Abstract

The climatological distribution of clouds is tightly coupled to large-scale circulation. Net cloud radiative forcing is mainly the result of boundary layer clouds in large-scale subsidence. Deep convective cloud systems exert long- and shortwave cloud forcing that nearly cancel out each other. The extent of this cancellation depends strongly on the vertical motion profile, suggesting that if the cancellation is not coincidental, dynamic feedbacks probably play a role in its maintenance. Low cloud radiative forcing is tied to how cold the surface is compared to the free troposphere. It is an open question how this correlation should be represented in a way that generalizes to a perturbed climate. Simple empirical representations of deep and low cloud forcing are shown to provide strong feedbacks on an idealized model of a tropical overturning circulation. Global weather and climate models, however, still have profound difficulties in accurately representing the cloud response to large-scale forcings.

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