Role of Microphysics and Convective Autoconversion for the Better Simulation of Tropical Intraseasonal Oscillations (MISO and MJO).

The seasonal prediction of the Indian summer monsoon (ISM) and Monsoon Intraseasonal Oscillations (MISO), as well as the Madden Julian Oscillations (MJO) that strongly modulate MISO, is of much importance to the agriculture sectors of the Indian Sub‐continent. This study highlights the importance of selecting proper "autoconversion" coefficients for precipitation formation in Coupled Global Climate Model's convective and microphysical schemes in simulating MISO and MJO. With a series of sensitivity experiments, we systematically examined the convective autoconversion and microphysical autoconversion coefficients in the National Centers for Environmental Prediction Coupled Forecast System version 2 (CFSv2). The mean and intraseasonal features of MISO and MJO are improved with a proper combination of autoconversion coefficients, which not only provide a better partition of cloud water and ice but also better feedback between the large‐scale condensation and convective parameterization. The results demonstrate a road map for the improvement of MISO as well as MJO simulation using a coupled climate model. Plain Language Summary: Simulation of the monsoon intraseasonal oscillations (MISOs), and Madden Julian Oscillations (MJO), in association with the seasonal Indian summer monsoon rainfall (ISMR), has been a real challenge for the state‐of‐the‐art global coupled climate models. Total rainfall in India during the monsoon season is useful for policymakers, farmers, and water managers who are keenly interested in the sub‐seasonal variations of rainfall. Thus, simulation of the MISOs, and MJO which have effects on the seasonal mean ISM rainfall has been evaluated here using coupled climate model simulations. Different autoconversion rates (convective and microphysics) which is a key process for the formation of rainfall in climate models are experimented to simulate MISO and MJO correctly. The proper combination of convective and microphysical autoconversion in climate models is needed to account for the sub‐seasonal variability by not only providing a better partition of cloud water and ice but also the better feedback between the large‐scale condensation and convective parameterization. Therefore, the results presented here demonstrate a road map for the improvement of MISO as well as MJO simulation by realistically simulating the physical processes associated with an accurate combination of autoconversion rate in a coupled climate model. Key Points: Importance of proper "autoconversion" coefficients in Coupled Global Climate Model's convective and microphysical schemes for Monsoon Intraseasonal Oscillation (MISO) and Madden Julian Oscillation (MJO)The study has unveiled the linkage between mean Indian summer monsoon rainfall (ISMR) and the sub‐seasonal variability, proper convection modulated by "áutoconversion"High fidelity in the simulation of MISO and MJO with better high cloud and stratiform rain fraction leads to the improved mean ISMR [ABSTRACT FROM AUTHOR]