登陆台风边界层风廓线特征的地基雷达观测

An analysis of the CINRAD-98D observations for the landfalling typhoon boundary layer wind profiles and their characteristics

中文关键词:  登陆台风  边界层风廓线  地基多普勒雷达  飓风速度体积分析法

英文关键词:Landfalling typhoon  Boundary layer wind profiles  Ground-based Doppler radar  HVVP method

中文摘要:

      为了分析登陆台风边界层风廓线特征,利用2004—2013年中国东南沿海新一代多普勒天气雷达收集的17个登陆台风资料,采用飓风速度体积分析方法,反演登陆台风的边界层风场结构特征。与探空观测对比表明,利用雷达径向风场可以准确地反演登陆台风的边界层风场结构,其风速误差小于2 m/s,风向误差小于5°。所有登陆台风合成的边界层风廓线显示,在近地层(100 m)以上,边界层风廓线存在类似急流的最大切向风,其高度均在1 km以上,显著高于大西洋观测到的飓风边界层急流高度(低于1 km)。陆地边界层内低层入流强度也明显大于过去海上观测,这主要是由陆地上摩擦增大引起。越靠近台风中心,边界层风廓线离散度越大,其中,径向风廓线比全风速以及切向风廓线离散度更大。将风廓线相对台风移动方向分为4个象限,分析边界层风廓线非对称特征显示,台风移动前侧入流层明显高于移动后侧。最大切向风位于台风移动左后侧,而台风右后侧没有显著的急流特征,与过去理想模拟的海陆差异导致的台风非对称分布特征一致。

英文摘要:

      In this study, 17 typhoons making landfall along the southeast China coast between 2004 and 2013 are selected to examine the characteristics of the boundary layer wind of landfalling typhoons. The wind profiles in the boundary layer are retrieved from the radial velocity data collected by ten coastal S-band Doppler radars, using the Hurricane Velocity Volume Processing (HVVP) methods. The retrieved wind profiles agree well with the sounding observations, with the root mean square errors of wind speed (wind direction) less than 2 m/s (5°). The composite wind profiles over the land exhibit a maximum tangential wind, similar to the nocturnal jet, above the surface layer (100 m) in the boundary layer. This is consistent with the results revealed by the dropsonde observations over the ocean. However, the height of the jet is above 1 km, higher than that (600 m) over the ocean. The inflow over the land in the boundary layer is much stronger than that over the ocean, due to the increase in surface friction over the land. Consistent with the observation over the ocean, the strength of the inflow is proportional to the intensity of typhoon, and the inflow depth is proportional to the distance to the typhoon center. The standard deviation errors of the wind profiles in the typhoon boundary increase toward typhoon center, indicating the distribution of the wind profiles becomes wider toward the typhoon center. Compared with the tangential wind and the total wind speed, the distribution of the inflow is the widest. Furthermore, the boundary layer wind profiles show the obvious asymmetric structures relative to the typhoon motion direction with the inflow layer being higher in the front quadrants than the rear quadrants; the most distinct jet feature exists in the left rear quadrant, while the right rear quadrant does not possess clear jet feature.