Rainfall extremes and pattern in the city of São Paulo

Abstract

The objective of this study is to analyze the precipitation variability, extreme events, and trends of this variable in the city of São Paulo. The data used covered the period between 1933 and 2020, originating from the IAG/USP Meteorological Station. The monthly averages for the study of seasonality, the boxplot diagram for the investigation of rare monthly events, and the quantile technique for classifying extreme precipitation events were considered for analysis. A trend analysis was performed through the accumulated annual precipitation and linear adjustment by a simple linear regression equation. In seasonal terms, the city of São Paulo has low precipitation in winter, with a minimum in August and an average of 38.05 mm, increasing total precipitation during spring. It was observed that the highest precipitation values occurred during the summer, with a peak in January and 232.14 mm. According to the boxplot diagram, the rare events of high precipitation occur mainly in winter, with emphasis on May and June. There is a greater concentration of extreme precipitation events in the second half of the observed years. The dry months have the highest occurrences of rare precipitation events. Simple linear regression analysis indicated a positive trend, indicating an average increase in annual precipitation of 508.43 mm in the city of São Paulo. In general, there is an indication of an precipitation increase in the city, especially due to the higher frequency of monthly extreme rainy events.

Keywords:  Seasonality. Extreme events. Rain. Dry. Climatological norms.