[Rda-users] Temperature observations in the ds337.0 PrepBufr data files

[Thomas Cram]

To all users of the NCEP PrepBufr observations in RDA dataset ds337.0:

It was recently discovered that many temperature observations at the top of the event stack in the NCEP PrepBufr data files have gone through the VIRTMP PREPBUFR processing step at NCEP and have been converted from sensible temperature to virtual temperature.  This conversion is done at NCEP as part of the PREPBUFR data processing which prepares the data for assimilation into the GDAS assimilation system.  Further information on this processing step can be found in the NCEP documentation at http://www.emc.ncep.noaa.gov/mmb/data_processing/prepbufr.doc/table_14.htm.

By default, the RDA subsetting utility for data requests from ds337.0 is configured to grab observations from the top of the PrepBufr event stack, thus many of the temperature observations in both the NetCDF and ASCII data files contain virtual temperature instead of sensible temperature.  We have fixed this bug in our subsetting services and now extract only the sensible temperature for all data subset requests.

We encourage all users who are unaware of this to examine the temperature observations previously downloaded from ds337.0 and, if necessary, submit new data requests at the ds337.0 subsetting request form located at the following URL:

http://rda.ucar.edu/datasets/ds337.0/index.html#forms/337_subset.php?_da=y

Please send questions and comments related to the ds337.0 data to tcram at ucar.edu.

Sincerely,
- Tom Cram

Thomas Cram
NCAR / CISL / Data Support Section
303-497-1217
tcram at ucar.edu
rda.ucar.edu





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