Relationship between atmospheric conditions at Dhaka, Bangladesh, and rainfall at Cherrapunjee, India
Relationship between atmospheric conditions at Dhaka, Bangladesh, and rainfall at Cherrapunjee, India
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DOI：
10.1007/s11069-007-9125-2
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发表时间：
2008-03
期刊：
影响因子：
3.7
通讯作者：
F. Murata;T. Terao;Taiichi Hayashi;Haruhisa Asada;J. Matsumoto
中科院分区：
文献类型：
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作者：
F. Murata;T. Terao;Taiichi Hayashi;Haruhisa Asada;J. Matsumoto
为了改进洪水预报，了解与强降雨相关的大气条件至关重要。我们利用高空探测分析了孟加拉国达卡的大气状况。然后，我们将这些条件与印度Cherrapunjee的每日降雨量变化进行了比较，Cherrapunjee是孟加拉国洪水的主要来源，也是异常强降雨事件的代表性样本。分析集中在2004年6月和7月。六月和七月是Cherrapunjee一年中降雨量最大的月份。2004年7月是过去31年来第四个最大的月降雨量，孟加拉国发生了严重的洪水。在Cherrapunjee的活跃降雨期对应于印度季风的“中断”。季风槽位于喜马拉雅山麓，强烈的西风主导了达卡长达7公里的地区。1km以下的近地面风具有偏南分量，风廓线具有Ekman螺旋结构。结果表明，降雨在Cherrapunjee强烈依赖于近地面风速和风向在达卡。由梅加拉亚高原抬升的近地面偏南气流被认为是造成切拉朋吉强降雨的主要原因。高对流有效位能（CAPE）也有助于强降雨。
To improve flood forecasting, the understanding of the atmospheric conditions associated with severe rainfall is crucial. We analysed the atmospheric conditions at Dhaka, Bangladesh, using upper-air soundings. We then compared these conditions with daily rainfall variations at Cherrapunjee, India, which is a main source of floodwater to Bangladesh, and a representative sample of exceptionally heavy rainfall events. The analysis focussed on June and July 2004. June and July are the heaviest rainfall months of the year at Cherrapunjee. July 2004 had the fourth-heaviest monthly rainfall of the past 31 years, and severe floods occurred in Bangladesh. Active rainfall periods at Cherrapunjee corresponded to “breaks” in the Indian monsoon. The monsoon trough was located over the Himalayan foothills, and strong westerly winds dominated up to 7 km at Dhaka. Near-surface wind below 1 km had southerly components, and the wind profile had an Ekman spiral structure. The results suggest that rainfall at Cherrapunjee strongly depends on the near-surface wind speed and wind direction at Dhaka. Lifting of the near-surface southerly airflow by the Meghalaya Plateau is considered to be the main contributor to severe rainfall at Cherrapunjee. High convective available potential energy (CAPE) also contributes to intense rainfall.