The influence of thermal states in the warm pool on tropical cyclones （TCs） in the westem North Pacific （WNP） is investigated. There are fewer typhoons during warm years of the warm pool in which tropical storms t...The influence of thermal states in the warm pool on tropical cyclones （TCs） in the westem North Pacific （WNP） is investigated. There are fewer typhoons during warm years of the warm pool in which tropical storms tend to form in the northwest quadrant and move westward. Inversely, typhoons tend to recurve northeastward to the southeast of Japan and increase in number in the southeast quadrant during cold years. Based on composite analyses, circulation-induced dynamic factors rather than thermal factors are identified as being responsible for TCs activities. During the warm state, the monsoon trough retreats westwards, which leads to anomalous vorticity in low-level and divergence in high-level in the western part of west Pacific. Above-normal TCs activity is found in this area. Furthermore, wind anomalies at 500 hPa determine the main track types. On the contrary, when the warm pool is in cold state, the atmospheric circulation is responsible for the formation of more TCs in the southeast quadrant and recurving track.展开更多
基金Natural Science Foundation of China (40575026)Natural Key Science Foundation of China(40231005)+1 种基金Key Directional Project for Knowledge Innovation Engineering from Chinese Academy of Sciences(KZCX2-SW-210)Key Planning for National Research and Development (2004CB1803)
文摘The influence of thermal states in the warm pool on tropical cyclones （TCs） in the westem North Pacific （WNP） is investigated. There are fewer typhoons during warm years of the warm pool in which tropical storms tend to form in the northwest quadrant and move westward. Inversely, typhoons tend to recurve northeastward to the southeast of Japan and increase in number in the southeast quadrant during cold years. Based on composite analyses, circulation-induced dynamic factors rather than thermal factors are identified as being responsible for TCs activities. During the warm state, the monsoon trough retreats westwards, which leads to anomalous vorticity in low-level and divergence in high-level in the western part of west Pacific. Above-normal TCs activity is found in this area. Furthermore, wind anomalies at 500 hPa determine the main track types. On the contrary, when the warm pool is in cold state, the atmospheric circulation is responsible for the formation of more TCs in the southeast quadrant and recurving track.
