| Summary: | The Wu-Kaplan radiation parameterization (Krishnamurthy, 1982) used in the GLA Global Circulation Model (GCM) was improved by replacing its fixed tables of CO2 transmittance in the 15 micron band with models developed by regression on line-by-line transmittances. The transmittances between layers are modeled as products of effective sublayer transmittances. The GLA GCM was integrated for 20 days starting at OZ, January 21, 1979, using the transmittance model. In the control run the fixed table of 15 micron CO2 transmittances is used. The effect of the change of initial cooling rate is illustrated by a map of the difference of 50 mb temperature after 6 hours. The cooling is reduced over high topography, where the fixed table underestimates the transmittance, and is reduced slightly throughout the tropics and the north polar area where the stratosphere is relatively cold. Over elevated topography the surface cooling increases, also as expected. The stratospheric temperature increases over a degree in the arctic and smaller amounts over Antarctica and elsewhere. Tropospheric equilibrium temperature response is obscured by time dependent differences in synoptic disturbances.
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