The present study examines the Kerala Flood Event (KFE, 15–16 August 2018, in India) that occurred along the west coast of India and resulted in ~400 mm of rainfall in one day. The KFE was unique in comparison to previous floods in India, not only due to the rainfall duration and amount, but also due to the fact that the dams failed to mitigate the flood, which made it the worst in history. The main goal of this study is to analyze and elucidate the KFE based on meteorological and hydrological parameters. A propagating low-pressure system (LPS) from the Bay of Bengal (BoB) caused the streak of plenty of rainfall over Kerala, the west coast, central India, and the BoB. Additionally, the upper-tropospheric anti-cyclonic system over the Middle East region inhibited a northward advancement of LPS. On the western coast of India, a non-propagating (with diurnal fluctuations) offshore trough was observed over the west coast (from Kerala to Gujarat state). Therefore, a synergic interaction between LPS, an intrusion of dry air in the middle-troposphere, and the offshore trough was the main reason for KFE. However, after around ten days, rainfall saturated the dam capacities; thus, the released water, along with the amount of precipitation on the day of the event, was one of the other possible reasons which worsened the flood over Kerala.

中文翻译：

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低压系统，近海槽和对流层中层干空气入侵的相互作用：2018年8月的喀拉拉邦洪水

本研究调查了印度西海岸发生的喀拉拉邦洪水事件（KFE，2018年8月15日至16日，印度），一天导致约400毫米的降雨。与印度以前的洪水相比，KFE的独特之处不仅在于降雨的持续时间和降雨量，还在于大坝未能缓解洪水的事实，这使其成为历史上最严重的洪水。这项研究的主要目的是根据气象和水文参数分析和阐明KFE。孟加拉湾（BoB）传播的低压系统（LPS）导致喀拉拉邦，西海岸，印度中部和BoB出现大量降雨。此外，中东地区上层的对流层反气旋系统抑制了LPS向北的发展。在印度西海岸，在西海岸（从喀拉拉邦到古吉拉特邦）观察到一个非繁殖（有昼夜波动）的海槽。因此，LPS，对流层中部的干燥空气侵入和近海槽之间的协同相互作用是形成KFE的主要原因。但是，大约十天后，降雨使大坝的容量饱和。因此，释放的水以及事件当天的降水量，是使喀拉拉邦洪灾恶化的其他可能原因之一。