Low frequency variability in the South Oriental Pacific and its relationship with the equatorial Pacific

Abstract

The aim of this study is to investigate the annual and interannual cycle of the variables of sea level anomaly (SLA) and atmospheric pressure in the equatorial and South Oriental Pacific regions. Harmonic analysis will be applied for the annual cycle and the Empirical Orthogonal Functions (EOFs) for the interannual cycle. Since the equatorial region is decisive for an ocean-atmosphere coupling event like the El Niño Southern Oscillation (ENSO), a relation with the El Niño 3.4 Index will be studied too. In this context, a relationship between the variables and the different processes dominating in the two different areas is expected, like the SLA with the ENSO and the atmospheric pressure with the South East Anticyclone. Some significant relationships between them were found. The SLA in the equatorial region, showed a ENSO like pattern for the first mode of the EOF analysis, and when correlating it with the El Niño 3.4 Index, the highest relation appeared of 83.6%. The South East Anticyclone pattern was shown for the second mode of the pressure in the PSO region, which explained a 24.9%, while the SLA showed a behavior dominated by the Rossby waves. The study finally provides a comprehensive view of the mechanisms that influence the fluctuations in the SLA and in the atmospheric pressure, determinating the characteristics of the annual cycle of them in the South Oriental Pacific and the relationship with the equatorial pacific, and seeing the characteristics of the interannual variability of the atmospheric pressure and the sea level anomaly.