Southern Hemisphere 500 hPa Height Anomaly Dynamics During South Pacific Warm and Cold Events

The phase and magnitude of the first harmonic of cold and warm event centred 24 month 500hPa height anomalies over the Southern Hemisphere are investigated in order to establish whether low and high latitude 500hPa 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 60oE in the Indian Ocean east Antarctic Indian Ocean 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 due to considerable warm to warm event variability. During warm events however, a clear wave train of anomalies occurs along the SPCZ. This is matched with a strong meridional contrast in the phase of 500hPa anomalies such that low and high latitudes are out of phase with mid-latitudes. This Pacific South American (PSA) pattern resembles the North Pacific PNA pattern and is thought to play a major role in the transport of ENSO signals from low to high latitudes.