Analysis of the Influence of Clear-Sky Fluxes on the Cloud-Type Mean Cloud Radiative Effects in the Tropical Convectively Active Regions With CERES Satellite Data

Abstract

Cloud radiative effects (CREs) and cloud-type mean CREs depend upon how clear-sky fluxes are computed over a large area: those of the immediate environment of clouds or the regional mean clear-sky fluxes. Five convectively active regions in the Tropics, two over land (Africa and Amazon) and three over ocean (eastern and western Pacific and Atlantic), are selected to understand the influence of immediate environment of clouds on CREs. Fluxes derived from 19 years of high-resolution CERES satellite data, categorized by cloud type, are utilized. The cloud types are classified based on the joint cloud top pressure and cloud optical depth distribution. For the entire tropical region, differences in cloud-type mean CRE with regional mean and immediate environment clear skies range from −7.8 to 10.7 Wm⁻² for shortwave (SW), 2.9 to 15.8 Wm⁻² for longwave (LW), and 6.1 to 17.9 Wm⁻² for net, respectively. The oceanic and Amazonia regions have negative (positive) SW (LW) CRE differences, typically 2–6 Wm⁻² in SW but 7–10 Wm⁻² in LW, whereas Africa has positive SW and LW CRE differences (typically 20–30 Wm⁻², up to 40–50 Wm⁻²). The influence of immediate environment reduces the regionally averaged, that is, cloud-type mean CREs weighted by cloud fractions, SW cloud cooling, and LW cloud warming in four of the five regions except for Africa. For Africa, it increases the SW cloud cooling and greatly reduces the LW cloud warming, resulting in net cloud cooling as in other regions instead of warming. The implications of these findings for observational and modeling studies are discussed.