Mechanism of the Asymmetric Monsoon Transition as Simulated in an AGCM
Abstract
Atmospheric general circulation model (AGCM) simulations are carried out to
test a hypothesis (Chang et al. 2005) for the asymmetric monsoon transition in
which the maximum convection marches gradually from the Asian summer
monsoon to the Asian winter monsoon during boreal fall but experiences a
sudden transition in the reverse during boreal spring. In the control run, the
AGCM is driven by the climatological mean sea-surface temperature (SST) with
a realistic annual cycle, and it reproduces the observed asymmetric monsoon
transition. In the sensitivity test, the model is driven by a similarly realistic SST
but whose annual cycle is symmetric. The northwestward march of the maximum
convection in boreal spring becomes more gradual, resulting in an overall nearsymmetric
pattern for the monsoon seasonal transition. The AGCM simulations
confirm the hypothesis that the atmospheric mass redistribution due to the
different land–ocean thermal memories leads to a seasonally different horizontal
convergence field and it facilitates the southeastward monsoon march in boreal
fall while hinders the northwestward monsoon march in boreal spring,
contributing to the asymmetric monsoon transition.Atmospheric general circulation model (AGCM) simulations are carried out to
test a hypothesis (Chang et al. 2005) for the asymmetric monsoon transition in
which the maximum convection marches gradually from the Asian summer
monsoon to the Asian winter monsoon during boreal fall but experiences a
sudden transition in the reverse during boreal spring. In the control run, the
AGCM is driven by the climatological mean sea-surface temperature (SST) with
a realistic annual cycle, and it reproduces the observed asymmetric monsoon
transition. In the sensitivity test, the model is driven by a similarly realistic SST
but whose annual cycle is symmetric. The northwestward march of the maximum
convection in boreal spring becomes more gradual, resulting in an overall nearsymmetric
pattern for the monsoon seasonal transition. The AGCM simulations
confirm the hypothesis that the atmospheric mass redistribution due to the
different land–ocean thermal memories leads to a seasonally different horizontal
convergence field and it facilitates the southeastward monsoon march in boreal
fall while hinders the northwestward monsoon march in boreal spring,
contributing to the asymmetric monsoon transition.
Description
J. Climate, 1829-1836. (manuscript)
Rights
This publication is a work of the U.S. Government as defined in Title 17, United States Code, Section 101. Copyright protection is not available for this work in the United States.Collections
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