Dominating Controls for Wetter South Asian Summer Monsoon in the Twenty-First Century

Journal Article · Wed Apr 01 04:00:00 EDT 2015 · Journal of Climate, 28(8):3400–3419

DOI:https://doi.org/10.1175/JCLI-D-14-00355.1· OSTI ID:1182905

Mei, Rui; Ashfaq, Moetasim; Rastogi, Deeksha; Leung, Lai-Yung R.; Dominguez, Francina

We analyze a suite of Global Climate Models from the 5th Phase of Coupled Models Intercomparison Project (CMIP5) archives to understand the mechanisms behind a net increase in the South Asian summer monsoon precipitation in response to enhanced radiative forcing during the 21st century despite a robust weakening of dynamics governing the monsoon circulation. Combining the future changes in the contributions from various sources, which contribute to the moisture supply over South Asia, with those in monsoon dynamics and atmospheric moisture content, we establish a pathway of understanding that partly explains these counteracting responses to increase in radiative forcing. Our analysis suggests that both regional (local recycling, Arabian Sea, Bay of Bengal) and remote (mainly Indian Ocean) sources contribute to the moisture supply for precipitation over South Asia during the summer season that is facilitated by the monsoon dynamics. Increase in radiative forcing fuels an increase in the atmospheric moisture content through warmer temperatures. For regional moisture sources, the effect of excessive atmospheric moisture is offset by weaker monsoon circulation and uncertainty in the response of the evapotranspiration over land, so anomalies in their contribution to the total moisture supply are either mixed or muted. In contrast, weakening of the monsoon dynamics has less influence on the moisture supply from remote sources that not only is a dominant moisture contributor in the historical period, but is also the net driver of the positive summer monsoon precipitation response in the 21st century. Our results also indicate that historic measures of the monsoon dynamics may not be well suited to predict the non-stationary moisture driven South Asian summer monsoon precipitation response in the 21st century.

• Research Organization: Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States). Oak Ridge Leadership Computing Facility (OLCF); Pacific Northwest National Laboratory (PNNL), Richland, WA (US)
• Sponsoring Organization: DOE Office of Science; USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 1182905
• Report Number(s): PNNL-SA-103075; KP1703010
• Journal Information: Journal of Climate, 28(8):3400–3419, Journal Name: Journal of Climate, 28(8):3400–3419
• Country of Publication: United States
• Language: English

Related Subjects

21st century
CMIP5
South Asia summer monsoon
global climate models