强台风海鸥登陆期间近地层风特性分析

Analysis on Wind Characteristics in Surface Layer During Landfall of Typhoon Kalmaegi

利用位于海南文昌市的90 m测风塔观测的强台风海鸥多层测风数据,分析了台风海鸥登陆期间近地层风场时空特征、湍流强度、垂直风切变及阵风因子等风场特性,分析结果表明:台风海鸥登陆期间,近地层各高度风速呈现"M"型双峰特征,最大风速出现在台风后风圈;台风过境前后,风向旋转了180°;近地层风速随高度升高而增大,各高度风速垂直切变符合对数和指数规律;粗糙度长度、风廓线幂指数、湍流强度、阵风系数等风场特性与风速呈负相关关系,随着风速的增加而降低;从台风外围至台风眼,粗糙度长度随风速呈现"增大-减小-增大"特征;台风眼内部风速垂直切变剧烈,前后风圈的风速垂直切变较弱;强风区湍流强度较弱,弱风区湍流强度较强;台风风圈的湍流强度随高度增加而减小,台风眼内湍流强度随高度先减小再增加;台风影响各阶段阵风系数随高度升高而减小,各高度层阵风系数遵循指数定律;阵风系数随风速的增大而减小,当风速达到一定强度时,阵风系数随风速变化不明显。

Using the multilayer wind data of the Typhoon Kalmaegi from the 90 m meteorological anemometer tower in Hainan Province,this paper analyzes the spatial and temporal characteristics,turbulence intensity,vertical wind shear and gust coefficient of the surface wind during the landing of Typhoon Kalmaegi.The results show that the near-surface wind at different heights presents the ＂M＂ pattern during the typhoon＇s landfall.The maximum wind speed appears in the rear wind circle.The wind direction rotates around by 180° before and after the typhoon sweeps the area.The near-surface wind increases along speed with the increase of height.The vertical shear of wind speed at different heights accords with logarithmic and exponential rule.Roughness,wind profile exponent,turbulence intensity and gust coefficient have negative correlations with the wind speed.They decrease with the wind speed＇s increasing.The roughness characteristic is ＂increasing-decreasing-increasing＂ with the wind speed from typhoon periphery to eye.The wind speed vertical shear is strong in the typhoon eye and weak in the wind circle.The turbulence intensity is weak in the strong wind area and strong in the weak wind area.The turbulence intensity decreases with height in the typhoon wind circle but the situation is opposite in the typhoon eye.In general,the gust coefficient increases with the hight and conforms to exponential rule in different layers.In addition,the gust coefficient decreases with the wind speed until the wind speed reaches a high level.