Cloudiness as a climatic feedback mechanism: effects on cloud amounts of prescribed global and regional surface temperature changes in the NCAR GCM.

Abstract

In a series of January experiments, prescribed changes of 2K to the ocean surface temperatures of the NCAR GCM are imposed either globally or in 1 of 2 zonal strips centered at 5oS and 15oN. The global perturbations cause a global response in 3km cloudiness of apposite sign to the surface temperature change, whereas a warm surface temperature perturbation at 15oN, under the subsiding branch of the Hadley cell, causes a cloudiness increase over the strip and smaller cloudiness decreases in zones adjacent to the strip. On the other hand, a 2K strip placed at 5oS under the ascending branch of the Hadley cells casuses little cloudiness response over the strip, but a statistically significant cloudiness decrease in adjacent zones. It is concluded that, in additon to a term which accounts for the effects on global cloudiness of global temperature changes, a comparably important additional term is needed to compute the global cloudiness feedback problem. -from Authors