Understanding the influence of ENSO patterns on drought over southern Africa using SPEEDY
Understanding the influence of ENSO patterns on drought over southern Africa using SPEEDY
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DOI：
10.1007/s00382-019-05002-w
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发表时间：
2019-10-04
期刊：
影响因子：
4.6
通讯作者：
Kucharski, Fred
中科院分区：
文献类型：
--
作者：
Gore, Michelle;Abiodun, Babatunde J.;Kucharski, Fred
厄尔尼诺南方涛动(ENSO)是南部非洲干旱的主要驱动因素，但ENSO变化的非线性阻碍了准确的干旱预测。虽然研究已经确定了与ENSO有关的多种海洋表面温度(SST)模式，但对南部非洲的大多数干旱预测仍然只基于两种模式。这项研究利用SPEADY检验了南部非洲干旱与8种ENSO海温模式之间的关系。通过比较历史模拟(1979-2008年)和观测，评估了快速再现南部非洲气候的能力。为了了解ENSO海温型对南部非洲干旱的影响，对每一型的海温进行了多集合模拟，分析了它们对标准化降水蒸散指数(SPEI)及其相关大气动力学的影响。结果表明，SPEACID模式能很好地反映南部非洲地区气候变量的时空分布特征，但有偏暖偏湿的特点。然而，其结果与更复杂的大气模型的结果是相当的。与之前的研究结果一致，结果表明厄尔尼诺(拉尼娜)条件削弱(加强)沃克环流，导致南部非洲部分地区更干燥(更潮湿)。然而，结果表明，厄尔尼诺条件的差异改变了南部非洲上空的水汽通量环流，从而影响了该地区干旱的空间格局和强度。拉尼娜现象也是如此。因此，这项研究表明，考虑到厄尔尼诺(或拉尼娜)条件的差异，可能会改善对南部非洲干旱的预测。
The El Nino Southern Oscillation (ENSO) is a major driver of southern Africa drought, but the nonlinearity of ENSO variation inhibits accurate drought prediction. While studies have identified multiple sea surface temperature (SST) patterns associated with ENSO, most drought predictions over southern Africa are still based on only two patterns. This study examines the relationship between southern Africa droughts and eight ENSO SST patterns using SPEEDY. The capability of SPEEDY in reproducing southern Africa climate was evaluated by comparing historical simulations (1979-2008) with observation. To understand the influence of ENSO SST patterns on southern Africa drought, multi-ensemble simulations were forced with SSTs of each pattern, and the impacts on the Standardized Precipitation Evapotranspiration Index (SPEI) and the associated atmospheric dynamics were analysed. The results show that SPEEDY generally captures the temporal and spatial distribution of climate variables over southern Africa well, although with a warm and wet bias. However, the results are comparable with those from more complex atmospheric models. In agreement with previous studies, the results show that El Nino (La Nina) conditions weaken (strengthen) the Walker circulation, causing drier (wetter) conditions over parts of southern Africa. However, the results show that differences in the El Nino conditions alter the moisture flux circulation over southern Africa, thereby influencing the spatial pattern and intensity of drought over the region. The same is true of the La Nina conditions. Hence, this study shows that accounting for the differences in El Nino (or La Nina) conditions may improve drought predictions in southern Africa.