Study On Land Surface Process And Remote Sensing Application Over Semi-arid Region

It is found that biosphere activity and human activity change not only land use and land cover, but also the matter, energy and water exchange. Because of biosphere system considered, land process researches have been developed from physical process to biosphere chemical process. As the main body of land process, biosphere activity and the relations between atmosphere and human activity are needed to resolve so as to evaluate biosphere frangibility and adaptability, all these need to developing a perfect land process model for climate model.Developping a good land processing model relays on developping a perfect parameterizing project. To these days, there are more than 50 land process experiments, all these experiments paying attentions to integrate observation of the interaction between land, vegetation and atmosphere, and analyzing land process character and parameterize relation from stations to wide range by using satellite and numerical model. On the basis of above means, the land process parameterize project is developed for atmospheric numerical model. Due to complex, heterogeneous surface, and sparse vegetation, some land process experiments results have never been used by land process model and satellite retrieval method. Because continuum and real vegetation activity information can be obtained from remote sensing, the perfect land process parameterizing project for improving land process model is important aiming at sparse vegetation.The research do some experiments, by combining experiment over Dingxi station in loess plateau, with remote sensing data, the parameterize researches in heterogeneous are done, and the parameterize model for remote sensing are built. The intention of land process parameterizing is obtaining land energy, water and matter, the energy parameters are net radiance, sensible heat flux, soil heat flux and latent heat flux, water parameter is evaportranspiration, matter parameter is Npp. The prime of these parameterizing is obtaining albedo, surface and air temperature, and aerodynamic resistance and aerodynamic roughness length. According to the parameter idea, paramterizing research is performed, the aerodynamic roughness length is parameterized for the first time.BRDF model is used for geometry revising of albedo retrieval. On the air temperature parameterizing, high vertical resolution and high spectrum resolution data was used for atmospheric profile retrieved so as to obtain surface air temperature for the first time.Except for evapor-transpiration, leaf water potential is parameterized for the first time for evaluating water status.In addition, on the basis of surface temperature retrieval and energy balance and matter balance theory, land energy flux and NPP is retrieved, the parameterizeing projects were used over loess plateau, and some interesting conclusions were drawn.a. Aerodynamic roughness length project over sparse vegetation region is put forward in the research, the project replace the experience relation performed former, and help to realize roughness length over sparse vegetation. Aerodynamic roughness length is sensible to vegetation density, land cover and wind speed. Under the condition of wind speed, with increasing of vegetation amount, zero displacement height and aerodynamic roughness are increased. Under the condition of vegetation amounts, with amounts increasing, zero displacement height and aerodynamic roughness are also increased.b. On the basis of aerodynamic roughness length, aerodynamic resistance is parameterized by using Choudh-1 arithmetic, according to canopy-air temperature difference.c. Albedo and surface temperature are two important parameters. Consider the effect of sparse vegetation on multi reflecting, BRDF model was used for retrieval albedo, so as to correct geometry domino effect, and the retrieval error is about 5% for many cases. TISIE algorithm is used for retrieval surface temperature, and the retrieval error is about±1.8℃for many cases.d. Air temperature is the complex parameter with large retrieval error, and which is replaced by observed value at weather stations.The research also retrieval boundary layer temperature and surface air temperature so as to get spatial temperature. And aerosol effect on atmospheric temperature structure within boundary layer and infrared remote sensing was considered. The retrieval error was improved about 0.38K after aerosol effect was considered.e. On the basis of above parameters parameterizing and energy balance theory, matter balance theory, the model including energy, C and land process parameterize is built, the model is used in loess plateau, testing results show that the model have good effect. There are inconsistent distributing between soil humidity and vegetation fraction due to regional precipitation difference, which results three distributing modes about albedo, energy flux and evaportranspiration.f. Except evapor-transpiration, leaf water potential is deemed to another moisture parameter.On the basis of roughness length, aerodynamic resistance, albedo and temperature parameterizing, and energy balance theory, leaf water potential model is put forward, the method is realized on microcosmic water usage, and it also connected microcosmic water with macroscopical water usage. The method also has application value, which can be used for water inspecting.