Journal
CLIMATE DYNAMICS
Volume 39, Issue 6, Pages 1413-1430Publisher
SPRINGER
DOI: 10.1007/s00382-011-1164-4
Keywords
ENSO; SST bias; Thermocline feedback; Air-sea coupling
Categories
Funding
- National Science Foundation [AGS-1005599]
- APEC Climate Center
- International Pacific Research Center
- NASA [NNX07AG53G]
- JAMSTEC
- NOAA [NA09OAR4320075]
- Quaternary Research Center at the University of Washington
- Directorate For Geosciences
- Div Atmospheric & Geospace Sciences [1034798] Funding Source: National Science Foundation
- Div Atmospheric & Geospace Sciences
- Directorate For Geosciences [1005599] Funding Source: National Science Foundation
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Associated with the double Inter-tropical convergence zone problem, a dipole SST bias pattern (cold in the equatorial central Pacific and warm in the southeast tropical Pacific) remains a common problem inherent in many contemporary coupled models. Based on a newly-developed coupled model, we performed a control run and two sensitivity runs, one is a coupled run with annual mean SST correction and the other is an ocean forced run. By comparison of these three runs, we demonstrated that a serious consequence of this SST bias is to severely suppress the thermocline feedback in a realistic simulation of the El Nio/Southern Oscillation. Firstly, the excessive cold tongue extension pushes the anomalous convection far westward from the equatorial central Pacific, prominently diminishing the convection-low level wind feedback and thus the air-sea coupling strength. Secondly, the equatorial surface wind anomaly exhibits a relatively uniform meridional structure with weak gradient, contributing to a weakened wind-thermocline feedback. Thirdly, the equatorial cold SST bias induces a weakened upper-ocean stratification and thus yields the underestimation of the thermocline-subsurface temperature feedback. Finally, the dipole SST bias underestimates the mean upwelling through (a) undermining equatorial mean easterly wind stress, and (b) enhancing convective mixing and thus reducing the upper ocean stratification, which weakens vertical shear of meridional currents and near-surface Ekman-divergence.
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