The Influence of Cloud‐Radiative Interactions on the Diurnal Cycle Over the Maritime Continent

Abstract The diurnal cycle is one of the predominant components of rainfall variability, yet accurately representing its timing and intensity remains challenging for general circulation models (GCMs). The accurate representation of diurnal convective‐scale processes in GCMs is particularly important over the Maritime Continent (MC), where complex terrain and oceans produce unique diurnal cycles. A process that has been identified to be important to the diurnal cycle is cloud‐radiative interactions. Idealized numerical modeling studies have shown that cloud‐radiative interactions influence the strength and behavior of diurnal convection, but gaps remain in understanding its potential role over coastal and complex topographical regions. Using the Weather Research and Forecasting model in a convection‐permitting framework, a 10‐day control simulation is conducted over the MC alongside a daily‐ensemble of sensitivity simulations where cloud‐radiative interactions are turned off. Diurnal rain rate is higher, and rainfall initiates earlier over land when cloud‐radiative interactions are absent, while no significant change is measured in diurnal rainfall offshore. The changes in diurnal cycle characteristics over land are primarily driven by the earlier and stronger diurnal increase in surface solar radiative flux, which increases surface sensible and latent heat flux relative to the control. The stronger surface fluxes increase daytime surface slope flow and convective triggering, with the greatest impact in regions of elevated terrain where high‐albedo low‐level clouds are abundant. These results imply that the accurate numerical representation of both clouds and their radiative interactions is vital to accurately predicting diurnal rainfall over complex topography, which remains a challenge in GCMs.