The Comprehensive Analysis And Study Of Boundary Layer In Wenjiang Station

Based on the boundary layer observation data of Wenjiang Station in the eastern edge of the Sichuan Basin during JICA Project, the characteristics of the turbulent variance, the diurnal and seasonal variation of sensible heat, latent heat, radiant flux and soil heat flux, energy budget closure in the near-surface layer are analyzed. Moreover, the methods of calculating the radiant flux and sensible heat flux are investigated.First, the stability parameter dependence on the normalized variance of velocity components can be fit to a power with a power index of 1/3, in accordance with the Monin-Obukhov similarity theory in the surface layer under both unstable and stable stratification. Under the near neutral condition, the similar constants are 2.34,2.30 and 1.26. The results validated the similarity theory on the flat area. The relations of normalized variances of temperature and humidity to the stability obey the law of-1/3 fractional power only under the unstable condition., the similar constants are 1.92 and 1.53. The sensible heat, latent heat and radiant fluxes show obviously diurnal and seasonal variation in Wenjiang station. Daily range of the latent heat is larger than the sensible heat flux. The sensible heat flux has small changes in the four seasons and its average intensity reaches to the maximum in spring while declines to the minimum in summer. The latent heat flux dominates throughout the year, especially in summer. The variations of effective long-wave radiation above the ground are not so far among the four seasons while the differences of net radiation are bigger, which show the seasonal differences are mainly dependent on the short-wave radiation flux. The soil heat flux shows clear diurnal variations but seasonal variations are not so obviously. Besides that, its total value of the contributions to the energy balance is small. Energy budget closure rate among May to November of 2008 is among 70% to 85%, which demonstrates the turbulence data of Wenjiang station is reliable.Second, based on general observation data of air pressure, vapor pressure, relative humidity, air temperature and surface temperature, the feasibility research of calculating radiant flux is done, using Wenjiang PBL radiant observation data verified the accuracy of the method. The results show that the method has a good effect and could be applied to calculate radiant flux in climate and climate change research, moreover, its parameterization scheme should to be further improved.Finally, based on eddy-correlation method, the three methods are compared and their feasibility is studied. The results show that the empirical formular method is simple by one layer data, but the errors are larger compared with the true value while the errors of gradient and ANN are smaller. Although the accuracy of gradient is better, it needs multilayer data to calculate flux. In fact, the climate stations have only one layer data, so there are limitations to calculate day value of fluxes. In addition, this method is complex with higher time resolution of data. The method of ANN to calculate fluxes is a new attempt and it can calculate sensible fluxes with stable data after better training.