基于风廓线雷达的广东登陆台风边界层高度特征研究

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

针对8个登陆广东省的热带气旋,利用经过数据质量控制的风廓线雷达连续、高时空分辨率的风场观测数据,对热带气旋边界层特征进行了分析。研究结果表明:热带气旋边界层中切向风速大值区垂直范围越大、风速越强、持续时间越久,则热带气旋强度越大、登陆后强度维持时间越久。眼区外入流层厚度越大,入流层气流越强,热带气旋登陆后强度维持时间则越久。风廓线雷达信噪比垂直梯度对大气湍流信息有一定的指示作用,对于入流层高度在2000 m以下的热带气旋,其入流层顶所在高度与信噪比梯度最大值所在高度相近,对于入流层较为深厚的热带气旋,用信噪比垂直梯度确定的边界层高度虽接近入流层顶高,但仍有一定差距。不同特点的热带气旋其边界层高度并不相同,对于登陆后强度迅速减弱的热带气旋边界层高度在500~1000 m;登陆后强度持续时间短的热带气旋,其边界层高度约1000~2000 m;登陆后强度持续时间长的热带气旋,其边界层高度在2000m之上,最高可达5000~7000 m。这些结果加深了对登陆台风边界层高度演变特征的认识。

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 verticalspans 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.