Role of Local Air-Sea Interaction in Tropical Atlantic Variability
Shang-Ping XieInternational Pacific Research Center
University of Hawaii
• Atlantic El Nino • SST Dipole?• Ocean GCM• Coupled Feedback• Atmospheric GCM• Processes that weaken cross-eq.
feedback
xZ20
SST dipole
Y_ITCZ
Servain ’99, GRL
Nobre and Shukla 1996, JC
NE Brazil rainfall
SST dipole
Quasi-decadal oscillation?
Mehta ’98, JC
Tourre et al. ’99, JC
Enfield et al. ’99, JGR
Black et al. ’99, Science
835-year sediment core
11.4 yr
SST’
Eq 30N30S
Cloud-SST Feedback
Okumura et al. ’01, GRLXie & Saito ’01, JC
Seager et al. 2001, JC
Carton et al. 1996, JPO
(Hakkinen and Mo 2001, JC)
x
h
SST
’=0
Xie et al. 1999, GRL
Chang et al. 2000, JC Sutton et al. 2000, JC
Okumura et al. (2001), GRL
SST and surface wind (JFM)
Chiang et al. 2001, JAS
Obs
LinearModel
Corr(NCEP, Model) 79-98
U
V
Also Chung et al. 2001, JGR
Chang et al. 2001, JC
Xie and Tanimoto ’98, GRL
Zonal-mean model simulation
Chang et al. ‘01, J. Climate
Cross-equatorial interaction
Obs
H. Okajima 2001
Processes that weaken inter-hemispheric interaction
Correlation
Equatorial mode with Bjerknes feedback
Meridional/dipole mode
Statistical evidence
Surface heat flux (wind & cloud) dominates off-eq. SST variability
Near-eq. baroclinic response and barotropic teleconnection into the subtropics
Two-way coupling among cross-eq. SST gradient, ITCZ, and near-eq. wind
Processes that weaken this interaction: Asymmetric ITCZ and external forcing (NAO & ENSO)
Conclusions
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