Sea surface height anomalies may help find more about El Nino/La Nina event

TOPEX/Poseidon (T/P) altimeter has been providing measurements of the variability of global ocean surface topography for the study of the variation of ocean circulation since it was launched in August 1992. Sea surface height anomaly (SSHA) from the T/P altimeter contains dynamical significance of the ocean movement including the well-known El Nino/La Nina events. Researchers on the El Nino/La Nina event have added much importance to the altimeter data since the SSHA changes dramatically when El Nino/La Nina takes place. However, this study suggested T/P data have more to say about the El Nino/La Nina event. SSHA from T/P altimeter products was used in this study to try depicting the dynamical process of El Nino/La Nino events. Using T/P SSHA data, a simple method for (relative) Potential Energy Torque (PET) of the Pacific Ocean was suggested and the PET time series was analyzed. Our results showed that along the equatorial Pacific the zonal PET moves rapidly to the east when the El Nino takes place, which goes well with previous conclusions. But we also found that the PET had a tremendous meridional change during the famous 1997-1998 El Nifio/La Nina event, which suggested that the El Nino/La Nina event might also have a strong meridional impact on the Pacific Ocean. The PET index may help better understand the El Nino/La Nina event and the Pacific Ocean. In the mean time, the PET might be a better index to the El Nino/La Nina event.