Radar observation of the inner-core structures of Landfalling Typhoons in China

This study examines the inner-core structure of typhoons prior to landfall using data collected by the coastal operational Doppler radar network of China between 2005 and 2012. The modified GBVTD technique (MGBVTD) has been developed to accurately retrieve the axisymmetric circulation, asymmetric circulation and the environmental wind in the inner core of typhoons, and then applied to nine typhoon cases in China. The general characteristics of the inner-core circulation of these typhoons can be classified into three types, including decaying typhoons with a single eyewall, typhoons with concentric eyewall and rapidly intensifying typhoons. The axisymmetric wind of Khanun (0515) decreased near landfall. The asymmetric circulation intensified owing to the combined effect of vertical wind shear, storm motion and land-typhoon interaction. The evolution of the double eyewall in Saomai (0608) is a bottom-up process. The existence of vortex Rossby wave near the inner eyewall is evident and its outward propagation affects the formation of outer eyewall. The rapid intensification of Vicente (1208) was accompanied by the transition of vorticity profile from an unstable ring vorticity structure with a polygonal eyewall to a more stable monopole vorticity structure, consistent with the role of barotropic instability on the typhoon intensity change. This study will further improve our understanding of the inner core dynamics and the intensity and structure forecasts of landfall typhoons in China.