Abstract:

We analyzed the characteristics of typhoon precipitation affecting Hainan Island and atmospheric circulation, and discussed the channels and sources of water vapor supply during process of the precipitation, using tropical cyclone track database from China Meteorological Administration and precipitation data at Hainan regional station from 1986 to 2016 as well as the Lagrangian airflow trajectory model.The results show that the effect of typhoon on Hainan Island and the typhoon precipitation mainly occur from June to October.In years with higher (lower) precipitation, the effect of cold air in the south of Yangtze River and the subtropical high is both relatively weak (strong), but that of the south trough is opposite.Meanwhile, the low level vapor flux field exhibits an anomalous cyclonic (anticyclonic) circulation.In years with higher precipitation, anomalous northeasterly flows and anomalously strong southwesterly flows usually affect the Hainan Island, which mostly come from the Northwest Pacific Ocean, the Indian Ocean, and the Bay of Bengal.However, in years with lower precipitation, moisture is mainly transported by the easterly flows from the Western Pacific Ocean and weak southwesterly flows from the South China Sea.The four major water vapor sources are the Western Pacific Ocean, the Bay of Bengal, the South China Sea and the Indian Ocean.The Western Pacific Ocean and the Bay of Bengal contribute most of water vapor in years with higher typhoon rainfall, accounting for 33% and 30%, respectively.There is sufficient water vapor supply from the east and west oceans.While in years with lower typhoon rainfall, Western Pacific Ocean provides most of water vapor, accounting for 38%, and the contribution of other water vapor sources is less than 30%.The main water vapor channel is located in the east of 110°E.

Key words: Hainan Island, Typhoon rainfall, Water vapor transport, Trajectory model