基于SEBAL模型和Landsat-8遥感数据的农田蒸散发估算

【目的】及时准确地获取农田蒸散发量,为科学管理农田灌溉、精准估算作物产量和预报土壤水分动态、合理开发水资源等提供有效依据。【方法】以广利灌区为研究对象,基于SEBAL模型利用Landsat-8数据对研究区域农田蒸散发进行估算,通过地表参数计算净辐射通量、土壤热通量和感热通量,利用余项法求得潜热通量及瞬时蒸散发。假定24 h内蒸散比不变,由瞬时蒸散发扩展到日蒸散发量,最终求得研究区的日平均蒸散发量,将模型计算结果与彭曼公式进行了对比,同时结合灌区提供数据对计算结果进行了验证。【结果】彭曼公式计算2014年5月6日和2015年9月14日蒸散量与实测结果相差分别为5.2%和9.4%,SEBAL模型估算得到2014年5月6日和2015年9月14日的日蒸散量与灌区提供日蒸散量相差4.5%、6.0%,且冬小麦及夏玉米蒸散发在空间上存在一定的差异性,主要集中在灌区中部区域及西南区域。【结论】SEBAL模型计算结果具有较高的精度,而且方法相对快捷高效。

Estimating Evapotranspiration Using the SEBAL Model and Landset-8 RS Data

【Objective】Evapotranspiration(ET) is a main process in hydrological cycle and its accurate estimation in natural and managed ecosystems is critical to improving water management. The purpose of this paper is to present a new method to estimate ET by taking Guangli Irrigation District in Henan province as an example.【Method】The method was based on the SEBAL model and the Landsat-8 data; it estimated the net radiation flux,soil heat flux using the land-surface parameters first, and the instantaneous evapotranspiration was then calculated using the energy residual method and the latent heat flux. The SEBAL model assumed the evapotranspiration was constant within 24 hours, and the instantaneous evapotranspiration was thus equivalent to the daily evapotranspiration.【Result】Comparison with field measurements revealed that the errors of the Penman-Monteith formula in calculating the daily evapotranspiration on 6 May 2014 and 14 September 2015 was 5.2% and 9.4% respectively,while the associated errors of the proposed model was 4.5% and 6%.【Conclusion】The SEBAL model, coupled with the Landset-8 RS data, can offer an efficient and adequate alternative to estimate ET at catchment scale, and its accuracy is comparable with if not better than the Penman-Monteith formula.