Disparity in spatiotemporal variability and risk of compound coastal extremes between India’s East-West coasts

The Indian East Coast is susceptible to concurrent storm surge-rainfall (SS-RF) extremes during June–November, driven by low-pressure systems of varying intensity from the Bay of Bengal during monsoon and post-monsoon seasons. Contrarily, the West Coast witnesses these extremes primarily during monsoon, driven by depressions in the Arabian Sea and troughs of low pressure along the coast. Higher frequency of these extremes was witnessed on the West (East) Coast when the positive (negative) phase of the Indian Ocean Dipole co-occurred with the Neutral (La Niña or Neutral) phase of El Niño Southern Oscillation. Further, the SS-RF extremes on the East Coast (West Coast except Mumbai) were storm surge (rainfall) dominant, with higher risk at Haldia (Mumbai). On the other hand, a higher (lower) frequency of concurrent sea level-rainfall extremes was witnessed on the East (West) Coast due to disparity in tidal ranges and seasonality of coastal currents.