Analysis of average annual temperatures and rainfall in southern region of the state of Rio Grande do Sul, Brazil

Abstract

This work aimed to analyze the average temperature and rainfall in the Southern and Steppe regions of the State of Rio Grande do Sul, Brazil, obtained by three global climate models regionalized by the Eta model (CANESM2, HADGEM2-ES and MIROC5) for the historical period, and two future climate scenarios (RCP 4.5 and RCP 8.5), subdivided into three periods: F1 (2006-2040), F2 (2041-2070), and F3 (2071-2099). The analysis was conducted by applying the trend tests Mann Kendall’s, Sen’s Slope and Pettitt’s to the dataset. The study noted an increase in temperature, and that the highest temperatures will occur at the end of the century. For the three climate models, temperatures will be milder in the RCP 4.5 scenario, mostly, when compared to the RCP 8.5. For those scenarios, a significant increase up to 0.95°C/year was observed in the temperature of all series, with the years of change in the mean values occurring between 2048 and 2060. The projections also suggest that there may be an increase in the average accumulated rainfall in the future periods analyzed, with exception of the result found with CANESM2 model at the RCP 8.5 scenario, which showed a significant decrease of annual rainfall in all series, ranging approximately from -3,1 to -6,6 mm/year. Those significant changes in mean of the rainfall series are expected for the late 2070's. With exception of this result, most cities and models indicate an increase in rainfall regimes, with clear variations between models and scenarios.