基于SEBAL模型与MODIS产品的松嫩平原蒸散量研究

Study on regional evapotranspiration over Songnen Plain based on SEBAL model and MODIS products

利用MODIS的地表温度/比辐射率、植被指数、地表反照率3种产品,结合气象站点的观测资料,通过基于地表能量平衡方程的SEBAL模型估算了松嫩平原2008年5月16日、6月16日、7月13日、8月15日、9月13日不同下垫面的地表蒸散量,并采用涡动相关数据对模型估算结果进行验证,发现估算值与实测值的变化趋势大体一致,平均误差在20%以内,基本上可以满足区域蒸散研究的精度要求。此外,还通过GIS空间分析方法探讨了松嫩平原2008年生长季内不同时相蒸散量的时空分布特征,并分析了蒸散量土地利用类型的关系,结果表明松嫩平原蒸散量的空间分布在很大程度上受气候特征、土壤供水条件及土地利用类型的影响,各时相的蒸散量大致表现为从西南部向东北部逐渐增加的变化趋势,水体、林地、沼泽湿地具有较高的蒸散量,耕地、居工地次之,草地的蒸散量最低。

Regional evapotranspiration for different land-use types over Songnen Plain in May 16th,June 16th, July 13th,August 15th and September 13th in 2008 were estimated by using the SEBAL model based on land surface energy balance equation,observed meteorological data,and three kinds of MODIS land surface products （ surface temperature/emissivity,vegetation index,surface albedo） . When evapotranspiration measured by eddy covariance system was used to verify SEBAL model estimation accuracy,it was found that the trends of both evapotranspiration calculated and measured were highly consistent at an average error within 20% and it indicated that the accuracy can meet the requirements of regional evapotranspiration estimation. In addition,spatial and temporal characteristics of the evapotranspiration distribution map in the growing season of 2008 over Songnen Plain were probed,relationship between evapotranspiration rate and different land-use types were analyzed by applying GIS analysis method. All the results showed that spatial and temporal characteristics of evapotranspiration were effected by the climatic factors,soil water conditions and the impact of land-use types,daily evapotranspiration gradually increased from the southwest part to the northeast part on the 5 days selected in this study; water-body,woodland and wetlands were at the highest evapotranspiration rate,cropland and built-up took the second place,while grassland showed the minimum evapotranspiration rate.