Numerical simulation of the genesis of typhoon Durian (2001) over the South China Sea: The effect of sea surface temperature

Abstract

Typhoon Durian (2001), which formed over the South China Sea (SCS), was simulated by using the Weather Research and Forecasting (WRF) model. The genesis of typhoon Durian which formed in the monsoon trough was reproduced by numerical simulations. The simulated results agree reasonably well with observations. Two numerical experiments in which the sea surface temperature (SST) was either decreased or increased were performed to investigate the impact of the SST on the genesis of the typhoon. When the SST was decreased by 5°C uniformly for all grids in the model, the winds calculated became divergent in the lower troposphere and convergent in the upper troposphere, creating conditions in which the amount of total latent heat release (TLHR) was low and the tropical cyclone (TC) could not be formed. This simulation shows the importance of the convergence in the lower troposphere and the divergence in the upper troposphere for the genesis of the initial vortex. When the SST was increased by 1°C uniformly for all grids, a stronger typhoon was generated in the results with an increase of about 10 m s−1 in the maximum surface wind speed. Only minor differences in intensity were noted during the first 54 h in the simulation with the warmer SST, but apparent differences in intensity occurred after 54 h when the vortex began to strengthen to typhoon strength. This experiment shows that warmer SST will speed the strengthening from tropical storm strength to typhoon strength and increase the maximum intensity reached, while only minor impact can be seen during the earlier stage of genesis before the TC reaches the tropical storm strength. The results suggest that the amount of TLHR may be the dominant factor in determining the formation and the intensification of the TC.