Atmospheric and Oceanic Processes Behind Extreme Precipitation: A Case Study of the Western Ghats

India has experienced a notable rise in the intensity, frequency, and spatial extent of extreme weather events in recent decades, with extreme precipitation along the southwest coast being particularly alarming. The drivers behind these events remain uncertain due to the variability in meteorological and oceanic factors and associated large-scale circulations. The present study attempted to identify a combination of dynamic, thermodynamic, and cloud microphysics processes contributing to the anomalous precipitation over the southwest coast of India from 1-10 August 2019 against its climatology using reanalysis and observational datasets. Key findings reveal the critical role of warm sea surface temperature anomalies (>1.4°C), reduced outgoing longwave radiation (<-50 W/m²), and elevated atmospheric temperatures (>1.6°C over the ocean) in enhancing atmospheric moisture capacity by nearly 10%. Strengthened low-level winds (anomalies >4 m/s) transported this moisture from the ocean to the land, while vertical updrafts (> -0.4 m/s anomalies) increased atmospheric instability and moisture convergence. Additionally, significant anomalies in cloud hydrometeors (>2.5×10⁻⁴ Kg/Kg) supported prolonged intense precipitation. These results improve our understanding of the interaction between ocean-atmosphere dynamics and wind patterns, highlighting their vital role in shaping regional weather and climate.

Keywords: Extreme precipitation, Western ghats, Atmospheric processes, Reanalysis.