1、Designation: D4430 00 (Reapproved 2010)Standard Practice forDetermining the Operational Comparability ofMeteorological Measurements1This standard is issued under the fixed designation D4430; the number immediately following the designation indicates the year oforiginal adoption or, in the case of re
2、vision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 Sensor systems used for making meteorological mea-surements may be tested for laboratory accuracy
3、in environ-mental chambers or wind tunnels, but natural exposure cannotbe fully simulated. Atmospheric quantities are continuouslyvariable in time and space; therefore, repeated measurementsof the same quantities as required by Practice E177 todetermine precision are not possible. This practice prov
4、idesstandard procedures for exposure, data sampling, and process-ing to be used with two measuring systems in determining theiroperational comparability (1,2).21.2 The procedures provided produce measurement samplesthat can be used for statistical analysis. Comparability isdefined in terms of specif
5、ied statistical parameters. Otherstatistical parameters may be computed by methods describedin 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 compa-rability is called functional precision
6、.1.4 Meteorological determinations frequently require simul-taneous measurements to establish the spatial distribution ofatmospheric quantities or periodically repeated measurement todetermine the time distribution, or both. In some cases, anumber of identical systems may be used, but in others amix
7、ture of instrument systems may be employed. The proce-dures described herein are used to determine the variability oflike or unlike systems for making the same measurement.1.5 This standard does not purport to address the safetyconcerns, if any, associated with its use. It is the responsibilityof th
8、e user of this standard to establish appropriate safety andhealth practices and determine the applicability of regulatorylimitations prior to use. (See 8.1 for more specific safetyprecautionary information.)2. Referenced Documents2.1 ASTM Standards:3D1356 Terminology Relating to Sampling and Analysi
9、s ofAtmospheresE177 Practice for Use of the Terms Precision and Bias inASTM Test Methods3. Terminology3.1 For additional definitions of terms, refer to TerminologyD1356.3.2 Definitions of Terms Specific to This Standard:3.2.1 difference (D)the difference between the systematicdifference (d) of a set
10、 of samples and the true mean () of thepopulation:D 5 d 2 (1)3.2.2 systematic difference (d)the mean of the differencesin the measurement by the two systems:d 51N(i 5 1NXai2 Xbi! (2)3.2.3 operational comparability (C)the root mean square(rms) of the difference between simultaneous readings fromtwo s
11、ystems measuring the same quantity in the same environ-ment:C 561N(i 5 1NXai2 Xbi!2(3)where:Xai= ith measurement made by one system,Xbi= ith simultaneous measurement made by anothersystem, andN = number of samples used.3.2.3.1 functional precisionthe operational comparabilityof identical systems.1Th
12、is practice is under the jurisdiction of ASTM Committee D22 on Air Qualityand is the direct responsibility of Subcommittee D22.11 on Meteorology.Current edition approved Oct. 1, 2010. Published March 2011. Originallyapproved in 1984. Last previous edition approved in 2006 as D4430 - 00(2006).DOI: 10
13、.1520/D4430-00R10.2The boldface numbers in parentheses refer to the list of references at the end ofthis practice.3For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to th
14、e standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.2.4 estimated standard deviation of the difference (s)ameasure of the dispersion of a series of differences around theirmean.s 56=
15、C22 d2(4)3.2.5 skewness (M)the symmetry of the distribution (thethird moment about the mean).M 5(i 5 1NXai2 Xbi! 2 d!3N3(5)M = 0 for normal distribution.3.2.6 kurtosis (K)the peakedness of the distribution (thefourth moment about the mean), K = 3 for normal distribution.K 5(i 5 1NXai2 Xbi! 2 d!4N4(6
16、)3.2.7 response time (T)the time required for the change inoutput of a measuring system to reach 63 % of a step functionchange in the variable being measured.3.2.8 identical systemssystems of the same make andmodel produced by the same manufacturer.3.2.9 resolution (r)the smallest change in an atmos
17、phericvariable that is reported as a change in the measurement.4. Summary of Practice4.1 The systems to be compared must make measurementswithin a cylindrical volume of the ambient atmosphere notgreater than 10 m in horizontal diameter. The vertical extent ofthe volume must be the lesser of1morone-t
18、enth H, where His the height above the earths surface of the base of thevolume. The sample volume must be selected to ensurehomogeneous distribution of the variable being measured.4.2 For some measurements (for example, visibility) thehorizontal distance or the height (for example, cloud height)may
19、be the variable of interest. In the first case, one of the twodimensions of horizontal distance is minimized and may notexceed 10 m while all other criteria remain the same. In thesecond case, all criteria for position and sampling described in4.1 remain unchanged and the measured height is treated
20、as ifit were an atmospheric variable. The physical dimension ofsome measuring systems may exceed the spatial limits of 4.1(for example, a rotating beam ceilometer with a 200-mbaseline). In those cases the systems must be installed so thatthe measurements are obtained from within the volume speci-fie
21、d in 4.1.4.3 Samples are taken in pairs and the time interval betweenthe pairs of samples must be no less than four times theresponse time (4T) of the measuring systems (4).4.4 The time between members of a pair of measurementsmust be as small as possible, but must not exceed one tenth theresponse t
22、ime.4.5 The root mean square (rms) of the measurement differ-ences is calculated to provide operational comparability orfunctional precision of the systems.4.6 Measurement differences may change with the magni-tude of the measurement (for example, the absolute value ofthe difference in the measureme
23、nt of wind speed by twosystems may be greater or smaller at high-wind speeds than atlow-wind speeds). To test the data for such dependence, therange of measurements shall be divided into no less than threeclass intervals and each class shall have a sufficient number ofsamples to represent the class.
24、 The change in rms differencebetween classes indicates the dependence of the measurementdifference on the magnitude of the measurement.5. Significance and Use5.1 This practice provides data needed for selection ofinstrument systems to measure meteorological quantities and toprovide an estimate of th
25、e precision of measurements made bysuch systems.5.2 This practice is based on the assumption that therepeated measurement of a meteorological quantity by a sensorsystem will vary randomly about the true value plus anunknowable systematic difference. Given infinite resolution,these measurements will
26、have a Gaussian distribution about thesystematic difference as defined by the Central Limit Theorem.If it is known or demonstrated that this assumption is invalidfor a particular quantity, conclusions based on the characteris-tics of a normal distribution must be avoided.6. Interferences6.1 Exposure
27、 of the systems shall be such as to avoidinterference from sources, structures, or other conditions thatmay produce a gradient in the measurement across the samplevolume.6.2 A mutual interference by systems may produce a sys-tematic difference (d) or bias that would not occur if onesystem were used
28、by itself. That bias is not a part of thecomparability and must be reported separately.6.3 A systematic difference greater than one increment ofresolution must be investigated by interchanging the positionof the sensors with an equal number of samples taken in eachposition. If the bias changes sign,
29、 it is due to the exposure andmust be reported separately.7. Apparatus7.1 The apparatus used is the combination of sensor systemsfor which the operational comparability or functional precisionis to be determined plus the data-processing equipment re-quired to extract the data and calculate the stati
30、stical param-eters.8. Precautions8.1 Safety precautions accompanying the sensor systemsmust be followed.8.2 Technical Precautions:8.2.1 Measurement-system mutual electrical interferencemust be minimized.8.2.2 Use of this practice is based on a statistical analysis ofthe distribution of differences u
31、sed to calculate operationalcomparability. Mean, standard deviation, skewness, and kurto-sis of the distribution are reported to facilitate such analysis.9. Sampling9.1 Samples are collected in pairs from two sensors sam-pling the free ambient atmosphere.D4430 00 (2010)29.2 Samples are collected fro
32、m a cylindrical volume of thefree atmosphere as defined in 4.1.9.3 The distance between sensors should be the smallestdistance that avoids sensor interaction but must meet 9.2.9.4 The time between pairs of samples ( Xai, Xbi, andXai+1,Xbi+ 1) must be equal to or greater than four times theresponse t
33、ime (4T) of the sensor system. The nature ofatmospheric data is such that time intervals between pairs ofsamples as long as an hour or more may be desirable.9.5 The time between members of a pair of samples (XaiandXbi) must not exceed one tenth of the response time (T/10).9.6 The comparability deter
34、mined is limited to the range ofatmospheric conditions encountered. The number of samplescannot be too large. The minimum number of samples thatmust be exceeded is found by using the criteria for a 99.7 % orgreater confidence interval that the absolute value of thedifference (D) between the systemat
35、ic difference (d) and thetrue mean () of the population of all samples is less than orequal to the absolute value of three times the standard deviation(3s) about the mean, divided by the square root of the numberof samples in the set of data. To calculate D the estimatedstandard deviation (s) is use
36、d to provide:D 5 ? d ?#U3s= NU(7)9.6.1 The sampling is not complete until D is less than orequal to one increment of resolution ( r) of the system beingtested. Stated another way, the number of samples needed Nnmust be:Nn$S3srD2(8)10. Preparation10.1 The systems to be compared must be prepared forop
37、eration individually according to manufacturers instruc-tions.10.2 Deliberate readjustment to obtain identical simulta-neous readings shall be avoided.11. Procedure11.1 Install two or more meteorological measuring systemsso that they are measuring the free ambient atmosphere from acylindrical volume
38、 as defined in 4.1.11.2 Record a measurement from each system separated byno more than T/10-s time interval.11.3 Repeat 11.2 at a time interval at least four times theresponse time (4T ) of the particular systems being tested. Ifsystems with different response times are being compared, thelongest sh
39、all be used to determine the minimum allowable timebetween pairs of samples. The period between the readingsmay be much larger than four times the response time (4T) forpractical and operational reasons. It is advisable to choose boththe time period between readings and the total period overwhich th
40、e determination is made long enough to include a widesample of naturally occurring meterological phenomena at thesite.11.4 Continue sampling until at least Nnsamples have beenobtained where:Nn$S3srD2(9)11.5 Divide the range of measurement into no less thanthree class intervals. Continue sampling unt
41、il the number ofsamples in each interval (Ni) is:Ni$S2srD2(10)11.6 Test the data for dependence between the differencemeasured and the magnitude of the measurement.11.7 Calculate the skewness (M) (see 3.1) and the kurtosis(K) (see 3.1) of the frequency distribution of the differences.12. Reports12.1
42、 Report C, the two-system operational comparability.12.2 Report d, the systematic difference in the measurementby the two systems.12.3 Report N, the number of samples used to calculate Cand d.12.4 Report t, the time interval between pairs of samples.12.5 Report the range of measurements across which
43、 sam-pling was made.12.6 Report on the dependence between the sample differ-ence measured and the magnitude of the measurement.12.7 Report any evidence of system interaction that wouldaffect the systematic difference d.12.8 Report M, the skewness of the frequency distributionof the differences.12.9
44、Report K, the peakedness of the frequency distributionof the differences.12.10 Report date and time of most recent calibration.12.11 Report r, the resolution of the measurements.12.12 Report date and time of beginning of data-gatheringperiod.12.13 Report date and time of end of data-gathering period
45、.13. Precision and Bias13.1 Sample sizes have been chosen to assure a 99.7 %confidence level for C and d within the resolution of themeasurements.14. Keywords14.1 atmosphere; functional precision; measurement com-parisons; meteorological measurementsD4430 00 (2010)3REFERENCES(1) Hoehne, W. E., “Stan
46、dardizing Functional Tests,” IEEE Transactionson Geoscience Electronics, Vol GE-11, No. 2, April 1973.(2) Stone, R. J., “National Weather Service Automated ObservationalNetworks and the Test and Evaluation Division Functional TestingProgram,” Fourth Symposium on Meteorological Observations andInstru
47、mentation, Denver, Colorado, April 1014, 1978.(3) Natrella, Mary Gibbon, “Experimental Statistics,” National Bureauof Standards Handbook, Vol 91, August 1, 1963.(4) Haykin, Simon S., Communication Systems, John Wiley or through the ASTM website(www.astm.org). Permission rights to photocopy the standard may also be secured from the ASTM website (www.astm.org/COPYRIGHT/).D4430 00 (2010)4
