1、raising standards worldwideNO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBSI Standards PublicationHydrometry Measurement of the rainfall intensity (liquid precipitation): requirements, calibration methods and field measurements PD CEN/TR 16469:2013National forewordThis Publis
2、hed Document is the UK implementation of CEN/TR 16469:2013. The UK participation in its preparation was entrusted to Technical CommitteeCPI/113, Hydrometry.A list of organizations represented on this committee can be obtained onrequest to its secretary.This publication does not purport to include al
3、l the necessary provisions of acontract. Users are responsible for its correct application. The British Standards Institution 2013.Published by BSI Standards Limited 2013.ISBN 978 0 580 77503 1 ICS 07.060 Compliance with a British Standard cannot confer immunity from legal obligations.This Published
4、 Document was published under the authority of the Standards Policy and Strategy Committee on 31 March 2013. Amendments issued since publicationDate Text affectedPUBLISHED DOCUMENTPD CEN/TR 16469:2013TECHNICAL REPORT RAPPORT TECHNIQUE TECHNISCHER BERICHT CEN/TR 16469 January 2013 ICS 07.060 English
5、Version Hydrometry - Measurement of the rainfall intensity (liquid precipitation): requirements, calibration methods and field measurements Mesurage de lintensit pluviomtrique (prcipitations liquides) : exigences, mthodes dtalonnage et mesures de terrain Hydrometrie - Messung der Regenintensitt (fls
6、siger Niederschlag): Anforderungen, Kalibrierverfahren und Feldmessungen This Technical Report was approved by CEN on 27 November 2012. It has been drawn up by the Technical Committee CEN/TC 318. CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Repu
7、blic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United Kingdom. EUROPEAN
8、 COMMITTEE FOR STANDARDIZATION COMIT EUROPEN DE NORMALISATION EUROPISCHES KOMITEE FR NORMUNG Management Centre: Avenue Marnix 17, B-1000 Brussels 2013 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. CEN/TR 16469:2013: EPD CEN/TR 16469
9、:2013CEN/TR 16469:2013 (E) 2 Contents Page Foreword 3 1 Scope 5 2 Normative references 5 3 Terms and definitions .5 4 Standardization of RI raingauge calibration and field requirements .7 5 Accuracy of rainfall intensity 7 5.1 Fundamentals and requirements .7 5.2 Laboratory calibration method (const
10、ant flow and step response) .8 5.3 Classification of gauges according to accuracy performances .9 5.4 Field calibration method (calibration verification) .9 5.5 Traceability of the RI measurements 10 6 Field rainfall intensity measurements 10 6.1 References gauges and field intercomparisons 10 6.2 R
11、elevant operational requirements for field RI measurements . 10 6.3 General requirements for siting and exposure (as indicated by WMO-No. 8, 7thedition) . 11 6.4 International field intercomparisons: role and outcomes 12 Annex A (informative) Laboratory tests . 13 Annex B (informative) Field measure
12、ments 17 PD CEN/TR 16469:2013CEN/TR 16469:2013 (E) 3 Foreword This document (CEN/TR 16469:2013) has been prepared by Technical Committee CEN/TC 318 “Hydrometry”, the secretariat of which is held by BSI. Attention is drawn to the possibility that some of the elements of this document may be the subje
13、ct of patent rights. CEN and/or CENELEC shall not be held responsible for identifying any or all such patent rights. The Executive Council of the WMO, noting the working arrangements between the ISO and WMO formally adopted on 16 September 2008, recognised the wide ranging benefits to National Meteo
14、rological and Hydrological Services and user communities resulting from the implementation of common Standards relevant for meteorology and hydrology and the need to established the benefit/cost implication to WMO Members of elevating an existing Technical Regulation/Manual/Guide to a common Standar
15、d. The EC finally approved procedures to be followed in proposing common technical standards (Resolution 8, Abridged Final Report of the sixty-first session of the WMO Executive Council). This document is not a European Standard but a Technical Report. It is a document to describe recent findings in
16、 rainfall intensity (RI) measurements and related accuracy aspects, following the results and outcomes of the most recent international RI gauges intercomparison organised by the World Meteorological Organisation (WMO). The Technical Report also provides informative documentation (in annexes) contai
17、ning methods for laboratory calibrations, field tests and reference field measurements. In consideration of the requirement for general standardization and homogeneity of precipitation intensity measurements and the need for instruments development to promote worldwide instrument compatibility and i
18、nteroperability, the WMO Lead Centre on Precipitation Intensity “B. Castelli” (Italy) has been designated by the WMO Commission of Instruments and Methods of Observation (CIMO General Summary of the fifteen Session, Helsinki, Finland, 2 - 8 September 2011). The Lead Centre is intended as a Centre of
19、 Excellence for instrument development and testing which would be established with the purpose of providing the scientific community with specific guidance and standard procedures about instrument calibration and their achievable uncertainty, performing laboratory and field tests and the intercompar
20、ison of instruments, and providing research advances and technical developments about the measurement of precipitation intensity and the related data analysis and interpretation. PD CEN/TR 16469:2013CEN/TR 16469:2013 (E) 4 Introduction The need for, and the importance of accurate and reliable rainfa
21、ll intensity (RI) measurements is ever increasing. This is the result of a number of factors, including the increased recognition of scientific and practical issues related to the assessment of possible climatic trends, the mitigation of natural disasters (e.g. storms and floods), the slowing down o
22、f desertification and the design of structures (buildings, construction works) and infrastructure (drainage). This has resulted in more rigorous and enhanced quality requirements for RI measurements. The volume of rainfall received by a collector through an orifice of known surface area in a given p
23、eriod of time has traditionally been adopted as the reference variable, namely the rainfall depth. Under the restrictive hypothesis that rainfall is constant over the accumulation period, a derived variable, “the rainfall rate, or intensity (RI)”, can be calculated. The estimated RI should get close
24、r to the actual flow of water ultimately reaching the ground as the recording time interval decreases. In view of the very high variability of RI, field measurements at short time scales (e.g. 1 min) are crucial to enable high quality measurement be taken to mitigate the impact of severe events and
25、save lives, property and infrastructures. As the probability of heavy rainfall events is small, long-term records of RI are required to estimate the frequency of occurrence of very intense rainfall at a given location and time. On completion of the most recent RI gauges intercomparison organised by
26、the World Meteorological Organisation (WMO), it has been recommended that RI measurements should be covered by International Standards. These standards should be based on the knowledge obtained from those latest WMO intercomparison and other current research and good practice. The adoption of such a
27、n approach will assist rainfall data collection practitioners to obtain homogeneous and compatible data sets. The procedure adopted for performing calibration tests in the laboratory should become a standard method to be used for assessing the instruments performance. Acceptance tests could be based
28、 on the adopted laboratory procedures and standards. A classification of instrument performance should also be developed to help users in selecting the most appropriate instrument for their applications. PD CEN/TR 16469:2013CEN/TR 16469:2013 (E) 5 1 Scope This Technical Report describes a method for
29、 calibrating rainfall intensity (RI) gauges and the measurement requirements to obtain accurate and compatible data sets from hydro-meteorological networks, as a forerunner to the development of full hydro-meteorological data collection standards. This Technical Report deals exclusively with catchin
30、g-type RI gauges (see Clause 3). It concentrates on the generic calibration, performance checking and estimation of uncertainties for RI gauges. It does not cover specific gauge measurement principles, technical characteristics and technology adopted in the design of RI gauges 2 Normative references
31、 The following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. EN 137
32、98, Hydrometry Specification for a reference raingauge pit 3 Terms and definitions For the purposes of this document, the following terms and definitions apply. 3.1 catching raingauge a raingauge which collects precipitation through an orifice, often a funnel, of well-defined size and measure its wa
33、ter equivalent, volume, mass or weight that has been accumulated in a certain amount of time Note 1 to entry: This type of gauge includes storage, level monitoring, tipping bucket and weighing raingauges. This is the most common type of recording raingauge in use in operational networks at the time
34、of preparing this Technical Report. 3.2 delay time of the output of a RI measuring gauge delay of the output message of some RI measuring raingauges Note 1 to entry: The internal calculation of the rainfall intensity in some raingauges can cause a delay of the output data message (e.g. 1 minute) whi
35、ch can easily be shifted automatically to the correct time without any degradation in measurement accuracy. This is typical of software corrected tipping bucket raingauges through embedded electronic chips or interfaces. The delay time should not be confused with the time constant. If real-time outp
36、ut is not needed, software induced delay times are less critical than longer time constants or any other effects, because delay times can easily be corrected to retrieve the original RI information. SOURCE: Adapted from WMO IOM 2009 3.3 measurand quantity intended to be measured SOURCE: VIM:2008 PD
37、CEN/TR 16469:2013CEN/TR 16469:2013 (E) 6 3.4 measurement uncertainty non-negative parameter characterizing the dispersion of the quantity values being attributed to a measurand, based on the information used SOURCE: VIM:2008 Note 1 to entry: The parameter may be, for example, a standard deviation ca
38、lled standard measurement uncertainty (or a specified multiple of it), or the half-width of an interval, having a stated coverage probability. Note 2 to entry: Measurement uncertainty comprises, in general, many components. Some of these may be evaluated by Type A evaluation of measurement uncertain
39、ty from the statistical distribution of the quantity values from series of measurements and can be characterised by standard deviations. The other components, which may be evaluated by Type B evaluation of measurement uncertainty, can also be characterised by standard deviations, evaluated from prob
40、ability density functions based on experience or other information: a) Instrumental measurement uncertainty (VIM 2008): component of measurement uncertainty arising from a measuring instrument or measuring system in use. Instrumental measurement uncertainty is obtained through calibration of a measu
41、ring instrument or measuring system, except for a primary measurement standard for which other means are used. Instrumental uncertainty is used in a Type B evaluation of measurement uncertainty. Information relevant to instrumental measurement uncertainty may be given in the instrument specification
42、s. b) Achievable measurement uncertainty (WMO no. 8, Part I Annex 1.B): it is intended as the measurement uncertainty achievable in field and/or operational conditions. 3.5 non-catching raingauge raingauge where the rain is not collected in a container/vessel Note 1 to entry: The rainfall intensity
43、or amount is either determined by a contact-less measurement using optical or radar techniques or by an impact measurement. This type of gauge includes optical disdrometers, impact disdrometers, microwave radar disdrometers, optical/capacitive sensors. 3.6 resolution smallest change in a quantity be
44、ing measured that causes a perceptible change in the corresponding indication SOURCE: VIM:2008 3.7 step function / heaviside function or unit step function an input signal that switches on at a specified time and stays switched on indefinitely for determining the response (output) of a dynamic instr
45、ument system 3.8 step response the time-varying response of an instrument system to a step function (heaviside function) 3.9 step response time duration between the instant when an input quantity value of a measuring instrument or measuring system is subjected to an abrupt change between two specifi
46、ed constant quantity values and the instant when a corresponding indication settles within specified limits around its final steady value SOURCE: VIM:2008 PD CEN/TR 16469:2013CEN/TR 16469:2013 (E) 7 3.10 time constant risetime characterizing the response of a instrument classified as a system of fir
47、st order response (the way the system responds is approximated by a first order differential equation) Note 1 to entry: It represents the time that the step response of an instrument system takes to reach the (1-1/e)100% 63 % of the final or asymptotic value. 4 Standardization of RI raingauge calibr
48、ation and field requirements An RI international intercomparison organised by the WMO was conducted in a laboratory and in the field. The results have been published as IOM series (Instruments and Observing Methods), respectively the IOM 84 (RI laboratory intercomparison, 2004-2005) and IOM99 (RI Fi
49、eld intercomparison, 2007-2009). This concluded that a standardization of RI measurements is recommended, in terms of uncertainty evaluation for laboratory calibration and field measurements in order to improve the measurement accuracy of meteorological network instruments. This should be based on the achievable RI measurement performance (accuracy) rather than on the involved measuring principle or gauge design/technical solutions. The following activities are recommended. a) The WMO procedure, or similar, adopted for performing calibratio
