Surface Evaporatranspiration In Beijing-Tianjing-Tangshan’s Urban Aggregation Area

Nowadays Jingjintang aggregation area(including Beijing, Tianjin, Tangshan) is the relatively matured and comprehensive city group in China. Based on the advantages of its location, the economic, social, cultural and urban construction in this region have undergone rapid development and improvement, which make Jingjintang region served as Chinese important political, economic and cultural center. Therefore, it would have the important guiding significance for the future development of small and medium-sized city groups by studying environmental change in Jingjintang region.In the past 30 years, with the acceleration of economy, Chinese cities are developing very rapidly, especially in the large cities such as Beijing, their populations have increased year by year, and land use/ cover change rapidly. Fast urbanization caused by environmental problems has become increasingly acute in large cities, and urban heat island effect is becoming one issue concerning these problems. Heat island effect is mainly resulted from city’s impervious surface increase and vegetation decrease, which change the latent heat flux and sensible heat flux, and result in evapotranspiration reducing and temperature rising. It is closely related to the surface evapotranspiration, and this thesis is based on this point.This thesis is one part of the research- "The large scale of land use and land cover change(LUCC) effects on the global climate",We first selected MODIS and meteorological data as the research sources, then used two-layer model to retrieve the surface evapotranspiration. We finally combined with the DEM and impervious surface index data to analyzes the spatial pattern of surface energy and different LUCC influence on surface evapotranspiration in Jingjintang area.The results show that:(1) Forest area with the high altitude is sensitive to natural conditions. Its temperature, albedo, soil heat flux and sensible heat flux is relatively low, however, its coverage, net radiation, latent heat flux and evapotranspiration is relatively high. And urban core area with low altitude is mainly affected by human activities. Its coverage, albedo, latent heat flux and evapotranspiration quantity is relatively low, however its index of impervious surface, temperature, net radiation, soil heat flux and sensible heat flux is relatively high.(2) We put different land use types’ evapotranspiration from low to high: water, woodland, grassland, cultivated land, urban land. From 2000 to 2010, the evapotranspiration in July had a downward trend in urban land and had an upward trend in woodland and cultivated land. The change of evapotranspirantion due to the land use change is unconspicuous in woodland, grassland and cultivated land. And the evapotranspirantion change due to the land use change from woodland, grassland and cultivated land to urban land had a downward trend.