稳定条件下盆地上空大气边界层湍谱特征

TURBULENT SPECTRAL CHARACTERISTICS OF THE STABLE ATMOSPHERIC BOUNDARY LAYER OVER A BASIN TERRAIN

本文利用100m^3系留气艇携带超声风温仪在复杂的盆地地形上空对1000m以下大气进行观测所获得的资料,研究小风稳定条件下大气边界层湍流结构特征。结果表明,在双对数坐标中,纵向速度u谱,垂直速度w谱,温度T谱在惯性区均遵循Kolmogorov的-2/3次律;横向速度V谱有其特殊的情形;协谱uw,wT及近地层的uT协谱在惯性区服从-4/3次律。和平坦、均一、开阔下垫面不同的是谱的峰值频率向高频移动,且没有发现近地层具有的谱峰随高度的明显变化关系。

To investigate the influence of the terrain on the turbulent structure, the turbulent characteristics under light wind and stable atmospheric boundary layer conditons over a basin terrain has been examined using wind and temperature fluctuation data obtained with a kytoon-mounted ultrasonic anemometer-thermometer system in the winter of 1986 at Chengde Atmospheric Observatory in North China. The result shows that in the inertial subrange, the logarithmic spectra of velocity components u, w and temperature T fall as f-2/3, which agree with Kolmogorov's local isotropy theory. The logarithmic spectrum of lateral velocity component v has an exceptional case. The logarithmic cospectra uw and wT fall asf-4/3. The behavior of the reduced peak frequency fm shows that the turbulence range moves toward high frequency due to the terrain influence. The heavily dependence of spectra or cospectra on height, which exists in flat, uniform, and open underlying surface, disappears in the complex terrains.