Determining water stress levels of vegetated surfaces is crucial for irrigation scheduling. This paper aims to evaluate a new method for obtaining crop water stress index (CWSI) based on the estimation of sensible heat flux using an aerodynamic temperature gradient approach. Data were collected on a deficit irrigated maize field at a research farm located in Greeley, Colorado, USA, in 2017 and 2018. The irrigation treatment used subsurface drip. Weather data were measured on-site at 3.3 m above ground level. RED and NIR surface reflectance data were obtained on-site through multispectral radiometer measurements. Nadir surface temperature data were measured using infra-red thermometers at 1 m above canopy. CWSI estimated values were used to assess daily soil water stress index (SWSI), calculated from measurements of volumetric soil water content (VWC) and management allowed depletion (MAD) of 40%. Results show that SWSI is best represented through a non-linear rational CWSI function. Modeled CWSI estimates were compared to measured surface heat fluxes, resulting in a mean bias error of − 0.02 and a root mean square error of 0.09, while errors were 0.02 and 0.06 when compared with observed CWSI based on canopy transpiration measured with plant sap flow devices. Results seem to validate the proposed sensible heat flux-based CWSI model. The CWSI approach presented could be used to manage irrigation and conserve water resources for maize in semi-arid regions.

中文翻译：

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通过基于遥感的表面能量平衡方法确定玉米水分胁迫

确定植被表面的水分胁迫水平对于灌溉计划至关重要。本文旨在评估一种基于使用空气动力学温度梯度方法估算显热通量的作物水分胁迫指数 (CWSI) 的新方法。数据是在 2017 年和 2018 年在位于美国科罗拉多州格里利的一个研究农场的亏缺灌溉玉米田上收集的。灌溉处理使用地下滴灌。天气数据是在离地平面 3.3 m 的现场测量的。RED 和 NIR 表面反射数据是通过多光谱辐射计测量现场获得的。天底表面温度数据是在冠层上方 1 m 处使用红外温度计测量的。CWSI 估计值用于评估每日土壤水分胁迫指数 (SWSI)，通过测量土壤体积含水量 (VWC) 和 40% 的管理允许消耗 (MAD) 计算得出。结果表明 SWSI 最好通过非线性有理 CWSI 函数来表示。将模拟的 CWSI 估计值与测量的地表热通量进行比较，导致平均偏差误差为 - 0.02，均方根误差为 0.09，而与基于使用植物液流装置测量的冠层蒸腾作用观察到的 CWSI 相比，误差分别为 0.02 和 0.06 . 结果似乎验证了提议的基于显热通量的 CWSI 模型。介绍的 CWSI 方法可用于管理灌溉和保护半干旱地区玉米的水资源。将模拟的 CWSI 估计值与测量的地表热通量进行比较，导致平均偏差误差为 - 0.02，均方根误差为 0.09，而与基于使用植物液流装置测量的冠层蒸腾作用观察到的 CWSI 相比，误差分别为 0.02 和 0.06 . 结果似乎验证了提议的基于显热通量的 CWSI 模型。介绍的 CWSI 方法可用于管理灌溉和保护半干旱地区玉米的水资源。将模拟的 CWSI 估计值与测量的地表热通量进行比较，导致平均偏差误差为 - 0.02，均方根误差为 0.09，而与基于使用植物液流装置测量的冠层蒸腾作用观察到的 CWSI 相比，误差分别为 0.02 和 0.06 . 结果似乎验证了提议的基于显热通量的 CWSI 模型。介绍的 CWSI 方法可用于管理灌溉和保护半干旱地区玉米的水资源。