A rare subseasonal-to-seasonal phenomenon – two consecutive flash drought events interrupted by a period of recovery – occurred across eastern Oklahoma, Arkansas, and southern Missouri, spanning the summer and early fall of 2022. These flash drought events (the first in June–July, the second in August–September) led to severe (D2) and extreme (D3) drought conditions via the United States Drought Monitor across much of the region following the first period of rapid drought intensification, and extreme (D3) and exceptional (D4) drought conditions by the end of the second event. A notable driver of both flash drought events included a persistent upper-level ridge either centered over or shifted west and upstream of the flash drought region, leading to broad-scale subsidence and reduced mid-level moisture which acted to limit precipitation development and increase evaporative demand. In addition, several heatwave events developed during the warm season in 2022 and either (1) acted to drive flash drought development via increased evaporative demand or (2) were enhanced by land surface desiccation and land-atmosphere feedbacks following rapid drought intensification. Furthermore, S2S composite forecasts predicted drought development for both events. However, only 20% of the ensembles predicted rapid drought development associated with flash drought for the first event and 16% of the ensembles predicted rapid drought development during the second event. This result highlights a key challenge in S2S prediction of rapidly developing drought conditions versus that of more conventional and slower drought development. The ensembles that did predict rapid drought intensification were associated with the forecasting of positive 500 hPa geopotential height anomalies over the south-central United States (first event) or an amplified wave pattern centered over the west-central United States (second event). Lastly, the compounding effects of two flash droughts in a single warm season led to substantial impacts on agricultural, environmental, and hydrologic sectors across the region.

中文翻译：

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2022 年美国中南部的闪电干旱：驱动因素、可预测性和影响


2022 年夏季和初秋，俄克拉荷马州东部、阿肯色州和密苏里州南部发生了一种罕见的次季节到季节性现象，即连续两次被恢复期打断的突发干旱事件。这些突发干旱事件（第一次在 6 月至 7 月，第二次在 8 月至 9 月）导致在第一个干旱快速加剧期之后，美国干旱监测系统在该地区大部分地区出现严重 （D2） 和极端 （D3） 干旱情况，并在第二次事件结束时出现极端 （D3） 和异常 （D4） 干旱情况。两次闪旱事件的一个显着驱动因素包括持续的高层脊，要么以速干地区为中心，要么向西和上游移动，导致大面积沉降和中层水分减少，从而限制了降水的发展并增加了蒸发需求。此外，在 2022 年的暖季期间发生了几次热浪事件，这些事件要么 （1） 通过增加蒸发需求来推动闪电干旱的发展，要么 （2） 在干旱快速加剧后因地表干燥和陆地大气反馈而增强。此外，S2S 综合预报预测了这两种事件的干旱发展。然而，只有 20% 的集合预测了第一次事件中与突发干旱相关的干旱快速发展，16% 的集合预测了第二次事件期间干旱的快速发展。这一结果凸显了 S2S 预测快速发展的干旱条件与更常规和较慢的干旱发展相比的一个关键挑战。 预测干旱快速加剧的集合与预测美国中南部 500 hPa 的正位势高度异常（第一次事件）或以美国中西部为中心的放模式（第二次事件）有关。最后，在一个温暖季节发生两次突发干旱的复合效应对整个地区的农业、环境和水文部门造成了重大影响。