Shortwave Cloud Feedback and the Response of the Atmospheric Circulation to Warming

Abstract:

Moist processes result in strong feedbacks that increase the gradient of net radiation as the climate warms. The gradient in net radiation causes a response of the atmospheric general circulation. Cloud feedbacks are a key contributor in this process. One of the important feedbacks in models is the cloud optical depth feedback in high latitudes, in which the liquid water content of clouds in middle and high latitudes increases with warming. It is shown that in models the shortwave cloud feedback in middle latitudes is caused by the ice microphysics, which decrease the sink of liquid water as the temperature increases. This brightening of the high latitude clouds, a negative shortwave cloud feedback, is shown to be the most important contributor to the poleward jet shift in an aquaplanet simulation.