Vertical Wind Profile and Water Vapour Mixing Ratio during Indian Summer Monsoon Season over Arabian Sea

Abstract

The purpose of this study is to examine the monthly variations in circulation fields and moisture content at different atmospheric levels (850, 500 and 200hPa) over the Arabian Sea (AS) during summer monsoon season. A regional climate model (RegCM3) was used for this purpose and two experiments like (a) Control (unperturbed SST) and sensitivity (perturbed SST by +0.50C) runs were conducted to examine the implications on monthly composite Vertical Zonal Wind Shear (VZWS) and Water Vapour Mixing Ratio (WVMR) during Indian Summer Monsoon Season. Monthly wind profile over AS (50-150N, 500-800E) has been studied. Monthly vertical distributions of the moisture content in terms of WVMR up to 200hPa during summer monsoon season were also calculated over entire AS centered at 62.50E-67.50E longitude and over Indian region centered at 750E-800E longitude. The analysis shows that the wind shears between the atmospheric levels 850-500 hPa and 500-200 hPa were increased in the warm SST run. The peak of the wind shear was obviously attained in July. The water vapour was found of high value mostly at all atmospheric levels in July and August in the case of increased SST of AS. In the experiments centered over AS (Indian region), maximum enhancement of moisture was noticed between 50N-150N (100N-150N) latitudes respectively. The model performance in perturbed SST state was found appreciable in the months of July and August (representative months of Indian monsoon season). Simulated average zonal winds between 850hPa and 500hPa in June (September) were sharply increased (decreased) in the SST run. In the study of Indian Monsoon Index (IMI) as an indicator of the strength of monsoon circulation, higher IMI was noted in the warm SST run as compared to the Control (CTL) run.