctuations for heat flux or temperature, or variance computations, or both. Measurements of heat flux and temperature variance require high precision measurements with a fast response to changes in the ambient atmosphere.
Purpose—This practice is designed to assist the user in selecting an appropriate temperature measurement system for the intended atmospheric application, and properly installing and operating the system. The manufacturer’recommendations and the U.S. Environmental Protection Agency handbook on quality assurance in meteorological measurements (3) should be consulted for calibration and performance audit procedures.
SCOPE
1.1 This practice provides procedures to measure representative near-surface atmospheric (outdoor air) temperature for meteorological purposes using commonly available electrical thermometers housed in radiation shields mounted on stationary or portable masts or towers.
1.2 This practice is applicable for measurements over the temperature range normally encountered in the ambient atmosphere, -50 to +50°C.
1.3 Air temperature measurement systems include a radiation shield, resistance thermometer, signal cables, and associated electronics.
1.4 Measurements can be made at a single level for various meteorological purposes, at two or more levels for vertical temperature differences, and using special equipment (at one or more levels) for fluctuations of temperature with time applied to flux or variance measurements.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.