强台风纳沙 (1117) 近地层风特性观测分析

根据琼州海峡两岸2个梯度塔和1部车载风廓线雷达共同获取的强台风纳沙 (1117) 实测风速资料，分析强台风纳沙影响期间大风特性，发现以下观测事实和变化规律:位于台风移动路径右侧的测风站，其风向呈顺时针方向旋转，台风眼区经过的测风站，其最大风速接近35 m·s-1，且风向旋转超过180°，台风外围大风区经过的测风站其最大风速达到30 m·s-1，风向旋转73°；大风风切变过程可用对数函数和指数函数拟合，对数函数和指数函数对光滑下垫面的拟合效果更好，且对数函数拟合效果要略优于指数函数；阵风系数随风速增大而减小，但风速达到6级以后，阵风系数不随风速大小产生趋势变化，阵风系数与下垫面粗糙度有关，在粗糙下垫面上阵风系数会偏大；大风阵风系数随高度变化可用指数函数来描述，且对来自光滑下垫面的近地层大风阵风系数拟合效果更好。该观测个例的大风风切变指数与GB/T 18710—2002的推荐值存在差异——粗糙下垫面的大风风切变指数大于标准推荐值，而来自光滑下垫面的大风风切变指数则小于GB/T 18710—2002的推荐值。

Observation and Analysis on Qiongzhou Strait Gales of Severe Typhoon Neasat (2011)

Based on wind data of a severe typhoon observed by two meteorological towers and one motive wind profile radar which are located on both sides of Qiongzhou Strait at the inshore sea, the gale features of the severe typhoon Neasat (2011), maximum wind speed, gust factor and wind profile index variation characteristics of typhoon Neasat (2011) are analyzed.On the right side of the typhoon path, the wind direction is clockwise on the Northern Hemisphere; the maximum 10-minute average wind speed observed in typhoon eye district is near 35 m·s-1, and the wind direction rotation is over 180°; the maximum 10-minute average wind speed in periphery district is near 30 m·s-1, and the wind direction around has rotated by 73°. Wind shear process can be fitted by exponential function and logarithmic function, which both fit well for smooth underlying surface, and the logarithmic function is slightly superior to exponential function.Gust factor decreases with increasing wind speed until the wind speed reaches level 6, and rougher underlying surface leads to bigger gust factor.The relation between wind gust factor and the height can be fitted by exponential function, especially when the surface is smooth.Compared with GB/T 18710—2002 recommended value, the gale shear index calculated over rough underlying surface during typhoon Neasat (2011) is higher than the recommended value, while over the smooth underlying surface it is lower than the recommended value.