Mesoscale Structure of Landfall Typhoon Khanun(0515) by Single Doppler Radar

Landfalling typhoon Khanun(0515) was observed by the CINRAD WSR-98D radar on the southeast coast of China.This study documents the structure and evolution of typhoon Khanun's circulation during its landing by using circulation derived from the Ground Based Velocity Track Display(GBVTD) technique.The axisymmetric structure analysis results are revealed as follows: Before landfall,the maximum tangential wind existed in the eyewall at about 2-km height and the radius of the maximum wind(RMW) tilted outward at about 30 degrees from the zenith.Meanwhile the inflow was confined at the low level and strong updrafts existed in both eyewall and outer rain band.During the landfall stage,the axisymmetric tangential wind decreased obviously,accompanied with slight contraction of the RMW and few fluctuation of wind speed at the low level.After landfall,the low-level inflow intensified and expanded both inward and outward in the radial direction,while the maximum tangential wind was elevated to 3-km height.Meanwhile,the updraft in outer rain band weakened obviously.The asymmetric circulation structure analysis results exhibited the distinct wave-1 structure during landfall.Both the maximum tangential wind and the maximum rainfall have remarkable regular locations in relation to the shear vector and the storm motion.Since Khanun was fast-moving typhoon and was in an environment of strong vertical wind shear,its asymmetry structure could be attributed to the influences of vertical wind shear,storm motion,and land-typhoon interaction.