Radiative Effects of Cloud-Type Variations

TLDR

Cloud types are defined by top height and optical thickness, and additional factors such as solar insolation and atmospheric and surface properties also influence regional cloud radiative effects. The study investigates how different cloud types alter radiative fluxes using ISCCP cloud data and a refined radiative transfer model from NASA/GISS. The analysis employs a refined radiative transfer model derived from the NASA/GISS general circulation model. Cloud‑type variations are as important as cloud cover in modifying the earth–atmosphere radiation field, with stratocumulus, altostratus, and cirrostratus producing the largest annual mean changes in global top‑of‑atmosphere and surface shortwave fluxes, while cirrus, cirrostratus, and deep convective clouds dominate top‑of‑atmosphere longwave changes and stratocumulus, cumulus, and altostratus drive surface longwave changes.

Abstract

Radiative flux changes induced by the occurrence of different cloud types are investigated using International Satellite Cloud Climatology Project cloud data and a refined radiative transfer model from National Aeronautics and Space Administration/Goddard Institute for Space Studies general circulation model. Cloud types are defined by their top height and optical thickness. Cloud-type variations are shown to be as important as cloud cover in modifying the radiation field of the earth–atmosphere system. Other variables, such as the solar insolation and atmospheric and surface properties, also play significant roles in determining regional cloud radiative effects. The largest “annual” mean (approximated by averaging the results of four particular days, one from each season) changes of the global top-of-atmosphere and surface shortwave radiative fluxes are produced by stratocumulus, altostratus, and cirrostratus clouds (i.e., clouds with moderate optical thicknesses). Cirrus, cirrostratus, and deep convective clouds (i.e., the highest-level clouds) cause most of the annual mean changes in the global top-of-atmosphere longwave radiative fluxes; whereas the largest annual mean changes of the global surface longwave radiative fluxes are caused by stratocumulus, cumulus, and altostratus.