Evidences for sunspot forcing of regional climate in South America

G. SILVESTRI; R. COMPAGNUCCI; V. VELASCO

Foz do Iguazu

Congreso; AGU2010 - The meeting of the Americas; 2010

American Geophysical Union

The Paraná river located in South America is one of the largest rivers in the world. The aim of this note is to present information that support the hypothesis that variations in solar activity has a very complex influence in the Paraná river flow. Annual values of the Paraná River (RIVER) discharge, annual sunspot number (SUN) and cosmic ray intensity (CRI) were analyzed. In order to investigate the band of frequency within the time series of SUN/CRI and RIVER are co-varying, a wavelet-squared coherency (WTC) analysis was made. The wavelet coherency demonstrates a strong relationship between the variability of SUN and RIVER in bands around 6-16 yrs before 1935 and in a narrow band around 14 yrs after 1980. Moreover, a strong linear connection exists in signals with period around 30 yrs being and in-phase connection during all the century. The connection between SUN and RIVER is not only observed in decadal or multidecadal temporal scales but also there is a significant nonlinear co-variability in bands around 3.5 yrs mainly before 1912, 1930-1950, the 1960s and after 1995, approximately. Similar results are obtained in the analysis of the relationship CRI-RIVER but with an inverse sign coherently with the inverse relationship that exists between CRI and SUN. This study describes how complex are the physical processes that are linking the solar activity with the regional climate. Further studies must be done to elucidate the nature of these processes. In particular for the Paraná river, the connection via sea surface temperature influence could be important.