Analyses of turbulent fluxes and micrometeorological characteristics in the surface layer at Litang of the eastern Tibetan Plateau.

A comprehensive field experiment of atmospheric boundary layer is briefly introduced. The experiment was held in Litang area of eastern Tibetan Plateau in November 2005. By using the observational data in January and July of 2006 which represent winter and summer season respectively, some micrometeorological characteristics and turbulent fluxes transport are preliminarily analyzed and compared. The main results are as follows: (1) Marked diurnal variations of wind speed, air temperature and relative humidity are found. Wind speed is higher in winter than in summer, and its maximum value occur in the afternoon in both winter. In winter, air temperature gradient is higher in the night time and early morning than in the daytime, while it is smaller in summer. Humidity gradient and summer is higher in the night time than in the daytime. (2) Wind speed profiles generally accord with the logarithm law. Temperature inversion phenomenon always occurs in the night time, and weak humidity inversion sometimes happens above a certain height. (3) In winter, sensible heat flux is large and latent heat flux is very small, while in summer latent heat flux is overwhelming, but the value of sensible heat flux is also large. Furthermore, turbulent fluxes and carbon dioxide flux in winter are much less than in summer, but momentum flux is on the contrary. Soil heat flux also presents an obvious diurnal variation at the depth of 2 and 5 cm. (4) Surface heat source shows a diurnal variation remarkably: strong heat source appears in the daytime and it is not very evident in the night time. On daily average, heat source dominates in both winter and summer, but it is stronger in summer (about 134 W/m 2) than in winter (about 35.3 W/m 2).