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ATMOSPHERIC RESEARCH, 91, 127-136, 2009.
An application of the tilted independent pixel approximation to cumulonimbus environments.
Jeffrey W. Frame, Jonathan L. Petters, Paul M. Markowski, Jerry Y. Harrington
Abstract
Most radiative transfer parameterizations in numerical cloud models transfer radiation in the
vertical direction only, utilizing the independent pixel approximation. This method cannot
correctly simulate neither the location nor the shape of cloud shadows because shortwave
radiation only propagates vertically, and thus it does not account for the slanted path the direct
solar beam takes through the atmosphere. Herein, the tilted independent pixel approximation,
which more properly accounts for the geometry of the direct solar beam, is applied to a
cumulonimbus cloud field. This computationally inexpensive method results in a more
accurately modeled cloud shadow at the surface, allowing for more accurate computations of
near-surface air temperatures.
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