基于SEBAL模型的北京市日蒸散发区域分布规律

Daily Evapotranspiration in Beijing: The Regional Distribution Law Based on SEBAL Model

为了对北京市地表水转换过程中的分量-蒸散发进行定量研究,基于Landsat7 ETM+遥感影像信息并结合气象数据,通过ERDAS构建了SEBAL模型,并通过模型计算得到北京市2014年7月26日的平均蒸散发为2.49 mm,同时利用彭曼公式和MOD16产品数据对SEBAL反演结果的可靠性进行验证。结果表明,通过SEBAL模型计算得到的蒸散发与彭曼公式法和MOD16数据产品的误差分别为3.2%和3.3%,其结果具有一定的可靠性,且通过Landsat7数据反演具有数据获取便捷、空间分辨率高的优点。通过对比各区域蒸散发分布,得出北京市蒸散发整体呈现西北山区高、东南平原低的趋势,西北山区林草植被覆盖率较高是导致这一趋势的主要原因。通过统计分析,水域的蒸散发最高,硬化面积及建筑物的蒸散发接近于0,在除去水体及硬化面积后,蒸散发的大小与NDVI呈现极显著的正相关关系,两者的决定系数达到0.9233,故下垫面类型是影响某一时刻区域蒸散发大小的主要因素之一。

To quantitatively study the component-evapotranspiration in the process of surface water conversion in Beijing,we built the SEBAL model through ERDAS based on Landsat7 ETM+remote sensing image information combined with meteorological data,calculated that the average evapotranspiration on July 26,2014 in Beijing was 2.49 mm,and verified the reliability of the SEBAL inversion results by using the Penman formula and MOD16 product data.The results showed that:the error of evapotranspiration calculated by SEBAL model and Penman’s formula method and MOD16 data product was 3.2%and 3.3%,respectively,which had certain reliability,and the data inversion by Landsat7 had the advantages of convenient data acquisition and high spatial resolution;by comparing the evapotranspiration distribution of each region,it was concluded that the overall evapotranspiration in Beijing was high in the northwest mountainous area and low in the southeast plain which resulted from the high coverage of forest vegetation in the northwest mountainous area;through statistical analysis,the evapotranspiration of the water area was the highest,and that of the hardening area and the building were close to zero;after removing the water body and the hardening area,the size of the evapotranspiration was significantly and positively correlated with NDVI,and the decision coefficient of both reached 0.9233,so the type of underlying surface was one of the main factors affecting the evapotranspiration in a certain time.