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Role of Local Air-Sea Interaction in Tropical Atlantic Variability. Shang-Ping Xie International Pacific Research Center University of Hawaii. Atlantic El Nino. SST Dipole? Ocean GCM Coupled Feedback Atmospheric GCM Processes that weaken cross-eq. feedback. SST dipole. Y_ITCZ.
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Role of Local Air-Sea Interaction in Tropical Atlantic Variability Shang-Ping Xie International Pacific Research Center University of Hawaii • Atlantic El Nino • SST Dipole? • Ocean GCM • Coupled Feedback • Atmospheric GCM • Processes that weaken cross-eq. feedback
SST dipole Y_ITCZ dxZ20 Servain ’99, GRL
Quasi-decadal oscillation? NE Brazil rainfall Enfield et al. ’99, JGR SST dipole Mehta ’98, JC 835-year sediment core 11.4 yr Tourre et al. ’99, JC Black et al. ’99, Science
SST’ 30S 30N Eq
Cloud-SST Feedback Okumura et al. ’01, GRL Xie & Saito ’01, JC
Dtx Dh t’=0 DSST Carton et al. 1996, JPO (Hakkinen and Mo 2001, JC) Seager et al. 2001, JC
Chang et al. 2000, JC Sutton et al. 2000, JC
SST and surface wind (JFM) Okumura et al. (2001), GRL
Corr(NCEP, Model) 79-98 Obs U Linear Model V Chiang et al. 2001, JAS Also Chung et al. 2001, JGR
Cross-equatorial interaction Zonal-mean model simulation Xie and Tanimoto ’98, GRL Obs Chang et al. ‘01, J. Climate
Processes that weaken inter-hemispheric interaction Correlation H. Okajima 2001
Conclusions 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)