This archive contains answers to questions sent to Unidata support through mid-2025. Note that the archive is no longer being updated. We provide the archive for reference; many of the answers presented here remain technically correct, even if somewhat outdated. For the most up-to-date information on the use of NSF Unidata software and data services, please consult the Software Documentation first.
>From: Robert Mullenax <address@hidden> >Organization: National Scientific Balloon Facility >Keywords: 199903052045.NAA17847 >I am trying to grid upper air files for use in producing u/a analyses in >Gempak. >I create a grid using oagrid with GRDAREA = 45;150;80;-100 and DTAAREA= > >The proram runs and creates a grid. When I use oabsnd to do an analysis >on the >grid I get the following error: > > >[GEMPLT -16] NIPBND - Invalid projection bounds. > [GR -7] Error defining grid navigation in GEMPLT. > [OABSND -9] No valid parameters have been entered > >Everything works fine if I don't define grdarea using the lat, lon, for >example if >I use grdarea=fai--, all is well. What have I done wrong? Thanks, and >sorry >for the barrage of questions. > >Robert Mullenax > > > Robert, Assumimg you have: DELTAN = DELTAX = DELTAY = for the above GAREA, oabsnd reports too few stations to calculate DELTAN at least for the IDD data I have. I can create the file with gdcfil, and I created a file for the above region as: GDOUTF = test.gem PROJ = ced GRDAREA = 45;150;80;-100 KXKY = 20;20 MAXGRD = 1000 CPYFIL = ANLYSS = GEMPAK-GDCFIL>r GDCFIL PARAMETERS: New grid file: test.gem Grid projection: CED Lower left corner: 45.00 150.00 Upper right corner: 80.00 -100.00 KX, KY: 20 20 X/Y grid spacing: 1.84 5.79 DELTAN = 8.592 EXTEND = 2; 2; 2; 2 Maximum number of grids that can be added to file 1000 Since oagrid would use a CED projection, that is what I specified in gdcfil. Running Oabsnd for 500mb hght, gives: SNFILE = $UPA/990304_upa.gem GDFILE = test.gem SNPARM = hght STNDEX = LEVELS = 500 VCOORD = pres DATTIM = 0000 DTAAREA = GUESS = GAMMA = .3 SEARCH = 50/EX NPASS = 2 GEMPAK-OABSND>r OABSND PARAMETERS: Output grid file: test.gem Number of x, y points: 20 20 Grid bnds: 45.00 150.00 80.00 -100.00 Grid xtnd: 2 2 2 2 Station spacing: 8.59 No first guess file is requested. Sounding file: $UPA/990304_upa.gem Data area: 40.00;-180.00;85.00;180.00 Level parameters: HGHT Levels: 500 Vertical coordinate: pres Station parameters: Time: 990304/0000 GAMMA: 0.30 SEARCH: 50.00 NPASS: 2 Data extrapolation may occur. Enter <cr> to accept parameters or type EXIT: Processing data at time 990304/0000 RMS values for pass 1 PARAMETER: HGHT LEVEL: 500 RMS: 48.29 #STN: 31 RMS values for pass 2 PARAMETER: HGHT LEVEL: 500 RMS: 26.87 #STN: 31 So, there is nothing intrinsically wrong with the grdarea you want to use. I think the problem exists with the EXTEND area. Depending on the KXKY that OAGRID ends up suggesting, it could be wrapping the north pole- which is very bad in a CED projection. Have you tried setting EXTEND = 0;0;0;0? can you send me the output from oagrid so I can see what the suggested station spaceing for the grid is, and if the extended area will wrap over the pole? Steve Chiswell