The Relationship between the El Nino/La Nina Cycle and the Transition Chains of Four Atmospheric Oscillations. Part I: The Four Oscillations

The first leading modes of the interannual variations in low-level circulation over the North and South Pacific are the Northern Oscillation (NO) and Southern Oscillation (SO), which are oscillations in sea level pressure anomalies (SLPAs) between the eastern and western Pacific Ocean. The second leading modes are the North Pacific Oscillation (NPO) and the Antarctic Oscillation (AAO), which reflect oscillations between the subtropics and the high and middle latitudes. The transition chains of these four oscillations were investigated using the National Centers for Environmental Prediction-National Center for Atmospheric Research (NCEP-NCAR) reanalysis data. The general pattern of the transition chain between the NO and NPO was from the negative phase of the NO (NO-) to the positive phase of the NPO (NPO+), then from NO+ to NPO- to NO-. The whole transition chain took about 4-6 years. The general pattern and period of the transition between the SO and AAO were similar to those between the NO and NPO. In addition, the transition chains between the NO and NPO, and the SO and AAO, were almost simultaneous. The transition chains of the four oscillations were found to be closely connected, with the eastward propagations of SLPAs occurring along both sides of the Equator.