Abstract
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.
Highlights
The quantity and availability of surface precipitation play important roles in hydrometeorology, and in water resource management
Around 80% of intense rainfall events along the west coast of India are associated with offshore troughs [12,19,20,27,28], strong cross-equatorial flow over the Arabian Sea [29], and the low-pressure system over the Arabian Sea near the Gujarat and Maharashtra coast [30]
It has been noted that the heavy rainfalls over Kerala state and the adjoining west coast of India are associated with a quasi-stationary trough, in which a cyclonic vortex is sometimes embedded [27]
Summary
The quantity and availability of surface precipitation play important roles in hydrometeorology, and in water resource management. Several research works have appeared on KFE, considering various aspects of this flood, e.g., hydrology [5,6,7], natural disasters [8], meteorological modeling [9], and a climate change perspective [10] They have analyzed rainfall data of more than 100 years and used generalized extreme value distributions [5,6]. Some of the valid questions that can be raised regarding KFE are as follows: Did intensification of the offshore trough, LPS over BoB, and mid-tropospheric dry air intrusion air from the Middle East region trigger extreme precipitation over the Kerala region? This study tried to fill the gap in the understanding of the interaction between monsoonal LPS, the offshore trough, and other regional features
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