| Located in the eastern part of our country, with the fast urbanization, Yangtze Delta now is the largest river delta, most rapidly developing, most complete and most potential economic belt in China. As the center of the Yangtze Delta, Shanghai is the most developed area of economic, financial, trade and traffic in China. Vigorously develop brought Shanghai huge changes, at the same time these changes will inevitably lead to land cover changes, thus changing the regional evapotranspiration, then influence the local climate.Evapotranspiration is a component of water balance and surface heat balance, while heat and moisture budget determine the changes of climate, thus, evapotranspiration plays an important role in urban climate. Evapotranspiration process is not only related to soil, vegetation, atmosphere which is closely related with the climate complex process, but also the key of improving the atmospheric circulation pattern. So, surface evapotranspiration research at home and abroad has been the research focus for many years.In recent 30 years, with the rapid development of remote sensing technology, computer technology and the mathematical method, satellite remote sensing has become one of the most important methods to estimate the regional evapotranspiration all around the world.Taking Shanghai as the research area, with the help of remote sensing and geographic information system, research regional evapotranspiration, regional surface parameters and surface radiation fluxes were studied, which can be summarized as:1,Data selection. This paper using NOAA-AVHRR remote sensing data, eliminate the cloud situation, choose the satellite data in June 2008 to June 2009 (2008 7-5,7-15,10-14,10-15,12-1,12-5,12-6,12-9 and 12-12,12 to 14,12-16, 200 91-11,1-13,1-14,2-10,2-11,2-12,3-26,4-9,4-29,5-6,5-7,5-8) about 23 of remote sensing image data, calculation these days' Shanghai regional surface parameters, energy fluxes and evapotranspiration.2,Surface parameters calculation. Through different retrieval model, this paper respectively calculated Shanghai regional land surface albedos (α), land surface emissivity (ε), normalized difference vegetation index (NDVI) and land surface temperature (Ts). These surface parameters are the base of calculating surface fluxes and evapotranspiration.3,Surface radiation fluxes calculation. Proving the land surface temperature by the ground measured data gained from stations including Xujiahui, Pudong, Baoshan, Jiading, Minhang, Qingpu, Songjiang, Jinshan, Fengxian, Nanhui.Useing surface parameters calculate net radiation flux, soil heat flux, latent heat flux and sensible heat flux, and these surface parameters and surface fluxes are the base of calculating evapotranspiration.4,Evapotranspiration Rertrieval. According to the theory of surface energy balance obtained surface energy balance formula:LE=Rn-H-G, using latent heat flux gained before and formula ET=3600*LE/2460000, calculatd the instantaneous evapotranspiration, then calculatd average daily evapotranspiration.5,Using measured data proving retrieval result. This paper use ground stations including data from Xujiahui, Pudong, Baoshan, Jiading, Minhang, Qingpu, Songjiang, Jinshan, Fengxian, Nanhui. Analysis the precision of retrieval data by using ground stations'land surface temperature and daily evapotranspiration data.6,Comparative analysis regional evapotranspiration and city heat island. Comparative analysis remote sensing Shanghai regional retrieval daily evapotranspiration data and the model simulation urban heat island data.This paper based on the surface energy balance system (SEBS), through the calculation of the land surface albedo, land surface emissivity normalized difference vegetation index and land surface temperature, further retrieval net radiation flux, soil heat flux and latent heat flux, then calculate the instantaneous evapotranspirationand average daily evapotranspiration. Study the Shanghai regional evapotranspiration, understand the distribution of water evapotranspiration and the influence of urban climate by evapotranspiration. |
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