The Effects of Clouds on the Partitioning of the Radiation in the Atmosphere and at the Surface

The reflection of solar radiation by clouds causes a strong reduction in the energy balance of the surface because most of the solar radiation that is not reflected is absorbed at the surface. At high latitudes where insolation is weak and the atmosphere is relatively dry, the addition of clouds can heat the surface through increased downward IR emission by the atmosphere. Whether cloud layers heat or cool the atmosphere relative to clear skies, and the amount of this heating or cooling that takes place is largely determined by the vertical location and distribution of the clouds. High clouds tend to warm the atmosphere relative to surrounding clear skies, whereas low clouds tend to enhance the cooling of the atmosphere. While the total incoming and outgoing radiation at the TOA can be measured, the amount of radiative heating that occurs within the atmosphere versus how much heating occurs at the surface cannot be directly measured. Thus, model parameterizations of the internal heating of the climate system cannot be tightly constrained by observations. This shortcoming is a significant source of uncertainty in understanding cloud feedbacks.

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