1、 Recommendation ITU-R P.837-6(02/2012)Characteristics of precipitationfor propagation modellingP SeriesRadiowave propagationii Rec. ITU-R P.837-6 Foreword The role of the Radiocommunication Sector is to ensure the rational, equitable, efficient and economical use of the radio-frequency spectrum by a
2、ll radiocommunication services, including satellite services, and carry out studies without limit of frequency range on the basis of which Recommendations are adopted. The regulatory and policy functions of the Radiocommunication Sector are performed by World and Regional Radiocommunication Conferen
3、ces and Radiocommunication Assemblies supported by Study Groups. Policy on Intellectual Property Right (IPR) ITU-R policy on IPR is described in the Common Patent Policy for ITU-T/ITU-R/ISO/IEC referenced in Annex 1 of Resolution ITU-R 1. Forms to be used for the submission of patent statements and
4、licensing declarations by patent holders are available from http:/www.itu.int/ITU-R/go/patents/en where the Guidelines for Implementation of the Common Patent Policy for ITU-T/ITU-R/ISO/IEC and the ITU-R patent information database can also be found. Series of ITU-R Recommendations (Also available o
5、nline at http:/www.itu.int/publ/R-REC/en) Series Title BO Satellite delivery BR Recording for production, archival and play-out; film for television BS Broadcasting service (sound) BT Broadcasting service (television) F Fixed service M Mobile, radiodetermination, amateur and related satellite servic
6、es P Radiowave propagation RA Radio astronomy RS Remote sensing systems S Fixed-satellite service SA Space applications and meteorology SF Frequency sharing and coordination between fixed-satellite and fixed service systems SM Spectrum management SNG Satellite news gathering TF Time signals and freq
7、uency standards emissions V Vocabulary and related subjects Note: This ITU-R Recommendation was approved in English under the procedure detailed in Resolution ITU-R 1. Electronic Publication Geneva, 2012 ITU 2012 All rights reserved. No part of this publication may be reproduced, by any means whatso
8、ever, without written permission of ITU. Rec. ITU-R P.837-6 1 RECOMMENDATION ITU-R P.837-6 Characteristics of precipitation for propagation modelling (Question ITU-R 201/3) (1992-1994-1999-2001-2003-2007-2012) Scope Recommendation ITU-R P.837-4 contains maps of meteorological parameters that have be
9、en obtained using the European Centre for Medium-Range Weather Forecast (ECMWF) ERA-40 re-analysis database, which are recommended for the prediction of rainfall rate statistics with a 1-min integration time, when local measurements are missing. Rainfall rate statistics with a 1-min integration time
10、 are required for the prediction of rain attenuation in terrestrial and satellite links. Data of long-term measurements of rainfall rate may be available from local sources, but only with higher integration times. This Recommendation provides a method for the conversion of rainfall rate statistics w
11、ith a higher integration time to rainfall rate statistics with a 1-min integration time. The ITU Radiocommunication Assembly, considering a) that information on the statistics of precipitation intensity is needed for the prediction of attenuation and scattering caused by precipitation; b) that the i
12、nformation is needed for all locations on the globe and a wide range of probabilities; c) that rainfall rate statistics with a 1-min integration time are required for the prediction of rain attenuation and scattering in terrestrial and satellite links; d) that long-term measurements of rainfall rate
13、 may be available from local sources with a 1-min integration time and also, with integration times of longer than 1-min, e) that using a model to convert local measurements with integration times up to 1 hour has been observed to provide higher accuracy than the use of the global digital maps in An
14、nex 1 of this Recommendation, recommends 1 that the model in Annex 1 should be used to obtain the rainfall rate, Rp, exceeded for any given percentage of the average year, p, and for any location (with an integration time of 1 min). This model is to be applied to the data supplied in the digital fil
15、es ESARAIN_xxx_v5.TXT (the data files may be obtained from that part of the ITU-R website dealing with Radiocommunication Study Group 3); 2 that, for easy reference, Figs 1 to 6 in Annex 2 should be used to select the rainfall rate exceeded for 0.01% of the average year. These figures were also deri
16、ved from the model and data described in Annex 1; 3 that local long-term measurements of rainfall rate with a 1-min integration time should be used if available; 2 Rec. ITU-R P.837-6 4 that long-term measurements of rainfall rate with longer integration times should be used if available and the mode
17、l in Annex 3 be used to convert to rainfall rate with a 1-min integration time; 5 that local measurements, if used, are collected over a sufficient period (typically longer than 3 years), to ensure statistical stability. Annex 1 Model to derive the rainfall rate exceeded for a given probability of t
18、he average year and a given location The data files ESARAIN_PR6_v5.TXT, ESARAIN_MT_v5.TXT and ESARAIN_BETA_v5.TXT contain respectively the numerical values for the variables Pr6, Mtand while data files ESARAINLAT_v5.TXT and ESARAINLON_v5.TXT contain the latitude and longitude of each of the data ent
19、ries in all other files. These data files were derived from 40 years of data from the European Centre of Medium-range Weather Forecast (ECMWF). Step 1: Extract the variables Pr6, Mtand for the four points closest in latitude (Lat) and longitude (Lon) to the geographical coordinates of the desired lo
20、cation. The latitude grid is from +90 N to 90 S in 1.125 steps; the longitude grid is from 0 to 360 in 1.125 steps. Step 2: From the values of Pr6, Mtand at the four grid points, obtain the values Pr6(Lat,Lon), MT(Lat,Lon) and (Lat,Lon) at the desired location by performing a bi-linear interpolation
21、, as described in Recommendation ITU-R P.1144. Step 3: Convert MTand to Mcand Msas follows: Mc = MT Ms= (1-) MT Step 4: Derive the percentage probability of rain in an average year, P0, from: ( ),(/),(0790.0606e1),(),(LonLatPLonLatMrrsLonLatPLonLatP= (1) If Pr6is equal to zero, the percentage probab
22、ility of rain in an average year and the rainfall rate exceeded for any percentage of an average year are equal to zero. In this case, the following steps are unnecessary. Step 5: Derive the rainfall rate, Rp, exceeded for p % of the average year, where p P0, from: mm/h24),(2AACBBLonLatRp+= (2) wher
23、e: A = a b (2a) B = a + c ln( p / P0(Lat,Lon) (2b) C = ln( p / P0(Lat,Lon) (2c) Rec. ITU-R P.837-6 3 and a = 1.09 (2d) b = 021797),(),(PLonLatMLonLatMsc+(2e) c = 26.02b (2f) NOTE 1 An implementation of this model and the associated data in MATLAB is also available from the ITU-R website dealing with
24、 Radiocommunication Study Group 3. 4 Rec. ITU-R P.837-6 Annex 2 FIGURE 1 Rain rate (mm/h) exceeded for 0.01% of the average year P.0837-019060180120Longitude(degrees)L a ti tu d e ( de g re e s )80 70 3050 40020 103010 20 6040 50 9070 8016014060100800402020406080100120140160180Rec. ITU-R P.837-6 5 F
25、IGURE 2 Rain rate (mm/k) exceeded for 0.01% of the average year P.0837-029080 70 60180Longitude (degrees)L a ti tu d e ( d e g r ees )50 40 30 20 101601401201008060406 Rec. ITU-R P.837-6 FIGURE 3 Rain rate (mm/h) exceeded for 0.01% of the average year P.0837-03010203080 60 40Longitude (degrees)Latit
26、ude(degrees)40506010Rec. ITU-R P.837-6 7 FIGURE 4 Rain rate (mm/h) exceeded for 0.01% of the average year P.0837-0470 60 502002040Longitude(degrees)L a t i t u d e ( d egr ees )408 Rec. ITU-R P.837-6 FIGURE 5 Rain rate (mm/h) exceeded for 0.01% of the average year P.0837-0504020 0 40Latitude(degrees
27、)Longitude (degrees)602030201010203040Rec. ITU-R P.837-6 9 FIGURE 6 Rain rate (mm/h) exceeded for 0.01% of the average year P.0837-06060L a ti tu d e (d e g re e s )Longitude(degrees)1208010014016018010204050 306070809010 Rec. ITU-R P.837-6 FIGURE 7 Rain rate (mm/h) exceeded for 0.01% of the average
28、 year P.0837-07120Longitude (degrees)Latitude(degrees)3080 100 1406005040201010Rec. ITU-R P.837-6 11 FIGURE 8 Rain rate (mm/h) exceeded for 0.01% of the average year P.0837-08120Longitude (degrees)Latitude(degrees)30140 180206050400101020160100Annex 3 1 The cumulative distribution of rainfall rate a
29、t 1-min integration time can be obtained by converting local cumulative distributions measured at integration times of between 5 and 60 minutes. 2 The recommended method requires as input both the cumulative distribution as well as the integration time of the source rainfall statistics and the geogr
30、aphical coordinates of the site of interest. 3 The method is based on the simulated movement of synthetic rain cells, whose parameters derive from the local input data and ECMWF products. 12 Rec. ITU-R P.837-6 4 The recommended method is incorporated in a computer program available from the ITU-R website dealing with Radiocommunication Study Group 3. The name of the software package implementing this part of the recommendation is CONVRRSTAT_ANNEX3_P837-6.ZIP.
