Mesoscale Parallel Experiment Change Log

Experiment Name:  Eta-32 with winter 2005 Eta change package

When Who What
2004/12/03/00 Ferrier, Ek, Mitchell
  • Changed the standard deviation of RH for grid-scale condensation from 2% to 1%
  • Changed "RHsat=.5*(RHgrd+H1)" to "RHsat=RHgrd", which will have the effect of an earlier onset for partial cloudiness, which will be mitigated by the change in the first bullet.
  • These changes make the cloud cover more "binary"
  • Added the effects of snow emissivity in the calculation of effective snow-ground sfc temperature, which is based on heat fluxes between the snow pack and the soil and on net raditaion
  • 2004/12/01/00 Ferrier
  • Adopted only one of the EtaL changes by decreasing the maximum number concentration of precipitation ice particles from 20 to 10 per liter. Also, the solar absorption by ice is a little less than a half of what's parameterized in operations. These changes are expected to reduce solar absorption by upper-level ice clouds and to increase the transmission of solar radiation into the lower troposphere, in which the goal is to reduce the warm (cold) bias at upper (lower) levels. A slight change was made in the order that solar zenith angle is called at the beginning of the radiation driver will speed up the code slightly but should not impact the forecast.
  • 2004/11/20/00 Ferrier
  • Changed the assumed number concentration of cloud droplets from 100 back to 200 /cm**3, which increases the threshold cloud water mixing ratio for autoconversion to rain from 0.838. Also increased the maximum number concentration of precipitation ice particles from 10 back to 20 per liter.
  • Changed cloud water absorption coefficients back to operational Eta values. The absorption coefficients for ice are unchanged and are slightly less than what's currently used in operations.
  • 2004/11/17/12 Ferrier
  • Decreased the assumed number concentration of cloud droplets from 200 to 100 /cm**3, which reduces the threshold cloud water mixing ratio for autoconversion to rain from 0.838 to 0.419 g/m**3. Also decreased the maximum number concentration of precipitation ice particles from 20 to 10 per liter. Both changes are intended to lower the amount of suspended condensate in the atmosphere, which should help reduce the cool bias that has developed below clouds in the parallel.
  • Fixed a minor bug in ADJPPT1 that limits the amount of cloud water from exceeding the autoconversion threshold
  • A new cloud cover scheme is introduced in order to increase the presence of forecast partial cloudiness. Two adjustable parameters in the scheme have been tuned to match the AFWA total cloud cover product. The first parameter (STSDM) is the assumed standard deviation of total grid-scale relative humidity in the grid box, and it is set to 2%. The second parameter (RHsat) is the total relative humidity associated with an assumed cloud fraction of 50%, and it is set to the average of the threshold relative humidity for the onset of grid-scale condensation (RHgrd) and a value of 100% (i.e., 98.3% for the 32-km runs).
  • 2004/11/03/00 Ek, Ferrier
  • Increase minimum stomatal conductance from 40s/m to 70s/m for cropland, pasture, and grassland vegetation types in order to decrease surface evaporation.
  • In calculating longwave emissivities in cloudy layers, the optical depths for cloud water are obtained using the downwelling longwave relationships of Smith and Shi (1992). The LW absorption coefficient for ice to be the same as what's currently used in the operational Eta.
  • In calculating solar absorption, the optical depths for cloud water and for ice (cloud ice and snow) are obtained using the relationships described by eqs. (5.2), (5.3), and Table 9 from Hou et al. (2002), assuming a constant effective radius of 10 microns for cloud water and 75 microns for ice. For cloud water optical depths, equal weighting is assumed for absorption of UV-VIS and near IR radiation.
  • In the operational radiation, a minimum optical depth is assumed for grid-scale liquid water clouds consistent with a minimum mixing ratio of 0.1 g/kg. This lower limit has been removed, and this change has been found to have the biggest impact.
  • 2004/10/26/12 Ferrier
  • Replaced GFS radiation with ops Lacis-Hansen scheme with modified water & ice absorption coefficients that are more consistent with those in the GFS radiation scheme
  • Revert back to operational version of cloud microphysics
  • Restarted cycled EDAS from ETAZ
  • 2004/10/20/12 Ferrier
  • Changed minimum size for precipitation ice particles back to 100 microns, as well as using the same temperature dependence for precipitation ice, reverting back to the formulation prior to 2004/09/2812.
  • Increased the temperature at which liquid water is assumed to glaciate completely to ice from -25C back to -10C, reverting back to what's used in operations.
  • 2004/10/01/00 Ek, Mitchell
  • Leaf area index (LAI) parameter in LSM physics changed from 1.0 to 2.0
  • 2004/09/28/12 Ferrier, Ek, Mitchell
  • 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.
  • 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.
  • In Noah LSM, LAI_DATA=1.0, SMHIGH=3.0
  • EDAS restarted from ETAZ
  • 2004/09/24/12 Pondeca, Rogers
  • Begin use of new 3DVAR analysis which uses a 2dvar surface analysis to assimilate surface temperature data.
  • 2004/09/16/00 Ferrier
  • Minimum size for precipitating ice particles is increased from 50 microns to 100 microns. This change will reduce the absorption of solar radiation by upper-level ice clouds based on tests in the EtaL.
  • 2004/09/09/00 Mitchell, Ek
  • Change "LAI_DATA" in LSM physics from 4.0 to 3.0
  • 2004/09/03/00 Ferrier, Mitchell
  • Change "LAI_DATA" in LSM physics from 5.0 to ops value of 4.0
  • 2004/09/01/12 Ferrier
  • Revert to operational version of shallow convection parameterization in CUCNVC
  • Restarted cycled EDAS from ETAV atmospheric states and ETAZ soil states
  • 2004/09/01/00 Ferrier
  • Revert to operational versions of PRODQ2 and MIXLEN, removing changes to these routines which removed mixing length limits under stable conditions.
  • 2004/08/31/00 Lin
  • New precipitation assimilation scheme (routine ADJPPT) modified to account for the fact that the variable F_rain is actually the fraction of liquid condensate that is rain, not the fraction of total condensate that is liquid rain
  • Page Last Modified: September 1, 2004