Study On Features Of Surface Energy Balance In Semi-arid Region

Using the data observed over movable dune at Naiman in Inner Mongolia, midl.-gansu region of loess plateau and the agrometeorological experiment station and meteorological station of Xifeng of Gansu province, the sensible and latent heat fluxes are calculated by the eddy correlation, Bowen ratio-energy balance and aerodynamic methods and the bulk transfer coefficients are calculated. Features of diurnal variation of the surface energy budget and the bulk transfer coefficients, the relation between the bulk transfer coefficients and the stability and the variation of water and heat in soil in semi-arid region are analyzed.1. The analysis of the surface energy budget in semi-arid region shows that, diurnal variation of the surface energy budget is obvious.In Inner Mongolia, at the daytime, most of the net radiation contributes to sensible heat flux and the soil heat flux, The ratio of the sensible heat flux to the net radiation is larger than that of the soil heat flux. In loess plateau, at the daytime, the net radiation contributes mainly to the latent heat flux, the sensible heat flux is minor and the soil heat flux is least.2. The analysis of the bulk transfer coefficients in semi-arid region shows that, diurnal variation of the bulk transfer coefficients is obvious and diurnal variation of the bulk transfer coefficient of sensible heat C_h is larger than that of the bulk transfer coefficient of momentum C_d .The value of the bulk transfer coefficient of momentum C_d is more than that of the bulk transfer coefficient of sensible heat C_h.In Inner Mongolia, the average bulk transfer coefficients of momentum and sensible heat are respectively equal to 4.69×10^-3 and 2.25×10^-3. In loess plateau: (a) in the wheat field, the average bulk transfer coefficients of momentum and sensible heat are respectively equal to 6.03×10^-3 and 3.40×10^-3. (b) in the naked field,the average bulk transfer coefficients momentum and sensible heat are respectivelyequal to 5.18×10^-3 and 4.08×10^-3. At the same observation height, C_{d wheat field}>C_{d naked field}, C_{h wheat field} < C_{h naked field}.3. At Naiman in Inner Mongolia, the turbulent variances in the surface layer satisfy the Monin-Obukhov similarity theory under the unstable stratification.4. In semi-arid area of loess plateau, under the background of the global climate warming, the trend of soil warming and drought is most obvious in spring and autumn.