Hobart

Seminar Abstract

Tuesday 2 February 2010, 11.30am (Tas time)
CSIRO Auditorium, Hobart

Xuebin Zhang
Scripps Institution of Oceanography
University of California
San Diego, USA

Local Forcing of SST in the Eastern Equatorial Pacific – Empirical Analyses and Numerical Sensitivity Experiments

Historical studies indicated that remote wind forcing from the central and western tropical Pacific is a dominant feature common to all El Nino – Southern Oscillation (ENSO) events. The sea surface temperature (SST) variations in the eastern equatorial Pacific are found to be highly connected with remote wind forcing on interannual time scales due to the Bjerknes feedback mechanism. Effects of local forcing on SST variations in the eastern equatorial Pacific have been usually neglected and not well-studied, which can nonetheless contribute to the unique characteristics of single ENSO event and event-to-event differences. So in this study, we try to systematically and quantitatively evaluate the effects of local forcing (including both wind stress and heat flux) on interannual SST variations in the eastern equatorial Pacific and associated physical processes causing these SST variations, using both empirical analyses and numerical sensitivity experiments based on ocean general circulation models. For numerical sensitivity experiments, both “forward” and “reverse” approaches are used. Results from empirical analyses and numerical experiments support each other. We find that the local dynamical forcing (mainly zonal wind stress) can in some circumstances leads to significant SST anomalies, while local net surface heat flux exerts a damping effect. Surface layer heat budget analysis indicates that the main local-forcing-induced physical process leading to interannual SST variations is advection of mean temperature gradient by anomalous vertical velocity. The sensitivity of Nino3 SST to local zonal wind stress (or equivalently the efficiency of local zonal wind stress affecting Nino3 temperature) depends on the “background”. Strong (weak) sensitivity can be found at the peak of La Nina (strong El Nino), where local thermocline depth is anomalously shallow (deep) and vertical temperature gradient is anomalously strong (weak).

Seminar recording

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Location:
CSIRO = Marine Laboratories Auditorium, Castray Esplanade, Hobart

For further information, or to schedule a seminar, contact:
To schedule a seminar, contact:
Clothilde Langlais, (Oceanographic seminars) CSIRO Marine and Atmospheric Research (03) 6232 5399
Natalie Kelly, (Biology/Modelling seminars) CSIRO Marine and Atmospheric Research 0438 452 483
Jillian Enraght-Moony, (seminar administrator) CSIRO Marine and Atmospheric Research (03) 6232 5320
Communications Manager, Antarctic Climate and Ecosystems CRC (03) 6226 2265
Margaret Hazelwood, Institute of Antarctic and Southern Ocean Studies (IASOS) University of Tasmania (03) 6226 2971

Last updated 11/05/10