1、 Recommendation ITU-R P.835-5(02/2012)Reference standard atmospheresP SeriesRadiowave propagationii Rec. ITU-R P.835-5 Foreword The role of the Radiocommunication Sector is to ensure the rational, equitable, efficient and economical use of the radio-frequency spectrum by all radiocommunication servi
2、ces, 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 Conferences and Radiocommunication
3、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 licensing declarations by p
4、atent 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 online at http:/www.itu.int/
5、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 services P Radiowave propagation
6、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 frequency standards emissions V
7、 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 whatsoever, without written permi
8、ssion of ITU. Rec. ITU-R P.835-5 1 RECOMMENDATION ITU-R P.835-5 Reference standard atmospheres (Question ITU-R 201/3) (1992-1994-1997-1999-2005-2012) Scope Recommendation ITU-R P.835 provides expressions and data for reference standard atmospheres required for the calculation of gaseous attenuation
9、on Earth-space paths. The ITU Radiocommunication Assembly, considering a) the necessity for a reference standard atmosphere for use in calculating gaseous attenuation along an Earth-space path, recommends 1 that the standard atmospheres in Annex 1 be used to determine temperature, pressure and water
10、-vapour pressure as a function of altitude, for calculating gaseous attenuation when more reliable local data are not available; 2 that the experimental data in Annexes 2 and 3 be used for the locations of interest when seasonal and monthly variations are concerned. Annex 1 1 Mean annual global refe
11、rence atmosphere The following reference standard atmosphere reflects the annual mean profiles when averaged across the globe. 1.1 Temperature and pressure The reference standard atmosphere is based on the United States Standard Atmosphere, 1976, in which the atmosphere is divided into seven success
12、ive layers showing linear variation with temperature, as given in Fig. 1. The temperature T at height h is given by: T(h) = Ti+ Li(h Hi) K (1) where: Ti= T(Hi) (2) and Liis the temperature gradient starting at altitude Hi and is given in Table 1. 2 Rec. ITU-R P.835-5 TABLE 1 Subscript, i Altitude, H
13、i(km) Temperature gradient, Li(K/km) 0 0 6.51 11 0.0 2 20 +1.0 3 32 +2.8 4 47 0.0 5 51 2.86 71 2.0 7 85 FIGURE 1 Reference profile of atmospheric temperature P.0835-01Temperature (K)1600102030405060708090180 200 220 240 260 280 300Altitude(km)Rec. ITU-R P.835-5 3 When the temperature gradient Li 0,
14、pressure is given by the equation: iLiiiiiHhLTTPhP/163.34)()(+= hPa (3) and when the temperature gradient Li= 0, pressure is obtained from the equation: =iiiTHhPhP)(163.34exp)( hPa (4) The ground-level standard temperature and pressure are: hPa25.0131K15.28800=PT(5) Note that above about 85 km altit
15、ude, local thermodynamic equilibrium of the atmosphere starts to break down, and the hydrostatic equation, on which the above equations are based, is no longer valid. 1.2 Water-vapour pressure The distribution of water vapour in the atmosphere is generally highly variable, but may be approximated by
16、 the equation: (h) = 0exp (h / h0) g/m3(6) where the scale height h0= 2 km, and the standard ground-level water-vapour density is: 0= 7.5 g/m3(7) Vapour pressure is obtained from the density using the equation (see Recommendation ITU-R P.453): 7.216)()()(hThhe= hPa (8) Water-vapour density decreases
17、 exponentially with increasing altitude, up to an altitude where the mixing ratio e (h)/P(h) = 2 106. Above this altitude, the mixing ratio is assumed to be constant. 1.3 Dry atmosphere for attenuation calculations The profile of the density of atmospheric gases other than water vapour (the “dry atm
18、osphere”) may be found from the temperature and pressure profiles given in 1.1. For attenuation calculations, this density profile may be approximated by an exponential profile according to equation (6) with: h0= 6 km (9) 2 Low-latitude annual reference atmosphere For low latitudes (smaller than 22)
19、 the seasonal variations are not very important and a single annual profile can be used. 4 Rec. ITU-R P.835-5 The temperature T (K) at height h (km) is given by: T(h) = 300.4222 6.3533 h + 0.005886 h2for 0 h 15 3 Mid-latitude reference atmosphere For mid-latitudes (between 22 and 45) the following p
20、rofiles may be used for the summer and winter. 3.1 Summer mid-latitude The temperature T (K) at height h (km) is given by: T(h) = 294.9838 5.2159 h 0.07109 h2for 0 h 15 Rec. ITU-R P.835-5 5 3.2 Winter mid-latitude The temperature T (K) at height h (km) is given by: T(h) = 272.7241 3.6217 h 0.1759 h2
21、for 0 h 10 4 High latitude reference atmosphere For high latitudes (higher than 45) the following profiles may be used for the summer and winter. 4.1 Summer high latitude The temperature T (K) at height h (km) is given by: T(h) = 286.8374 4.7805 h 0.1402 h2for 0 h 15 6 Rec. ITU-R P.835-5 4.2 Winter
22、high latitude The temperature T (K) at height h (km) is given by: T(h) = 257.4345 + 2.3474 h 1.5479 h2+ 0.08473 h3for 0 h 10 Bibliography BRUSSAARD, G., DAMOSSO, E. and STOLA, L. October, 1983 Characterisation of the 50-70 GHz band for space communications. CSELT Rapporti Tecnici, Vol. XI, 5. Annex
23、2 1 Experimental data of atmospheric vertical profiles Monthly averages of vertical profiles of temperature, pressure and relative humidity were calculated for 353 locations over the world, using 10 years (1980-1989) of radiosonde observations. This dataset (DST.STD) is available from ITU/BR and con
24、tains the mean monthly vertical profiles, for both 00.00 UTC and 12.00 UTC, of pressure, temperature and relative humidity. These profiles, calculated in the absence of rain, range from 0 to 16 km with a step of 500 m. The mean monthly profiles are contained in ASCII files named .dat, where WMO_code
25、 is the code name of the site according to the World Meteorological Organization (e.g.: 03496.dat, 03496 is the WMO station code for Hemsby-in-Norfolk). An example of one profile is given in Table 2. The list of locations is contained in an ASCII file (using the comma separated value file, CSV, file
26、 format) called dst_std_lst.csv. Each record of this file contains the following field: WMO_CODE, Station Name, Country, Latitude, Longitude, Altitude above sea level. An example of such a record is given in Table 3. Above the maximum altitude, extrapolation can be performed by using the reference p
27、rofiles given in Annex 1. To translate the relative humidity into absolute values of water-vapour density, the formulae contained in Recommendation ITU-R P.453 should be used. Rec. ITU-R P.835-5 7 TABLE 2 DST.STD data format Example of month average profile (station 10410) YYMMDDHH NL 99 199 0 33 Pr
28、ess (hPa) Z (km) Temp (K) RH (%/100) 1 016.905 0.00 273.62 0.864E+00 956.686 0.50 273.33 0.830E+00898.555 1.00 271.74 0.754E+00 844.014 1.50 269.59 0.665E+00791.860 2.00 267.15 0.591E+00 742.661 2.50 264.56 0.518E+00696.285 3.00 261.89 0.470E+00 651.977 3.50 258.94 0.458E+00610.086 4.00 255.88 0.448
29、E+00 570.467 4.50 252.69 0.445E+00533.076 5.00 249.33 0.451E+00 497.767 5.50 245.90 0.453E+00464.123 6.00 242.32 0.450E+00 432.441 6.50 238.75 0.450E+00402.414 7.00 235.16 0.443E+00 374.177 7.50 231.59 0.437E+00347.236 8.00 228.12 0.433E+00 322.281 8.50 224.88 0.427E+00298.474 9.00 221.89 0.421E+00
30、276.492 9.50 219.27 0.416E+00255.527 10.00 217.08 0.411E+00 236.297 10.50 215.62 0.402E+00218.415 11.00 214.79 0.393E+00 201.366 11.50 214.14 0.348E+00186.214 12.00 214.02 0.205E+00 172.093 12.50 214.24 0.104E+00158.709 13.00 214.66 0.368E-01 146.492 13.50 214.94 0.351E-02135.813 14.00 214.88 0.120E
31、-02 125.690 14.50 214.50 0.117E-02116.027 15.00 214.01 0.113E-02 106.798 15.50 213.56 0.110E-0298.291 16.00 213.26 0.107E-02 8 Rec. ITU-R P.835-5 Legend to Table 2: YY = Year (99 for mean monthly profiles) MM = Month (1 = January, 2 = February, .) DD = Day of the month (99 for mean monthly profiles)
32、 HH = Hour of the day (UTC) NL = Number of vertical levels (NL = 33 for STD.DST) Press (hPa) = Atmospheric total pressure Z (km) = Height above the Earths surface Temp (K) = Air temperature RH (%/100) = Relative humidity (as a fraction) NOTE 1 The level values of Temp and Press may be set to zero if
33、 unrecorded. TABLE 3 DST_STD_LST.CSV station information file Example of record structure WMO code Station name Country Latitude (degrees) Longitude (degrees) Asl (m) 10 410 ESSEN DL 51.4 6.967 153 NOTE 1 Latitude and longitude values are in decimal degrees (i.e. 51.4 = 51 24). Annex 3 1 Numerical w
34、eather prediction data of atmospheric vertical profiles Monthly averages, conditioned to the hour of the day, of vertical profiles of temperature, pressure and water-vapour density were calculated using the ECMWF 15-year data set (ERA15) from the re-analysis project. This dataset (ESA_STD_PROF) is a
35、vailable from ITU/BR and contains the mean monthly vertical profiles, for 00.00, 06.00, 12.00 and 18.00 UTC, of total air pressure, air temperature and water-vapour density. These profiles extend from a reference height located around the local Earths surface up to about 30 km above the Earths surfa
36、ce and contains 32 levels derived from ERA15 model levels. The data are from 0 to 360 in longitude and from +90 to 90 in latitude, with a resolution of 1.5 in both latitude and longitude. All the data are stored in files using the IEEE floating point single precision standard (4 bytes, 32 bits) in a
37、 Big-Endian format. The mean monthly profiles of each meteorological parameter are contained in binary files named _.bin, where param is the name of the meteorological parameter (pres = total air pressure hPa, temp = air temperature K, vapd = water-vapour density g/m3) and hh is the hour of the day
38、(i.e. 00, 06, 12 and 18 UTC). The heights of the profile levels are contained in a separate binary file, named hght.bin, in which vertical profiles of mean monthly level heights are contained. An example of the data contained in the database for a specific is given in Table 4. Rec. ITU-R P.835-5 9 T
39、ABLE 4 ESA_STD_PROF content Example of profile at grid point (latitude = 45 (degrees) and longitude = 9 (degrees) at 12 UTC of July Height (m) Press (hPa) Temp (K) Vapd (g/m3) 668.309 939.255 298.373 9.823 701.645 935.673 298.125 9.617819.406 923.092 296.598 9.302 1 029.200 900.957 294.292 8.811 1 3
40、12.119 871.693 291.459 8.099 1 653.510 837.298 288.287 6.992 2 042.286 799.373 285.107 5.706 2 470.212 759.191 282.116 4.555 2 931.283 717.723 279.045 3.641 3 421.197 675.691 275.934 2.692 3 937.159 633.633 272.913 1.855 4 477.475 591.936 269.707 1.286 5 040.996 550.876 266.183 0.911 5 627.126 510.6
41、56 262.354 0.636 6 235.769 471.427 258.213 0.428 6 867.105 433.307 253.687 0.277 7 521.528 396.390 248.780 0.173 8 199.571 360.767 243.521 0.103 8 901.801 326.527 237.971 0.058 9 629.047 293.764 232.319 0.034 10 382.883 262.580 226.984 0.019 11 167.396 233.064 222.845 0.009 11 990.928 205.263 220.48
42、3 0.003 12 864.380 179.195 219.279 0.001 13 799.389 154.827 218.154 0.001 14 812.536 132.043 217.057 0.001 15 934.765 110.604 216.026 0.000 17 228.709 90.110 215.674 0.000 18 821.158 70.037 216.262 0.000 20 964.607 50.038 219.300 0.000 24 270.756 30.039 223.166 0.000 31 430.756 10.320 232.854 0.000
43、10 Rec. ITU-R P.835-5 Legend to Table 4: Z (m) = Height with respect to sea level Press (hPa) = Atmospheric total pressure Temp (K) = Air temperature Vapd (g/m3) = Water-vapour density NOTE 1 The Matlab and Fortran procedures to access the ESA_STD_ PROF dataset are available from the ITU-R website dealing with Radiocommunication Study Group 3. _
