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首页> 外文期刊>Hydrology and Earth System Sciences Discussions >Long-term water stress and drought assessment of Mediterranean oak savanna vegetation using thermal remote sensing
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Long-term water stress and drought assessment of Mediterranean oak savanna vegetation using thermal remote sensing

机译：使用热遥感的长期水分压力和地中海橡木大草原植被的干旱评估

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Drought is a devastating natural hazard that is difficult to define, detect and quantify. The increased availability of both meteorological and remotely sensed data provides an opportunity to develop new methods to identify drought conditions and characterize how drought changes over space and time. In this paper, we applied the surface energy balance model, SEBS (Surface Energy Balance System), for the period 2001–2018, to estimate evapotranspiration and other energy fluxes over the dehesa area of the Iberian Peninsula, with a monthly temporal resolution and 0.05 ° pixel size. A satisfactory agreement was found between the fluxes modeled and the measurements obtained for 3 years by two flux towers located over representative sites (RMSD? = ?21?W?m ?2 and R 2 =0.76 , on average, for all energy fluxes and both sites). The estimations of the convective fluxes (LE and H ) showed higher deviations, with RMSD? = ?26?W?m ?2 on average, than R n and G , with RMSD? = ?15?W?m ?2 . At both sites, annual evapotranspiration (ET) was very close to total precipitation, with the exception of a few wet years in which intense precipitation events that produced high runoff were observed. The analysis of the anomalies of the ratio of ET to reference ET (ET o ) was used as an indicator of agricultural drought on monthly and annual scales. The hydrological years 2004/2005 and 2011/2012 stood out for their negative values. The first one was the most severe of the series, with the highest impact observed on vegetation coverage and grain production. On a monthly scale, this event was also the longest and most intense, with peak negative values in January–February and April–May 2005, explaining its great impact on cereal production (up to 45?% reduction). During the drier events, the changes in the grasslands' and oak trees' ground cover allowed for a separate analysis of the strategies adopted by the two strata to cope with water stress. These results indicate that the drought events characterized for the period did not cause any permanent damage to the vegetation of dehesa systems. The approach tested has proven useful for providing insight into the characteristics of drought events over this ecosystem and will be helpful to identify areas of interest for future studies at finer resolutions.
机译：干旱是一种毁灭性的自然危害，难以定义，检测和量化。气象和远程感测数据的可用性增加提供了开发新方法来识别干旱条件的机会，并表征如何在空间和时间变化。在本文中，我们应用了地表能量平衡模型，SEBS（表面能量平衡系统），2001 - 2018年，以估算伊比利亚半岛的脱光区的蒸发和其他能量通量，每月时间分辨率和0.05 °像素尺寸。在模拟的助熔剂之间发现了令人满意的协议，并且通过位于代表性位点的两个磁通塔（RMSD？=Δ21≤2.2和R 2 = 0.76之间，为所有能量通量平均而获得3年的测量两个站点）。对流助焊剂（LE和H）的估计显示出更高的偏差，RMSD？ =？26？W？m？2平均而不是R n和g，用RMSD？ =？15？W？m？2。在这两个地方，年蒸散（ET）非常接近总降水，除了几年潮湿的年份，观察到产生高径流的强烈降水事件。分析ET参考等（ETO）的比例的分析用作每月和年度尺度的农业干旱指标。水文年2004/2005和2011/2012突出了他们的负值。第一个是最严重的系列，在植被覆盖和粮食生产中观察到的最高影响。每月规模，这一事件也是最长，最激烈的，1月至2005年1月至4月至4月至4月，对谷物产量的影响（减少了45倍），解释了其巨大影响。在干燥事件期间，草地和橡树树的变化允许单独分析两层采用水分压力的策略分析。这些结果表明，其特征在此期间的干旱事件并未对DISHA系统的植被造成任何永久性损害。该方法经过证明，该方法已证明有助于深入了解对该生态系统的干旱事件的特征，并有助于确定未来决议未来研究的兴趣领域。

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