资源环境科技发展态势分析平台

North Indian Ocean (NIO) has shown an increase in the frequency of extremely severe and higher-category cyclonic storms (ESCS), with maximum frequency during May. Analyses of datasets and coupled model experiments reveal that anomalous increase in Potential intensity (PI) and ocean heat-content with higher increase during May and weakening summer monsoon circulation has led to increasing ESCS with peak frequency during May. PI is a function of environmental conditions that influence thermodynamic atmosphere–ocean disequilibrium and thermodynamic efficiency. Increase in air-sea disequilibrium by the accelerated warming of NIO dominates the PI trend, contributes more than 70% of PI trend, remaining by the thermodynamic efficiency from increased tropical-tropopause layer cooling. Additionally, weakening of summer monsoon circulation weakens vertical wind-shear, weakens southward ocean heat-transport and enhances heat accumulation, leading to increase in ESCS. Projected changes in PI and wind-shear may further increase ESCS, making densely populated NIO region vulnerable to climate change.