Simulation of Boundary Layer Structure over the Indian Summer Monsoon Trough during the Passage of a Depression

The planetary boundary layer (PBL) structure over the Indian summer monsoon trough region has been simulated using a regional numerical model during the passage of a monsoon depression along the monsoon trough. Monin–Obukhov similarity theory for the surface layer coupled with turbulent kinetic energy closure scheme (1½-order closure) for the mixed layer is used for parameterizing the PBL in the model. The results show that the model is able to simulate the evolution and the structure of the monsoon trough boundary layer and its associated features. The main observed characteristic features of the monsoon trough, such as the southward tilt of the trough with height and warmer air mass toward the northern side of the trough line, are simulated well by the model. Numerical results also indicate that the dynamic and thermodynamic characteristics of the monsoon trough boundary layer are modified by the passage of monsoon depressions.