台风“妮妲”(1604)登陆期间近地层风特性分析

The analysis of the near-surface wind characteristics during the landfalling of Typhoon Nida (1604)

利用深圳350 m气象梯度观测铁塔获取的台风"妮妲"(1604)登陆期间近地多层风观测资料,分析"妮妲"登陆期间风场和阵风系数等变化特征。结果显示:"妮妲"登陆期间,近地面风速随时间呈增强—减弱—增强—减弱的"M"型特征,风向由西北方向转为南东南;风速随高度增加而增加,其中风速垂直变化最大的时段为"妮妲"后风圈经过期间;垂直方向上,"妮妲"前外围向前风圈过渡期间风向多变,而其他时段风向随高度基本不变;在"妮妲"前外围、前风圈和眼区经过期间,350 m高度以下的风速随高度的变化遵循对数关系,而在"妮妲"后风圈和后外围时段仅适用于150 m以下高度;在"妮妲"登陆过程中,铁塔观测的粗糙度长度约为0.52 m;阵风系数随高度增加而减小,"妮妲"登陆前和眼区的阵风系数较大;另外,阵风系数与风速呈负相关关系,随着风速增加而减小,尤其是风速小于10 m/s时。

Using the observed muhilayer near-surface wind data from the 350 m meteorological gradient observation iron tower in Shenzhen city, the variation characteristics of wind field and gust factor are analyzed during the landfalling of Typhoon Nida （1604） in August 2016. The results show that the near- surface wind speed at different heights presents the ＂M＂ pattern （increasing-decreasing-increasing- decreasing） with time, and the wind direction shifts from northwest to the south-southeast during the landing of the tropical cyclones. The wind speed increases with the increased height and the maximum vertical variation of the wind speed appears in the rear wind circle. In vertical direction, the wind direction is highly variable during the period from the front periphery to the front wind circle, while it remains ahnost unchanged with height during other periods. The vertical variation of wind speed follows logarithmic rule below 350 m during the periods of the front periphery, the front wind circle and the typhoon eye, while it only confirms to the same rule below 150 m during the periods of the rear periphery and the rear wind circle. During the landing of the Typhoon Nida, the roughness length observed from iron tower is about 0. 52 m. Gust factor is decreased with the increased height, and its value is larger during the periods of the front periphery and the typhoon eye. Moreover, there is a negative correlation between gust factor and wind speed. The gust factor is decreased with increasing wind speed, especially when the wind speed is less than 10 m/s.