prEN 18097
(Main)Hydrometry - Measurement of precipitation intensity - Metrological requirements and test methods for non-catching type rain gauges
Hydrometry - Measurement of precipitation intensity - Metrological requirements and test methods for non-catching type rain gauges
This document considers atmospheric precipitation and defines the procedures and equipment to perform laboratory and field tests, in steady-state conditions, for the calibration, check and metrological confirmation of non-catching precipitation measurement instruments.
It provides a classification of non-catching measurement instruments based on their laboratory performance. The classification does not relate to the physical principle used for the measurement, nor does it refer to the technical characteristics of the instrument assembly but is solely based on the instrument calibration.
Attribution of a given class to an instrument is not intended as a high/low ranking of its quality but rather as a quantitative standardized method to declare the achievable measurement accuracy to provide guidance on the suitability for a particular purpose, while meeting the user’s requirements.
Hydrometrie - Messung der Niederschlagsintensität - Metrologische Anforderungen und Prüfverfahren für nicht auffangende Niederschlagsmessgeräte
Dieses Dokument befasst sich mit dem atmosphärischen Niederschlag und definiert die Verfahren und Ausrüstungen zur Durchführung von Labor- und Feldprüfungen unter stationären Bedingungen für die Kalibrierung, Überprüfung und messtechnische Bestätigung von nicht auffangenden Niederschlags-messgeräten.
Es bietet eine Klassifizierung von nicht auffangenden Messgeräten auf der Grundlage ihrer Laborleistung. Die Klassifizierung bezieht sich nicht auf das physikalische Prinzip, das für die Messung verwendet wird, und auch nicht auf die technischen Merkmale der Gerätebaugruppe, sondern basiert ausschließlich auf der Kalibrierung des Geräts.
Die Zuordnung einer bestimmten Klasse zu einem Messgerät ist nicht als Hoch /Niedrig-Einstufung seiner Qualität gedacht, sondern vielmehr als quantitatives, standardisiertes Verfahren zur Angabe der erreichbaren Genauigkeit einer Messung, um eine Orientierungshilfe für die Eignung für einen bestimmten Zweck zu geben und gleichzeitig die Anforderungen des Benutzers zu erfüllen.
Hydrométrie - Mesurage de l'intensité des précipitations - Exigences métrologiques et méthodes d'essai relatives aux pluviomètres non collecteurs
Le présent document traite des précipitations atmosphériques et définit les modes opératoires et l’équipement permettant d’effectuer des essais en laboratoire et sur le terrain, dans des conditions stables, pour l’étalonnage, le contrôle et la confirmation métrologique des pluviomètres non collecteurs.
Il fournit une classification des pluviomètres non collecteurs d’après leurs performances en laboratoire. La classification ne concerne ni le principe physique utilisé pour le mesurage, ni les caractéristiques techniques de l’ensemble de l’instrument, mais uniquement l’étalonnage de l’instrument.
L’attribution d’une classe à un instrument n’est pas destinée à servir de classement de sa qualité mais plutôt de méthode quantitative normalisée pour déclarer l’exactitude de mesure atteignable pour fournir des recommandations sur l’adéquation avec un objectif particulier, tout en satisfaisant aux exigences de l’utilisateur.
Hidrometrija - Merjenje intenzivnosti padavin - Meroslovne zahteve in preskusne metode zanelovne merilnike dežja
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
01-julij-2024
Hidrometrija - Merjenje intenzivnosti padavin - Meroslovne zahteve in preskusne
metode zanelovne merilnike dežja
Hydrometry - Measurement of precipitation intensity - Metrological requirements and test
methods for non-catching type rain gauges
Hydrometrie - Messung der Niederschlagsintensität - Metrologische Anforderungen und
Prüfverfahren für nicht auffangende Niederschlagsmessgeräte
Hydrométrie - Mesurage de l'intensité des précipitations - Exigences métrologiques et
méthodes d'essai relatives aux pluviomètres non collecteurs
Ta slovenski standard je istoveten z: prEN 18097
ICS:
07.060 Geologija. Meteorologija. Geology. Meteorology.
Hidrologija Hydrology
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
DRAFT
EUROPEAN STANDARD
NORME EUROPÉENNE
EUROPÄISCHE NORM
June 2024
ICS 07.060
English Version
Hydrometry - Measurement of precipitation intensity -
Metrological requirements and test methods for non-
catching type rain gauges
Hydrometrie - Messung der Niederschlagsintensität -
Metrologische Anforderungen und Prüfverfahren für
nicht auffangende Niederschlagsmessgeräte
This draft European Standard is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee
CEN/TC 318.
If this draft becomes a European Standard, CEN members are bound to comply with the CEN/CENELEC Internal Regulations
which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.
This draft European Standard was established by CEN in three official versions (English, French, German). A version in any other
language made by translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC
Management Centre has the same status as the official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and
United Kingdom.
Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are
aware and to provide supporting documentation.
Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without
notice and shall not be referred to as a European Standard.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2024 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 18097:2024 E
worldwide for CEN national Members.
Contents Page
European foreword . 3
Introduction . 4
1 Scope . 5
2 Normative references . 5
3 Terms, definitions and symbols . 5
3.1 Terms and definitions . 5
3.2 Symbols . 5
4 Measurement of rainfall intensity using non-catching rain gauges . 6
4.1 General. 6
4.2 Optical . 6
4.3 Impact . 7
4.4 Radar . 7
5 Classification of non-catching rainfall intensity gauges . 7
5.1 Characteristics of the laboratory device . 7
5.2 Testing protocol . 8
Bibliography . 14
European foreword
This document (prEN 18097:2024) has been prepared by Technical Committee CEN/TC 318
“Hydrometry”, the secretariat of which is held by BSI.
This document is currently submitted to the CEN Enquiry.
Introduction
According to CEN/TR 17993:2023 “Calibration and accuracy of non-catching precipitation measurement
instruments”, although numerous attempts were made and various approaches were tested, no fully
traceable calibration procedure exists for most of the non-catching gauges (NCGs) available on the
market.
The document was prepared following a request for research development submitted by CEN/TC 318 in
October 2017 to EURAMET, the European Association of National Metrology Institutes, through the
cooperation programme between STAIR (the joint CEN-CENELEC strategic Working Group supporting
standardization in research and innovation) and EMPIR (the European Metrology Programme for
Innovation and Research of EURAMET). This led to the approval and funding of the EURAMET pre-
normative Research Project “EMPIR 18NRM03 - INCIPIT Calibration and accuracy of non-catching
instruments to measure liquid/solid atmospheric precipitation” (Merlone et al., 2022 [1]) where a
calibration procedure was developed and proposed for consideration as a basis for standardization. The
text is derived from the work of Chinchella (2022) [2].
1 Scope
This document considers atmospheric precipitation and defines the procedures and equipment to
perform laboratory and field tests, in steady-state conditions, for the calibration, check and metrological
confirmation of non-catching precipitation measurement instruments.
It provides a classification of non-catching measurement instruments based on their laboratory
performance. The classification does not relate to the physical principle used for the measurement, nor
does it refer to the technical characteristics of the instrument assembly but is solely based on the
instrument calibration.
Attribution of a given class to an instrument is not intended as a high/low ranking of its quality but rather
as a quantitative standardized method to declare the achievable measurement accuracy to provide
guidance on the suitability for a particular purpose, while meeting the user’s requirements.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
EN 17277:2019, Hydrometry — Measurement requirements and classification of rainfall intensity
measuring instruments
3 Terms, definitions and symbols
3.1 Terms and definitions
No terms and definitions are listed in this document.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https://www.iso.org/obp/
— IEC Electropedia: available at https://www.electropedia.org/
3.2 Symbols
C
is 3,6·10 the numerical factor for the conversion of the rate of rainfall from
c
-1 -1
[m s ] to [mm h ];
D mm drop nominal diameter
D mm mean and standard deviation of the actual equivolumetric diameter
eqv
D mm mean and standard deviation of the measured drop diameter
m
mm investigated (nominal) diameter
D
i
% percentage relative deviation
e
rel
N number of drops per unit volume of air and unit drop size interval
-1
RI rainfall intensity
mm h
-1
measured ranfall intensity
mm h
RI
meas
-1
reference rainfall intensity
RI mm h
ref
mm mean measured drop diameter
µ
Deqv
-1
mean fall velocity
µ m s
wact
-1
w actual fall velocity
m s
act
-1
w drop terminal velocity
m s
T
-1 -3
scale parameter
mm m
N
Λ -1
slope parameter
mm
D mm drop nominal diameter
D mm actual equivolumetric diameter
eqv
D mm measured drop diameter
m
mm investigated (nominal) diameter
D
i
% percentage relative deviation
e
rel
4 Measurement of rainfall intensity using non-catching rain gauges
4.1 General
The initial manual measurement methods for the study of the hydrometeor’s characteristics evolved due
to advances in technology and electronics. Nowadays different techniques are involved in the
determination of liquid/solid particle characteristics, like devices to measure the displacement and
mechanical energy caused by raindrops/graupels hitting a surface, and optical detection, whereby the
size, shape, velocity, and diameter of hydrometeors are measured while they cross a light or laser beam,
etc.
4.2 Optical
Optical disdrometers use visible or infrared (IR) light to detect falling hydrometeors. The available
instruments use different technical solutions but all of them present a similar structure. The instrument
is equipped with an IR or visible light emitter/transmitter that illuminates a volume of the atmosphere
and with an optical sensor to detect the emitted light. The illuminated measuring volume is usually
defined by the shape of the lens and the relative position between the emitter and the receiver. When
droplets cross the sensing volume, the light changes its intensity and scatters in various directions. This
variation is detected by the sensor allowing the physical properties of the particle (e.g. the diameter and
the falling speed) to be derived. Scattering can be broadly defined as the redirection of radiation out of
the original direction of propagation.
4.3 Impact
Impact disdrometers exploit the kinetic energy of the falling drops when impacting the exposed surface
of the sensor. A plastic or metal membrane is used at the measurement surface to sense the impact of
single precipitation particles. In some systems, the mechanical movement of the membrane is transduced
into an electric signal by an attached moving magnet/coil system. In other solutions, the amplitude and
the frequency spectrum of vibrations generated by precipitation particles hitting the membrane are
detected and analysed to determine the number and size of particles. Impact methods is therewith
suitable to determine the precipitation intensity, the rain rate and the drop size distribution over a given
time window.
Impact disdrometers can be divided in two categories: acoustic and displacement disdrometers. Both
types are commercially available and are devoted to measuring liquid precipitation, since the droplets
energy is directly related to the mass and density of the water; snowflakes and hailstones, for example,
have completely different impacts on the sensors, and could lead to underestimation or overestimation
of the precipitation amount.
4.4 Radar
Since the sixties, microwave-based technologies have been developed and improved in both the
communication and meteorological fields. Ground-based microwave radiometry has its traditional
applications in meteorology in the estimation of columnar profiles of vapour content, non-raining clouds
liquid water and temperature. Precipitation measurements employing microwave sensors appeared in
the last decades and are based on the signal power reduction through the atmosphere during a
precipitation event. The attenuation and scattering of the sensor emissions are related to the
precipitation rate, but also depend on the physics of the precipitation particles, such as the liquid or solid
phase and the different particles size, but also the frequency of the emitting signal has a fundamental role.
Microwave disdrometers use the doppler effect to measure hydrometeors passing nearby. A falling
droplet moving vertically towards the instrument produces a return signal, when it enters the
measurement volume, which frequency is a function of the velocity at which the object crosses the equi-
phase surfaces. These are surfaces defined by the points having R1 + R2 = constant, where R1 is the
distance between the emitting antenna and the falling droplet and R2 is the distance between the droplet
and the receiving antenna.
5 Classification of non-catching rainfall intensity gauges
5.1 Characteristics of the laboratory device
The measurable quantities for the non-catching rain gauges are the drop size and velocity. To produce
reference drops in a controlled manner, three drop generators were developed within the INCIPIT
project. The first drop generator, hereinafter named DG1, was developed by the Teknologisk Institut
(DTI) in Denmark, the second one, DG2, was developed by the University of Genova (UNIGE) in Italy and
the third one, DG3, by the FPS Economy, Metrology, National Standards (SMD) in Belgium.
...
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