Impacts of cloud-system resolving regional modeling on the simulation of monsoon depressions

Abstract

The impacts of high-resolution (<10 km) and cloud-system-resolving regional modeling (CSRM) on the simulation of an intense south Asian monsoon depression (MD) were examined using the WRF-ARW model. Spatial resolution in this range was necessary to realistically simulate the MD's propagation, intensity, and precipitation. Simulations were however highly sensitive to the moist convection and cloud microphysics. The best scenarios were created by the microphysics parameterization (MP) that generated the most robust post-landfall condensation associated with the MD, alone or in combination with the cumulus parameterization that triggered vigorous convection overland in the coarser setup. A sensitivity study of the MP schemes in CSRM suggested that more sophisticated mixed-phased schemes contributed to higher simulation fidelity. Insufficient condensation and weak convection overland might induce spurious low systems over the Bay of Bengal through low-level moisture advection, which further interfered with the MD and degraded several simulations.