Diagnostic Classification of Flash Drought Events Reveals Distinct Classes of Forcings and Impacts
Diagnostic Classification of Flash Drought Events Reveals Distinct Classes of Forcings and Impacts
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突发干旱事件的诊断分类揭示了不同的强迫和影响类别
DOI：
10.1175/jhm-d-21-0134.1
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发表时间：
2022
影响因子：
3.8
通讯作者：
Hain, Christopher
中科院分区：
文献类型：
--
作者：
Osman, Mahmoud;Zaitchik, Benjamin F.;Badr, Hamada S.;Otkin, Jason;Zhong, Yafang;Lorenz, David;Anderson, Martha;Keenan, Trevor F.;Miller, David L.;Hain, Christopher
近年来，人们越来越认识到迅速加剧的突发性干旱是具有重大经济和生态影响的重大气候灾害。这促使人们努力盘点、监测和预测突发性干旱事件。这里我们考虑的问题是，术语“突发性干旱”是否包括多个不同类别的事件，这意味着理解和预测突发性干旱可能需要不止一个框架。为此，我们首先扩展和评估了我们在之前的工作中引入的基于土壤水分挥发性的突发性干旱定义，并用它来盘点1979-2018年期间美国连续地区（CONUS）突发性干旱的发生日期和严重程度。利用这一清单，我们研究了与突发性干旱发生和恢复有关的气象和陆地表面条件。然后，这些相同的气象和陆地表面条件被用来根据可能代表该事件可预测驱动因素的前兆条件对突发性干旱进行分类。我们发现在事件清单中可以诊断出不同类型的突发性干旱。具体来说，我们描述了三种类型的暴发性干旱：“干渴型”事件，其前兆蒸发需求高，土壤湿度低；“蒸发型”事件，前兆蒸发需求和土壤湿度异常较为温和，但前兆蒸发异常为正；“隐形型”暴发性干旱，与其他两种类型不同，前兆气象异常相对于其他类型较为温和。这三种植物的地理和季节分布有些不同。我们得出的结论是，土壤水分突发性干旱确实是不同类型快速加剧的干旱的复合，并且突发性干旱分析和预测将受益于认识到多种现象路径存在的方法。
Recent years have seen growing appreciation that rapidly intensifying flash droughts are significant climate hazards with major economic and ecological impacts. This has motivated efforts to inventory, monitor, and forecast flash drought events. Here we consider the question of whether the term “flash drought” comprises multiple distinct classes of event, which would imply that understanding and forecasting flash droughts might require more than one framework. To do this, we first extend and evaluate a soil moisture volatility–based flash drought definition that we introduced in previous work and use it to inventory the onset dates and severity of flash droughts across the contiguous United States (CONUS) for the period 1979–2018. Using this inventory, we examine meteorological and land surface conditions associated with flash drought onset and recovery. These same meteorological and land surface conditions are then used to classify the flash droughts based on precursor conditions that may represent predictable drivers of the event. We find that distinct classes of flash drought can be diagnosed in the event inventory. Specifically, we describe three classes of flash drought: “dry and demanding” events for which antecedent evaporative demand is high and soil moisture is low, “evaporative” events with more modest antecedent evaporative demand and soil moisture anomalies, but positive antecedent evaporative anomalies, and “stealth” flash droughts, which are different from the other two classes in that precursor meteorological anomalies are modest relative to the other classes. The three classes exhibit somewhat different geographic and seasonal distributions. We conclude that soil moisture flash droughts are indeed a composite of distinct types of rapidly intensifying droughts, and that flash drought analyses and forecasts would benefit from approaches that recognize the existence of multiple phenomenological pathways.