Causes of wave number-1 asymmetric rainfall distribution of tropical storm Bilis (2006) during its landfall

The mesoscale numerical model WRF-ARW was used to simulate iment and two sensitivity experiments in which the effects of terrain and Bilis (2006) in a control experunderlying surface factor were studied. The dynamic factors to form wave number-1 asymmetric rainfall structure of Bilis (2006) during its landfall were diagnosed. The results of the three experiments were analyzed comprehensively to show that the influence of environmental vertical wind shear on wave number-1 asymmetric rainfall structure of Bilis was significantly more important than the terrain, change of underlying surface properties during landfall, and storm speeds. On the other hand, the intrusion of cold air also played an important role in forming local rainfall. Heavy rainfall formed in downshear left quadrant under the effects of vertical wind shear, while heavy precipitation appeared in downshear direction and downshear right quadrants due to vertical shear and the intrusion of modest cold air.