Latitudinal positioning of the subtropical anticyclone along the Chilean coast

Abstract

In the past various authors have investigated climatic change (CC) by using the latitude of the subtropical ridge in the mean sea-level pressure (MSLP) for a range of geographic regions. In this paper the index L is defined as the latitudinal position of the subtropical anticyclone along the Chilean coast. This L index on the South American coast of the South Pacific is analysed using an instrumental record, covering the 1901-2004 period. An objective methodology is proposed for estimating L, and the physical consistency is assessed with the SOI and pressure at sea level in Valdivia, Chile. The analysis of a shorter period is compared with other authors’ results. The L variable can be useful in CC studies or in the analysis of low-frequency fluctuations in climate variability, and it is analysed as a dependent and independent time series. L was displaced towards the south over the last century but not to a statistically significant extent. Natural fluctuations of 50 years and another, shorter, of 16-22 years were also observed. In this paper, the greatest persistence and distant associations between anomalies of monthly L are shown; these associations can be useful for climate forecasting.