The Role of High-resolution Air-Sea coupling on the Indian Monsoon

Seasonal forecasting of monsoons has always been a challenging task. This study highlights the importance of the air-sea coupling for seasonal prediction of Indian Monsoon in a regional modeling system. Sensitivity experiments at high-resolution (10 Km) were carried out using a fully coupled regional ocean-atmosphere modeling system, which contains the RSM (Regional Spectral Model) as the atmospheric part and ROMS (Regional Ocean Modeling System) as the ocean counterpart. The RSM has 28 terrain following sigma levels that is identical to the NCEP-DOE reanalysis, while ROMS has 30 vertical ocean sigma levels. High-resolution ETOPO5 bathymetry is used in ROMS for coupled simulation. The RSM and ROMS share the same domain and resolution to avoid interpolation between ocean and atmosphere model grids. SST flux is exchanged between atmosphere and ocean model without using any SST-flux coupler. Coupled downscaling is a free run without any heat or salinity corrections. Seasonal Forecast from Climate Forecast System (CFSv2) is used at lateral boundaries. SST’s from CFS forecasts are provided to RSM for uncoupled experiment. Analyses of the results shall be presented.