Changes in rainfall patterns in southern Brazil over 1961-2020 period detected by rain gauge data

Long-term instrumental climate records are a major source of data for historical trends and extreme event analysis. Time series analysis of several rain gauges shows that the mid-latitudes of Brazil experienced an increase in both annual and extreme rainfall over the last 60 years (1961-2020). The annual time series shows a significant upward trend, while changes in the frequency and intensity of heavy rainfall indicate a shortening of the recurrence interval for extreme precipitation events. In support of these results, the standardized precipitation index (SPI) also shows a positive trend for rainfall anomalies. Thus, the flood risk is higher at present than a few decades ago, while drought intensity is lower for both short and long monthly intervals used for the SPI calculation. The 60-year instrumental rainfall data for southern Brazil shows that the amount of rainfall and changes in intensity could be higher than climate projections from models based on a broader spatial scale.