Abstract:
Tropical cyclones (TCs) often bring about heavy rainfalls when they make landfall. Generally rainfalls gradually diminish after their landfall. However, some landfalling TCs may produce even stronger rains than those during their landfalling. Such precipitation reinvigorating phenomena are known as rainfall reinforcement associated with landfalling tropical cyclones. Taking use of the NCEP/NCAR reanalysis data and a dynamic composite technique, the characteristics of atmospheric large scale circulation of rainfall reinforcement associated with landfalling tropical cyclones are investigated. The results show that the rainfall reinforcement with the TCs is mainly attributed to the strong divergence to the south side of the high level jet entrance, their interaction with the westerly trought, and the low level jet and vapor flux maintenance as well as a secondary circulation to the east of the TCs. While for the TCs without rainfall reinforcement, there is the weak high level divergence, no westerly trough interaction aloft, the low level jet and vapor flux weaken quickly after their landfall and no secondary circulation. There is prominent ageostrophic motion in the high levels for the TCs with rainfall reinforcement, in which strong subageostrophic motion in the souther jet entrance has a close relation to rainfall reinforcement.