Sensitivity of convective parameterization schemes in regional climate model precipitation extremes over India

摘要

An effort is made to identify a suitable convective parameterization scheme (CPS) in a regional climate model (RegCM4.5) for simulating the spatiotemporal variability of precipitation extremes over India. In this regard, a set of seven sensitivity experiments are conducted using different CPS. The performance of the mixed scheme, MIT over land and Grell over ocean (MLGO), bears a considerable resemblance to observations in the spatial distribution of mean extreme precipitation compared to other schemes. All schemes underestimate the mean precipitation due to heavy and extreme events, particularly over central India. However, this underestimation is considerably reduced in MLGO. The overestimation of the rainy days and underestimation of the dry days is one of the possible regions of higher mean rainfall in MLGO. Despite having considerable performance in simulating mean rainfall, MLGO fails to correctly simulate rainy days, dry days, and the frequency of events for very low intensities. However, Grell simulates the intensity and frequency of events closer to observation. In general, the Grell has the highest performance in simulating extreme events, dry/wet days, and daily precipitation intensity. The better performance of Grell and MLGO in simulating the precipitation extremes is due to the stronger south-westerly wind from the Arabian Sea (AS), and convergent flow from the northern Bay of Bengal (BoB) to central India (CI) facilitates the moisture pulling mechanisms enhancing moisture availability and hence precipitation. In addition, the higher atmospheric instability in MLGO enhances the moist convection, strengthening convective activity, leading to enhanced precipitation.