北京北郊冬季大风过程湍流通量演变特征的分析研究

利用中国科学院大气物理研究所325 m气象观测塔1993年12月～1994年1月大气边界层实验资料, 计算分析了大风过境过程中47 m和120 m高度湍流通量演变特征及其影响因子, 以及与风速、 稳定度等参数的关系。结果表明: 大风过程对近地面层的物质能量输送有着重要影响, 大风之前出现短时间动量上传和热量下传; 大风过程中的湍流通量数值明显高于过境后, 水平方向湍流通量数值和能量增加幅度大于垂直方向; 当风速大于临界值5 m/s时, 湍流通量与风速、 湍流动能的相关迅速增大; 湍流谱特征表现为湍流能量的低频部分增加、 湍流谱曲线变宽; 大风能强烈影响近地面层的能量收支。

Characteristics of Turbulent Transfer during the Strong Wind Period in the Northern Suburbs of Beijing

Based on the data collected from the 325-m meteorological tower operated by the Institute of Atmospheric Physics of Chinese Academy of Sciences in the northern suburbs of Beijing during the period from December 1993 through January 1994, the characteristics of the turbulent fluxes measured at the heights of 47 m and 120 m, and their variations with respect to the wind speed and stability parameters during the passage of strong wind are analyzed. The results indicated that the strong wind has great influence on the turbulent transfer in the near surface layer. There is a short period before the strong wind when the momentum flux is upward, and the heat flux is downward. The turbulent fluxes during the strong wind episode are obviously larger than those after the passage of strong wind. The horizontal turbulent fluxes and the energy increment are larger than the vertical values. The correlations between the turbulent fluxes and the wind speed, and turbulent kinetic energy increase rapidly when the wind speed exceeds the threshold value. The low-frequency component in the spectrum of turbulence rises, and the turbulent spectral curve widens. The energy budget in the surface layer can be strongly influenced by the strong wind.