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20050830: RUC tropopuase field - two queries

John,

You can use the GDPOINT program which is installed in the distribution
from the $NAWIPS/comet/gdpoint source directory, eg:

 GDATTIM  = fall
 GDFILE   = ruc_20
 GLEVEL   = 0
 GPOINT   = IAD
 GVCORD   = trop
 GFUNC    = pres
 SCALE    = 0
 GEMPAK-GDPOINT>r
 
GDFILE: $MODEL/ruc/2005083015_ruc252.gem                  
GPOINT: IAD                                               
GVCORD: trop                                              
GLEVEL: 0                                                 
GFUNC : pres                                              
SCALE : 0                                                 
     050830/1500F000 :    122.86554
     050830/1500F001 :    117.84518
     050830/1500F002 :    116.58470
     050830/1500F003 :    131.66049
 Parameters requested: GDATTIM,GDFILE,GLEVEL,GPOINT,GVCORD,GFUNC,SCALE.
 GEMPAK-GDPOINT>

Steve Chiswell
Unidata User Support




>From: John Merrill <address@hidden>
>Organization: UCAR/Unidata
>Keywords: 200508301528.j7UFSljo000382

>Hello, Steve:
>   I'm working with .gem files from the CONDUIT RUC analysis
>source. I've gotten useful results using GDCROSS and other
>routines, but I find it difficult to use the Tropopuase field.
>   As you know, there are four variables for vcord=trop, all at
>level 0: THTA, PRES, UREL and VREL. To start, I use GDLIST to
>list a few rows and columns of data. The values of the tropopause
>pressure, PRES, seem reasonable. But to use them fully I need to
>interpolate them to a specific lat/lon point, and it appears this
>is not something Gempak is inclined to to from the user interface.
>(I tried the routine GDTHGT, but was rebuffed; reading a values of
>of a plot would have been a compromise in any event.) Because the
>pressure (or THTA) are values at a single level, the contouring
>routines won't touch this, so I don't have a way to indicate the
>model tropopause on a cross section, for example. Any suggestions?
>   Thinking about using data listed by GDLIST and interpolating in
>another program leads to the simple question of how to list the grid
>latitude and longitude values for a limited area. I know of the
>GDPFUN parameter PLAT and PLON, but GDLIST doesn't seem to know of
>these. I know this can be done, but can't recall how we managed it.
>   There are several points at which I want the tropopuase height, for
>many days in a sequence. I suppose I could make a contour plot of the
>tropopause pressure on a map, and put a marker symbol at each site, and
>interpolate subjectively.
>   Thanks for any help you can provide.
>
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