区域土壤植被系统蒸散发二源遥感估算

Estimation of Regional Evapotranspiration Using Two Source Energy Balance Model and ETM+ Imagery

针对干旱半干旱复杂地形区地表起伏、覆被不均一、植被稀疏的特征,论文对N′95二源遥感模型中地表净辐射计算方案以及地表反照率、零平面位移、动量粗糙长度、热量粗糙长度、动量和热量的稳定度校正项、土壤表面的空气动力学阻抗等算法有针对性地进行了修改。利用修改后的N′95模型,选择位于黄土高原的地表起伏大,植被稀疏的陕甘宁交界区为研究区,计算了研究区的土壤蒸发、植被蒸腾和土壤-植被总蒸散发;并利用附加阻抗法计算实际蒸散发的方法对N′95二源模型法遥感估算结果进行了间接精度评价,比较验证表明N′95二源模型法估算的蒸散发结果合理,精高较高。

Concerning with the complex characteristics of the arid, semi-arid terrain surface, such as undulating topography, un-unique land use/covers and less vegetated land surface, etc. the N＇95 model integrated with remote sensing techniques for the estimation of actual evapotranspiration was modified and improved with the focus on the estimation of the net radiation received by surface considering the influence of slope and aspect to the solar shortwave irradianee and surface long-wave irradiance. In addition to that, albedo, displacement height, roughness length for momentum, roughness length for heat, the diabatie correction factors for momentum and heat, the resistance to heat flow in the boundary layer directly ediately above the soil surface in the original N＇ 95 model were modified with new approaches to enable the application of the model more easier in operation and much accurate in computation in terms of specific terrain surface conditions. The instantaneous evapotranspiration was estimated with the modified N＇ 95 model by using the Landsat ETM＋ data for an experimental study site located on the conjuncture area of Shaanxi, Gansu and Ningxia where the terrain surface is very undulating with less vegetation developed, heavy soil and water loss loess plateau. And then the spatial pattern of the instantaneous evapotranspiration was analyzed. Actual instantaneous evapotranspiration of 3033 verification points of the study area was calculated with the extra resistance method to compare with the modified N＇95 model estimated, which suggested that the modified N＇95 model can be used for the accurate estimation of evapotranspiration in arid and semi-arid rugged terrain area covered by sparse vegetation.