Modelling the precipitation response over southern Africa to the 2009-2010 El Niño using a stretched grid global atmospheric model
Modelling the precipitation response over southern Africa to the 2009-2010 El Niño using a stretched grid global atmospheric model
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使用拉伸网格全球大气模型模拟南部非洲降水对 2009-2010 年厄尔尼诺现象的响应
DOI：
10.1007/s00382-018-4362-5
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发表时间：
2018
期刊：
影响因子：
4.6
通讯作者：
Driver P
中科院分区：
文献类型：
--
作者：
Driver P
2009-2010年的厄尔尼诺Niño事件是一个中等强度的中太平洋型ENSO，因此，预计将在南部非洲夏季导致严重干旱。然而，该地区的许多地区在这个季节经历了平均到远高于平均水平的降雨。考虑到季节性预报技术往往只在ENSO季节才有效，而次大陆的许多地区依赖雨养农业，了解为什么在这次El Niño事件期间降雨如此异常是很重要的。为此，在观测到和理想海温强迫的区域上应用了一个水平分辨率为0.5°× 0.5°的全球拉伸网格大气环流模式。在后一种实验中，将海温作为一个海洋盆地（如太平洋）的观测值和另外两个海洋盆地（如大西洋、印度洋）的气候学值保存下来，或者作为一个海洋盆地的气候学值和另外两个海洋盆地的观测值保存下来，以帮助了解这三个盆地中哪一个可能对2009-2010年夏季观测到的降水异常贡献最大。研究发现，太平洋强迫导致南部非洲大部分地区夏季降水异常，而大西洋的作用与太平洋的影响相反。然而，在莫桑比克上空，在某种程度上还有津巴布韦上空，印度洋更为重要，而大西洋又起了相反的作用。南部非洲大部分地区的降雨增加似乎主要是由于一个更强的安哥拉低压环流系统和来自热带西印度洋以及热带东南大西洋的异常强的水汽通量，在较小程度上。
The 2009–2010 El Niño event was a moderately strong Central Pacific type ENSO and, as such, expected to lead to a substantial drought over southern Africa during austral summer. However, many parts of the region experienced average to well above average rainfall during this season. Given that seasonal forecasting skill tends only to be good during ENSO seasons and many parts of the sub-continent rely on rain-fed agriculture, understanding why the rainfall was so anomalous during this El Niño event is important. To this end, a global stretched grid atmospheric general circulation model with relatively high horizontal resolution of 0.5° × 0.5° is applied over the region with observed and idealised SST forcing. In the latter experiments, SSTs are kept as observed over one ocean basin (e.g. Pacific) and as climatology over the other two basins (e.g. Atlantic, Indian), or as climatology over one basin and as observed over the other two basins in order to help understand which of these three basins may have contributed most to the observed rainfall anomalies in summer 2009–2010. It is found that Pacific Ocean forcing contributed to the summer rainfall anomalies over most regions of southern Africa with the Atlantic acting to oppose the effects of the Pacific. However, over Mozambique, and to some extent Zimbabwe, the Indian Ocean was more important with the Atlantic again acting in opposition. The increased rainfall over most of southern Africa appears mainly due to a stronger Angola Low circulation system and to anomalously strong moisture flux from the tropical western Indian Ocean and, to lesser extent, the tropical South East Atlantic Ocean.