>From: "Geoff Dimego" <Geoff.Dimego@noaa.gov>
Date: Mon, 25 Feb 2002 14:32:50 -0500

Subject: Notice of Change to Meso Eta for 12z 26 February

NCEP Operations has scheduled the following crisis change to be made
to the Meso Eta Model runs starting with 12z 26 February 2002.

The change addresses complaints this winter about nighttime surface 
temperatures over snow being too cold in the Meso Eta.  The problem
has been linked to two factors.  The first is that our new gridscale
cloud scheme has less cloud than the one it replaced.  This results 
in more radiational cooling situations.  While the old scheme had a
definite bias (too much cloud), we feel the new scheme may have too 
little cloud.  This is being looked into and will be addressed in 
the future.  The second factor relates to thermal conductivity of
the land-surface layer when snow cover is present.  The formulation
of this was refined in July 2001 to incorporate a treatment of patchy
snow.  There was nothing wrong with that treatment, however, we have
found that more heat needs to get through to the atmosphere to keep 
the skin, shelter and 1st layer temperatures from cooling too much
at night.  Consequently, this change will increase the treatment of
thermal conductivity for both patchy snow and full snow cover. A
brief presentation can be found at
ftp://ftp.ncep.noaa.gov/pub/emc/wd20er/caftiinfo.feb02/v3_document.htm

[1] "Geoff.DiMego.vcf", DATA, 370 bytes