CESM simulation of monsoon low-pressure systems over India and a sensitivity analysis

Abstract: Monsoon low-pressure systems (LPS) during the summer monsoon season (June-September) over India are a lifeline for the agriculture-dependent country. We use the Community Earth System Model (CESM1.2.2) to simulate the LPS characteristics (genesis, propagation direction, tracks, intensity, and precipitation) over India and the Bay of Bengal and analyze the influence of Southeast Asian mountains (SAMs) on these characteristics. CESM reproduced most of the LPS characteristics. However, a southward latitudinal shift of about 4° is simulated in the median of the tracks, which is likely due to the weaker simulated upper tropospheric meridional temperature gradient (MTG) in the Indian region. Removal of SAMs is found to have little influence on LPS characteristics. Further, it causes only a slight reduction in mean summer monsoon precipitation (by 5%) and LPS related precipitation (from 10.7±1.0 to 10.3±0.8 mm/day) over India, as SAMs have negligible influence on in-situ westward propagating LPS which are the major contributors to LPS related precipitation. The insensitivity of LPS characteristics and precipitation over India to the removal of SAMs can be attributed to their low height and the insensitivity of MTG to the height of these mountains.

Date/Time
Date(s) - 04/04/2022
5:00 pm - 6:00 pm