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Climatology of marine shallow-cloud-top radiative cooling
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  • Youtong Zheng,
  • Yannian Zhu,
  • Daniel Rosenfeld,
  • Zhanqing Li
Youtong Zheng
University of Maryland, College Park

Corresponding Author:zhengyoutong@gmail.com

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Yannian Zhu
School of Atmospheric Sciences, Nanjing University
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Daniel Rosenfeld
Hebrew University of Jerusalem
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Zhanqing Li
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A one-year’s worth of global (except poleward of 65 º N/S) marine shallow single-layer cloud-top radiative cooling (CTRC) is derived from a radiative transfer model with inputs from the satellite cloud retrievals and reanalysis sounding. The mean cloud-top radiative flux divergence is 61 Wm-2, decomposed into the longwave and shortwave components of 73 and -11 W m-2, respectively. The CTRC is largely a reflection of free-atmospheric specific humidity distribution: a dry atmosphere enhances CTRC by reducing downward thermal radiation. Consequently, the cooling minimizes in the “wet” tropics and maximizes in the “dry” eastern subtropics. Poleward of 30 º N/S, the CTRC decreases slightly due to the colder clouds that emit less effectively. The CTRC exhibits distinctive seasonal cycles with stronger cooling in the winter and has amplitudes of order 10~20 Wm-2 in stratocumulus-rich regions. The datasets were used to train a machine-learning model that substantially speeds up the retrieval.