A Study on Boundary Layer Height Characteristics of Landing Typhoons by Wind Profilers in Guangdong Province

Based on eight tropical cyclones (TCs) landing in Guangdong Province, the boundary layer characteristics of tropical cyclones are analyzed using high spatial and temporal resolution wind profiler observations after data quality control. The results show that maximum tangential wind area exists in the tropical cyclone boundary layer. Larger vertical spans of the tangential winds, stronger tangential wind velocity, and longer duration of strong winds usually correspond to stronger and longer maintained tropical cyclone intensity. Radial inflow characteristic of landing TCs are different from each other. Larger depth of radial inflow in the outer-core region often means stronger inflow speed and longer maintenance of the TC intensity. Since the vertical gradient of wind profiler SNR (signal to noise ratio) is a good indicator of atmospheric turbulence, TC boundary layer heights evaluated by the top of the radial inflow and by the vertical gradient of wind profiler SNR are quite consistent when the depth of the radial inflow is below 2000 m, but the difference becomes larger when the depth of radial inflow is thick. The boundary layer heights of different TCs are not the same. If the TC intensity weakens rapidly after landing, the boundary layer height is within 500-1000 m. If the TC intensity maintains in a relatively short period of a few hours, the boundary layer height is within the range of 1000-2000 m. If the TC intensity maintains for a long time, the boundary layer height is above 2000 m with the maximum up to 5000-7000 m. All these results are important for us to better understand the boundary layer characteristics of TCs after their landfall.