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>From: Anthony James Wimmers <address@hidden> >Organization: UVa >Keywords: 200104101932.f3AJWCL20597 McIDAS-X gribdec.k AVN Tony, >I was wandering if you could take some time off of solving >the compiler problem to help me out with this other thing. ??? I am not quite sure what you are referring to. >I'm trying to decode some grib files from an ncep archive, >and it's not working out correctly. I did an experiment to >find out whether it was a problem in the files, or a problem >related to the decoder, and I think I've narrowed the problem >down to the decoder (gribdec). OK. I hate to remind you of this, but gribdec.k is not officially supported. >Here's the experiment that you can try over there, and maybe >you can point out my mistake based on that. (BTW, I'm using >mcidas version 7.600.) > >1. ftp a recent initialization of the AVN from the NCEP ftp server: > >ftp.ncep.noaa.gov/pub/data/grib/avn > >2. Decode using gribdec.k, for example: > >gribdec.k avn_010410_06_00 6000 MAX=6000 OK, I grabbed avn_010411_06_00 since that was what was available today. I did the decoding: gribdec.k avn_010411_06_00 6000 MAX=6000 and all seemed to go smoothly. A GRDLIST of the GRID file produced looked normal as well: GRDLIST MYDATA/GRIDS.6001 NUM=ALL Dataset position 6001 Directory Title= PAR LEVEL DAY TIME SRC FHOUR FDAY FTIME GRID PRO ---- --------- ------------ -------- ---- ----- ------------ -------- ----- ---- Z 1000 MB 11 APR 01101 06:00:00 AVN 0 11 APR 01101 06:00:00 1 MERC Z 975 MB 11 APR 01101 06:00:00 AVN 0 11 APR 01101 06:00:00 2 MERC Z 950 MB 11 APR 01101 06:00:00 AVN 0 11 APR 01101 06:00:00 3 MERC ... >3. Display one of the grids in mcidas, for example: > >GRDDISP LOCALDATA/GRIDS.6010 PAR=RH LEV=500 I chose T for 850: EG;GRDDISP MYDATA/GRIDS.6001 PAR=T LEV=850 CINT=5 UNIT=C MAP=CHINA >What it shows me at this point is a set of very horizontal >contours that occupy rectangle on the map that goes from >the equator to about 70 degrees north-south, and from east >Asia to the prime meridion east-west. (Maybe it goes all the >way north to the pole, but doesn't change enough to contour.) I got a similar plot, but mine only went as far west as about -100 (this is why I did my plot over CHINA). >Do you think it's a scaling problem with the lat/lon coordinates? No, after checking to see that GEMPAK could decode the grid correctly, I am left with the impression that the decoder doesn't seem to understand the grids (type 3) in this grib file. It is decoding it as if were a type 2 grid (2.5 degree spacing, etc.). gribdec.k is creating output grids that are 2.5 degree, when the grids are actually 1 x 1 degree. Why this is the case, I can't answer. >I think that would be strange, because I don't have a >problem decoding ruc2 gribs from the same site. I will have to see why gribdec.k is not reading the PDUS word that tells it what grid type the grib messages contain. >Thanks, Sorry I couldn't come up with anything right off that would make things work. Tom