Examining the evolution of extreme precipitation event using reanalysis and the observed datasets along the Western Ghats

Abstract

In recent decades, India has witnessed an increase in the intensity, frequency, and spread of extreme weather events. The widespread increase in extreme precipitation over the Western Coast of India is a matter of great concern. The factors contributing to such devastating extreme precipitation remain unclear due to the variability present in meteorological and oceanic variables and associated large-scale circulations. Using reanalysis and observed datasets, we attempted to identify a combination of dynamic, thermodynamic, and cloud microphysics processes contributing to the anomalous precipitation from August 1 to 10, 2019 against its climatology. Our key findings highlight the crucial role of warm sea surface temperatures (anomaly >1.4°C), outgoing longwave radiation (anomaly <−50 W·m⁻²), and atmospheric temperature (anomaly over the ocean is >1.6°C) in enhancing the moisture-holding capacity of the atmosphere by almost 10%. This elevated moisture, propelled by intensified low-level winds (anomalies exceeding 4 m·s⁻¹), leads to a shift from ocean to land. Notably, we observe that vertical updrafts (anomalies >−0.4 m·s⁻¹) contribute to increased atmospheric instability and moisture convergence. The presence of an ample amount of cloud hydrometeors, with anomalies surpassing 2.5 × 10⁻⁴ kg·kg⁻¹, establishes conditions conducive to sustained intense precipitation. Our findings deepen our understanding of the complex relationships between ocean and atmospheric dynamics, and wind patterns, and emphasize their pivotal influence on regional weather patterns and land surface hydrology.