京津唐地区城市扩张对地表蒸散发的影响

以京津唐地区为例,基于SEBS模型,利用MODIS遥感数据和气象数据,计算了2000、2005和2010年四季代表月份的平均日蒸散发量,并结合3期土地利用图,定量评估了由城市扩张引起的日蒸散发量的变化。结果表明,不同土地利用类型的日蒸散发量在不同季节表现出不同的分布规律,春、夏和秋季的日蒸散发量分布规律为水域>林地>草地>耕地>城市用地,冬季的日蒸散发量在三年的分布不一致:2000年为林地>草地>水域>城市用地>耕地,2005年为水域>林地>草地>耕地>城市用地,2010年为林地>水域>草地>城市用地>耕地。以研究区土地利用变化不明显的区域为背景区域,评估了除土地利用/覆被变化外的其他因素对京津唐地区夏季日蒸散发的影响。除去该影响后得出土地利用/覆被变化,对日蒸散发的影响,结果表明,各土地利用类型转化为城市用地会使日蒸散发降低,且水域转化成城市用地后,其日蒸散发量降低最多,2000-2005年降低了0.977mm,2000-2010年其降低值为0.983mm。

Urbanization and Its Impact on the Evapotranspiration in Beijing-Tianjin-Tangshan Area

Evapotranspiration(ET) is a key of water resources management. Even in the same climatic and meteorological conditions, ET may have a different value among different land use / land cover. So it’s important to estimate the distribution of the ET. The main objectives of this study are: (1) to estimate ET of different land use / land cover in different seasons; and (2) to find out the impact of urbanization on ET. In this article, based on SEBS model, remote sensing data and meteorological data were used to calculate the average daily ET of Beijing- Tianjin-Tangshan Area. Combined the information of land use / land cover changed area and the result of ET estimation map, the total change of ET could be calculated. Taking ET of land cover pixels without any change as the control plots and ruling out the change of ET of the background then isolated the impact of LUCC on ET in Beijing-Tianjin-Tangshan Area. We found out the temporal distribution of daily ET in the four seasons was decreased gradually in the sequence of summer, spring, fall and winter. Furthermore, the spatial distribution was that the ET decreased gradually in the sequence of water area, woodland, grassland, cultivated land and urban land in summer, spring and fall. The sequence of daily ET in winter for the three years was different. In 2000, it was the ET of forest > grassland > water area > urban land > farmland; in 2005, it was ET of water area > forest > grassland > farmland > urban land; and in 2010, it was ET of forest > water area > grassland> urban land > farmland. Finally, besides the effect of non-land use factors, ET decreased when land use convert to urban land. When land use converts from water area to urban land, the decrease of ET was the most significant, the following was grassland, woodland and cultivated land in sequence.