<2008MAR25> This is to demonstrate how to use the GrADS utility on BAMS cdrom to display the monthly mean/variance reanalysis data available from http://dss.ucar.edu/pub/reanalysis/monthly or http://dss.ucar.edu/pub/reanalysis/monthly/{presa,rest,theta} directories. If you are getting files from {presa,rest,theta} subdirectories, you need to be aware that the files in them are unix tar files. Although wgrib or GRIB decoder may work with tar files, you need to untar those files first to get individual data files like: HGT.150.mon.98 from 1998.PRESA, CPRAT.mon.98 from 1998.REST, ABSVtht.270.mon.98 from 1998.THETA. Those individual data files are GRIB files. Any GRIB decoders should be able to handle those GRIB files gracefully. If you plan to use GrADS to display theta GRIB files, please see the last section. **************************************************************************** The GrADS software on the March 1996 BAMS cdrom is GrADS version 1.5.1.3. If you have a correct control file, you may use gbmap.exe to generate its grib map index file. For example, we use 1981HGT.500 and 1981PRES.msl in the following examples. GRIB data file: 1981HGT.500, from http://dss.ucar.edu/pub/reanalysis/monthly/HGT.500 directory GrADS control file: 1981hgt5.ctl, it has the following content : dset ^1981HGT.500 dtype grib options yrev template index ^1981hgt5.idx undef -9.99E+33 title 1981HGT.500 xdef 144 linear 0 2.5 ydef 73 linear -90 2.5 zdef 1 levels 500 tdef 12 linear 00Z01jan81 1mo vars 2 HGTprs 1 7,100,500,113 ** Geopotential height monthly mean HGTvar 1 7,100,500,118 ** Geopotential height variance ENDVARS To generate 1981hgt5.idx, use the gbmap.exe from the grads directory on the cdrom, and execute the next line: gbmap -v -i 1981hgt5.ctl You should see messages on the screen to indicate matching GRIB records. Once you have the index file, go ahead to use GrADS to display the data. GRIB data file: 1981PRES.msl, from http://dss.ucar.edu/pub/reanalysis/monthly/PRES.msl directory GrADS control file: 1981Pmsl.ctl, its content looks like this. dset ^1981PRES.msl dtype grib options yrev template index ^1981Pmsl.idx undef -9.99E+33 title 1981PRES.msl xdef 144 linear 0 2.5 ydef 73 linear -90 2.5 tdef 12 linear 00Z01jan81 1mo vars 2 PRESmsl 0 1,102,0,113 ** MSL pressure monthly mean PRESvar 0 1,102,0,118 ** MSL pressure variance ENDVARS zdef 1 levels 1 Again, use gbmap.exe to generate the index file. gbmap -v -i 1981Pmsl.ctl The index file, 1981Pmsl.idx, will be generated in the same directory. And you are ready to use GrADS to display the data. **************************************************************************** To use GrADS to display the monthly mean isentropic level data, you need to separate the monthly averages from their variances into two files first. For example, using VMAStht.650.mon.98 as an example, you can make an average file and a variance file by wgrib VMAStht.650.mon.98 | egrep ":TR=113:" | \ wgrib VMAStht.650.mon.98 -i -o VMAStht.650.avg -grib and wgrib VMAStht.650.mon.98 | egrep ":TR=118:" | \ wgrib VMAStht.650.mon.98 -i -o VMAStht.650.var -grib Then, make the ctl file with grib2ctl script by grib2ctl VMAStht.650.avg > avg.ctl The resulting avg.ctl looks like: dset ^VMAStht.650.avg index ^VMAStht.650.avg.idx undef 9.999E+20 title VMAStht.650.avg * produced by grib2ctl v0.9.11 options yrev dtype grib 2 xdef 144 linear 0 2.5 ydef 73 linear -90 2.5 tdef 12 linear 00Z01jan98 1mo zdef 1 linear 1 1 vars 1 VMAStht 0 179,113,650 ** Mass weighted v [gm/m*K*s] ENDVARS Then you can run gribmap with avg.ctl and display the plots. You need to do the same for the variance file. **************************************************************************** Example of GrADS control file using Gaussian grids: Here is the ctl file for 2001TMP.2m file: dset ^2001TMP.2m dtype grib 255 options yrev index ^2001TMP2m.idx undef -9.99E+33 title 2001TMP.2m xdef 192 linear 0.0 1.875 ydef 94 levels -88.542 -86.653 -84.753 -82.851 -80.947 -79.043 -77.139 -75.235 -73.331 -71.426 -69.522 -67.617 -65.713 -63.808 -61.903 -59.999 -58.094 -56.189 -54.285 -52.380 -50.475 -48.571 -46.666 -44.761 -42.856 -40.952 -39.047 -37.142 -35.238 -33.333 -31.428 -29.523 -27.619 -25.714 -23.809 -21.904 -20.000 -18.095 -16.190 -14.286 -12.381 -10.476 -8.571 -6.667 -4.762 -2.857 -0.952 0.952 2.857 4.762 6.667 8.571 10.476 12.381 14.286 16.190 18.095 20.000 21.904 23.809 25.714 27.619 29.523 31.428 33.333 35.238 37.142 39.047 40.952 42.856 44.761 46.666 48.571 50.475 52.380 54.285 56.189 58.094 59.999 61.903 63.808 65.713 67.617 69.522 71.426 73.331 75.235 77.139 79.043 80.947 82.851 84.753 86.653 88.542 tdef 12 linear 00Z01jan01 1mo zdef 1 linear 1 1 vars 2 avgTMP2 0 11,105,2,113 ** TMP at 2m mean varTMP2 0 11,105,2,118 ** TMP at 2m variance ENDVARS ****************************************************************************