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20000912: Gempak, gridded fields

>From: Luis Farfan <address@hidden>
>Organization: UCAR/Unidata
>Keywords: 200009122037.e8CKbjb02366

>Steve,
>
>I am interested in my options to modify the characteristics of a gridded
>file in gempak format.
>
>I have a grided file that contains precipitation from observed data. This
>data was converted into a surface-type file and then into a gridded field
>via the program "oabsfc". This field has a size of about 120X150 points
>and covers a portion of the Southwest United States: CA,AZ,NV,UT,CO and
>NM.
>
>I would like to perform a numerical comparison between this observed field
>and the precipitation derived from model forecasts with the eta model. I
>have the data from this model in their nawips grid #211, which is not the
>same as the grid with the observed data. My eta field have a size of
>93x63 and cover North America.
>
>Is there any way(s) to combine gempak programs to modify my eta gridded
>data into a another (smaller in grid spacing and areal coverage) grid?
>Once I have the observed and modeled data in similar grids, I can use a
>contour program to plot the differences.
>
>Please, let me know what you recommend for this application.
>
>Thank you, Luis M Farfan.
>
>


Luis,

One option you have is to use the gdbiint program to interpolate
from one grid projection to another. To convert your ETA gridded
data tou the finer grid, first create a new output file of
your desired output projection. In gdbiint (which stands for grid
bi-linear interpolation), specify the GDFILE to be your
input #211 grid, and GDOUTF to the new grid output file.

Once you have your grids on the same projection, you can
perform mathmatical operations etc on the fields between
the two data files.

Steve Chiswell