Abstract:

Satellite observations and numerical simulations show that the small net Cloud Radiative Effect (CRE) of tropical anvil clouds results from a near-cancellation between large but opposing longwave (LW) and shortwave (SW) components over the cloud’s lifecycle. We develop an analytical model that captures this behavior by combining: (1) simple parameterizations of LW and SW CRE as functions of SW cloud optical depth; (2) a two-phase cloud spreading model, incorporating both initial convective detrainment and subsequent radiatively driven expansion; and (3) a minimal cloud microphysics scheme. The model performs well when tested against data from a cloud-resolving model simulation, suggesting it is capturing the essential physics governing anvil cloud lifecycles. Sensitivity tests reveal a strong dependence of the total net CRE on initial cloud temperature, as well as substantial sensitivity to solar insolation and precipitation efficiency, highlighting the importance of these factors for understanding and modeling high-cloud feedbacks in a changing climate.