A new study by researchers from the Advanced Centre for Atmospheric Radar Research, Cochin University of Science and Technology (Cusat), in collaboration with scientists from the UK Met Office and France, has identified a significant connection between tropical atmospheric waves and extreme rainfall events along India’s west coast.

Published in Scientific Reports, the study reveals that invisible atmospheric disturbances known as Kelvin, Rossby and Mixed Rossby-Gravity waves significantly enhance heavy rainfall by organising deep convective cloud systems and increasing moisture convergence over the Arabian Sea and the Western Ghats.

The study was led by Prajwal. K, and Ajil Kottayil of the Advanced Centre for Atmospheric Radar Research in collaboration with Prince Xavier of the UK Met Office, and Aurélien Podglajen from LMD, France.

“Among these, Rossby waves were found to exert the strongest influence, amplifying extreme rainfall over land by 20-60%. The research represents the first comprehensive assessment of the role of these tropical waves in modulating rainfall extremes over the region. The findings carry special significance for Kerala, which has witnessed a series of devastating floods and landslides in recent years,” said Mr. Kottayil.

The study observed that the catastrophic rainfall events of 2018 and 2019, which caused widespread flooding across Kerala, were associated with strong Rossby wave activity. Similarly, the deadly 2024 Wayanad landslides, which claimed around 300 lives, coincided with intense Kelvin wave activity.

Mr. Kottayil said that one of the most promising outcomes of this research is its potential to improve early warning systems. “Unlike local thunderstorms that are difficult to predict, tropical wave activity can often be monitored several days in advance. Incorporating these signals into weather forecasting models could provide valuable lead time for anticipating heavy rainfall and reducing disaster risks,” he said.

The researchers stated that a better understanding of these atmospheric waves could enhance early warning systems and strengthen preparedness for extreme rainfall in vulnerable coastal regions as climate change continues to warm the oceans and intensify the hydrological cycle. The study was part of a project funded by the Ministry of Earth Sciences.