利用双波长方法对非均匀地形人工林蒸散的测量

千米级地表蒸散通常利用遥感影像并结合经验或半经验模型进行估算,且估算结果还需结合地表实测数据进行验证,但实际中很难获得与遥感像元尺度匹配的实测数据.本研究在黄河小浪底森林生态系统定位研究站人工林的生长期(2016年7月1日-10月19日),基于近红外与微波联合观测技术进行千米级地表蒸散的观测分析.结果表明:近红外与微波联合技术在不同天气条件下均能表现出良好的日变化特征,且整体能量闭合率可达0.87.该技术对空气湿度的变化敏感,土壤湿度的变化对该项技术的结果影响较小.不同波文比条件和大气稳定度均会使该技术的观测产生不同程度的误差,与涡动相关方法相比,误差在合理范围.采用双波长方法研究得出,该区域的最大日蒸散量为3.5 mm,总蒸散量为162.4 mm.

Estimating evapotranspiration of plantation with non-uniform terrain based on two-wavelength method.

Kilometer-scale evapotranspiration is usually estimated by remote sensing images, combined with empirical or semi-empirical models, with results being verified with empirical data. However, it is usually difficult to obtain real-time measurements which can match the pixel scale of remote sensing. We analyzed kilometer-scale evapotranspiration by the combination of near-infrared and microwave technique in the Ecosystem Research Station of the Yellow River in Xiaolangdi, during period of plantation growth (1st July to 19th October 2016). Results showed that the combination of near-infrared and microwave technique could obtain well diurnal cycles in different weather conditions, with the overall energy balance reaching 0.87. The technique was sensitive to the variation of relative humidity of air, but not sensitive to that of soil moisture. The error of estimation was resulted from Bowen ratios and atmospheric stability. Compared with the eddy covariance method, the error was within a reasonable range. As estimated by the two-wavelength method, the maximum daily and total evapotranspiration of the study area was 3.5 mm and 162.4 mm, respectively.