Effects of Domain Choice on the Simulation of Tropical Storms Activity in the WRF 30-km Regional Climate Model

The climatological feature of tropical storms (TS) activity over the western North Pacific from 2000 to 2010 are simulated by the Weather Research and Forecasting (WRF) Regional Climate Model (RCM) at 30-km resolution with three different domains to investigate the relative contributions from tropical Eastern Pacific Ocean, Indian Ocean and land-sea contrast. The results show that the gross features of large-scale circulations are well captured by all three experiments. Nevertheless, monsoon troughs are too strong, while subtropical highs are too weak in two experiments without Indian Ocean and Asian continent. Associated with these simulation discrepancies, the TS genesis numbers are overestimated and TS genesis location shifts to the east and north of the observation in these two experiments. With the inclusion of Indian Ocean and land-sea contrast in the third numerical experiment, the monsoon trough and TS activity are well represented in the numerical simulation. In addition, the enhancement (reduction) of TS activity during intraseasonal oscillation westerly (easterly) phase is well simulated in the experiment. This indicates that TS activity, intraseasonal oscillation and monsoon trough are influenced not only by the tropical Eastern Pacific Ocean, but also by the Indian Ocean and land–atmosphere interaction. It is suggested that the TS activity over the western North Pacific is strongly influenced by the Indian Ocean SST and may be simulated by WRF Regional Climate Model at 30-km resolution with a large domain covering the central Pacific and Indian Ocean.