Abstract
A number of numerical experiments have been carried out to investigate the climatic effects of the cirrus cloud thickness and location in various atmospheric conditions on the thermal equilibrium temperature of the earth's atmosphere. While the convective adjustment program utilized follows the procedures outlined previously by Manabe and his associates, several new endeavors for treating the transfer of solar and infrared radiation through semitransparent and nonblack clouds are incorporated into the radiative-convective progarm. The numerical program is developed in such a manner that the solar and infrared radiative properties of cirrus can be carefully treated in conjunction with the temperature profile determination. We show that the presence of a 0.1km thin cirrus with an infrared emissivity of 0.45 and a solar reflectivity of 0.08 heats the atmosphere by as much as 20°K regardless of the cloud location. However, the influence of thick clouds depends strongly on their atmospheric location. The presence of low thick ice clouds will cool the atmosphere significantly, a conclusion shared by several investigators. A composite thermal equilibrium temperature profile is constructed using the climatological water vapor and ozone profiles and cloud parameters for the tropical atmosphere. Comparison with the climatological temperature profile in the tropics reveal a close agreement (within 1°K) in the troposphere and about l0°K difference in the stratosphere. Using the tropical data, we show that increasing the cirrus cloud cover by 10% at the expense of the clear column will warm the surface temperature by about 0.2°K.
