Temperature and Precipitation Extremes in the Brazilian Legal Amazon: A Summary of Climatological Patterns and Detected Trends

The continuous understanding of extreme weather events in the Amazon is fundamental due to the importance of this biome for the regional and planetary climate system. Climate characterization and the identification of changes in the current climate can be key findings for adaptation and mitigation measures. This study examined climatology and trends in 20 climate extreme indices associated with air temperature and precipitation in the Brazilian Legal Amazon (BLA). Daily observed data, interpolated at grid points, were analyzed from 1961 to 2020. Statistical tests were employed to determine the trend’s significance and magnitude. The results indicate that prolonged heat, hot days, and annual temperature records have become increasingly frequent in practically all of BLA over the last decades. Warm days and nights are increasing at approximately +11 days/decade. Heat waves have gone from 10 to 20 consecutive days on average in the 1960s to around 30–40 days in recent years. Indices associated with the intensity and frequency of extreme precipitation show a reduction, especially in the rainiest portion of the BLA, the western sector. In the east/south region of BLA, where consecutive dry days reach 100 days/year, they continue to increase at a rate of +1.5 days/decade, a fact related to the delay at the beginning of the rainy season. These aspects deserve attention since they impact local circulation, reducing the convergence of humidity not only over the BLA but also in central-southern region of Brazil.