RTTOV-7 Users Guide Roger Saunders
Contents
1. L V 8 teal V 8 BV Tou f B V Tat 5 where tcia v 9 is the cloud top to space transmittance and Tc the cloud top temperature the emissivity of the cloud top is assumed to be unity which is a tolerable assumption for optically thick water cloud at infrared radiances but not valid for optically thin cloud and all cloud at microwave frequencies For microwave frequencies the liquid water profile can be supplied in array PAV 1 LEV 4 IPROF as cloud liquid water concentration in units of kg kg Only layers from the surface to the level jJmwcldtop set in the MOD_CPARAM f90 file see below are taken into account in the computation The default value set is for a level at 321 hPa For cloud water drops scattering is assumed to be negligible below 200 GHz and so it follows that the extinction per unit mass is independent of radius and thus the sensitivity of changes in optical depth to changes in liquid water mass is independent of the drop size distribution This allows a calculation of the optical depth if an assumed dependence of the permittivity of the liquid water with temperature is assumed Ice extinction is assumed to be zero so the input cloud water profile is all assumed to be liquid Scattering becomes important for ice crystals above 100GHz If the liquid water concentration value at the top level of 0 1hPa is set to negative the liquid water path transmittance calculation is not performed regardless of the input profile which reduc2. 4 38E 05 1 20E 06 1 63E 05 7 00E 07 9 69E 06 2 0 3 335 8 173 1 4 65E 05 1 20E 06 1 69E 05 1 00E 06 1 00E 05 3 0 7 352 8 168 9 4 61E 05 1 20E 06 1 70E 05 2 10E 06 1 01E 05 4 1 4 354 4 160 9 4 51E 05 1 20E 06 1 71E 05 2 11E 06 1 02E 05 5 26 349 4 160 5 4 29E 05 1 20E 06 1 71E 05 2 11E 06 1 02E 05 6 4 4 328 8 160 3 4 26E 05 1 20E 06 1 71E 05 2 11E 06 1 02E 05 7 7 0 321 4 158 5 4 36E 05 1 20E 06 1 71E 05 2 11E 06 1 02E 05 8 10 4 300 3 154 7 4 35E 05 1 20E 06 1 71E 05 2 11E 06 1 02E 05 9 14 8 295 0 154 9 4 01E 05 1 20E 06 1 72E 05 2 11E 06 1 01E 05 10 20 4 289 0 151 1 4 03E 05 1 20E 06 1 61E 05 2 11E 06 9 36E 06 11 27 3 286 5 151 2 4 18E 05 1 20E 06 1 60E 05 2 03E 06 8 10E 06 12 35 5 285 3 151 6 3 62E 05 1 20E 06 1 14E 05 8 33E 07 6 72E 06 13 45 3 284 2 152 5 3 43E 05 1 20E 06 1 11E 05 5 49E 07 5 19E 06 14 56 7 283 8 154 2 3 33E 05 1 20E 06 9 82E 06 2 85E 07 3 72E 06 15 70 0 282 7 155 7 3 23E 05 1 20E 06 6 46E 06 2 13E 07 2 58E 06 16 85 2 282 7 153 9 3 01E 05 1 20E 06 5 31E 06 1 71E 07 1 72E 06 17 102 1 281 5 151 5 2 90E 05 1 20E 06 4 10E 06 6 96E 08 1 19E 06 18 122 0 280 1 156 7 3 58E 05 1 20E 06 3 63E 06 1 18E 08 8 45E 07 19 143 8 278 6 157 4 8 61E 05 1 20E 06 3 06E 06 1 03E 08 6 50E 07 20 168 0 278 8 159 7 1 64E 03 1 20E 06 2 24E 06 8 72E 09 5 27E 07
3. 21 Temperature profile unphysical 22 Water vapour profile unphysical 23 Ozone profile unphysical 24 Surface temperature unphysical 25 Surface water vapour unphysical 26 Surface wind unphysical 27 Surface pressure unphysical Table 6 Values for IFAIL flag from RTTOV Annex A RTTVI interface CALL RTTVI KERR KPPF KPNSAT KPLEV KPCH KPCHUS KPNAV KPNSAV KPNSSV KPNCV NRTTOVID PLATFORM SATELLITE INSTRUMENT NUMCHANS PRESLEV OTMIN OTMAX OQMIN OQMAX OOZMIN OOZMAX IVCH NIU1 RTTVI is called only once for all platforms satellites and instruments The table below lists the variables and gives an example of what the arrays should contain to set up RTTOV for simulating NOAA 16 AMSU A AMSU B and METEOSAT 7 MVIRI radiances for up to 6 profiles in each call of RTTOV The jPXXx array sizes are set up by the module MOD_CPARAM f90 For this example setting jpnsat 3 jpch 15 jppf 6 and nlev 43 is optimum to allow all the calling options given in Annexes B E to work Parameter and size if gt 1 Type IN OUT Description Example of contents KERR INTEGER OUT Error if not 0 0 KPPF INTEGER OUT No of profiles 6 KPNSAT INTEGER OUT No of sensors 3 KPLEV INTEGER OUT No of levels 43 KPCH INTEGER OUT No of channels 15 KPCHUS INTEGER OUT No of channels 15 KPNAV INTEGER OUT No of profile vars 4 KPNSAV INTEGER OUT No of 2m surface vars 5 KPNSSV INTEGER OUT No of surface skin
4. PEMIS PAV_D PSAV_D PSSV_D PCV_D PEMIS_D RADOV_D PRAD PTB RADOV LCLOUD IFAIL RTTOVTL is called once for each sensor for KPPF profiles at a time The table below lists the variables and gives an example of what the arrays should contain for RTTOV to simulate NOAA 16 AMSU A for 1 profile and all 15 channels for a zenith angle of 15 deg This assumes the calling sequence to RTTVI in Annex A is followed The variables ending in _D denote direct value same as RTTOV input output Example of Parameter and size if gt 1 Type IN OUT Description contents for H 1 1 1 AMSU A 1 KNPF INTEGER IN No of profiles 1 KLENPF INTEGER IN No of levels in profiles 43 PPRES jplev REAL IN Pressure levels hPa Table 2 PANGL jppf REAL IN Sat zenith angle deg 15 PANGS jppf REAL Not used Solar zenith angle deg 0 KSURF ppf INTEGER IN O land 1 sea 2 sea ice 1 KSAT INTEGER IN Sequence number as loaded 1 by RTTVI see annex A KNCHPF INTEGER IN No chans No profiles 15 1 15 KCHANQGpchus jppf INTEGER IN Channel numbers 1 2 3 15 KPROF jpchus jppf INTEGER IN Profile numbers 1 1 1 1 PAV jplev 4 jppf REAL IN TL of profile array 1 profile PSAV 5 jppf REAL IN TL of surface 2m array 1 profile PSSV 6 jppf REAL IN TL of surface skin array 1 profile PCV 2 jppf REAL IN TL of cloud array 1 profile PEMISQpchpf REAL IN OUT TL of surface emiss table 4 1 profile PAV_D j
5. the coefficients requested and secondly the call to RTTOV itself which actually computes the radiances Users requiring the TL AD K routines may also call RTTOVTL RTTOVAD RTTOVK as required It is recommended that users look at the header section of the coefficient file for the sensor they wish to simulate as there is useful information such as the definition of channel number for that instrument etc The following steps are recommended in coding a program which calls RTTOV 1 Include the module MOD_CPARAM f90 in your program see tstrad f90 as an example 2 Edit MOD_CPARAM f90 for your application to minimise the array sizes This will normally consist of setting the channel number parameters JPCH and JPCHUS to the maximum number of channels you require computations for in one call to RTTOV Secondly setting the number of profiles parameter JPPF to the maximum number of profiles you want to compute in one call to RTTOV this is normally set to 1 as there is only a significant advantage to process many profiles per call on vector machines Thirdly JPNSAT should be set to the maximum number of sensors simulated in the program e g for ATOVS only it would be 3 HIRS AMSU A and AMSU B JPLEV should be set to the number of levels assumed in the coefficient file which is currently 43 for the files distributed with the code All other parameters are normally left unchanged See RTTOV technical report for listing of parameters 3 Initialise the varia
6. the executable or a symbolic link to the file is made 6 You should now be able to run the program to compute radiances It is wise to check the FAIL flag from RTTOV to check it is zero If it is non zero there are a number of possible reasons according to the number returned see Table 6 1 It is planned to make available some standard code to do this interpolation robustly in the near future 7 7 Note that if you set the PEMIS array to zero on input to call the internal surface emissivity routines ISEM or FASTEM then on output the array contains the computed emissivities for each channel Before calling RTTOV again you must reinitialise the array to zero 8 The RTTOVTL RTTOVAD RTTOVK routines are called in the same way as RTTOV see annexes C E Again ensure all arrays are initialised before calling the routines 9 The RTTOVCLD routines are a level up from RTTOV but they have almost the same calling structure and arrays to fill Again the test program supplied main_testad f90 can be used as an example Note however the cloud parameter arrays are input on user defined model levels More details on the RTTOVCLD routines are planned for the next version of this user manual 5 Reporting bugs to the NWP SAF The procedure to report bugs or make comments on the code to the NWP SAF is as follows Send a bug report to rttov nwpsaf metoffice com including the following information RTTOV version number i e 5 6 or 7 Pla
7. 8035226599E 00 15 gt BRUTE FORCE 0 2829711886E 02 0 1000000381E 01 6 gt BRUTE FORCE 0 2829710937E 02 0 1000000046E 01 i gt BRUTE FORCE 0 2829711178E 02 0 1000000131E 01 8 gt BRUTE FORCE 0 2829712855E 02 0 1000000724E 01 9 gt BRUTE FORCE 0 2829702339E 02 0 9999970074E 00 10 gt BRUTE FORCE 0 2829381174E 02 0 9998835099E 00 11 gt BRUTE FORCE 0 2828812740E 02 0 9996826292E 00 12 gt BRUTE FORCE 0 2859223969E 02 0 1010429745E 01 13 gt BRUTE FORCE 0 3069544618E 02 0 1084755591E 01 14 gt BRUTE FORCE 0 1136868377E 02 0 4017613299E 00 15 872 873c872 873 lt PROFILE 1 SUMRAD 0 7225097989E 01 SUMPROF 0 7225097989E 01 lt PROFILE 2 SUMRAD 0 5618514327E 01 SUMPROF 0 5618514327E 01 gt PROFILE 1 SUMRAD 0 7074762965E 01 SUMPROF 0 7074762965E 01 gt PROFILE 2 SUMRAD 0 1075604858E 02 SUMPROF 0 1075604858E 02 Table 5 Example of typical differences found between NWPSAF generated output and that from the users machine The numbers can differ from run to run 14 IFAIL value Meaning 0 Profile OK 11 Temp profile outside limits 12 Water vapour profile outside limits 13 Ozone profile outside limits 14 Surface temp outside limits 15 Surface water vapour outside limits 16 Surface wind speed outside limits 17 Zenith angle outside ISEM 6 limits 20 Input pressure levels do not match coef file
8. profile PAV_D plev 4 jppf REAL IN Input profile array 1 profile PSAV_D 5 jppf REAL IN Input surface 2m array 1 profile PSSV_D 6 jppf REAL IN Input surface skin array 1 profile PCV_D 2 jppf REAL IN In put cloud array 1 profile PEMIS_DQGpchpf REAL IN OUT Input surface emiss Table 4 1 profile PRAD_Dgpchpf REAL OUT Radiances in mW m sr cm 2 radiances PTB_D Gpchpf REAL OUT Brightness temps in degK 2 Br E KINRAD INTEGER IN Switch 1 radiance 2 BT LCLOUD LOGICAL IN Switch for IR cloud calcs fon IFAILGppf kpnsat INTEGER OUT See Table 6 3 3 0 RADOV lt jpchpf 2 jplev 2 REAL IN OUT K of overcast cloudy radiances radiances Tf the array VCH is non zero on input to RTTVI then this channel index refers to the subset of channels requested in VCH normally only used for AIRS The RADOV array contains the following radiances for possible cloud computations outside RTTOV e g used by RTTOVCLD RADOV jpchus 1 njplev RADOV jpchus njplev 1 2 njplev RADOV jpchus 2 njplev 1 RADOV jpchus 2 njplev 2 overcast radiances at given cloud top contribution to radiance of downward cloud emission at given cloud top if LCLOUD false then this is zero clear sky radiance without reflection term reflected clear sky downwelling radiance zero if LCLOUD false Annex D RTTOVTL interface CALL RTTOVTL KNPF KLENPF PPRES PANGL PANGS KSURF KSAT KNCHPF KCHAN KPROF PAV PSAV PSSV PCV
9. profiles PSSV 6 jppf REAL IN Surface skin array Table 1 3 profiles PCV 2 jppf REAL IN Cloud array Table 1 3 profiles PEMIS Qpchpf REAL IN OUT Surface emissivity Table 4 3 profiles IFAIL jppf kpnsat INTEGER OUT See Table 6 3 3 0 PRAD pchpf REAL OUT Radiances in mW m sr cm 12 radiances PTBGpchpf REAL OUT Brightness temps in degK 12 Br Temps RADOV jpchpf 2 jplev 2 REAL OUT Overcast cloudy radiances 1056 rads RADO jpchpf REAL OUT O cast radiance from cld top 12 radiances TAU pchpf jplev REAL OUT Layer to space transmittances 43 12 trans TAUSFC jpchpf REAL OUT Surface to space transmittances 12 trans LCLOUD LOGICAL IN Switch for IR cloud calcs false Tf the array IVCH is non zero on input to RTTVI then this channel index refers to the subset of channels requested in IVCH normally only used for AIRS 1The RADOV array contains the following radiances for possible cloud computations outside RTTOV e g used by RTTOVCLD RADOV jpchus njplev RADOV jpchus njplev 1 2 njplev RADOV jpchus 2 njplev 1 RADOV jpchus 2 njplev 2 overcast radiances at given cloud top contribution to radiance of downward cloud emission at given cloud top if LCLOUD false then this is zero clear sky radiance without reflection term reflected clear sky downwelling radiance if LCLOUD false then this is zero Annex C RTTOVK interface CALL RTTOVK KNPF KLENPF PPRES PANGL PAN
10. scr to just test for your particular application by commenting out calls to some of the scripts The rt coefficient files for all instruments supported as listed in Table 3 and input files for running tstrad out the test program are all in the subdirectories rtcoef and data respectively Output files from the runs on the NWPSAF machine at the Met Office are given in reftest The files in reftest can be compared with the output produced locally the scripts write the output to a subdirectory test as st files and difference files from those in reftest are also created as diff files in the test subdirectory To check the installation has been successful you should check the diff files are all of size zero Note however the TL AD K test outputs will differ slightly due to machine precision differences and use of a random number generator in the test code and so typical differences between machines are shown in the listing in Table 5 These differences are normal Once the code does reproduce the results in the sample files the code can then be linked into the users own particular applications The subroutine interfaces and file structures are described in detail in the annexes and the RTTOV 7 technical report 4 Running RTTOV 7 for your applications To run RTTOV 7 for a user s application the program tstrad f90 can be used as a rough guide or template There are only 2 subroutines that must be called RTTVI to initialise the arrays and read in
11. 1 cloud top pressure ignored if cloud cover is hPa zero Set to 500 as default 2 Cloud fractional cover set to 0 for clear sky 0 1 1 for 100 cloud cover Position in vector PEMIS Surface Emissivity Array Contents Units 1 to NCHAN Surface emissivity if set to zero or 1 0 1 provide default value as defined in Table 4 If unavailable initialise to reference ozone profile listed in any rt_coef file and ozone will be assumed constant f This variable only affects microwave cloudy radiance simulations default set to zero and set top level to 0 1 to switch off transmittance computation to save time if not required IR and MW cloudy radiances also governed by PCV vector Only used by FASTEM 1 2 to compute microwave sea surface emissivity If not required set to zero See Table 1 of English and Hewison 1998 or Table 3 of RTTOV 7 science and validation report for typical values for different surface types Set to zero if not required Table 1 State vector for RTTOV 7 model NLEV is the number of profile levels currently 43 and NCHAN the number of channels Default values are also given where appropriate Level Pressure Tmax Tmin Qmax Qmin Osmax Osmin O3Ref number hPa degK degk Kg Kg Kg Kg Kg Kg _ Kg Kg _ Kg Kg 1 0 1 335 5 162 0
12. 2 2 70E 01 6 57E 05 1 65E 07 8 10E 10 4 79E 08 41 985 9 356 6 155 0 2 79E 01 6 57E 05 1 63E 07 8 10E 10 4 44E 08 42 1005 4 357 9 135 0 2 82E 01 6 57E 05 1 62E 07 8 10E 10 4 20E 08 43 1013 3 385 9 135 0 2 84E 01 6 57E 05 1 62E 07 8 10E 10 4 10E 08 Table 2 Pressure levels adopted for RTTOV 7 and the profile limits within which the transmittance calculations are valid The default ozone profile is also given in the right hand column Platform RTTOV id Sat id range NOAA 1 1to16 DMSP 2 8 to 16 Meteosat 3 5to7 GOES 4 8 to 12 GMS 5 5 FY 2 6 2 TRMM 7 1 ERS 8 1to2 EOS 9 1to2 ENVISAT 11 1 MSG 12 1 FY 1 13 3to4 Sensor RTTOVid Sensor RTTOV Channel Channel HIRS 0 1to19 1to19 MSU 1 1to4 1to4 SSU 2 1to3 1to3 AMSU A 3 1 to 15 1 to 15 AMSU B 4 1to5 1to5 AVHRR 5 3b to 5 1to3 SSMI 6 1to7 1to7 VTPR1 7 1to8 1to8 VTPR2 8 1to8 1to8 TMI 9 1 to9 1to9 SSMIS 10 1 to 24 1 to 24 AIRS 11 1 to 2378 1 to 2378 MODIS 13 1 to 17 1 to 17 ATSR 14 1to3 1to3 MVIRI 20 1to2 1to2 SEVIRI 21 4to 11 1to8 GOES Imager 22 1to4 1 to4 GOES Sounder 23 1 to 18 1 to 18 GMS imager 24 1 to 2 1 to2 FY2 VISSR_ 25 1 to2 1 to2 FY1 MVISR_ 26 1to3 1to3 channels 19 21 are not simulated accurately Table 3 Platforms and sensors s
13. 21 194 4 280 1 163 2 2 79E 03 1 20E 06 1 64E 06 7 43E 09 4 13E 07 22 222 9 282 3 165 3 4 44E 03 1 20E 06 1 47E 06 7 14E 09 3 03E 07 23 253 7 285 3 166 7 7 64E 03 1 20E 06 1 09E 06 1 20E 08 2 11E 07 24 286 6 288 7 167 6 1 12E 02 1 20E 06 7 60E 07 1 16E 08 1 56E 07 25 321 5 294 0 170 6 1 68E 02 1 20E 06 5 90E 07 1 59E 08 1 23E 07 26 358 3 300 5 174 2 2 54E 02 1 20E 06 3 83E 07 7 94E 09 1 08E 07 27 396 8 306 4 175 3 3 62E 02 1 20E 06 3 13E 07 1 13E 08 1 01E 07 28 437 0 312 2 178 8 5 00E 02 1 20E 06 2 45E 07 6 58E 09 9 60E 08 29 478 5 317 2 182 1 6 50E 02 1 95E 06 2 34E 07 6 24E 09 9 17E 08 30 521 5 321 1 185 0 7 75E 02 4 51E 06 2 31E 07 4 95E 09 8 91E 08 31 565 5 325 2 187 8 8 95E 02 1 04E 05 2 13E 07 2 76E 09 8 47E 08 32 610 6 328 2 190 3 1 05E 01 1 29E 05 2 01E 07 2 41E 09 8 12E 08 33 656 4 333 0 192 8 1 24E 01 1 42E 05 2 07E 07 2 27E 09 7 78E 08 34 702 7 336 8 195 4 1 41E 01 1 71E 05 2 21E 07 2 07E 09 7 57E 08 35 749 1 340 7 197 1 1 59E 01 3 63E 05 1 87E 07 7 24E 10 7 12E 08 36 795 1 344 4 198 4 1 78E 01 5 34E 05 1 91E 07 7 24E 10 6 63E 08 37 840 0 348 0 199 0 2 00E 01 6 42E 05 1 81E 07 7 24E 10 6 16E 08 38 882 8 350 3 197 5 2 14E 01 6 68E 05 1 73E 07 8 10E 10 5 68E 08 39 922 5 352 2 195 5 2 40E 01 6 57E 05 1 68E 07 8 10E 10 5 21E 08 40 957 4 354 7 188
14. GS KSURF KSAT KNCHPF KCHAN KPROF PAV PSAV PSSV PCV PEMIS PAV_D PSAV_D PSSV_D PCV_D PEMIS_D PRAD_D PTB_D KINRAD LCLOUD IFAIL RADOV RTTOVK is called once for each sensor for KPPF profiles at a time The table below lists the variables and gives an example of what the arrays should contain for RTTOVK to simulate METEOSAT MVIRI for 1 profile and both channels for a zenith angle of 30 deg This assumes the calling sequence to RTTVI in Annex A is followed The variables ending in _D denote direct value same as RTTOV input output Example of Parameter and size if gt 1 Type IN OUT Description contents for MVIRI KNPF INTEGER IN No of profiles 1 l KLENPF INTEGER IN No of levels in profiles 43 PPRES jplev REAL IN Pressure levels hPa Table 2 PANGL ppf REAL IN Sat zenith angle deg 30 PANGS jppf REAL Not used Solar zenith angle deg 0 KSURF ppf INTEGER IN O land 1 sea 2 sea ice 1 KSAT INTEGER IN Sequence number as loaded 3 by RTTVI see annex A KNCHPF INTEGER IN No chans No profiles 2 1 2 f KCHANQ pchus jppf INTEGER IN Channel numbers 1 2 KPROF jpchus jppf INTEGER IN Profile numbers 1 1 PAV plev 4 jpchpf REAL OUT K of profile array 1 profile PSAV 5 jpchpf REAL OUT K of surface 2m array 1 profile PSSV 6 jpchpf REAL OUT K of Surface skin array 1 profile PCV 2 jpchpf REAL OUT K of cloud array 1 profile PEMIS Qpchpf REAL IN OUT K of surface emiss Table 4 1
15. RTTOV 7 Users Guide Roger Saunders Room 408 Met Office London Rd Bracknell Berks RG12 2SZ U K This documentation was developed within the context of the EUMETSAT Satellite Application Facility on Numerical Weather Prediction NWP SAF under the Cooperation Agreement dated 25 November 1998 between EUMETSAT and the Met Office UK by one or more partners within the NWP SAF The partners in the NWP SAF are the Met Office ECMWF KNMI and M t o France Copyright 2002 EUMETSAT All Rights Reserved Change record Version Date Author changed by Remarks 1 11 12 01 R Saunders Initial draft to code developers for comments 2 31 01 02 R Saunders Modified draft after comments 3 13 03 02 R Saunders Modified after comments from J Eyre and MTR RIDs 4 27 05 02 R Saunders Corrected IFAIL documentation RTTOV 7 Users Guide 1 Introduction and scope This document gives an overview of the RTTOV 7 fast radiative transfer model in sec 2 how to install the RTTOV 7 fast radiative transfer model code on a UNIX platform and run it sec 3 and how to apply it to the users particular problem sec 4 The procedure for reporting bugs or making comments to the NWP SAF are given in sec 5 Finally a frequently asked questions FAQ section is provided at section 6 If you want to order a copy of the RTTOV 7 code send an email to mailto rttov nwpsaf metoffice com or fax 44 1344 854026 requesting
16. V PSSV PCV PEMIS PAV_D PSAV_D PSSV_D PCV_D PEMIS_D PRAD PTB RADOV KINRAD LCLOUD IFAIL RTTOVAD is called once for each sensor for KPPF profiles at a time The table below lists the variables and gives an example of what the arrays should contain for RTTOV to simulate NOAA 16 AMSU A for 6 profiles and 2 channels chans 3 8 for a zenith angle of 25 deg This assumes the calling sequence to _D denote direct value same as RTTOV RTTVI in Annex A is followed The variables ending in input output Example of Parameter and size if gt 1 Type IN OUT Description contents for AMSU A KNPF INTEGER IN No of profiles 6 KLENPF INTEGER IN No of levels in profiles 43 PPRES jplev REAL IN Pressure levels hPa Table2 PANGL jppf REAL IN Sat zenith angle deg 6 25 PANGS jppf REAL Not used Solar zenith angle deg 6 0 KSURF jppf INTEGER IN O land 1 sea 2 sea ice 6 1 KSAT INTEGER IN Sequence number as loaded 1 by RTTVI see annex A KNCHPF INTEGER IN No chans No profiles 2 6 12 KCHANQ pchus jppf INTEGER IN Channel numbers 3 8 3 8 KPROF jpchus jppf INTEGER IN Profile numbers 1 1 2 2 3 3 PAV jplev 4 jppf REAL OUT AD of profile array 6 profiles PSAV 5 jppf REAL OUT AD of surface 2m array 6 profiles PSSV 6 jppf REAL OUT AD of surface skin array 6 profiles PCV 2 jppf REAL OUT AD of cloud array 6 profiles PEMIS jpchpf REAL IN OUT AD of
17. a copy of the code You will need to sign a RTTOV 7 licence form before the code is sent to you The old RTTOV 6 code is still available in FORTRAN 90 or FORTRAN 77 but will no longer be upgraded for new instruments Note RTTOV 7 is not available in FORTRAN 77 Bugs reported with RTTOV 6 will continue to be announced and users informed of fixes Coefficient files for RTTOV 6 will continue to be made available from the NWP SAF web site The RTTOV 6 code took part in the Garand fast model intercomparison see Garand et al 2001 for details and has been distributed to over 40 users worldwide Before attempting to use the RTTOV 7 model the reader is advised to also read the RTTOV 7 technical report for more details of the code and its operation The RTTOV 7 scientific and validation report describes or gives links to the scientific basis of the model and also describes in more details any new scientific changes made It documents the test results carried out on the new code before delivery The most up to date versions of these reports like this users guide can be viewed at the NWP SAF web site http www metoffice com research interproj nwpsaf rtm in pdf format on the RTTOV 7 page 2 Overview of RTTOV 7 This section gives a brief overview of the RTTOV 7 model and its limitations More details can be found in the references given in this section RTTOV 7 is a development of the fast radiative transfer model for TOVS RTTOV originally dev
18. be rttov7 tar Z and be copied to your top RTTOV directory e g user rttov7 from which subdirectories will be created Text in italics refers to specific commands to execute during the installation or file names 3 1 Unpacking the code First uncompress the tar file uncompress rttov7 tar Z and expand it tar xvf rttov7 tar The following subdirectories are created and contain src Fortran source code make files for a variety of platforms scripts Unix test scripts for running test programs dataAssociated input data files required for testing rtcoef RT coefficient files for all sensors supported test Output of test programs run on user s machine reftest Output of test programs run by NWP SAF docs Documentation 3 2 Compiling the code First go to the source code directory cd src The fortran code consists of subroutines and modules and 3 top level test programs TSTRAD 90 MAIN_TESTAD f90 MAIN_TESTK f90 in src for complete testing of the RTTOV and RTTOVCLD subroutines The first step is to compile the code and make an executable using the makefiles supplied Edit the file called Makefile in src so that the 90 compiler options match those available on your machine A selection of compiler flags for different platforms are listed so if you are running using one of these compilers you should be able to just uncomment the relevant section Once this is done type make and with luck the code will compile and produc
19. bles input to RTTVI and RTTOV in your code These are defined in Annexes A and B In particular you need to fill the state vector arrays listed in Table with the values in the correct units and on the 43 pressure levels This may require an interpolation step from your original profile levels The channel number array KCHAN must be filled with the required channel numbers see rt_coef files for their definition and the satellite zenith angle array with the required satellite zenith angle s in deg The latter is the angle from the zenith at which an observer on the surface observes the satellite It is not the nadir scan angle If you are simulating more than one sensor in each run then the order in which you load up the coefficient files of the sensors in RTTVI becomes important i e the order of values in the PLATFORM SATELLITE and INSTRUMENT id arrays The KSAT index number used in RTTOV then refers to the order they are loaded in RTTVI e g KSAT 1 refers to the first sensor KSAT 2 to the second and so on 4 Compile the RTTOV modules first followed by the RTTOV subroutines followed by your main calling program see makefile supplied You do not have to compile in double precision r8 flag on some compilers as this is only used in the test programs supplied to ensure there is enough precision to check the code is giving the correct answers 5 Make sure the coefficient file for the instrument you want to simulate is in the same directory as
20. e an executable tstrad out for the RTTOV tests main_testad out and main_testk out for the RTTOVCLD tests The Makefile should copy these three executable files to the scripts subdirectory If the compilation was not successful then either edit the makefile again until it does or if all else fails compile the code manually as follows Note you must first compile the modules then the subroutines and program Step 1 f90 c your flags MOD_ f90 Step 2 f90 c your flags f90 Step 3 rm f main_test o to ensure the clear air test code tstrad compiles Step 4 f90 o This should produce an executable file a out in your src directory which you should then move to your scripts directory renamed as tstrad out This only provides code to test the RTTOV routines and not the RTTOVCLD routines above RTTOV If you want to test the cloudy routines also restart from step 3 and rm f tstrad o and recompile main_testad f90 3 3 Running the code There are test scripts for running the executables tstrad out etc which must be in the scripts directory The controlling script is tstrad_all scr This script calls the other scripts in sequence to test RTTOV for clear air cloudy air and all instruments and in both forward model test mode and using tstrad_full scr to fully test the TL AD K routines If you only want to use the code in forward mode and or for 1 instrument or clear air you may wish to reduce the number of test scripts called in tstrad_all
21. eloped at ECMWF in the early 90 s Eyre 1991 for TOVS Subsequently the original code has gone through several developments e g Saunders et al 1999 Matricardi et al 2001 more recently within the EUMETSAT NWP Satellite Application Facility SAF of which RTTOV 7 is the latest version The model allows rapid simulations 1 ms for 40 channel ATOVS on a HP workstation of radiances for satellite infrared or microwave nadir scanning radiometers given an atmospheric profile of temperature variable gas concentrations cloud and surface properties referred to as the state vector The only variable gases for RTTOV 7 are water vapour and ozone with all other constituents assumed to be constant The state vector for RTTOV 7 is given in Table 1 Not all parameters have to be supplied as actual values although sensible defaults need to be supplied as indicated RTTOV 7 can accept state vectors on any set of pressure levels but the coefficients are supplied for the 43 pressure levels defined in Table 2 To work on other pressure levels users would have to supply their own generated coefficients with their own transmittances on these levels Currently the spectral range of the RTTOV 7 model is 3 20um 500 3000 cm in the infrared governed by the range of the GENLN2 line by line dataset on which it is based In the microwave the frequency range from 10 200 GHz is covered using the Liebe 89 MPM line by line model The full list of currently supp
22. es execution time of the model For the standard RTTOV model at infrared frequencies clouds are assumed to be at one level have unit emissivity and a top at a fixed cloud top pressure with a fractional coverage for each input profile The outputs of RTTOV can be used however to simulate a more realistic multilevel infrared and microwave cloudy radiance and the RTTOVCLD routines now supplied with RTTOV 7 provide this capability RTTOVCLD and its associated TL K AD routines take a profile input on 43 levels for the normal state variables in Table 1 and the gaseous transmittances are computed on the 43 levels In addition RTTOVCLD also takes a profile of temperature cloud cover cloud liquid water kg kg and cloud ice water kg kg on user defined model pressure levels and computes infrared and or cloudy radiances for multilevel and multiphase cloud fields The clear and cloudy radiative transfer computation is done on the user defined model levels in RTTOVCLD The advantage of using this method for computing cloudy microwave radiances is there is no interpolation to the RTTOV levels for the cloudy radiance computations and there is a consistent random overlap scheme with the infrared More details are given in Chevallier et al 2001 and the RTTOV 7 science and validation plan for this enhancement of RTTOV 2 3 Current limitations of RTTOV 7 There are a number of limitations of RTTOV 7 the user should be aware of Some are fundamental and some are n
23. expected The important thing is SUMPROF SUMRAD to machine precision 5 More to be added here please make suggestions Good Luck and please provide me with any feedback on your experiences Remember do not pass this code on to anyone else without the permission of EUMETSAT The code is provided to you on an as is basis and there is no commitment to maintain it 6 References Chevallier F P Bauer G A Kelly C Jakob and T McNally 2001 Model clouds over oceans as seen from space comparison with HIRS 2 and MSU radiances J Climate 14 4216 4229 DeBlonde G and S J English 2001 Evaluation of the FASTEM 2 fast microwave oceanic surface emissivity model Tech Proc ITSC XI Budapest 20 26 Sept 2000 67 78 English S J and T J Hewison 1998 A fast generic millimetre wave emissivity model Microwave Remote Sensing of the Atmosphere and Environment Proc SPIE 3503 22 30 Eyre J R 1991 A fast radiative transfer model for satellite sounding systems ECMWF Research Dept Tech Memo 176 available from the librarian at ECMWF Garand L Turner D S Larocque M Bates J Boukabara S Brunel P Chevallier F Deblonde G Engelen R Hollingshead M Jackson D Jedlovec G Joiner J Kleespies T McKague D S McMillin L Moncet J L Pardo J R Rayer P J Salathe E Saunders R Scott N A Van Delst P Woolf R 2001 Radiance and Jacobian intercomparison of radiative transfer models applied
24. is not always necessary to store and access the full Jacobian matrix H and so the RTTOV package has routines to only output the tangent linear values dy the change in top of atmosphere radiances for a given change in atmospheric profile 6x about an initial atmospheric state x The tangent linear routines all have TL as an ending Conversely the adjoint routines ending in AD compute the change in the gradient of any scalar quantity with respect to the atmospheric state x given a change in the gradient of that quantity with respect to the radiances y These routines are normally used as part of the variational assimilation of radiances For users only interested in the forward model the TL AD K routines are not required The model can simulate both clear sky radiances and cloudy radiances It uses an approximate form of the atmospheric radiative transfer RT equation The top of the atmosphere upwelling radiance L v at a frequency v and viewing angle from zenith at the surface neglecting scattering effects is written as L v 8 1 N L v 0 NL v 8 3 where L v 9 and L v 9 are the clear sky and fully cloudy top of atmosphere upwelling radiances and N is the fractional cloud cover 1 1 Simulation of clear air radiances If N the cloud cover parameter in array PCV is set to zero and the LWP path profile vector is set to zero in array PAV LEV 4 IPROF both the infrared and microwave radiances computed are f
25. or clear air with the second right hand term of equation 3 being zero L v 9 can be written as L v 0 2 V 8 e VO B V T B V Tidt 1 v 0 2 V 0 fl oe ae 4 i o T where T is the surface to space transmittance is the surface emissivity and B v T is the Planck function for a frequency v and temperature T The transmittances Tt are computed by means of a linear regression in optical depth based on variables from the input profile vector as described in Matricardi et al 2001 To compute s over water there are fast surface emissivity routines for both the infrared ISEM Sherlock 1999 and for the microwave FASTEM 1 English and Hewison 1998 or FASTEM 2 DeBlonde and English 2001 These models all compute a surface emissivity for the channel of interest at the given viewing angle 8 FASTEM 2 makes a better correction for reflected radiation at the surface Note that using FASTEM requires the surface wind speed to be provided in the state vector Over the land and sea ice surfaces only approximate default values are provided for the surface emissivity in both the infrared and microwave see refs above for details and Table 4 The user also has the option of providing their own estimate of surface emissivity to the model if desired see Table 4 for input options 1 2 Simulation of cloudy radiances Assuming black opaque clouds at a single level the simulation of cloud affected radiances L v 9 is defined as
26. orted platforms and sensors is given in Table 3 although this list will be updated as new sensors are launched or as improved line by line model data are generated Updated coefficient files will be made available from the RTTOV pages on the NWP SAF web site An important feature of the RTTOV model is that it not only computes the forward or direct radiative transfer calculation but also the gradient of the radiances with respect to the state vector variables for the input state vector values Given a state vector x a radiance vector y is computed y H x 1 where H is the radiative transfer model also referred to as the observation operator The Jacobian matrix H gives the change in radiance y for a change in any element of the state vector 6x assuming a linear relationship about a given atmospheric state Xo dy H x x 2 The elements of H contain the partial derivatives dy 0x where the subscript i refers to channel number and j to position in state vector The Jacobian gives the top of atmosphere radiance change for each channel from each level in the profile given a unit perturbation at any level of the profile vectors or in any of the surface cloud parameters It shows clearly for a given profile which levels in the atmosphere are most sensitive to changes in temperature and variable gas concentrations for each channel RTTOVK and its associated subroutines ending in K compute the H xo matrix for each input profile It
27. ot The main ones are listed here e RTTOV 7 only simulates top of atmosphere radiances from a nadir or off nadir view which intersects with the Earth s surface i e no limb paths e RTTOV 7 does not include any reflected solar component e RTTOV 7 does not include scattering effects e RTTOV 7 only allows for water vapour and ozone to be variable gases with all others included in the mixed gases transmittance calculation e RITTOV 7 does not simulate IASI or CRIS radiances Other lower resolution IR or MW sensors can be simulated if their filter responses are known e RTTOV 7 as supplied can only provide simulations with a 43 level profile as input on the defined pressure levels in Table 2 However if users have an alternate dependent set of LbL transmittances on different levels they can compute a new coefficient set on these levels e The accuracy of simulations for very broad channels e g SEVIRI channel 4 at 3 9 microns is poor with significant biases noted 1 2K This is the case for all versions of RTTOV e RTTOV 7 does not include the variation of the zeeman effect with magnetic field strength for the high peaking AMSU A and SSMIS channels Only a constant correction factor is included 3 FORTRAN 90 UNIX installation Some basic information on installing the RTTOV 7 Fortran 90 code in a UNIX environment follows This assumes the code is obtained as a compressed unix tar file via ftp or on CD ROM from ECMWF The file name should
28. parameter and if set to a non zero value defines the fortran unit numbers through which the coefficient files are read in This file should have already been opened Annex B RTTOV interface CALL RTTOV KNPF KLENPF PPRES PANGL PANGS KSURF KSAT KNCHPF KCHAN KPROF PAV PSAV PSSV PCV PEMIS IFAIL PRAD PTB RADOV RADO TAU TAUSFC LCLOUD RTTOV is called for every sensor required for KPPF profiles at a time The table below lists the variables and gives an example of what the arrays should contain for RTTOV to simulate NOAA 16 AMSU B for 3 profiles and 4 out of the 5 channels omitting channel 2 This assumes the calling sequence in Annex A is followed Example of Parameter and size if gt 1 Type IN OUT Description contents for AMSU B KNPF INTEGER IN No of profiles 3 l KLENPF INTEGER IN No of levels in profiles 43 PPRES jplev REAL IN Pressure levels hPa Table 2 PANGL ppf REAL IN Sat zenith angle deg 30 32 34 PANGS jppf REAL Not used Solar zenith angle deg 0 0 0 KSURFGppf INTEGER IN O land 1 sea 2 sea ice 1 1 0 KSAT INTEGER IN Sequence number as loaded 2 by RTTVI see annex A KNCHPF INTEGER IN No chans No profiles 4 3 12 KCHAN pchus jppf INTEGER IN Channel numbers 1 3 4 5 1 3 KPROF jpchus jppf INTEGER IN Profile numbers 1 1 1 2 2 2 PAV jplev 4 jppf REAL IN Profile array Table 1 3 profiles PSAV 5 jppf REAL IN Surface 2m array Table 1 3
29. plev 4 jppf REAL IN Input profile array 1 profile PSAV_D 5 jppf REAL IN Input surface 2m array 1 profile PSSV_D 6 jppf REAL IN Input surface skin array 1 profile PCV_D 2 jppf REAL IN In put cloud array 1 profile PEMIS_D jpchpf REAL IN OUT Input surface emiss table 4 1 profile RADOV_D jpchpf 2 jplev 2 REAL OUT Overcast cloudy radiances Radiances PRAD pchpf REAL OUT TL of radiances in 15 radiances mW m 7 sr cem PTBGpchpf REAL OUT TL of Brightness temps in 15 B Temps degk RADOV jpchpf 2 jplev 2 REAL OUT TL of overcast cloudy Radiances radiances LCLOUD LOGICAL IN Switch for IR cloud calcs false IFAILGppf kpnsat INTEGER OUT See Table 6 0 If the array IVCH is non zero on input to RTTVI then this channel index refers to the subset of channels requested in VCH normally only used for AIRS The RADOV array contains the following TL radiances for possible cloud computations outside RTTOV e g used by RTTOVCLD RADOV jpchus njplev TL overcast radiances at given cloud top RADOV jpchus njplev 1 2 njplev TL contribution to radiance of downward cloud emission at given cloud top zero if LCLOUD false RADOV jpchus 2 njplev 1 TL clear sky radiance without reflection term RADOV jpchus 2 njplev 2 TL reflected clear sky downwelling radiance zero if LCLOUD false Annex E RTTOVAD interface CALL RTTOVAD KNPF KLENPF PPRES PANGL PANGS KSURF KSAT KNCHPF KCHAN KPROF PAV PSA
30. surface emiss table 4 6 profiles PAV_D plev 4 jppf REAL IN Input profile array 6 profiles PSAV_D 5 jppf REAL IN Input surface 2m array 6 profiles PSSV_D 6 jppf REAL IN Input surface skin array 6 profiles PCV_D 2 jppf REAL IN In put cloud array 6 profiles PEMIS_DQGpchpf REAL IN OUT Input surface emiss table 4 6 profiles PRAD jpchpf REAL IN AD of radiances in Ignored for mW m sr cm kinrad 2 PTBQpchpf REAL IN AD of Brightness temps in 12 B Temps degk RADOV jpchpf 2 jplev 2 REAL IN OUT AD of overcast cloudy Radiances radiances KINRAD INTEGER IN Switch 1 radiance 2 BT 2 LCLOUD LOGICAL IN Switch for IR cloud calcs false l IFAIL jppf kpnsat INTEGER OUT See Table 6 3 3 0 l If the array IVCH is non zero on input to RTTVI then this channel index refers to the subset of channels requested in IVCH normally only used for AIRS The RADOV array contains the following AD radiances for possible cloud computations outside RTTOV e g used by RTTOVCLD RADOV jpchus 1 njplev AD overcast radiances at given cloud top RADOV jpchus njplev 1 2 njplev AD contribution to radiance of downward cloud emission at given cloud top zero if LCLOUD false AD clear sky radiance without reflection term AD reflected clear sky down welling radiance zero if LCLOUD false RADOV jpchus 2 njplev 1 RADOV jpchus 2 njplev 2 20 21
31. tform and operating system you are running the code on e g HP UNIX Compiler used e g HP FORTRAN 90 Classification of report as serious cosmetic or improvement Copy of file MOD_CPARAM 90 for RTTOV 7 or cparam h for RTTOV 5 6 Report of problem including any input output files the SAF can use to reproduce the problem Once the problem has been analysed it will be posted on the RTTOV web site with a description of the fix if appropriate There is also a RTTOV email list which you can subscribe to by sending an email to mailto rttov nwpsaf metoffice com where bugs are announced 6 Frequently asked questions This section will be updated on the web pages from time to time 1 Can I compile the code in single precision Yes the Makefiles supplied only compile the code in double precision for the purposes of testing 2 I dont have an ozone profile to include in the state vector What can I do You should fill the input state vector PAV lev 3 prof with the reference ozone profile units kg kg listed in the right hand column of Table 2 for all values of lev and repeated for each profile stored in PAV 3 Iam only simulating radiances from 1 instrument what should KSAT be set to Set KSAT to 1 as it is the first and only instrument coefficient files loaded by RTTVI 4 Why do the numbers in the TSTRAD output see Table 5 change from run to run A random number generator is included in the code so different values can be
32. to HIRS and AMSU channels J Geophys Res 106 D20 24 017 Matricardi M F Chevallier and S Tjemkes 2001 An improved general fast radiative transfer model for the assimilation of radiance observations ECMWF Research Dept Tech Memo 345 available from the librarian at ECMWF Saunders R W M Matricardi and P Brunel 1999 An Improved Fast Radiative Transfer Model for Assimilation of Satellite Radiance Observations OJRMS 125 1407 1425 Sherlock V 1999 ISEM 6 Infrared Surface Emissivity Model for RTTOV 6 NWP SAF report available from the librarian at Met Office London Rd Bracknell U K Position in vector PAV Profile Array Contents Units 1 to NLEV 1 Temperature profile degK 1 to NLEV 2 Water vapour profile Kg Kg 1 to NLEV 3 Ozone profile Kg Kg 1 to NLEV 4 Liquid water concentration profile Kg Kg Position in vector PSAV Surface 2m Array Contents Units 1 Surface 2m temperature degK 2 Surface 2m water vapour Kg Kg 3 Surface pressure hPa 4 2 m vector wind speed u m s 5 2 m vector wind speed v m s Position in vector PSSV Surface Skin Array Contents Units 1 Radiative skin temperature degK 2 FASTEM 2 land coef f 3 FASTEM 2 land coef J 4 FASTEM 2 land coef v J GHz 5 FASTEM 2 land coef Osman T mm 6 FASTEM land coef Gtarge or Q I mm Position in vector PCV Cloud Array Contents Units
33. upported by RTTOV 7 as at 1 Jan 2002 Sensors in italics are only supported by RTTOV 7 Input Forward Output Tangent Linear Output de INFRARED CHANNELS 0 Land 0 98 sea ice 0 99 sea E1sem dg about 0 98 0 99 isem Non zero as input dg about input MICROWAVE CHANNELS f Land sea ice dg about Land sea ice computed from coefs FASTEN 0 in PSSV 0 6Vsea E r stini sea e computed from du Ov Osst about EFAsTEM1 Land sea ice computed from coefs Land sea ice dg about pastem2 1 in PSSV 2 6 sea FastEM2 sea 0g computed from du Ov Osst about EFAsTEM2 Non zero as input de about input Table 4 Used and output values of and arrays for infrared and microwave channels for forward and gradient routines lt BRU FORCE 0 2829711887E 02 0 1000000381E 01 6 lt BRU FORCE 0 2829710928E 02 0 1000000043E 01 7 lt BRU FORCE 0 2829711349E 02 0 1000000191E 01 8 lt BRU FORCE 0 2829712571E 02 0 1000000623E 01 9 lt BRU FORCE 0 2829696655E 02 0 9999949986E 00 10 lt BRU FORCE 0 2829438017E 02 0 9999035979E 00 TL lt BRU FORCE 0 282966539IEF02 0 9999839502E 00 12 lt BRU FORCE 0 2862066140E 02 0 1011434148E 01 13 lt BRU FORCE 0 3012701200E 02 0 1064667524E 01 14 lt BRU FORCE 0 2273736754E 02 0
34. vars 6 KPNCV INTEGER OUT No of cloud variables 2 NRTTOVID INTEGER IN No of sensors 3 PLATFORM jpnsat INTEGER IN Platform ids Table 3 1 1 3 SATELLITE jpnsat INTEGER IN Satellite ids Table 3 16 16 7 INSTRUMENT pnsat INTEGER IN Instrument ids Table 3 3 4 20 NUMCHANS Gpnsat INTEGER IN OUT Number of channels 15 5 2 PRESLEV nlev REAL OUT Pressure levels for coeffs Table2 OTMIN nlev REAL OUT Min valid Temp Table 2 OTMAX nlev REAL OUT Max valid Temp Table 2 OQMIN nlev REAL OUT Min valid specific hum Table 2 OQMAX nlev REAL OUT Max valid specific hum Table 2 OOZMIN nlev REAL OUT Min valid ozone Table 2 OOZMAX nlev REAL OUT Max valid ozone Table 2 IVCH jpch jpnsat INTEGER IN OUT See note 1 below 1 15 1 5 1 2 l NIU Gpnsat INTEGER IN OUT See note 2 below _ 10 Note 1 Normally IVCH on input should be initialised to zero and the output will contain all valid channel numbers for each sensor This can be used to check RTTOV is not called with an invalid channel number For sensors with large number of channels e g AIRS the VCH array and NUMCHANS array can be set to non zero values on input to allow coefficients for only those channels required to be read in to memory In this case the number of channels required is in NUMCHANS and their numbers are given in the IVCH array If VCH is zero on input coefficients for all valid channels are read into memory Note 2 NIU1 is an optional
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