The Research Of Evapotranspiration In Yangtze Delta Based On RS And GIS

The Yangtze Delta is one of region, which is the most dense population, the most developed economy, the highest citilization and economy going up most quickly in China. With the construction of the PuDong borough in Shanghai, its economic development will bring important influence on the whole drainage area of the Yangtze, even on the whole country. But at present, the region is faced the question that the environment developed laggard, even suffered serious destruction .Therefore , it's very urgent to work over the Yangtze Delta environment. Especially to gain all kinds of surface parameter , which is urgent affairs to provide a technical support and decision-making gist for a sustainable development to this region.When 21st century is coming ,it's more and more urgent to require geography to be developed in ration and in multi-dimension .This is inevitable trend in the future too. The reciprocity between terrene surface with atmosphere is one of the important research content on geography, what's more , it's the key in many fields. Especially, global transformation , the water balance, carbon balance and drought forecast in district, etc , which all require quantitative surface flux .By all appearances, these fluxes all don't need to be distributed in spots, but in area.In the latest decades , to utilize Remote sensing data to calculate regional surface flux is paid more and more importance attention to by people. Surface parameters is retrieved from Remote Sensing ,which is the main connotation of the surface flux retrieved from quantitative Remote Sensing model. This is because the surface parameters is not only dominant in the reciprocity of earth and atmosphere, but also are closely linked with all aspects of environment.Whereas all above, in this dissertation Remote Sensing(RS) and Geographical Information System(GIS) methods are used for the research of surface parameters, regional surface flux and ET of the Yangtze Delta. The main contents are as follows: (1)RS method is used for the research of all surface parameters. One AVHRRimage of the Yangtze Delta at 13:00 on 15th Apr., 2003 is used to retrieve the regional parameter such as surface albedo , NDV1 , surface emissivity and surface temperature , which is based on regional trait of the Yangtze Delta to choose different model. All above will give a methodological support to gain the regional surface parameters, what's more , it will afford the parameter support to calculate the regional ET too.(2)Based on gaining the surface parameters, to compare to diversified retrieve model to choose optimal one to retrieve net radiance flux , soil heat flux and latent heat flux , which settle the groundwork to calculate the regional ET .(3)Evapotranspiration(ET) is an important parameter for water resource management. Compared to the traditional ET computation methods, the ET computation method based on Remote Sensing has the characteristics of quickness, precision, large-scale and visualization mapping. ET is computed using NOAA images which have the visible ,near infrared and infrared bands .(4)Finally, the dissertation utilize the observation datum of weather station and prior harvest to validate the result. The results indicate that the computation methods and models based on Remote Sensing have large practical value .In short ,through retrieving the parameter such as surface albedo , surface temperature and surface emissivity , all the energy flux such as net radiance flux , soil heat flux and latent heat flux can be computed in sequence further , then latent heat flux which provide energy for ET can be computed based on energy balance equation , finally instantaneous ET and daily ET can be obtained . This study is the foundation for the temporal and spatial analysis of crop water demand in Yangtze Delta . Furthermore , this research is helpful for the agriculture water allocation properly in Yangtze Delta.