摘要:蒸散发是土壤-植被-大气系统中水循环和能量交换的主要组成部分，准确估算区域蒸散发对农业用水调度与水资源的管理至关重要。利用MODIS数据产品结合地面气象站的观测资料，基于能量平衡原理建立的SEBAL（Surface Energy Balance Algorithms for Land）模型对西北农牧交错带2015年生长季（4-10月）的地表蒸散发量进行反演研究，并用Penman-Monteith（P-M）公式结合作物系数对模型的估算结果进行对比，结果表明：SEBAL模型估算结果与P-M公式之间的平均绝对误差为0.79mm/d，均方根误差为0.94mm/d，R²=0.76，整体反演值偏高，但基本能满足本地区的研究需求。生长季区域日均蒸散发的变化范围为0.12-10.66mm/d，日蒸散量均值为4.31mm/d，呈东北、西南部较高，西部偏低的空间分布特征。将蒸散发估算值与地表特征参数统计分析发现蒸散发与NDVI和地表净辐射之间呈正相关，与地表温度和地表反照率之间呈负相关；不同土地利用/覆被类型的日蒸散发量由大到小依次为：耕地、林地、未利用地与草地。



Abstract:Evapotranspiration (ET) is the major component of water cycle and energy balance in the soil-vegetation-atmosphere system. Accurate estimation of regional ET is crucial to agricultural water allocation and water resources management. Combining the MODIS data and the meteorological observations from national weather stations, this paper used the SEBAL (Surface Energy Balance Algorithms for Land) model of energy balance theory to estimate the ET pattern of agro-pastoral ecotone in Northwest China during the growing season in 2015 (April to October). The Penman-Monteith formula (P-M), together with the crop coefficients, was used to compare the ET results by the SEBAL model. The results show that the average absolute error between the SEBAL and the P-M ET values is 0.79mm/d, the root mean square error (RMSE) is 0.94mm/d, and R²=0.76. While slightly higher than the actual ET values, the SEBAL estimated ET values reasonably represent ET pattern in the study region. The range of daily average ET is 0.12-10.66mm/d, and the average daily ET is 4.31mm/d during the growing season. Spatially, the ET is higher in the southeastern and northeastern areas and lower in the western area of the study region. Statistical analysis of the ET and land surface parameters shows a significant positive correlation between the ET and NDVI and net radiation, and a negative correlation with the surface temperature and surface albedo. The daily ET values display a decreasing order with the following land use/cover types: cultivated land > forest land > unutilized land > grassland.





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