Estudo da mudança nos padrões de precipitação no estado do Paraná

Abstract

Precipitation events have undergone significant changes in their behavior over the past decades, primarily influenced by global climate change. Understanding these variations is essential for the proper design of hydraulic structures, urban planning, and the management of water and agricultural resources. In this context, the present study aimed to analyze the temporal trends of the inter-event time (IET) and the annual number of rainfall events (λ) in the state of Paraná, seeking to identify potential changes in the rainfall regime over time. Historical precipitation series with more than 50 years of records, obtained from 66 meteorological stations distributed throughout the state, were used. The methodology was based on the application of statistical tests, such as the t-test and F-test, for the comparison of means and variances between two distinct periods in order to detect changes in the pattern, in addition to the analysis of differences between past and present mean values for stations with statistically significant changes. The study considered three precipitation thresholds: 25 mm, 50 mm, and 75 mm. The results showed that most of the significant changes occurred at the 25 mm threshold, indicating an increase in the frequency of lower-magnitude rainfall events and a reduction in the average interval between events, suggesting a more frequent rainfall regime. In contrast, for higher thresholds, changes were less pronounced, although they evidenced the intensification of extreme events in some regions. Spatial analysis revealed that the transformations do not occur uniformly across the state, being more pronounced in the Eastern region, possibly due to orographic and maritime influences. It is concluded that the rainfall regime in Paraná shows signs of potential non-stationarity, reflecting greater temporal and spatial variability of rainfall. These results reinforce the importance of reviewing hydrological models and infrastructure planning, as well as the need for public policies aimed at adapting to and mitigating the impacts of climate change.