Variabilidad temporal de la precipitación en la ciudad de La Plata durante el período 1909-2007: tendencia y fluctuaciones cuasiperiódicas

the variability of the time series of monthly precipitation totals of la plata observatorio is analyzed for the period 1909-2007. the analysis is performed with a technique known as singular spectrum analysis (ssa). results show oscillations with a dominant 4-5-year period and another one with ~3- year period. an increasing trend is also detected, particularly during the second half of the analyzed period. there are also oscillations with 7-8-year period, although they are not statistically significative. an analysis of seasonal and half-year precipitation series also exhibits oscillations with a 3-5-year dominant period. on the other hand, the trend only persists during the warmer season. linear correlation coefficients are computed between precipitation and southern oscillation index series (soi). in particular, results suggest that precipitation tends to be higher (lower) than average during october-march after the onset of el ni？o (la ni？a). the most robust correlation occurs between october-december precipitation totals and the previous july-september soi average.