Analysis of Turbulent Characteristics in the Surface Layer in Litang Region on the East Edge of Tibetan Plateau

A comprehensive field experiment of atmospheric boundary layer over grassland surface is introduced.The experiment has been held in Litang region on the east edge of Tibetan Plateau by IPM,CMA(Institute of Plateau Meteorology,China Meteorological Administration) since November 2005.Some micrometeorological characteristics of wind speed,wind direction,atmospheric stability,and turbulent intensity,variance similarity,surface fluxes in the near-surface layer are analyzed and compared based on the observational data acquired by using the eddy correlation method in January and July 2006(representing winter and summer,respectively).The main results are as follows: Atmospheric stability mostly varies from-0.5 to 0.5 in January,from-0.25 to 0.25 in July.Turbulence is very active when wind speed is less than 2 m·s-1 and decreases rapidly as wind speed increasing.The normalized variance of three-dimensional winds and z/L satisfies the similarity under both unstable and stable stratification,their universal functions also can be fitted according to the law of 1/3 fractional power.The diurnal variations of surface fluxes are evident,and sensible heat flux is leading,latent heat flux is very weak in January while reversely in July.