e3afa375_on_and_or_cloud_microphysics____What
[When] 2004/10/27/00 [Who] Ferrier [What] 
In calculating longwave emissivities in cloudy layers, the optical depths for cloud water and for ice (cloud ice and snow) are obtained using the downwelling longwave relationships of Smith and Shi (1992). 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. With respect to the EtaW, the biggest impact of these changes is to increase the optical depths for ice clouds by a factor of 5 when calculating (longwave) cloud emissivities. The net effect of all of the other changes are minor (i.e., less than 2.5%).
Mesoscale Parallel Experiment Change Log for " Eta-32 with winter 2005 Eta change package, experimental changes to GFS radiation and/or cloud microphysics "
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