CESM simulation of monsoon low pressure systems over India

• Published in: International journal of climatology 2022-09, Vol.42 (11), p.5964-5984
• Main Authors: Thomas, Tresa Mary, Bala, Govindasamy, Vemavarapu, Srinivas Venkata
• Format: Article
• Language: English
• Subjects: Agriculture; downstream amplified systems; Height; Low pressure; Low pressure systems; LPS tracks; monsoon low pressure systems; Monsoon precipitation; Monsoons; Mountains; Precipitation; Removal; Simulation; southeast Asian mountains; Summer; Summer monsoon; Temperature gradients; Wind
• ISSN: 0899-8418; 1097-0088
• DOI: 10.1002/joc.7571

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 analyse 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. We use the NCAR Community Earth System Model (CESM) to simulate the statistics of summer monsoon low pressure systems (LPS) over India and study the influence of the southeast Asian mountains (SAMs) on these characteristics. CESM could reproduce most of the LPS characteristics but a southward latitudinal shift of 4° is simulated in the median of the tracks. The removal of SAMs is found to have little influence on LPS characteristics and summer monsoon rainfall over India.