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Geographical and Seasonal Variability of Cloud‐Radiative Feedbacks on Precipitation
Author(s) -
Naegele A. C.,
Randall D. A.
Publication year - 2019
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
eISSN - 2169-8996
pISSN - 2169-897X
DOI - 10.1029/2018jd029186
Subject(s) - longwave , atmospheric sciences , outgoing longwave radiation , precipitation , downwelling , latitude , environmental science , climatology , atmosphere (unit) , radiative transfer , arc (geometry) , tropics , radiative cooling , meteorology , geology , geography , upwelling , convection , physics , oceanography , geometry , mathematics , geodesy , quantum mechanics , fishery , biology
We have used observations to study the temporal covariability of precipitation and atmospheric radiative cooling (ARC, defined as positive when the atmosphere is radiatively cooled) on seasonal and longer time scales. Clouds act to decrease the globally averaged ARC, but their radiative effect on the ARC varies with latitude. Clouds decrease the ARC in the tropics, mainly by reducing the outgoing longwave radiation, but they increase the ARC in higher latitudes, primarily by increasing the downwelling longwave radiation at the surface. The temporal correlation of the zonally averaged precipitation rate and the zonally averaged ARC is about −0.7 in the tropics and +0.5 in higher latitudes, and it changes sign almost discontinuously toward the poles at approximately 30°N and 30°S. This suggests that changes in the ARC feed back negatively on precipitating tropical systems and positively on precipitating systems at higher latitudes.