Using regrid2 and/or lats4d

[Dan Leins]

All,

Apologies in advance if this is a duplicate post....

I was wondering if anyone could lend me some insight into using regrid2. I
ended up getting a pre-compiled binary which seems to be working ok (i.e. it
doesn't seg-fault when I run it). I've basically got 2 datasets I want to
subtract from one another, one is a model grib file, the other is a binary
file.I've come up with a control file which will allow me to view the field
in the binary file, and I've already got a functioning control file for my
model grib file. The binary file contains 1km gridded data, the model grib
file contains 3km gridded data, and I believe both are on different map
projections. Here's a portion of each of the control files....

Binary control file:
dset /usr/local/leins/test/us_ssmv01025SlL01T0024TTNATS2007040705DP001.dat
title test
#undef 65535
undef 55537
UNPACK 0.1 0.0
options yrev
xdef 6935 linear -124.729583333333 0.00833333333333333
ydef 3351 linear  24.9495833333324  0.00833333333333333
zdef 1 levels 1000
tdef 1 linear 22jul2007 1dy


Model grib file:
set /usr/local/leins/test//07040700_arw_d01.GrbF02400
index /usr/local/leins/test//07040700_arw_d01.GrbF02400.idx
undef 9.999E+20
title /usr/local/leins/test//07040700_arw_d01.GrbF02400
*  produced by grib2ctl v0.9.12.5p34c
dtype grib 255
pdef 263 250 lcc 39.447000 -87.971000 1 1 42.900000 42.900000 -83.4000003000 30
00
xdef 263 linear -87.971000 0.0353176389800391
ydef 250 linear 39.447000 0.0272727272727273
tdef 1 linear 00Z08apr2007 3hr

In short, if I attempt to subtract one from the other, GrADS complains with
"Entire Grid Undefined". Thinking that because they are on different map
projections and of different resolutions, I thought I'd have to regrid the
binary data to "dumb it down" to the model 3km resolution. Does that sound
right? So far I haven't seen a whole lot of helpful documentation on
regrid2, but I did find some help for lats4d. From what I understand, It
looks like lats4d works hand in hand with regrid2 provided that you have a
control file for the desired resolution, which I do in the model grib
control file.

Regardless, does anyone have any insight or any examples of how I can make
these two datasets see "eye to eye" so I can easily subtract one from the
other? One contains observed liquid equivalent snowfall, the other is a
model forecast. You can probably see how it'd be advantageous to be able to
subtract these.

Thanks for any help!
Dan
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