Re: [idvusers] Problem with plotting thermal wind vectors from GRIB2 files

  • To: "Kevin R. Tyle" <ktyle@xxxxxxxxxxxxxxxx>
  • Subject: Re: [idvusers] Problem with plotting thermal wind vectors from GRIB2 files
  • From: Don Murray <don.murray@xxxxxxxx>
  • Date: Fri, 03 Feb 2012 10:14:30 -0700
The problem is that for grib2 data, the pressure levels are in Pascals, so you need to use 50000 and 10000.

GEMPAK always stores levels to hPa - the benefit of having a known vocabulary, but then again, you have to convert to GEMPAK format. ;-)

Don

On 2/3/12 9:52 AM, Kevin R. Tyle wrote:
Hi all,

I set up a formula in IDV to plot thermal wind vectors, a la:
<derived description="thermal wind in a layer"
formula="thrm(F1,user_Top_of_Layer[default=500],user_Bottom_of_Layer
[default=1000])" id="thermalWind" isdefault="false" isenduser="true">

Whenever I do this on a GRIB2 format grid file, e.g. realtime NAM or GFS
from the motherlode or atm-nsf opendap servers, I end up with all
missing data when I load in the formula, specify my levels, and choose
the 3D geopotential height from the GRIB2 file.

If I do the same on the same model data that has been converted to
GEMPAK, and also with the sample model data used in the IDV Workshop
(which I believe is GRIB1), the thermal wind vectors plot fine.

I suspect there is some issue specifically related to GRIB2 format here ...

Thanks for looking into this!

--Kevin

_____________________________________________
Kevin Tyle, Systems Administrator
Dept. of Atmospheric & Environmental Sciences
University at Albany
Earth Science 235, 1400 Washington Avenue
Albany, NY 12222
Email: ktyle@xxxxxxxxxx
Phone: 518-442-4578
_____________________________________________

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--
Don Murray
NOAA/ESRL/PSD and CIRES
303-497-3596
http://www.esrl.noaa.gov/psd/people/don.murray/