Dynamic Impact of the Vertical Shear of Gradient Wind on the Tropical Cyclone Boundary Layer Wind Field

• Published in: Acta meteorologica Sinica Vol. 28; no. 1; pp. 127 - 138
• Main Author: 蔡凝昊 徐昕 宋丽莉 白莉娜 明杰 王元
• Format: Journal Article
• Language: English
• Published: Heidelberg The Chinese Meteorological Society 01.02.2014; Key Laboratory of Mesoscale Severe Weather of Ministry of Education, School of Atmospheric Sciences, Nanjing University, Nanjing 210093%Public Meteorological Service Center, China Meteorological Administration, Beijing 100081%Shanghai Typhoon Institute of China Meteorological Administration,Shanghai,200030
• Subjects: Atmospheric Protection/Air Quality Control/Air Pollution; Atmospheric Sciences; Earth and Environmental Science; Earth Sciences; Ekman抽吸; Geophysics and Environmental Physics; Meteorology; 垂直切变; 径向速度; 梯度风; 热带气旋; 自由大气; 边界层; 风场; tropical cyclone; vertical shear; gradient wind; boundary layer
• ISSN: 0894-0525; 2191-4788
• DOI: 10.1007/s13351-014-3058-y

This work studies the impact of the vertical shear of gradient wind （VSGW） in the free atmosphere on the tropical cyclone boundary layer （TCBL）. A new TCBL model is established, which relies on five- force balance including the pressure gradient force, Coriolis force, centrifugal force, turbulent friction, and inertial deviation force. This model is then employed to idealize tropical cyclones （TCs） produced by DeMaria＇s model, under different VSGW conditions （non-VSGW, positive VSGW, negative VSGW, and VSGW increase/decrease along the radial direction）. The results show that the free-atmosphere VSGW is particularly important to the intensity of TC. For negative VSGW, the total horizontal velocity in the TCBL is somewhat suppressed. However, with the maximum radial inflow displaced upward and outward, the radial velocity notably intensifies. Consequently, the convergence is enhanced throughout the TCBL, giving rise to a stronger vertical pumping at the TCBL top. In contrast, for positive VSGW, the radial inflow is significantly suppressed, even with divergent outflow in the middle-upper TCBL. For varying VSGW along the radial direction, the results indicate that the sign and value of VSGW is more important than its radial distribution, and the negative VSGW induces stronger convergence and Ekman pumping in the TCBL. which favors the formation and intensification of TC.