Simulation of Extreme Rainfall Events Using the Indian Ocean-Land- Atmospheric (IOLA) Coupled Modeling Framework

Abstract

In the context of global warming, the extreme rainfall frequency and intensity have significantly increased. Such events often trigger floods and landslides, causing severe damage to human life, infrastructure, and socio-economic assets. As defined by the India Meteorological Department (IMD), a cloudburst is high-intensity rainfall exceeding 100 mm/hr at a station or over a 20-30 sq km area. This study analyzes heavy rainfall events, including the cloudburst event, using the latest Indian Ocean Land Atmosphere (IOLA) coupled model. The IOLA model experiments are performed in two modes, with and without ocean coupling. The results show that the IOLA model well simulates cloudburst events with minimal spatial and temporal errors. The ocean-coupled simulation of the IOLA model yields better results than the uncoupled simulation: rainfall intensity prediction improves, and the thermodynamic parameters, especially omega and the 2 m surface temperature, are improved. The skill score tests also indicate that the IOLA model consistently simulates well, with better scores (>0.4 for lower thresholds <10 mm and >0.2 for higher thresholds >10 mm). The Skill score tests also show that, after coupling the IOLA model, rainfall prediction skills improve by ~10-15%. Overall, the coupled IOLA model simulation can help to improve predictions of heavy rainfall events and cloudbursts. Overall, this study provides valuable insights for the modeling community, enhancing understanding of cloudburst dynamics through an advanced coupled Ocean–Land–Atmosphere modeling framework.