Spatial and temporal patterns linking southern low and high latitudes during South Pacific warm and cold events

Abstract

The phase and magnitude of the first harmonic of cold and warm event-centred 24-month 500 hPa height anomalies over the Southern Hemisphere are investigated in order to establish whether low and high latitude 500 hPa pressure anomalies are linked during Pacific Ocean warm (El Niño) and cold (La Niña) events. Study results revealed a linkage of pressure anomalies centred on 60°E in the Indian Ocean–East Antarctic region during cold events. In contrast to cold events, warm event signals in this area, as well as in the Antarctic Peninsula region, lack clarity because of considerable warm event variability. During warm events, however, a clear wave train of anomalies occurs along the South Pacific Convergence Zone (SPCZ). This is matched with a strong meridional contrast in the phase of 500 hPa anomalies such that low and high latitudes are out of phase with mid-latitudes. This Pacific/South American (PSA) pattern resembles the Pacific/North American (PNA) pattern, and is thought to play a major role in the transport of El Niño–Southern Oscillation (ENSO) signals from low to high latitudes. Copyright © 2000 Royal Meteorological Society