Multidecadal Cycles of the Climatic Index: Sunspots that Affect North and Northeast of Brazil

TL;DR

This study investigates the multidecadal cycles of sunspot activity and their association with surface temperature anomalies in Northern and Northeastern Brazil using wavelet analysis and correlation tests.

Contribution

It identifies multidecadal and shorter cycles in sunspot activity and explores their influence on regional surface temperatures in Brazil.

Findings

Significant multidecadal cycles of 11, 2.66, and 5.33 years were observed in sunspot data.

Weak 21.33-year signal detected in Sea Surface Temperature component of AMM index.

Minimum temperature anomalies in most locations negatively correlated with sunspot activity.

Abstract

Using the 1951--2017 historical series of the Atlantic Meridional Mode (AMM) index and the monthly number of sunspots, it was possible to observe a significant association between them. The use of wavelet and cross-wavelet analysis showed the presence of multidecadal cycles pronounced in eleven years, as well as cycles of 2.66 and 5.33 years. The AMM index showed, in the Sea Surface Temperature (SST) component, the presence of a weak signal of 21.33 years. The influence and association of sunspot variability on surface temperature in Northern and Northeastern regions of Brazil were investigated. Using a non-parametric statistical correlation test, the historical series of surface temperature anomalies in five locations (Bel\'em, S\~ao Luiz, Fortaleza, Fernando de Noronha, and Natal) were compared with the monthly solar-series anomalies. The temperature series used were the minimum monthly average, the monthly average, and maximum monthly average temperatures, with their respective anomalies in relation to the mean. However, among all the series (except for S\~ao Luiz), the analyzed minimum temperature anomalies showed a negative correlation with sunspots. As a preliminary result, the analyzed climatic indices present an apparent degree of memory associated with the variability of sunspot activity.