The PSU-NCAR mesoscale model MM5 with an 81-km (27-km) resolution coarse (fine) grid is used to simulate the formation of Typhoon Robyn (1993) in the western North Pacific. This study examines the roles of mesoscale convective system (MCS) during Robyn’s formation, and also focuses on the sensitivity of the simulations of Robyn’s intensification to the choice of cumulus parameterization, planetary boundary layer (PBL) parameterization, and the explicit moisture scheme in the model.
Although the magnitudes of impacts from different explicit moisture calculations are less than that of the cumulus parameterization, they do affect the intensification of Typhoon Robyn through their interaction with the cumulus parameterization. All three explicit schemes (simple ice calculation, mixed-phase model, and Schultz scheme) underestimate the intensity of Robyn. Examination of the convective rainfall shows that the deviations among these experiments are due to modified convective cloud patterns by the explicit moisture variables.