Spatial and temporal seasonal trends in coastal upwelling off Northwest Africa, 1981-2012
Spatial and temporal seasonal trends in coastal upwelling off Northwest Africa, 1981-2012
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DOI：
10.1016/j.dsr.2014.01.007
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发表时间：
2014-04-01
影响因子：
2.4
通讯作者：
Bigg, Grant R.
中科院分区：
文献类型：
--
作者：
Cropper, Thomas E.;Hanna, Edward;Bigg, Grant R.
从1981年到2012年，分析了沿非洲西北部海岸线(北纬11-35度)的季节性沿岸上升流。上升流强度由风速指数、海面温度指数计算，并由气象站、海面高度和垂直水柱输送资料推算。根据先前研究的气候学，在北纬21-35度范围内记录了一种永久性的年度上升流制度，在北纬12-19度范围内记录了一种季节性制度。上升区分为三个区：(1)毛里塔尼亚-塞内加尔上升区(北纬12-19度)，(2)强的永久性年上升区(北纬21-26度)和(3)弱的永久性上升区(北纬26-35度)。我们在我们的各种指数中发现了令人信服的证据来支持巴昆上升流增强假说，这是由于沿海夏季风速的显著增加，导致北纬20度以北的上升流有利风速增加和北纬20度以南的下行有利风增加。北大西洋涛动在改变其他季节(秋春)的年际变化方面发挥了主导作用，其影响在冬季占主导地位。东大西洋涛动与春季上升流有很强的相关性，而厄尔尼诺南方涛动和大西洋多年代际涛动的遥相关不存在。探讨了基于观测的风速产品和再分析得出的数据之间的不一致之处。对非洲西北部的巴昆上升流增强假说进行了修正，该假说解释了夏季风场的纬向差异。(C)2014年提交人。爱思唯尔有限公司出版。
Seasonal coastal upwelling was analyzed along the NW African coastline (11-35 degrees N) from 1981 to 2012. Upwelling magnitudes are calculated by wind speed indices, sea-surface temperature indices and inferred from meteorological station, sea-surface height and vertical water column transport data. A permanent annual upwelling regime is documented across 21-35 degrees N and a seasonal regime across 12-19 degrees N, in accordance with the climatology of previous studies. Upwelling regions were split into three zones: (1) the Mauritania-Senegalese upwelling zone (12-19 degrees N), (2) the strong permanent annual upwelling zone (21-26 degrees N) and (3) the weak permanent upwelling zone (26-35 degrees N). We find compelling evidence in our various indices for the Bakun upwelling intensification hypothesis due to a significant coastal summer wind speed increase, resulting in an increase in upwelling-favorable wind speeds north of 20 degrees N and an increase in downwelling-favorable winds south of 20 degrees N. The North Atlantic Oscillation plays a leading role in modifying interannual variability during the other seasons (autumn-spring), with its influence dominating in winter. The East Atlantic pattern shows a strong correlation with upwelling during spring, while El Nino Southern Oscillation and Atlantic Multi-decadal Oscillation teleconnections were not found. A disagreement between observationally-based wind speed products and reanalysisderived data is explored. A modification to the Bakun upwelling intensification hypothesis for NW Africa is presented, which accounts for the latitudinal divide in summer wind regimes. (C) 2014 The Authors. Published by Elsevier Ltd.