华南海岸带近地层湍流参数观测研究

Observational Study on Surface-Layer Turbulent Parameters over the South China Coast

利用广州茂名2008年5月-2009年8月期间三维湍流观测资料，采用涡动相关法计算摩擦速度等湍流动力参数，研究不同风向下湍流参数随风速等的分布特征。结果发现：不同气流来向对华南海岸带局地湍流特性造成较大差异。华南海岸带近地层常年平均摩擦速度值为0．235m／s，离岸风和向岸风下分别为0．274和0．209m／s，可以分别与风速拟合为线性函数：u=0．066U＋0．060（离岸风），u=O．034U＋0．028（向岸风）。三维平均湍强值为Iu=0．136，Iv=0．121，1w=0．075，离岸风和向岸风下分别为Iu=O．245，Iv：0．199，Iw=O．125，和Iu=O．092，Iv=0．089，1w=0．055。研究还发现，拖曳系数与大气稳定度存在较密切关系，大气层结越偏向中性，拖曳系数越大，动量通量输送越强。

Based on the turbulent data collected from the South China coast from May, 2008 to August, 2009, the turbulent parameters are calculated by the eddy covariance method first, then their relations with wind speed under different wind direction are analyzed. The main finding is that different airflows cause significant different effects on turbulent characteristics over coastal zone. So when refers to problems of parameterization in the coastal boundary layer, the direction of the airflow must be seriously considered. The observed average friction velocity is 0. 235 m/s, while the values are 0. 274 m/s in offshore wind and 0. 209 m/s in onshore wind. Friction velocity increases linearly with wind speed respectively. The fitting equations are u. =0. 066U-F0. 060 in offshore wind and u. =0. 034U-F0. 028 in onshore wind. The aver- age values of the three-dimension turbulent intensities are Iu = 0. 245, Iv = 0. 199, Iw = 0. 125 under off- shore wind, and Iu=O. 092, Iv=O. 089, Iw=0. 055 under onshore wind. Drag coefficient has a close rela- tionship with atmospheric stability. The more neutral the stability approaches, the larger the drag coeffi- cient appears, and the stronger the momentum flux transports.