Equatorial Indian Ocean Response during Extreme Indian Summer Monsoon Years Using Reliable CMIP5 Models

Abstract

Monsoon droughts are characterized by the weakening of surface winds over the equatorial Indian Ocean and increased upper ocean heat storage, thus providing a sustained heat source for deep convection. This in turn increases rainfall over the eastern equatorial Indian Ocean and weakens the regional Hadley circulations, along with the subsidence of these circulations over the Indian subcontinent. To simulate reliable future climate projections, it is necessary to simulate the observed features during extreme monsoon events. In this study we examine the ability of climate models to simulate extreme rainfall events and their associated observed features over the Equatorial Indian Ocean (EIO) in the historical simulations of reliable IPCC CMIP5 models. Here we analyzed the Sea Surface temperature (SST), Ocean vertical temperature and rainfall anom alies during extreme rainfall events in the time period 1951–2005. In addition, we utilized reliable CMIP5 models which can simulate the Indian summer monsoon (ISM) and tried to study ocean features during extreme years. Drought years produce an abnormal su bsurf ace warming (0.5–1.5°C) over the Eastern Equatorial Indian Ocean (EEIO). This subsurface warming changes the wind pattern and causes drought in land regions of India. At the same time during excess monsoon years there is an abnormal cooling over the EEIO.