[gembud] Interpolating fields below terrain

[David Novak]

Gembud,

I have model data that was converted to a GEMPAK file in sigma 
coordinates. I want to convert the data to pressure coordinates, and I 
want values below ground level. Is this possible? Here's my gdvint 
settings. I'm running on version 5.9.3.

gdfile=18z.gem
gdoutf=18z.gem
gdattim=021225/0000F018
gvcord=sgma:100/pres
glevel=$level
maxgrd=1000
garea=grid
vcoord=pres;none/L

I thought the "/L" was the trick according to the gdvint help, but I 
still have missing values below ground level. I do know that it works 
with thta, but maybe not pressure?

Thanks for any insight,
Dave