南沙永暑礁近海面风的特征分析

选用南沙永暑礁1989年1月到2009年12月的水文气象月报表资料,运用概率统计的方法将风向和风速记录资料进行分析,定义了永暑礁的4个风期,通过风向风速的年内变化分析得出永暑礁盛行风风向在年内变化成顺时针向右偏移;无论是东北季风期,还是西南季风期,盛行风平均风速都大于非盛行风。东北季风期主导风向顺时针偏移时风力减小,西南季风期主导风向顺时针偏移时,到南南西风时最大,在西南风时略有减弱,呈现波状发展趋势。通过引入风速不稳定指数概念,发现永暑礁西南季风期风速变化突然,更不稳定。

Characteristic Analysis of Near Surface Wind around Fiery Cross Reef of Nansha Islands

Statistics of probability is applied to the analysis of wind speed and direction by using hydro-meteorological data of Fiery Cross Reef from Jan1989 to Dec 2009, and four wind seasons are defined within a year. The seasonal shifting of wind direction is a clockwise variation. Average wind speed of the prevailing wind is larger than non-prevailing ones in either north- east monsoon season or southwest monsoon season. In northeast monsoon season, prevailing wind speed tends to decrease dur- ing clockwise shifting of wind direction. While in southwest monsoon season, prevailing wind speed varies in wave pattern, and reaches its peak at south-southwest direction during clockwise shifting of wind direction. Velocity instability index is introduced to show that wind speed change more rapidly and unstably near Fiery Cross Reef.