Possible changes in the characteristics of Indian Summer Monsoon under warmer climate

摘要

The Indian Summer Monsoon (ISM) spans four months starting from June and ending in September and produced wide spread rainfall over Indian continents mainly due to land-sea heating contrast between Indian Ocean and large Asian land mass. ISM is controlled by semi permanent features such as heat low over northwest sector of India, cross-equatorial flow and the low level westerly jet over the Arabian Sea at 850 hPa, the tropical easterly jet over the Indian Ocean at 200 hPa, Mascarene High, and anti-cyclone over the Tibet. Any fluctuation in Indian Summer Monsoon Rainfall (ISMR) during ISM on intra seasonal to inter annual is manifestation of change in wind circulation and temperature distribution. Therefore, in order to understand the change in magnitude and pattern of ISMR under warmer climate, it is necessary to qualitatively and quantitatively assess the change in associated monsoon wind circulation and temperature distribution. The current study examines the changes in magnitude and spatial distribution of ISMRand associated change in wind circulation and temperature distribution under forced scenarios in selected climate models contributed to International Panel of Climate Change (IPCC) 4th Assessment Report (AR4). It is found that under A2, Bl and A1B emission scenarios, future projected change in spatial distribution of ISMR shows deficit and excess of over the lower part of western and eastern coast of India in simulation of HadGEMl, ECHAM5, and MIROC (Hires) model which seems to be manifestation of anomalous anticyclonic flow at 850 hPa in Arabian Sea and anomalous westerly flow at 200 hPa