Zhiying Ding Song Gao Xiaohui Zhao Liguang Wu
Key Laboratory of Meteorological Disaster of Ministry of Education, Nanjing University of Information Science and Technology, Nanjing, China
Three tropical cyclones (Goni, Morakot and Etau) formed in August, 2009 over the western North Pacific and their interactions are investigated in terms of three dimensional vorticity tubes in this study. Based on the successful simulation of the activity of the three tropical cyclones simulation with the WRF model, the associated fields of horizontal and vertical vorticity is analyzed. The results show that the interactions of the three tropical cyclones are associated with a relatively fixed mode in the vorticity tubes. While the horizontal vorticity convergence occurs below 900 hPa, the outward (inward) horizontal vortex tube is present between 900 hPa and 800 hPa (between 800 hPa and 700 hPa). The gradient of typhoon wind speed decreased and the horizontal vortex tube moved eastward to another typhoon below 850 hPa. The horizontal vortex tube converts into the vertical vorticity component due to vertical motion, intensifying the typhoon. In the presence of the interaction of three tropical cyclones, we find that the conversion can occur at a larger distance than that described in Brand et al (1970). Above 300 hPa, on the other hand, the vortex tube moved westward toward the west tropical cyclone. It is found that the horizontal vorticity is consistent with the vertical circulation of tropical cyclones, suggesting that that the horizontal vorticity is an important factor in analysis of the interactions of tropical cyclones. The detail will be presented in the conference.
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