[gradsusr] Different output values from Grads and wgrib2

Wesley Ebisuzaki Wesley.Ebisuzaki at noaa.gov
Thu Oct 20 15:01:14 EDT 2011


Bo,

   I am using the latest wgrib2 and grads v2.0a9 and the results are the 
same.  I am not able to
reproduce your wgrib2 results (index is off by one).  Using the gdas/fnl 
obtained from nomad3.ncep.noaa.gov

Trying to reproduce your results:
> bash-3.2$ wgrib2 gdas2010050806f00.grib2 -match TMP -s -ij 181 91
> 3:120296:d=2010050806:TMP:10 mb:anl::val=239
> 8:393851:d=2010050806:TMP:20 mb:anl::val=220.5
> 13:666758:d=2010050806:TMP:30 mb:anl::val=215.5
> 18:961202:d=2010050806:TMP:50 mb:anl::val=204.5
Adding the lat-lon information:
> bash-3.2$ wgrib2 gdas2010050806f00.grib2 -match TMP -s -ijlat 181 91
> 3:120296:d=2010050806:TMP:10 
> mb:anl::(181,91),lon=180.000000,lat=0.000000,val=239
> 8:393851:d=2010050806:TMP:20 
> mb:anl::(181,91),lon=180.000000,lat=0.000000,val=220.5
> 13:666758:d=2010050806:TMP:30 
> mb:anl::(181,91),lon=180.000000,lat=0.000000,val=215.5
> 18:961202:d=2010050806:TMP:50 
> mb:anl::(181,91),lon=180.000000,lat=0.000000,val=204.5
Reproducing your values using a different grid point.
> bash-3.2$ wgrib2 gdas2010050806f00.grib2 -match TMP -s -ijlat 180 90
> 3:120296:d=2010050806:TMP:10 
> mb:anl::(180,90),lon=179.000000,lat=-1.000000,val=240.5
> 8:393851:d=2010050806:TMP:20 
> mb:anl::(180,90),lon=179.000000,lat=-1.000000,val=220.9
> 13:666758:d=2010050806:TMP:30 
> mb:anl::(180,90),lon=179.000000,lat=-1.000000,val=215.9
> 18:961202:d=2010050806:TMP:50 
> mb:anl::(180,90),lon=179.000000,lat=-1.000000,val=204.1
Reproducing the wgrib2 values using GrADS:
> ga-> set lat 0
> LAT set to 0 0
> ga-> set lon 180
> LON set to 180 180
> ga-> d tmpprs(lev=10)
> Result value = 239
> ga-> d tmpprs(lev=20)
> Result value = 220.5
> ga-> d tmpprs(lev=30)
> Result value = 215.5
> ga-> 
I wasn't able to reproduce John's results.  Note: I had problems 
downloading your data file.

           Wesley Ebisuzaki


Huddleston, John wrote:
> Jennifer
>
> It appears Bo is correct in his analysis for this GRIB2 file. I took Wesley's latest g2ctl and regenerated a new CTL file and IDX file using the latest GrADS-2.0.0 and have the same results. At 30mb GrADS displays temperature data that is much greater than expected. Here is my output. Note at z=24 the temperature range.
>
> ga-> open fnl_20100508_06_00.ctl
> Scanning description file:  fnl_20100508_06_00.ctl
> Data file fnl_20100508_06_00 is open as file 1
> LON set to 0 360
> LAT set to -90 90
> LEV set to 1000 1000
> Time values set: 2010:5:8:6 2010:5:8:6
> E set to 1 1
> ga-> set z 26
> LEV set to 10 10
> ga-> d tmpprs
> Contouring: 195 to 240 interval 5
> ga-> set z 25
> LEV set to 20 20
> ga-> d tmpprs
> Contouring: 195 to 230 interval 5
> ga-> set z 24
> LEV set to 30 30
> ga-> d tmpprs
> Contouring: 230 to 310 interval 10
> ga-> set z 23
> LEV set to 50 50
> ga-> d tmpprs
> Contouring: 195 to 225 interval 3
>
> John Huddleston
>
> ________________________________________
> From: gradsusr-bounces at gradsusr.org [gradsusr-bounces at gradsusr.org] On Behalf Of Bo Zhang [bzhang3 at mtu.edu]
> Sent: Thursday, October 13, 2011 6:59 PM
> To: gradsusr at gradsusr.org
> Subject: [gradsusr] Different output values from Grads and wgrib2
>
> Hi great grads users,
>
> I was trying to plot temperature profile with Grads and just found different results from Grads and wgrib2. I am sure that I am reading the same data file. I got the attached profile plot from Grads and the following result from wgrib2 at the same position. One thing should be noticed is that Gtads and wgrib2 number the grid box in different ways. The (0, 0) grid box in Grads (-180:179, -90,90) should be (181,91) in a (0:360, 0,181) system. The bump at 30 mb in the figure exists for any lon-lat position I try, which is wired to me. The other values are also slightly various.
>
> $ ./wgrib2 ***/Grads/fnl_20100508_06_00 -s -ij 181 91 | grep :TMP
> 3:120296:d=2010050806:TMP:10 mb:anl::val=240.5
> 8:393851:d=2010050806:TMP:20 mb:anl::val=220.9
> 13:666758:d=2010050806:TMP:30 mb:anl::val=215.9
> 18:961202:d=2010050806:TMP:50 mb:anl::val=204.1
> 23:1271647:d=2010050806:TMP:70 mb:anl::val=193.5
> 28:1588656:d=2010050806:TMP:100 mb:anl::val=190.7
> 36:1997953:d=2010050806:TMP:150 mb:anl::val=207.4
> 43:2356630:d=2010050806:TMP:200 mb:anl::val=223.1
> 50:2732191:d=2010050806:TMP:250 mb:anl::val=235.9
> 57:3106953:d=2010050806:TMP:300 mb:anl::val=244.9
> 64:3498361:d=2010050806:TMP:350 mb:anl::val=254.5
> 71:3898258:d=2010050806:TMP:400 mb:anl::val=260.8
> 78:4302495:d=2010050806:TMP:450 mb:anl::val=266.3
> 85:4751606:d=2010050806:TMP:500 mb:anl::val=270.9
> 92:5208947:d=2010050806:TMP:550 mb:anl::val=274.5
> 99:5689297:d=2010050806:TMP:600 mb:anl::val=277.9
> 106:6172793:d=2010050806:TMP:650 mb:anl::val=282.1
> 113:6640256:d=2010050806:TMP:700 mb:anl::val=284.2
> 120:7112632:d=2010050806:TMP:750 mb:anl::val=286
> 127:7585314:d=2010050806:TMP:800 mb:anl::val=289.1
> 134:8055101:d=2010050806:TMP:850 mb:anl::val=291.8
> 141:8545830:d=2010050806:TMP:900 mb:anl::val=294.6
> 148:9033256:d=2010050806:TMP:925 mb:anl::val=296.2
> 155:9515141:d=2010050806:TMP:950 mb:anl::val=297.4
> 162:9986444:d=2010050806:TMP:975 mb:anl::val=299.5
> 169:10444342:d=2010050806:TMP:1000 mb:anl::val=301.6
>
>
> Bo Zhang
> Dow 824,Civil and Environmental Engineering
> Michigan Tech University
> 1400 Townsends Drive.
> Houghton, MI, 49931
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