Análise das possíveis relações entre os ciclos solares e as anomalias de TSM dos oceanos Pacífico e Atlântico tropicais.

Abstract

Recent studies show that the solar cycle influences stratospheric and tropospheric meteorological systems, thus providing a new conceptual framework that reconsiders the evidence of solar influence on climate. Therefore, the main proposal of this work is to investigate the possible effects of solar cycles on Sea Surface Temperature Anomalies (SSTA). In order to do so, we used data of sunspot number (SN) from the Royal Observatory of Belgium, SST anomalies in the areas of Niños 1 + 2, 3, 3.4 and 4 in the Pacific, and North Atlantic and South Atlantic, in the Atlantic, obtained from the CPC/NCEP/NOAA and ESRL/NOAA sites, respectively, and Pacific Decadal Oscillation (PDO), from the ESRL/NOAA, all monthly data during the period of December/1949 to January/2017. A three-month moving average filter was applied on all series to remove the intraseasonal oscillations. The quantile method was used to classify the cold, neutral and warm periods of each area, considering the 25% lower values as cold periods, the 25% intermediate as neutral and the 25% higher as warm. The means and standard deviations of the SN were calculated for each period and Student's t-test was performed to compare these means. It was verified that, in periods of SN maxima, the SSTA in the Pacific and North Atlantic tended to neutral conditions and those from the South Atlantic to the cold. In order to verify details of the relation into the series of SSTA and SN, the spectral analysis of the Continuous Wavelet Transform, Cross-Wavelet Transform and Wavelet Coherence was used, based on Morlet wavelet. The results showed that there were influences of solar cycles of Hale (256 months), Schwabe (128 months) and its second harmonic (64 months) in the behavior of SSTA. It has also been observed that the SSTA in the Pacific and Atlantic oceans respond differently to the solar forcing. It was concluded that the solar cycles effects on SSTA occur in a non-linear way, as there were phase changes between the series over time. As for the difference in the response of the Pacific and Atlantic SSTA to the solar forcing, it is believed to be due to the Southern Hemisphere Geomagnetic Anomaly and associated atmospheric phenomena, but there have been no conclusive studies on this matter, so much so that researches are suggested on the influence of solar cycles on the atmospheric circulation, most importantly for the South Atlantic region.