Mesoscale Convective Systems Dominate the Energetics of the South Asian Summer Monsoon Onset. Issue 17 (2nd September 2021)

• Record Type: Journal Article
• Authors: Chen, Xingchao; Leung, L. Ruby; Feng, Zhe; Song, Fengfei; Yang, Qiu
• Is Part Of: Geophysical research letters. Volume 48:Issue 17(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-09-02
• Subjects: monsoon -- onset -- MCS; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1029/2021GL094873
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: The rapid onset of the South Asian summer monsoon (SASM) is featured as an abrupt increase of rainfall and atmospheric column‐integrated moist static energy (MSE). Using convection‐permitting simulations, a novel cloud tracking technique, and an MSE budget, the relative roles of mesoscale convective systems (MCSs) and non‐MCS deep convection in the SASM onset energetics are studied. The analysis shows MCSs greatly contribute to the sudden increases of rainfall, diabatic MSE sources, and the subsequent enhanced export of column‐integrated MSE during the rapid onset phase. A "diabatic sources‐energy export" plane analysis delineates the different roles of MCSs and non‐MCS deep convection. Although deep convection always leads to a net energy export, mesoscale organization of deep convection dominates the convection‐associated positive feedbacks that accelerate the energy cycle of the SASM onset. Sensitivity experiment shows that the results are insensitive to the model resolutions. Plain Language Summary: The start of the South Asian summer monsoon (SASM) is characterized as a sudden increase of precipitation over South Asia, which is known as the SASM onset. The total energy in the atmosphere also considerably increases during the SASM onset. In this study, the roles of deep convection in the SASM onset are investigated using high‐resolution simulations, a novel cloud feature tracking technique, and theoretical analysis tools. Results show that organized convective storms associated with mesoscale convective systems (MCSs) dominate the energetics of the rapid SASM onset. The organization of MCSs modulates the positive convective feedbacks, produces enhanced diabatic forcings and energy export, and further impacts the energy cycle of the SASM onset. The result suggests that mesoscale organization of deep convection plays an important role in the SASM onset. Key Points: The roles of deep convection in the South Asian summer monsoon onset are investigated using convection‐permitting simulations Mesoscale convective systems greatly contribute to the rapid increases of rainfall, diabatic sources, and energy export during the onset Mesoscale organization of deep convection can modulate the positive convective feedbacks and the monsoon onset energetics