The Influence of Atmospheric Rivers over the South Atlantic on Winter Rainfall in South Africa
The Influence of Atmospheric Rivers over the South Atlantic on Winter Rainfall in South Africa
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DOI：
10.1175/jhm-d-17-0111.1
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发表时间：
2018-01-01
影响因子：
3.8
通讯作者：
Reason, C. J. C.
中科院分区：
文献类型：
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作者：
Blamey, R. C.;Ramos, A. M.;Reason, C. J. C.
使用自动检测算法和两个再分析产品作为输入，开发了 1979 年至 2014 年期间在南方冬季（4 月至 9 月）期间撞击南非西海岸（南纬 29 度至 34.5 度）的大气河流 (AR) 的气候学。这两个产品显示出相对较好的一致性，每个冬季平均发生 10-15 个持续 AR（持续 18 小时或更长时间），其中近三分之二的系统发生在南纬 35 度的极地。使用南非气象局降雨数据证明了持续 AR 活动与冬季降雨之间的关系。大多数位于地势较高地区的站点，持续性 AR 贡献的降雨量百分比最高，而顺风站、主要地形屏障以东的降雨量贡献最低。该地区的极端降雨日也按其强度和空间范围进行排名。结果表明，尽管持续的 AR 是强降雨事件的重要促成因素，但它们不一定是先决条件。研究发现，南非冬季 50 次极端降雨量中，约有 70% 在某种程度上与 AR 相关（持续性和非持续性）。总体而言，这项研究的结果支持对北大西洋和北太平洋的 AR 进行类似的调查。
A climatology of atmospheric rivers (ARs) impinging on the west coast of South Africa (29 degrees-34.5 degrees S) during the austral winter months (April-September) was developed for the period 1979-2014 using an automated detection algorithm and two reanalysis products as input. The two products show relatively good agreement, with 10-15 persistent ARs (lasting 18 h or longer) occurring on average per winter and nearly two-thirds of these systems occurring poleward of 35 degrees S. The relationship between persistent AR activity and winter rainfall is demonstrated using South African Weather Service rainfall data. Most stations positioned in areas of high topography contained the highest percentage of rainfall contributed by persistent ARs, whereas stations downwind, to the east of the major topographic barriers, had the lowest contributions. Extreme rainfall days in the region are also ranked by their magnitude and spatial extent. The results suggest that although persistent ARs are important contributors to heavy rainfall events, they are not necessarily a prerequisite. It is found that around 70% of the top 50 daily winter rainfall extremes in South Africa were in some way linked to ARs (both persistent and nonpersistent). Overall, the findings of this study support similar investigations on ARs in the North Atlantic and North Pacific.