The bulk transfer coefficients and surface fluxes on the western Tibetan Plateau

On the gradient observational data of the atmospheric surface layer from September 1997 to December 1998 collected by two sets of Automatic Weather Station (AWS) installed in Gaize and Shiquanhe on the western Tibetan Plateau, mean surface roughness lengths at the two stations above are determined to be 2.7 and 2.9 cm, respectively. The bulk transfer coefficients each day are computed by the profile-flux method, means of the bulk transfer coefficient for momentum (i.e. drag coefficient) in 1998 are 4.83×10⁻³ and 4.75×10³ at the two stations. The surface fluxes of momentum, sensible heat and latent heat each day are further estimated by the bulk formulas, annual mean of these fluxes is 3.4×10⁻² and 1.8×10²N/m², 73.1 and 67.2 W/m², 15.4 and 2.9 W/m², respectively. The diurnal and seasonal variations are obtained by a composite method and the relationships among the heat transfers between land and atmosphere, plateau monsoon and plateau rain season are also discussed.