基于风廓线雷达观测的台风“天兔”边界层演变特征研究

垂直探测台风边界层特征对于认清台风结构具有重要意义。基于1319号台风“天兔”途经的三个边界层风廓线雷达站的观测资料，结合探空数据，本文分析了“天兔”的边界层径向、切向风特征，结果表明：1）最大切向风速出现在眼区附近，在“天兔”稳定维持为强台风级别期间，最大切向风速基本稳定在1800 m高度左右，随着登陆后强度的迅速减弱，最大切向风速减弱、最大切向风速垂直范围缩小；2）最大风速所在高度和台风入流层顶高基本相近，大于依据理查森数或位温梯度所判断出的边界层高度，而基于信噪比（SNR）或其梯度所判断的混合层高度时常偏低；3）“天兔”登陆前边界层高度可以达到2100 m以上，在台风级别及以上时，各站观测到的边界层高度变化不大，基本在1200～1600 m之间，登陆后随着台风强度的减弱，边界层高度迅速减小。

The research on boundary layer evolution characteristics of Typhoon Usagi based on observations by wind profilers

Vertically exploring the characteristics of the typhoon boundary layer (TBL) plays an important role in recognizing typhoon structure. The boundary layer radial direction and tangential wind characteristics of Typhoon Usagi based on the observational data of three boundary layer wind profiler stations along the route of Typhoon Usagi (No. 1319) and by combining with sounding data. The results show that: (1) maximum tangential wind appears in the vicinity of the eye area of Usagi, and it basically maintains a height of around 1 800 m when Usagi keeps a strong typhoon level, with the rapidly decreasing strength of Usagi after it lands, the speed of the maximum tangential wind and its vertical range both decrease; (2) the height of the maximum tangential wind is close to that of the inflow layer top of the typhoon, and is greater than that of the boundary layer estimated on the basis of Richardson number or potential temperature gradient, while the height of mixed layer judged on the basis of the signal-to-noise ratio (SNR) or its gradient is usually low; (3) the the boundary layer height can reach higher than 2 100 m before Usagi lands. When the typhoon level or above is achieved, the boundary layer height observed by various stations does not change much, basically staying at between 1 200 and 1 600 m. With the decreasing strength of Usagi after its landfall, the boundary layer height rapidly drops.