This study examines the modulation of tropical cyclogenesis over the South China Sea （SCS） by the E1 Nifio-Southem Oscillation （ENSO） Modoki during the boreal summer. Results reveal that there were more tropical c...This study examines the modulation of tropical cyclogenesis over the South China Sea （SCS） by the E1 Nifio-Southem Oscillation （ENSO） Modoki during the boreal summer. Results reveal that there were more tropical cyclones （TCs） formed over the SCS during central Pacific warming years and less TC frequency during central Pacific cooling years. How different environmental factors （including low-level relative vorticity, mid-level relative humidity, vertical wind shear, and potential intensity） contribute to this influence is investigated, using a genesis potential （GP） index developed by Emanuel and Nolan. Composite anomalies of the GP index are produced for central Pacific warming and cooling years separately, which could account for the changes of TC frequency over the SCS in different ENSO Modoki phases. The degree of contribution by each factor is determined quantitatively by producing composites of modified indices in which only one of the contributing factors varies, with the others set to climatology. The results suggest that the vertical wind shear and low-level relative vorticity, which are associated with the ENSO Modold-induced anomalous circulations in Matsuno-Gill patterns, make the largest contributions to the ENSO Modoki modulation of tropical cyclogenesis over the SCS as implied by the GP index. These results highlight the important roles of dynamic factors in the modulation of TC fre-quency over the SCS by the ENSO Modold during the boreal summer.展开更多
基金funded by the Strategic Priority Research Program of the Chinese Academy of Sciences with Grant No.XDA11010000the National Natural Science Foundation of China (No.41205026)+6 种基金the National Basic Research Program of China (2011CB403500)the Innovation Group Program of State Key Laboratory of Tropical Oceanography (LTOZZ1201)Dr.Lei Wang was also sponsored by the Knowledge Innovation Program of the Chinese Academy of Sciences (SQ201208)the foundation for returned scholars of Ministry of Education of Chinathe specialized research fund for the doctoral program of Higher Education for Youthsthe foundation of Guangdong Educational Committee for Youths (2012 LYM_0008)the open fund of the Key Laboratory of Ocean Circulation and Waves of Chinese Academy of Sciences (KLOCAW1309)
文摘This study examines the modulation of tropical cyclogenesis over the South China Sea （SCS） by the E1 Nifio-Southem Oscillation （ENSO） Modoki during the boreal summer. Results reveal that there were more tropical cyclones （TCs） formed over the SCS during central Pacific warming years and less TC frequency during central Pacific cooling years. How different environmental factors （including low-level relative vorticity, mid-level relative humidity, vertical wind shear, and potential intensity） contribute to this influence is investigated, using a genesis potential （GP） index developed by Emanuel and Nolan. Composite anomalies of the GP index are produced for central Pacific warming and cooling years separately, which could account for the changes of TC frequency over the SCS in different ENSO Modoki phases. The degree of contribution by each factor is determined quantitatively by producing composites of modified indices in which only one of the contributing factors varies, with the others set to climatology. The results suggest that the vertical wind shear and low-level relative vorticity, which are associated with the ENSO Modold-induced anomalous circulations in Matsuno-Gill patterns, make the largest contributions to the ENSO Modoki modulation of tropical cyclogenesis over the SCS as implied by the GP index. These results highlight the important roles of dynamic factors in the modulation of TC fre-quency over the SCS by the ENSO Modold during the boreal summer.
