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.