| Description |
The RUC 20 analyses files for hours 00z and 12z may be missing
raob data between 04/18/2002-02/04/2003. This affects datastreams
sgpallruc20isobX1.00, sgpallruc20isobX1.c1, sgpruc20isobX1.c1,
sgpsynruc20isobX1.c1. sgpallruc20hybrX1.00, sgpallruc20hybrX1.c1,
and sgpruc20hybrX1.c1.
The situation was that we were picking up all data from the ruc2a directory
from NCEP's ftp server. Apparently, the 00z and 12z files in this directory
are "early look" "A" analysis files which miss most of the raob data.
Starting on 2/5/03, we started to pick up the 00z and 12z files from the
second "B" analysis from the ruc2b directory. Only data for hours 00z
and 12z are affected. Below are exerpts from Stan Benjamin of FSL regarding this
problem and how it affects the data.
Stan Benjamin in reply to a question on how the data is affected:
Feb 19 15:16:11 2003
" ... In your second question, the fields from the A analyses
will not be drastically in error. The quality for
the near-surface grids would be about equal to that of the B analysis.
The wind conditions aloft would be slightly degraded
but not much. The fields with the most degradation
would be the details of the vertical profiles of
humidity and, to a lesser extent, temperature..."
General message from Stan Benjamin (Feb 3, 2003):
"... Basically, the problem is that unless you've taken special precautions in your
ftp scripts, you've been accessing RUC analyses at 0000 and 1200 UTC that do not
assimilate most of the raob data.
Let me explain: There are 2 RUC analyses in the operational NCEP version at 00z
and 12z only. The first is an "early look" analysis, called the "A" analysis
that misses most of the raob data (although it does have most of the other obs
in it - profiler, aircraft, sfc, etc.). The 00z and 12z RUC forecasts do NOT
run off the "A" analysis. Instead, a second analysis called the "B" analysis
with a later (30 min) data cut-off to catch raob data is run, and then the
forecast is run.
At the NCEP ftp site, the ruc2a directories contain the "A" analyses and
forecasts initialized from the "B" analysis. Yes, a little confusing. To
obtain the "B" analyses, you must go to the corresponding ruc2b directory.
In other words, you must access two different directories to obtain the best
RUC analysis and forecast (from the B run) at 0000 and 1200 UTC. Again,
there is no B run at times other than 0000 and 1200 UTC.
The information on the RUC web site about ftp'ing from the NCEP-ftp site was NOT
correct about this issue until this afternoon. It is now corrected (see
http://ruc.fsl.noaa.gov/ruc20.data-access.html). ..."
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