Cloud Resolving Simulation of Indian Monsoon Precipitation and Implications on Cumulus Parameterizations

The Indian ocean region is characterized by large precipitation and convective available potential energy (CAPE) during the South Asian summer monsoon season. General circulation models (GCM) have traditionally performed poorly in simulating the precipitation over the Indian subcontinent during this season. We perform a cloud resolving model simulation with explicit microphysics over the region to investigate the convection initiation and intensification and find that the comsumption of CAPE is the consequence of propagating convective systems rather than being the cause of the convection initiation. The convection, once initiated, can get intensified by the availability of large CAPE. The mass flux based cumulus parameterization schemes which are popularly used in the GCMs and use the quasi-equilibrium assumption in some form do not simulate the initiation of the convection correctly. The vertical distribution of mass flux itself depends on the horizontal wind shear structure of the environment. This poses some serious implications on closure assumptions used in the mass flux based cumulus parameterization schemes used in the GCMs.