Avaliação da possível influência de forçantes geofísicos sobre a variabilidade da temperatura na região litorânea do Rio Grande do Sul no último século

Abstract

The goal of this work is to investigate the influence of galactic cosmic rays (RCG) and the solar activity on the annual average temperature variability registered in three weather stations, covering the period between 1931 and 2014 along the coast of the Rio Grande do Sul (RS) State. The study area was chosen considering the lower intensity of geomagnetic field resulting of the influence of the South Atlantic Magnetic Anomaly (AMAS) during the last century, which can make possible effects associated to the RCG more significant on this region. Besides the geomagnetic field, RCG are modulated by the Sun’s magnetic field, more specifically by solar activity/magnetic cycles of ~11 and ~22 years. As a result of solar and geomagnetic modulation, regions with low geomagnetic field intensity are characterized by high RCG fluxes which, as a consequence of solar modulation, show decadal periodic variations similar to solar periodicities. Results of classical spectral analysis using the Análise por Regressão Iterativa de Séries Temporais (ARIST) method and spectral Coherence analysis using Wavelet Transform (WTC) revealed typical signals of the RCG and solar activity on the climatic data, through 11 and 22 year cycles. This result is an mathematical indication that part of temperature variations in the coast of RS can be attributed to these geophysical forcings.