ISO/TC 146/SC 5 - Meteorology

This document provides requirements for the evaluation and use of test method for snow depth sensors. This document is applicable to the following types of automatic snow depth sensors which employ different ranging technologies by which the sensors measure the distance from the snow surface to the sensor: a) Ultrasonic type, also known as sonic ranging depth sensors; b) Optical laser snow depth sensors including single point and multipoint snow depth sensors; c) Other snow depth sensors. This document mainly covers two major tests: a laboratory(indoor) test and a field (outdoor) test. The laboratory test includes the basic performance test and other tests under various environmental changes. The field test is proposed to ensure the performance of the snow depth sensors in field measurement conditions. For the field test, both the natural ground and artificial target surface such as snow plates are considered for the procedures defined in this document.

ISO 19926-1:2019 specifies system performance of ground-based weather radar systems measuring the atmosphere using frequencies between 2 GHz and 10 GHz. These systems are suitable for the area-wide detection of precipitation and other meteorological targets at different altitudes. This document also describes ways to verify the different aspects of system performance, including infrastructure. ISO 19926-1:2019 is applicable to linear polarization parabolic radar systems, dual-polarization and single-polarization radars. It does not apply to fan-beam radars [narrow in azimuth (AZ) and broad in elevation (EL)], including marine and aeronautical surveillance radars, which are used for, but are not primarily designed for, weather applications. Phased-array radars with electronically formed and steered beams, including multi-beam, with non-circular off-bore sight patterns, are new and insufficient performance information is available. ISO 19926-1:2019 does not describe weather radar technology and its applications. Weather radar systems can be used for applications such as quantitative precipitation estimation (QPE), the classification of hydrometeors (e.g. hail), the estimation of wind speeds and the detection and surveillance of severe meteorological phenomena (e.g. microburst, tornado). Some of these applications have particular requirements for the positioning of the radar system or need specific measurement strategies. However, the procedures for calibration and maintenance described in this document apply here as well. ISO 19926-1:2019 addresses manufacturers and radar operators.

This document specifies the requirements and performance test procedures for monostatic heterodyne continuous-wave (CW) Doppler lidar techniques and presents their advantages and limitations. The term "Doppler lidar" used in this document applies solely to monostatic heterodyne CW lidar systems retrieving wind measurements from the scattering of laser light by aerosols in the atmosphere. Performances and limits are described based on standard atmospheric conditions. This document describes the determination of the line-of-sight wind velocity (radial wind velocity). NOTE Derivation of wind vector from individual line-of-sight measurements is not described in this document since it is highly specific to a particular wind lidar configuration. One example of the retrieval of the wind vector can be found in ISO 28902-2:2017, Annex B. This document does not address the retrieval of the wind vector. This document can be used for the following application areas: — meteorological briefing for e.g. aviation, airport safety, marine applications, oil platforms; — wind power production, e.g. site assessment, power curve determination; — routine measurements of wind profiles at meteorological stations; — air pollution dispersion monitoring; — industrial risk management (direct data monitoring or by assimilation into micro-scale flow models); — exchange processes (greenhouse gas emissions). This document can be used by manufacturers of monostatic CW Doppler wind lidars as well as bodies testing and certifying their conformity. This document also provides recommendations for users to make adequate use of these instruments.

ISO 28902-2:2017 specifies the requirements and performance test procedures for heterodyne pulsed Doppler lidar techniques and presents their advantages and limitations. The term "Doppler lidar" used in this document applies solely to heterodyne pulsed lidar systems retrieving wind measurements from the scattering of laser light onto aerosols in the atmosphere. A description of performances and limits are described based on standard atmospheric conditions. This document describes the determination of the line-of-sight wind velocity (radial wind velocity). NOTE Derivation of wind vector from individual line-of-sight measurements is not described in this document since it is highly specific to a particular wind lidar configuration. One example of the retrieval of the wind vector can be found in Annex B. ISO 28902-2:2017 does not address the retrieval of the wind vector. ISO 28902-2:2017 may be used for the following application areas: - meteorological briefing for, e.g. aviation, airport safety, marine applications and oil platforms; - wind power production, e.g. site assessment and power curve determination; - routine measurements of wind profiles at meteorological stations; - air pollution dispersion monitoring; - industrial risk management (direct data monitoring or by assimilation into micro-scale flow models); - exchange processes (greenhouse gas emissions). ISO 28902-2:2017 addresses manufacturers of heterodyne pulsed Doppler wind lidars, as well as bodies testing and certifying their conformity. Also, this document provides recommendations for the users to make adequate use of these instruments.

ISO 19289:2015 indicates exposure rules for various sensors, but what should be done when these conditions are not fulfilled? There are sites that do not respect the recommended exposure rules. Consequently, a classification has been established to help determine the given site's representativeness on a small scale (impact of the surrounding environment). The classification process helps the actors and managers of a network to better take into consideration the exposure rules and thus it often improves the siting. At least, the siting environment is known and documented in the metadata. It is obviously possible and recommended to fully document the site but the risk is that a fully documented site might increase the complexity of the metadata, which would often restrict their operational use. That is why this siting classification is defined to condense the information and facilitate the operational use of this metadata information. A site as a whole has no single classification number. Each parameter being measured at a site has its own class and is sometimes different from the others. If a global classification of a site is required, the maximum value of the parameters' classes can be used. In ISO 19289:2015, the classification is (occasionally) completed with an estimated uncertainty due to siting, which has to be added in the uncertainty budget of the measurement. This estimation is coming from bibliographic studies and/or some comparative tests. The primary objective of this classification is to document the presence of obstacles close to the measurement site.

This part of ISO 28902 mainly specifies the requirements in order to perform visual range lidar measurements for the determination of direction-dependent meteorological optical range (MOR). The term "visual-range lidar" is used in this part of ISO 28902 to apply to the lidar systems making visual-range measurements, commonly referred to as "visibility measurements". Due to physical approximations, quantitative determination is limited to a meteorological optical range of between 30 m and 2 000 m. For this range, this part of ISO 28902 specifies the performance of visual-range lidar systems utilizing the method of range‑integrated visual-range measurements based on light extinction. The following parameters can be calculated based on the directiondependent meteorological optical range: a) horizontal visual range; b) vertical visual range; c) slant visual range. NOTE The measures for visibility are strongly related to the historical definitions of visibility, which are related to human observers. The lidar technique extends the definitions to various conditions, such as daylight and night-time conditions. In addition, this measurement principle enables the user to retrieve information on cloud base height, boundary layer depth, fog banks and aerosol profiles due to the signal attenuation by water vapour and/or aerosols. Examples of these applications are given in Annex C. This part of ISO 28902 can be applied in the following areas: — meteorological stations; — airports; — harbours; — waterways; — roads and motorways; — automotive; — oil platforms.

ISO 17714:2007 defines characteristics of a thermometer shield/screen. It also defines test methods to inter-compare the behaviour of different screen designs. Although screens are usually used for both air temperature and humidity measurements, ISO 17714:2007 is applicable only to temperature measurements. Both naturally and artificially ventilated screens are considered.

ISO 17713-1:2007 describes wind tunnel test methods for determining performance characteristics of rotating anemometers, specifically cup anemometers and propeller anemometers. It also describes an acceptance test and unambiguous methods for measuring the starting threshold, distance constant, transfer function and off-axis response of a rotating anemometer in a wind tunnel.

ISO 16622:2002 defines test methods of the performance of sonic anemometers/thermometers which employ the inverse time measurement for velocity of sound along differently oriented paths. It is applicable to designs measuring two or three components of the wind vector within an unlimited (360°) azimuthal acceptance angle.