松嫩平原不同地表覆盖蒸散特征的遥感研究

为了准确估算松嫩平原不同地表覆盖的蒸散量，以MODIS产品及实测气象资料为数据源，通过SEBAL模型估算了松嫩平原2008年生长季（5－9月）的蒸散量，并利用涡动相关数据验证估算结果，发现估算值与实测值的变化趋势相吻合，整个生长季蒸散量的相对误差为18.26%，基本可以满足区域蒸散研究需求。通过探讨松嫩平原蒸散量的时空格局，发现2008年生长季蒸散量为183～1 003 mm，具有从西南部向东部、东北部逐渐增加的变化趋势，水体、林地、湿地的平均蒸散量最高，耕地、居工地次之，草地最低。最后，将蒸散量与降水量进行对比，分析了2008年生长季水分亏缺状态，发现松嫩平原平均水分亏缺量为195.96 mm，97%以上区域的蒸散量大于降水量，蒸散过程中很大程度上还需依靠地下水、径流来弥补降水量不足，生长季蒸散强烈，而降水量相对不足，对松嫩平原生态环境的稳定发展造成了重大影响及压力。

Analysis of evapotranspiration characteristics for different land covers over Songnen Plain based on remote sensing

In order to accurate estimation of ET, in this study, the SEBAL model combined with MODIS products and observed weather data were used to estimate regional ET over Songnen Plain during the 2008 growing season (from May to September). When ET measured by eddy covariance system was used to verify the SEBAL model estimation accuracy, it was found that the trends of both ET calculated and observed were highly consistent, ET estimation error of the whole growing season was 18.26%. The results indicated that the ET retrieval method based on remote sending would meet the requirements of regional ET estimation. ET over Songnen in the growing season of 2008 ranged from 183 mm to 1 003 mm and it increased from the southwest part to the east part and northeast part; average ET of each land cover type decreased in the order of: water-body > woodland > wetlands > cropland > built-up > grassland. Finally, ET and precipitation were compared to analyze the water deficit condition; it was found that the average value of water deficit over Songnen Plain was 195.96 mm. In more than 97% of the whole study area, ET was greater than precipitation, it indicated that the ET process rely on groundwater and runoff to compensate for lack of precipitation to a large extent. The higher ET rate and relative lower precipitation in the growing season would do great influence on the ecological environment of Songnen Plain.