Analysis of land surface parameters and turbulence characteristics over the Tibetan Plateau and surrounding region

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• 作者：Yinjun Wang ; Xiangde Xu ; Huizhi Liu ; Yueqing Li ; Yaohui Li ; Zeyong Hu ; Xiaoqing Gao ; Yaoming Ma ; Jihua Sun ; Donald H. Lenschow ; et al
• 刊名：Journal of Geophysical Research: Atmospheres
• 出版年：2016
• 出版时间：27 August 2016
• 年：2016
• 卷：121
• 期：16
• 页码：9540-9560
• 全文大小：5.9MB
• ISSN：2169-8996

文摘

Based on the results from 11 flux sites during the third Tibetan Plateau (TP) Experiment (TIPEX III), land surface parameters and the turbulence characteristics of the atmospheric surface layer over the TP and surrounding region are analyzed. Monin-Obukhov similarity theory has been used to calculate the aerodynamic roughness length z_0m and the excess resistance to heat transfer kB^− 1 = ln(z_0m/z_0h), and the factors that cause variations of z_0m and kB^− 1 are investigated. The main drivers for the diurnal variations of surface albedo (α) at different sites are solar elevation, solar radiation, and soil moisture. The eddy correlation method is utilized to inversely calculate bulk transfer coefficients for momentum (C_D) and heat (C_H) at different sites. The relationships between C_D and C_H and the wind speed at 10 m follow a power law for unstable stratification. For stable stratification, both C_D and C_H increase with increasing wind speed when wind speed is less than 5 m/s. Diurnal variations of turbulent fluxes are compared at different sites, and the relationships between turbulent fluxes and other variables are analyzed. Wind speed variance normalized by the friction velocity (σ_u/u_*, σ_v/u_*, σ_w/u_*) for neutral stratification (C_u1, C_v1, C_w1), and temperature and humidity variance normalized by a temperature and humidity scale (σ_T/T_*, σ_q/q_*) under free convection (z/L < −0.1) (C_T, C_q) are fitted with similarity relations. The differences in similarity constants (C_u1, C_v1, C_w1, C_T, C_q) at different sites are discussed. For stable stratification, cases are divided into weakly stable conditions and intermittent turbulence, and the critical values for these two states are determined. Shear and buoyancy terms in the turbulence kinetic energy equation for different stratifications are analyzed.