Microphysical and Dynamical Cloud Regimes as Tools for Studying the Impacts of Aerosol–Cloud Interactions on Radiation

The presentation will examine whether the diagnostic relationships between aerosol and Cloud Radiative Effect (CRE) obtained from sparse temporal resolution measurements of polar orbiting satellites are a manifestation of actual aerosol effects on clouds. The analysis relies exclusively on Level-3 (gridded) data and comprises systematic cloud classification in terms of either “microphysical” or “dynamical” cloud regimes (µCRs and dCRs, respectively, collectively called “CRs” below), aerosol optical depth (AOD) variations relative to a region’s local seasonal climatology, and exploitation of the 3-hour difference between Terra (morning) and Aqua (afternoon) overpasses. Specifically, our presentation will assess whether Aerosol-Cloud-Radiation interactions (ACRI) can be diagnosed by investigating: (a) The variations with AOD of afternoon CRE composited by morning or afternoon CRs; (b) CR morning-afternoon transitions composited by morning AOD quartiles; (c) whether clouds represented by ensemble [cloud effective radius – cloud optical thickness] or [cloud top pressure – cloud optical thickness] joint histograms look distinct under low and high AOD conditions when preceded or followed by specific CRs. We will explain how our approach addresses long-standing themes of the ACRI problem such as the optimal ways to decompose the problem by cloud class, the prevalence and detectability of 1st/2nd aerosol indirect effects and invigoration, and the effectiveness of aerosol changes in inducing cloud/radiation modifications at different portions of the AOD distribution.