In the preliminary experiment, a two-way two-nested domain is set up in ARW. The outer domain covers from 7°S to 40°N and from 40°E to 125°E which includes the entire India, the Bay of Bengal, parts of the Arabian Sea, parts of the South East Asia, and the Tibetan Plateau with 30-km horizontal resolution. The inner domain is set up with 10-km resolution to better resolve the mesoscale organizations in the depression. Boundary conditions and initial conditions are generated from the NCEP Final (FNL) global analysis and the NCEP Real-time Global Sea Surface Temperature (RTG SST) analyses.
Model sensitivity to cumulus parameterizations has been examined using Kain-Fritsch, Betts-Miller-Janjic, and Grell-Devenyi ensemble schemes. In all experiments, the initial location of the depression at the northern tip of BoB is correctly simulated; its movement towards the seasonal low over Pakistan is captured. However, the model still has difficulty realizing characteristics which would have great societal and economic impacts during the evolution of the depressions, such as the detailed trajectory and the extreme precipitation. The simulated depression moves either too slowly that consequently brings much greater accumulated rainfall for central India, or too rapidly and dissipates too soon. In contrast to the observation which shows asymmetric precipitation concentrated on the southwestern flank of the observed depression, the model rainfall tends to be symmetrically distributed. Simulations with higher resolution aimed at resolving cloud systems are to be conducted. The influence of the steady-state monsoon circulation on the formation and propagation of the depressions will be assessed. Ensemble experiments will be conducted to further quantify the dynamical predictability of monsoon depressions.