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首页> 外文期刊>International Journal of Geosciences >Invariance in the Seasonal Median Dates for Mono-Modal Monsoonal Rainfall Distribution over the Semi-Arid Ecotone of Sub-Saharan West Africa
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Invariance in the Seasonal Median Dates for Mono-Modal Monsoonal Rainfall Distribution over the Semi-Arid Ecotone of Sub-Saharan West Africa

机译：撒哈拉以南非洲半干旱交错带单峰季风降雨分布的季节中位数不变

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摘要

Seasonal distribution of mono-modal, monsoonal rainfall across the semi-arid ecotone of sub-Saharan of West Africa is highly variable and unpredictable. The ever-present risk of drought and crop failure in this environment often results in food shortages that are met by emergency food aid. Humanitarian assistance planners would be better prepared for such interventions in a timely manner if they have reliable indicators that forewarn the impending failure of the rains. A good indicator would be a characteristic of the seasonal rainfall distribution that can be shown to be reasonably invariant over time and space. The objective of this study is to investigate whether such invariance existed for the seasonal median date (meaning the date when 50% of the seasonal total occurs). Such invariance is expected since the sun’s cyclic declination forces the advance and retreat of the Inter-tropical Front over West Africa. We examined the statistical properties of the seasonal median date for 1349 station-years of rainfall records for 30 rainfall stations in Burkina Faso and Niger with coordinates ranging from 9.88° to 18.5° north latitude and -4.77° to 13.2° longitude. The results showed that the median date was quite narrowly distributed over years with rather weak dependence on geographical coordinates. It can therefore be used as a reasonable ex-ante indicator of the success or failure of the rains as the rainy season progress.
机译：西非撒哈拉以南半干旱过渡带的单峰季风性雨量的季节性分布是高度变化且不可预测的。在这种环境下，干旱和作物歉收的风险始终存在，往往导致粮食短缺，而紧急粮食援助可以解决这一问题。如果人道主义援助计划人员有可靠的指标可以预知即将发生的降雨，那么它们将为及时进行此类干预做好更好的准备。一个好的指标将是季节性降雨分布的特征，可以证明它在时间和空间上是合理不变的。本研究的目的是调查季节性中位数日期（即发生季节性总数的50％的日期）是否存在这种不变性。由于太阳的周期性偏角迫使西非热带前锋的进退，所以这种不变性是可以预料的。我们检查了布基纳法索和尼日尔的30个降雨站的1349站年降水记录的季节中位数日期的统计特性，其坐标范围为北纬9.88°至18.5°和经度-4.77°至13.2°。结果表明，中位数日期在几年中分布较窄，对地理坐标的依赖性较弱。因此，随着雨季的进行，它可以用作雨水成败的合理事前指标。

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