Spatiotemporal sensitivity of thermal stress for monitoring canopy hydrological stress in near real-time
Spatiotemporal sensitivity of thermal stress for monitoring canopy hydrological stress in near real-time
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DOI：
10.1016/j.agrformet.2019.02.016
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发表时间：
2019-05
影响因子：
6.2
通讯作者：
B. Seyednasrollah;J. Domec;J. Clark
中科院分区：
文献类型：
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作者：
B. Seyednasrollah;J. Domec;J. Clark
使用最少的现场数据实时监测干旱对于生态系统管理和保护来说是一个挑战。大多数方法需要大量的数据收集和现场校准，并且准确性难以评估。在这里，我们展示了空间传播的冠层“热应力”（定义为地表空气温差）如何为干旱引起的植被水分胁迫提供可靠的替代。利用适应不确定性的基于物理的关系，我们展示了地面测量的冠层水通量变化如何与表面能量平衡和遥感热应力相关。美国东南部和西北部的蒸散量现场测量验证了这种基于大范围大气和气候条件下蒸散量对热应力的敏感性的方法。我们发现，根据地点和气候条件，热应力 1°C 的变化相当于 1–1.2mm day−1 的蒸散量。我们量化了蒸散量对热应力的时间和空间敏感性，并表明它与温暖和干燥季节的蒸散量具有最强的关系，此时监测干旱至关重要。仅使用空气和地表温度，我们就预测了 15 年来美国本土热应力的年际异常，并将其与传统的干旱指数进行了比较。在本研究考虑的干旱指标中，热应力具有最高的相关值。我们的敏感性结果表明，热应力是温暖季节和地区用水的一个特别有力的指标。这个简单的指标可以在不同的时间尺度上用于近乎实时地监测大空间范围内的地表蒸散和干旱。
Monitoring drought in real-time using minimal field data is a challenge for ecosystem management and conservation. Most methods require extensive data collection and in-situ calibration and accuracy is difficult to evaluate. Here, we demonstrated how the space-borne canopy “thermal stress”, defined as surface-air temperature difference, provides a reliable surrogate for drought-induced water stress in vegetation. Using physics-based relationships that accommodate uncertainties, we showed how changes in canopy water flux from ground-based measurements relate to both the surface energy balance and remotely-sensed thermal stress. Field measurements of evapotranspiration in the southeastern and northwestern US verify this approach based on sensitivity of evapotranspiration to thermal stress in a large range of atmospheric and climate conditions. We found that a 1 °C change in the thermal stress is comparable to 1–1.2 mm day−1of evapotranspiration, depending on site and climate conditions. We quantified temporal and spatial sensitivity of evapotranspiration to the thermal stress and showed that it has the strongest relationship with evapotranspiration during warm and dry seasons, when monitoring drought is essential. Using only air and surface temperatures, we predicted the inter-annual anomaly in thermal stress across the contiguous United States over the course of 15 years and compared it with conventional drought indices. Among drought metrics that were considered in this study, the thermal stress had the highest correlation values. Our sensitivity results demonstrated that the thermal stress is a particularly strong indicator of water-use in warm seasons and regions. This simple metric can be used at varying time-scales to monitor surface evapotranspiration and drought in large spatial extents in near real-time.