ON THE CHARACTERISTICS OF THE RAINFALL EVENTS IN THE SAHEL WITH A VIEW TO THE ANALYSIS OF CLIMATIC VARIABILITY
ON THE CHARACTERISTICS OF THE RAINFALL EVENTS IN THE SAHEL WITH A VIEW TO THE ANALYSIS OF CLIMATIC VARIABILITY
复制标题
结合气候变化分析研究萨赫勒地区降雨事件的特征
DOI：
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发表时间：
1998
期刊：
影响因子：
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通讯作者：
T. LEBELb
中科院分区：
文献类型：
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作者：
N. D’AMATOa;T. LEBELb
缺乏适当的数据长期以来一直是研究事件尺度的萨赫勒降雨的主要障碍。本文利用 EPSAT-尼日尔记录的雨量计数据来描述萨赫勒中部的对流降雨事件。尽管一些考虑导致了中尺度对流系统的两种主要类型的识别，但这里表明，在事件降雨分布的统计分析方面最相关的分层是在雨季边缘事件和核心事件之间。事实上，平均暴雨深度在时间上似乎是非平稳的，雨季核心的暴雨深度略高于边缘地区。因此，核心和边缘之间的分离允许将指数模型拟合到每个时期（核心和边缘）观测到的风暴雨深分布，尽管如果对时间非平稳性进行适当的建模，肯定会获得更好的拟合。然后表明，给定年份的平均暴雨深度与相应雨季的总体丰度之间几乎没有相关性（如果有的话）。这是对之前研究的验证，之前的研究仅使用每日降雨数据得出了相同的结论。这项工作的一个主要成果是，与观测到的季节性总降雨量相比，萨赫勒地区降雨事件的统计数据显示，无论是在空间上还是逐年波动都很小。每年每个站点的平均风暴降雨量在雨季边缘保持接近 12 毫米，在核心区域接近 15 毫米。同一时期，研究区域的平均季节性降雨量为 400 至 660 毫米，对于任何给定年份，最大点和最小点季节性降雨量之间的比率约为 2。因此得出的结论是，萨赫勒地区降雨量变化的主要来源与事件数量的变化有关，而不是与这些事件的强度有关。 © 1998 英国皇家气象学会。
The lack of appropriate data has long been a major obstacle to the study of the Sahelian rainfall at the event scale. In this paper, use is made of the EPSAT-Niger recording rain-gauge data to characterize the convective rain events of the central Sahel. Although some considerations lead to the identification of two main types of mesoscale convective systems, it is shown here that the most relevant stratification in terms of statistical analysis of the event rainfall distribution is between the events of the margins and those of the core of the rainy season. In fact, the average storm rain-depth appears to be non-stationary in time, with storm rain-depths slightly higher in the core of the rainy season than on the margins. Separation between the core and the margins thus allows the fitting of an exponential model to the observed storm rain-depth distributions of each period (core and margins), although a better fit would certainly be obtained if a proper modelling of the time non-stationarity was carried out. It is then shown that there is little, if any, correlation between the mean storm rain-depth of a given year and the overall abundance of the corresponding rainy season. This is a validation of previous works, which reached the same conclusion using daily rainfall data only. One major result of this work is that the statistics characterizing the rain events in the Sahel display little fluctuations, either in space or from year-to-year, as compared with those observed for the total seasonal rainfall. Each year and at each station the average storm rainfall remains close to 12 mm during the margins of the rainy season and close to 15 mm in the core. During the same period, the average seasonal rainfall over the study area ranged from 400 to 660 mm and for any given year the ratio between the maximum and the minimum point seasonal rainfall was of the order of 2. It is therefore concluded that the main source of rainfall variability in the Sahel is linked to the variability in the number of events rather than in the magnitude of these events. © 1998 Royal Meteorological Society.