Deciphering the weakening of the Indian summer monsoon circulation using a regional climate model RegCM 4.5

In this study, the weakening of the Indian summer monsoon circulation is analyzed using the regional climate model RegCM 4.5. It is seen that the when sulfate aerosol component is included in the model run, the simulated temperature shows a cooling at 925 hPa during the 2000 -2011 period for the JJA season. Almost similar pattern is shown when compared with the JRA-55 reanalysis data. At the same time, the Indian Ocean warming has caused an increase in the temperature of the surface waters. Concurrently, the steep temperature that is essential for the strength of the summer monsoon circulation has weakened, resulting in the reduction of the monsoon rainfall over India.