Cascading effect of meteorological forcing on extreme precipitation events: Role of atmospheric rivers in southeastern US
Cascading effect of meteorological forcing on extreme precipitation events: Role of atmospheric rivers in southeastern US
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DOI：
10.1016/j.jhydrol.2021.126641
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发表时间：
2021-10
影响因子：
6.4
通讯作者：
S. Mukherjee;Anshuman Mishra
中科院分区：
文献类型：
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作者：
S. Mukherjee;Anshuman Mishra
过去几十年来，由大气河流（AR）引发的极端降水（EP）事件加剧，导致大规模洪水，凸显了研究与此类事件相关的物理机制的重要性。本研究旨在调查1979-2019年期间美国东南部沿海州（SUES）AR和相关极端降水（AR-EP）事件的时空演变，以及天气尺度气象模式对潜在过程的级联效应。与 AR 相关的 EP 事件的季节性频率表明，AR-EP 事件在较冷的月份（11 月至 4 月）发生的频率更高。相比之下，在温暖的月份（5 月至 10 月），AR-EP 事件发生频率较低，但更为严重。 1979 年至 2019 年 11 月至 4 月的 3 个月重叠季节中，共观测到 12 至 15 次 AR-EP 事件，严重程度超过 99% 降水阈值，影响了佐治亚州、佛罗里达州、阿拉巴马州和南卡罗来纳州。另一方面，在温暖的月份（5 月至 10 月），AR-EP 事件的平均降水量相对较高（55-90 毫米/天）。为了探索相关气象强迫对有利于此类事件的物理过程的级联性质，我们分别根据在延长的冷季和暖季期间观测到的前 100 个严重 AR-EP 事件进行了以事件为中心的综合分析。据观察，在 AR-EP 事件的进展过程中，与综合平均海平面压力（MSLP）和 850mb 位势高度（Z850）相关的异常随着百慕大高压在冷季向东南延伸而从海槽过渡到山脊形成。研究发现，这些气象变量的时空演变对综合水汽输送 (IVT) 所指示的水分输送模式和与主要 AR-EP 事件相关的总水汽柱所显示的水分可用性具有级联效应。暖季 IVT 场在 AR-EP 事件发生前 2 天变得更强，表明流入墨西哥湾和大西洋沿海平原的水分持续增加。在寒冷季节，墨西哥湾沿岸平原的 IVT 也出现了类似的加强。事件发生前 2 天，墨西哥湾上空的总水汽柱 (TCWV) 显着增加，表明可用水分存在级联效应。总体而言，冷季 AR-EP 是由相对较强的动力系统驱动的，表现为较高的 IVT 强度。相反，暖季 AR-EP 与较弱的 IVT 场、较高的大气不稳定性和更潮湿的条件有关。
The past few decades have witnessed an intensification of extreme precipitation (EP) events triggered by atmospheric rivers (ARs), leading to massive flooding, highlighting the importance of studying the physical mechanisms associated with these types of events. This study aims to investigate the spatiotemporal evolution of ARs and related extreme precipitation (AR-EP) events, and the cascading effect of the synoptic-scale meteorological patterns on underlying processes in the Coastal States of the Southeastern United States (SUES) during the 1979–2019 period. The seasonal frequency of EP events associated with ARs suggests that more frequent AR-EP events occur during the colder months (November to April). In contrast, the AR-EP events are less frequent but more severe in the warmer months (May to October). A total of 12–15 AR-EP events, with severity exceeding the 99th percentile precipitation threshold, were observed during the 3-month overlapping seasons between November and April from 1979 to 2019 that affected Georgia, Florida, Alabama, and South Carolina. On the other hand, the average precipitation magnitude of the AR-EP events is relatively higher (55–90 mm/day) in the warmer months (May to October). To explore the cascading nature of relevant meteorological forcing on the physical processes that favor such events, we performed an event-centered composite analysis based on the top 100 severe AR-EP events observed during the extended cold and warm season, separately. It was observed that during the progression of the AR-EP events, the anomalies associated with composite mean sea level pressure (MSLP) and 850mb geopotential height (Z850) make a transition from the trough to ridge formation along with a south-eastward extension of Bermuda High in the cold season. The spatiotemporal evolution of these meteorological variables is found to have a cascading effect on the mode of moisture transport indicated by integrated vapor transport (IVT) and moisture availability shown by total column water vapor associated with the major AR-EP events. The warm season IVT field gets stronger 2-days before the AR-EP event occurrences indicating a continuous increase in moisture influx into the Gulf and Atlantic Coastal Plains. Similar strengthening of IVT is noted over the Gulf Coastal Plains during the cold season. A cascading effect is also noted for the moisture availability indicated by a significant increase in total column water vapor (TCWV) over the Gulf of Mexico 2 days before the events. Overall, the cold season AR-EPs are driven by relatively stronger dynamical systems indicated by greater IVT intensity. In contrast, the warm season AR-EPs are associated with a weaker IVT field, higher atmospheric instability, and more moist conditions.