Global warming and the weakening of the Asian summer monsoon circulation: assessments from the CMIP5 models

The evolution of the Asian summer monsoon (ASM) in a global warming environment is a serious scientific and socio-economic concern since many recent studies have demonstrated the weakening nature of large-scale tropical circulation under anthropogenic forcing. But, how such processes affect the ASM...

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Bibliographic Details
Published in:Climate dynamics 2015-07, Vol.45 (1-2), p.233-252
Main Authors: Sooraj, K. P., Terray, Pascal, Mujumdar, M.
Format: Article
Language:English
Subjects:
Analysis
Anthropogenic factors
Atmosphere
Atmospheric circulation
Climate change
Climate models
Climatology
Earth and Environmental Science
Earth Sciences
Geophysics
Geophysics/Geodesy
Global warming
Heating
Monsoons
Oceanography
Physics
Rain
Rainfall
Storms
Summer
Temperature gradients
Thermodynamics
Troposphere
Water vapor
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Summary:The evolution of the Asian summer monsoon (ASM) in a global warming environment is a serious scientific and socio-economic concern since many recent studies have demonstrated the weakening nature of large-scale tropical circulation under anthropogenic forcing. But, how such processes affect the ASM circulation and rainfall is still a matter of debate. This study examines the climate model projections from a selected set of Coupled Model Inter-comparison Project 5 (CMIP5) models to provide a unified perspective on the future ASM response. The results indicate a robust reduction in the large-scale meridional gradient of temperature (MGT) at upper levels (200 hPa) over the ASM region, associated with enhanced ascendance and deep tropospheric heating over the equatorial Pacific in the future climate. The differential heating in the upper troposphere, with concomitant increase (decrease) in atmospheric stability (MGT), weakens the ASM circulation, promotes a northward shift of the monsoon circulation and a widening of the local Hadley cell in the eastern Indian sector. An examination of the water vapour budget indicates the competing effects of the thermodynamic (moisture convergence) and dynamics processes (monsoon circulation) on future ASM rainfall changes. The former component wins out over the later one and leads to the intensification of Indian monsoon rainfall in the CMIP5 projections. However, the diagnostics further show a considerable offset due to the dynamic component.
ISSN:0930-7575
1432-0894
DOI:10.1007/s00382-014-2257-7