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19990809: GEMPAK GDCROSS Question
- Subject: 19990809: GEMPAK GDCROSS Question
- Date: Mon, 09 Aug 1999 13:32:35 -0600
>From: "John H. E. Clark" <address@hidden>
>Organization: .
>Keywords: 199908091531.JAA18398
>Steve,
>
>I have a question for you. I have been trying to contour the difference
>between potential vorticity, pvor(thte,geo), at two times in GDCROSS. There
>is no problem in contouring it at one time.
>
>I have tried every combination I can think of, for instance setting
>GFUNC=sub(pvor(thte^f14,geo^f14),pvor(thte^f12,geo^f12)) without success.
>
>Do you have a solution?
>
>Thanks
>John
>
>
>
>
John,
if thte and geo are having to be computed, then you may be getting an error
about number of grids exceeding space. This is because thte(pres,tmpc,dwpc)
and geo(hght) for the 2 times requested would require 8 input grids
for each level plus the output grid. The maximum number of grids you
will have room for is dependent upon the number of grid points you have.
If your gridded data already has thte and geo computed, then the problem may
be that you need to use lav() for the computation.
At any rate, here is one solution:
1) use gddiag to compute your delta equivalent potential vorticity
Here is a script that computes this for today's eta file with data
at 50mb pressure intervals:
#!/bin/csh -f
set GDFILE=$HDS/1999080912_eta_grid211.gem
@ GLEV1 = 1000
while($GLEV1 > 100)
@ GLEV2 = $GLEV1 - 50
@ GLEVA = $GLEV1 + $GLEV2
@ GLEVA = $GLEVA / 2
gddiag << EOF1
gdfile = $GDFILE
gdoutf = testpvor.gem
gfunc = pvor(thte,geo)
gdattim = f000
glevel = ${GLEV1}:${GLEV2}
gvcord = pres
grdnam = epvor@${GLEVA}
gpack =
r
gdattim = f012
r
gdfile = testpvor.gem
grdnam = delpvor
gdattim = f012:f000
gfunc = tdf(epvor@${GLEVA})
r
e
EOF1
@ GLEV1 = $GLEV1 - 50
end #end while GLEV
gpend
----------------------------------------------------------------
I created the testpvor.gem output grid file using gdcfil- but
you could use the same file as the input. As a result I get:
NUM TIME1 TIME2 LEVL1 LEVL2 VCORD PARM
1 990809/1200F000 975 PRES EPVOR
2 990809/1200F000 925 PRES EPVOR
3 990809/1200F000 875 PRES EPVOR
4 990809/1200F000 825 PRES EPVOR
5 990809/1200F000 775 PRES EPVOR
6 990809/1200F000 725 PRES EPVOR
7 990809/1200F000 675 PRES EPVOR
8 990809/1200F000 625 PRES EPVOR
9 990809/1200F000 575 PRES EPVOR
10 990809/1200F000 525 PRES EPVOR
11 990809/1200F000 475 PRES EPVOR
12 990809/1200F000 425 PRES EPVOR
13 990809/1200F000 375 PRES EPVOR
14 990809/1200F000 325 PRES EPVOR
15 990809/1200F000 275 PRES EPVOR
16 990809/1200F000 225 PRES EPVOR
17 990809/1200F000 175 PRES EPVOR
18 990809/1200F000 125 PRES EPVOR
19 990809/1200F012 975 PRES EPVOR
20 990809/1200F012 990809/1200F000 975 PRES DELPVOR
21 990809/1200F012 925 PRES EPVOR
22 990809/1200F012 990809/1200F000 925 PRES DELPVOR
23 990809/1200F012 875 PRES EPVOR
24 990809/1200F012 990809/1200F000 875 PRES DELPVOR
25 990809/1200F012 825 PRES EPVOR
26 990809/1200F012 990809/1200F000 825 PRES DELPVOR
27 990809/1200F012 775 PRES EPVOR
28 990809/1200F012 990809/1200F000 775 PRES DELPVOR
29 990809/1200F012 725 PRES EPVOR
30 990809/1200F012 990809/1200F000 725 PRES DELPVOR
31 990809/1200F012 675 PRES EPVOR
32 990809/1200F012 990809/1200F000 675 PRES DELPVOR
33 990809/1200F012 625 PRES EPVOR
34 990809/1200F012 990809/1200F000 625 PRES DELPVOR
35 990809/1200F012 575 PRES EPVOR
36 990809/1200F012 990809/1200F000 575 PRES DELPVOR
37 990809/1200F012 525 PRES EPVOR
38 990809/1200F012 990809/1200F000 525 PRES DELPVOR
39 990809/1200F012 475 PRES EPVOR
40 990809/1200F012 990809/1200F000 475 PRES DELPVOR
41 990809/1200F012 425 PRES EPVOR
42 990809/1200F012 990809/1200F000 425 PRES DELPVOR
43 990809/1200F012 375 PRES EPVOR
44 990809/1200F012 990809/1200F000 375 PRES DELPVOR
45 990809/1200F012 325 PRES EPVOR
46 990809/1200F012 990809/1200F000 325 PRES DELPVOR
47 990809/1200F012 275 PRES EPVOR
48 990809/1200F012 990809/1200F000 275 PRES DELPVOR
49 990809/1200F012 225 PRES EPVOR
50 990809/1200F012 990809/1200F000 225 PRES DELPVOR
51 990809/1200F012 175 PRES EPVOR
52 990809/1200F012 990809/1200F000 175 PRES DELPVOR
53 990809/1200F012 125 PRES EPVOR
54 990809/1200F012 990809/1200F000 125 PRES DELPVOR
2) Now I can use delpvor in gdcross like:
GDATTIM = f012:f000
GVCORD = pres
GFUNC = lav(delpvor)
If your model output has geo and thte so that you don't exceed the maximum
internal space, then you may need to use lav() for your quantity
since the internal grid naming after computing pvor will be a layer quantity.
Steve Chiswell
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