Interaction of Tropical Cyclone and Summer Monsoon over South China Sea

Interaction of tropical cyclone and South China Sea(SCS) summer monsoon,especially the mechanism for intensification of low level jet over SCS caused by tropical cyclone landfall,is discussed base on case study and statistical analysis.In case study,different sets of numerical experiments during the landfall of tropical storm BILIS(0604) are carried out using mesoscale model MM5.Result shows that the moist southwestly summer monsoon retarded the decay of tropical cyclone and enhanced the rainfall.On the other hand,the backward reaction from tropical cyclone to low level jet over SCS cannot be ignored.Mesoscale convection systems accompanied with tropical cyclone landfall would enhance the pressure gradient force in low atmosphere over SCS,which would lead to intensification of the low level jet in summer monsoon.Statistical analysis of 30 tropical cyclones with similar track as BILIS dating from 1950 to 2009 also shows that 80% tropical cyclone activities accompany with positive low level wind speed anomaly in SCS.