TURBULENCE CHARACTERISTICS OF THE ATMOSPHERIC SURFACE LAYER OVER AN OPEN GRASSLAND^*

Described in this paper is an experiment on atmosphere-surface turbulent exchange and boundary layer turbulence properties conducted in July 1994 over the Kerqin Grassland,Jilin,China.The characteristics of the turbulent spectrum,and the relationships of the standard deviation of the turbulent velocity components and sensible heat flux with the atmospheric stability are studied using data from a sonic anemometer and a fast-response platinum resistance thermometer mounted on a 100 m tower.The results show that in the surface layer over a flat,uniform and open grassland,for a broad stability range(-22.12≤ZiL≤17.98),the velocity spectra obey the-2/3 power law in the inertial subrange,and 1 power law at low frequencies.Under near neutral stratification,σu/u*=1.20,σv/u*=1.23 and σw/u*=1.02.For Zi/L≤-0.2,the standard deviations of the turbulent velocity components follow a 1/3 power law.For Zi/L≤-0.1,the standard deviation of the temperature fluctuations follows a-1/3 power law,and as Zi/L≤-0.08,it exhibits nonlinear behavior.Sensible heat flux is well correlated to the stability parameter.