Temporal trends in extreme rainfall indices in Santa Catarina, Brazil

Código

I-EBHE0137

Autores

Jéssica Aurora Bernardo, Bruno Rech, Julia dos Santos da Silva, Patrícia Kazue Uda, ALEXANDRA RODRIGUES FINOTTI

Tema

WG 1.08: Deep Explanation & Evaluation for Practices in Hydrological Changes (DEEPHY)

Resumo

Climate extremes are increasingly frequent, significantly impacting daily life in social, economic, and environmental terms. Understanding climate trends is crucial for planning water resource usage and developing mitigation and adaptation strategies. This study aims to identify changes in extreme annual precipitation using 10 main indices developed by the Climate Change Detection and Indices Expert Team, which express climate variations. The study focuses on analyzing annual trends in daily extreme precipitation over a 45-year period, from 1976 to 2021, using data from 62 rainfall stations in the state of Santa Catarina, southern Brazil. As a selection criterion, series with less than 5% gaps were chosen, and a consistency analysis was carried out using the double-mass test. The index series were generated, with trends calculated using the Mann-Kendall test and magnitudes indicated using the Sen's slope method. The SDII (Simple Daily Intensity Index) was one of the indices with the highest and most well-distributed number of statistically significant results; most showed increasing trends. It provides a simple indication of intensity, highlighting either increasing precipitation or decreasing number of precipitation days. More details regarding intensity can be obtained by considering R25 (Number of heavy precipitation days above 25mm) and R50 (Number of very heavy precipitation days above 50mm). In both cases, most stations with significant trends indicate an increase in the number of days with higher volumes of precipitation (not necessarily extremes). The same can be said for R95p (Very wet days) and R99p (Extremely heavy precipitation days), which show that extreme events are becoming either more extreme or more common. This behavior is not well-distributed over Santa Catarina (less significant in the central region) but includes all mesoregions. In Vale do Itajaí (mid-eastern), a region known for flooding issues, it's noteworthy that indices representing more extreme events are usually located in the higher portions of the basin (the most affected by floods). Another region of interest is Oeste Catarinense (western), historically known for droughts, but with the highest number of stations showing significant increases in median and high precipitation quantiles. The results highlight the urgent need for policies and adaptive measures to address the increasing occurrence of extreme weather events, emphasizing the importance of regionalized understanding of these patterns to ensure effective water resource management and the resilience of affected communities.