Mesoscale Parallel Experiment Change Log
Eta-32 with winter 2005 Eta change package, experimental changes to GFS radiation and/or cloud
Reduced the absorption coefficients for ice to a fixed value (.00328),
corresponding to an ice effective radius of 500 microns. This change is intended
to reduce the positive height errors above 500 hPa by reducing the absorption of
solar radiation in upper-level ice clouds.
Revert back to ETAY version of GFS radiation physics
Leaf area index (LAI) parameter in LSM physics changed from 1.0 to 2.0
Revert back to new versions of Noah LSM (With hi-res soil, veg types) and
test versions of routines DIFCOF, TURBL, and SFCDIF
Two parameters in the new cloud cover scheme have been tuned
to match the AFWA total cloud cover product. The
first parameter (STSD) is the assumed standard deviation of total
grid-scale relative humidity in the grid box, which is set to a value
of 1%. The second parameter (RHsat) is the threshold relative humidity
for the onset of grid-scale condensation, which is made to be the sum
of the threshold relative humidity for the onset of condensate (RHgrd)
and the parameter STSD.
Code related to the new cloud cover parameterization in the radiation
driver was streamlined in order to run more efficiently.
Set the glaciation temperature (T_ICE) from -25C back to -10C in order
reduce the presence of supercooled liquid water. Also reduce the assumed
cloud droplet number concentration from 100 /cm**3 to 50 /cm**3, which
will lead to larger cloud droplets and more rapid initiation of rain.
Both changes are intended to increase solar transmission through low-level
liquid water clouds at higher latitudes.
In order to reduce the solar absorption by ice, the number concentrations of
small ice crystals is assumed to be the same as the number concentrations
of large (precipitating) ice particles. Currently in operations the number of
small ice crystals are assumed to be a factor of 5-10 larger than those of
precipitating ice particles (FLARGE=0.5 rather than 0.1 or 0.2 in the grid-scale
In Noah LSM, LAI_DATA=1.0, SMHIGH=3.0
EDAS restarted from ETAZ
Begin use of new 3DVAR analysis which uses a 2dvar surface analysis
to assimilate surface temperature data.
Removed all references to cloud water and ice (cloud ice + snow)
paths for convective cloudiness in RADTN, RDLWSW, and SWR95. Instead,
cloud water and ice paths for convective clouds are merged with grid-scale
cloudiness, but only if the convective cloud fractions are larger than the
grid-scale cloud fractions at each model level.
Cloud water mixing ratios for convection are assumed to be 0.05 g/kg,
and ice mixing ratios for convection are assumed to be the minimum of 0.05 g/kg
or the ice mixing ratio associated with a large particle concentration of 5 per liter.
The solar constant is reduced by at most 2.12% rather than by 4.74%.
The minimum effective radius for cloud water is increased from 5 microns to 10 microns.
The minimum size assumed for precipitation ice particles is increased from 100 microns
to 150 microns. The temperature dependence assumed for the size of these particles
was also changed so that at a temperature of -40C the mean diameter increased from
117 microns to 201.9 microns.
RADTN changed to decrease longwave absorption coefficient for ice to be similar to
that in Kiehl et al. (1998)
Revert back to ops Eta version of DIFCOF, TURBL, SFCDIF, and the Noah LSM physics
Minor changes to RADTN to tweak cloud cover scheme
Minimum size for precipitating ice particles is increased
from 50 microns to 100 microns. This change should hopefully reduce the
absorption of solar radiation by upper-level ice clouds.
Changed parameters in the new cloud cover scheme based
on results from Mary Hart's verification of the parallel runs against
AFWA total cloud cover. Reduced the amount of partial cloudiness and
increased the amount of total overcast skies, closer to the cloud cover
in the control run. Also reduced the amount of cloud condensate
associated with fractional cloudiness.
Page Last Modified: September 9, 2004