A Study on Energy Balance and Transfer in the Surface Layer over SemiArid Grassland of Nyainrong Area in Central Tibetan Plateau in Summer

Based on gradient and turbulence data observed in the near surface layer over semi-arid grassland of Nyainrong area in the central Tibetan Plateau from 18 July 2014 to 31 August 2014, characteristics of several basic meteorological elements and energy balance and transfer are analyzed. The main results are:(1) The downward and upward short-wave radiation and net radiation fluxes have a similar diurnal variation pattern, and the diurnal fluctuation of the downward and upward long-wave radiation fluxes are small. The surface albedo shows a "U" type distribution with large values in the morning and evening and small values in the noon. The mean surface albedo over Nyairong area in summer is 0.20. (2) The latent heat flux is obviously larger than the sensible heat flux, which indicates that the latent heat plays a dominate role in the heat transfer between the atmosphere and surface. The closure rate of surface energy balance increases significantly from 0.65 to 0.80 after considering the heat storage in the shallow soil layer and heat advection caused by vertical movement. (3) The bulk transfer coefficients CD and CH for momentum and heat are 4.7×10^-3 and 3.5×10^-3 respectively under unstable stratification; their values are 3.4×10^-3 and 1.8×10^-3 under stable stratification, and 4.30×10^-3 and 2.39×10^-3 under near neutral stratified condition.