The Coupling of Convection and Circulation of Monsoon Depressions during the South Asian Summer Monsoon
A strong MD in the well-established monsoon flow, also known as the monsoon depression (MD), during August 1 to 5 2006 has been previously simulated with ensembles of the WRF-ARW V.3.0.1 by Wang and Tung (2010). They reported that high-resolution (< O(10 km)) horizontal mesh is necessary in order to obtain realistic genesis and propagation of an MD. Beyond that, the simulation is obviously sensitive to the model moist convective processes including cumulus parameterization and, in particular in the cloud-system-resolving modeling (CSRM), the microphysical assumptions. Based upon their CSRM ensemble, further analyses to reveal how various microphysical assumptions lead to different radiative and convective heating and influence the convection-environment coupling are in progress. Preliminary kinematic analysis of the MD anomalous circulations and temperature has been performed for this ensemble, and validated with the anomalous MD structure in the reanalysis. The model and the reanalysis both show that, despite its vertically tilted structure in wind and temperature, the maximum warm anomaly within the MD is collocated with the maximum updraft over the surface precipitation maximum. This preliminarily supports the hypothesis that convective heating contributes as an energy source for the MD. The roles of convection in the MD system-wide heat and moisture balances will be evaluated by applying Q1 and Q2 analysis to both the reanalysis and the spatially-filtered CSRM simulations.