Latitudinal Profiles of Seasonal Rainfall-Enso Association along the Coast of Central and South America, Using Contingency Tables

Abstract

The Influence of the ENSO events over the west coast of Central and South America (22oN - 45S) precipitation was investigated using Pearson's association index and a generalized logit models. Data consisted on a couple of indices representing the ocean atmosphere interaction along the Equatorial Pacific and 5x5 degrees gridded locations over the pacific coast of Central and South America, each represented by a rainfall monthly time series starting since 1900. We used a seasonal ocean-atmosphere ENSO index as predictor for the seasonal rainfall, to fit logit models to estimate the probability of classifying any seasonal observation into terciles (warm, neutral and cool) and associate with terciles in the response variable (dry, neutral, wet). We analyzed three way contingency tables, in which the third category corresponds to the lagged classification of the predictor. Results generally confirm preceding studies on influence of El Niño Southern Oscillation over the west coast of Southern America, i.e., warm/cool events are generally associated with wet/dry situations along the west coast, but it also gives further insight by providing estimates for the probability that a warm/cool ENSO event induces dry/wet seasons and vice versa along the coast of South America for each season.