Characteristics and thermodynamics of Sahelian heatwaves analysed using various thermal indices
Characteristics and thermodynamics of Sahelian heatwaves analysed using various thermal indices
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DOI：
10.1007/s00382-020-05438-5
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发表时间：
2020-09
期刊：
影响因子：
4.6
通讯作者：
Kiswendsida H. Guigma;M. Todd;Yi Wang
中科院分区：
文献类型：
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作者：
Kiswendsida H. Guigma;M. Todd;Yi Wang
在不断变化的气候中，长时间的极端高温也被称为热浪，这是一个越来越令人担忧的问题。在西非炎热和半干旱的萨赫勒地区，人们对气候变化的了解和管理仍然相对不足。在这项研究中，来自ERA 5数据库的五个多变量热指数被用来表征萨赫勒热浪的统计分析，并作为抽样基础，调查其根本的热力学原因。结果表明，萨赫勒地区大多数地方平均每年遭受一次或两次热浪，持续3-5天，但强度很大。萨赫勒东部比西部面临更大的风险，经历更频繁和更持久的事件。尽管热浪指数的强度、持续时间和频率的统计数据相似，但对于给定的昼夜阶段，事件发生的时间却出奇地一致。此外，白天和夜间的热浪几乎没有同步性。在相关的热力学过程方面，热平流和湿度的温室效应被确定为萨赫勒热浪的主要原因。然而，过程是敏感的指数，其各自的样本的独特性的后果。因此，在对热浪进行业务监测和预报时，应注意两种指标的选择。这将有助于有效地针对不同的受影响社会经济群体，从而提高预警系统的效率。
Prolonged periods of extreme heat also known as heatwaves are a growing concern in a changing climate. Over the Sahel, a hot and semi-arid region in West Africa, they are still relatively poorly understood and managed. In this research, five multivariate thermal indices derived from the ERA5 database were used to characterize Sahelian heatwaves for statistical analysis and as a sampling basis to investigate their underlying thermodynamic causes. Results show that on average most locations in the Sahel suffer from one or two heatwaves a year lasting 3–5 days but with severe magnitude. The eastern Sahel is more at risk than the west, experiencing more frequent and longer lasting events. Despite similar statistics of intensity, duration and frequency across the heatwave indices, for a given diurnal phase, there is surprisingly low agreement in the timing of events. Furthermore daytime and nighttime heatwaves have little synchronicity. In terms of associated thermodynamic processes, heat advection and the greenhouse effect of moisture are identified as the main causes of Sahelian heatwaves. The processes are nevertheless sensitive to the indices, consequence of the distinctness of their respective samples. Therefore attention should be given to the choice of either index in operational monitoring and forecasting of heatwaves. This will allow to effectively target different exposed socio-economic groups and resultantly enhance the efficiency of early warning systems.