Spatial and temporal structures of trends and interannual variability of precipitation over the La Plata Basin

Abstract

The paper explores the climatic variability displayed by precipitation over the La Plata Basin in South America. Using a 1.0° lat × 1.0° long grid and 18 months of low-pass-filtered anomalies of monthly precipitation, a principal component analysis (PCA) was performed. The leading 10 spatial principal components were retained for a subsequent analysis. The spatial-temporal structure of the trend and interannual oscillatory components of precipitation over the whole La Plata Basin has been investigated in this study, using the M-SSA technique. We present evidence that precipitation has cycles in the IFB, with about 6 and 3.5 yr and a quasi-biennial oscillation, together with a trend component that explains less than 5% of the total variance. In order to determine if the oscillatory components (in the IFB) detected in rainfall are reflected in streamflows, an SSA was applied to the series of annual mean discharges corresponding to gauging stations on the major rivers of the region. Oscillatory components with dominant periods of about 6 and 3.5 yr were found in some rivers. For this reason, it could be said that the river behavior in the interannual frequency band is a clear reflection of what occurs with precipitation over the basin. © 2003 Elsevier Science Ltd and INQUA. All rights reserved.