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20000821: 20000814: Composites with gempak-format files

>From: Luis Farfan <address@hidden>
>Organization: UCAR/Unidata
>Keywords: 200008211831.e7LIVgN23484

>Steve,
>
>thank you for the information regarding the computation of average fields
>with gempak. I have been using this method and things work well for me. I
>already made composite fields for 500 mb heights and P06M from the Eta
>model forecasts for July 1999.
>
>The only problem I have now and do not how to solve is the following: 
>I have average 2-m hagl temperature (AVETMPC) and 2-m hagl relative
>humidity (AVERELH). By using these parameters, how can I tell my gdplot
>program to display the dew-point temperature?
>
>Thanks for your assistance, again, Luis M Farfan.
>
>On Tue, 15 Aug 2000, Unidata Support wrote:
>> Luis,
>> 
>> The program GDSTAT computes the average, standard deviation, and number
>> of reporting times at each grid point for a time series of grids.
>> 
>> You will want to use GDMOD to copy each field from separate files
>> to a single file for use with GDSTAT. You can create an empty file
>> with grid 211 projection with GDCFIL using CPYFIL=#211. Then,
>> for each file you have, use GDMOD to copy the HGHT@500 at F000 and P06M
>> for F006 into the new output file.
>> 
>> GDSTAT will compute fields named HGHT_AVE, HGHT_CNT and HGHT_STD etc
>> for each parameter you chose.
>> 
>> Steve Chiswell
>


Luis,

DWPC is a gfunc parameter that can be calculated from TMPC and RELH,
but AVETMPCAVE and AVERELH are unknown to this function.

There are 2 ways around this problem. The easiest is to use GFUNC=DWPC
in gdstat. The gfunc will compute the DWPC field at all the times to compute
AVEDWPC etc. 

The other solution would be to rename the average fields as just TMPC and RELH
using GDDIAG and specifying the GRDNAM without the prefix.

Steve Chiswell