基于NPP VIIRS数据和SEBS模型的河南省冬小麦蒸散量估算与时空特征

Estimation and spatio-temporal characteristics of winter wheat evapotranspiration in Henan Province based on NPP VIIRS data and SEBS model

  • 摘要: 农田蒸散量 (evapotranspiration, ET)是农田水热交换过程的关键变量, 准确估算农田ET对了解农田土壤水分变化动态, 监测预测作物旱情, 指导科学灌溉等具有重要作用。将Suomi NPP (National Polar-orbiting Partnership)卫星的新型遥感数据源可见光红外成像辐射仪(visible infrared imaging radiometer suite, VIIRS)数据用于ET反演, 基于地表能量平衡理论, 将NPP VIIRS反演的地表温度、地表反照率等参数和优化计算的VIIRS NDVI (normalized difference vegetation index)数据, 与SRTM DEM数据和气象观测数据输入地表能量平衡系统(surface energy balance system, SEBS)模型, 估算了2016—2018年河南省冬小麦关键生育时期——返青期至灌浆期的农田ET (VIIRS ET)。分别对比了VIIRS ET与彭曼公式(Penman-Monteith, P-M)计算的P-M ET、大型土壤蒸渗仪实测Real ET和MODIS (moderate-resolution imaging spectroradiometer)数据估算ET (MODIS ET)的结果, 并进行了ET时空变化特征分析。结果表明, VIIRS ET与Real ET的RMSE为0.203 mm∙d−1, 且VIIRS ET与P-M ET和MODIS ET均具有较高的一致性。该方法可为利用NPP VIIRS数据和SEBS模型估算ET提供方法、技术上的支持。研究区冬小麦关键生育时期ET的时间特征表现为自返青期后逐日上升, 抽穗期达到最大值, 灌浆期开始下降的趋势, 与冬小麦生长发育规律具有较好的一致性。综合空间特征来看, 在关键生育时期河南省冬小麦ET均呈现中部和东南部较高, 向西北部和西南部逐渐降低的趋势, 与灌溉条件具有较强的对应性。河南省冬小麦ET时空特征可为河南省农业水资源管理、分配和高效利用等提供重要依据。

     

    Abstract: Crop evapotranspiration (ET), a key variable in water and heat exchange in agricultural fields, is of great significance for understanding the dynamics of soil moisture changes in agricultural fields, monitoring and predicting crop drought conditions, and guiding scientific irrigation. This study combined the surface energy balance system (SEBS) model to estimate ET of winter wheat in Henan Province during the critical growth period from 2016 to 2018 using the visible infrared imaging radiation suite (VIIRS) data of the Suomi National Polar-orbiting Partnership (NPP) satellite. Experimental accuracies were compared between VIIRS ET and the other three ET products (estimated by Penman-Monteith formula, P-M ET; estimated with MODIS data, MODIS ET; and macro-weighing lysimeter-measured ET, Real ET), and the spatial and temporal variation characteristics of ET in winter wheat area of Henan Province were analyzed. The results showed that comparing the VIIRS ET estimated by our proposed method with the P-M ET, the total average relative deviation was 10.1%, and VIIRS ET exhibited high consistency with P-M ET. The measured ET of the macro-weighing lysimeter was used to verify accuracy, and the root mean square error (RMSE) of the calculated VIIRS ET was 0.203 mm·d–1. The verification results showed that the NPP VIIRS data are suitable for ET inversion. The determination coefficients of linear regression analysis of VIIRS ET and MODIS ET were 0.804, 0.734, and 0.802 for the April 17th in 2016, 2017 and 2018, respectively. The three years RMSE of VIIRS ET based on MODIS ET were 0.222 mm·d–1, 0.158 mm·d–1, and 0.211 mm·d–1, respectively. This shows that there is good consistency between VIIRS ET and MODIS ET, and that VIIRS data can be used as an effective supplement and substitute. The ET spatial distribution was generally higher in the middle and southeast and gradually decreased to the northwest and southwest. The spatial variation characteristics of ET corresponded well with that of irrigation conditions. According to the time characteristics of farmland ET during the key growth period of winter wheat in the study area, the average daily ET in the regeneration stage was the lowest, and then it increased gradually, reached a maximum at the heading stage, and began to decrease at the filling stage. The temporal and spatial characteristics of winter wheat field ET in Henan Province were closely related to the local field management mode. The accurate estimation of winter wheat field ET can provide a scientific basis for the design of irrigation management systems. This is important for the management, distribution, and efficient utilization of agricultural water resources.

     

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