Extreme daily precipitation events in a city of the Ceará semiarid region

Abstract

The study applied the precipitation maxima methodology to analyze extreme daily rainfall events in the city of Juazeiro do Norte/CE, from 1991 to 2021, identifying the genesis of these events and the atmospheric systems involved. Precipitation data were obtained from the FUNCEME database, and the quantile statistical technique was employed to define a rainfall threshold for the municipality. Once the thresholds were established, the data were used in the precipitation maxima methodology to determine reference values for analyzing extreme daily events. Synoptic charts and satellite images were then examined to identify the potential genesis of these events. Based on the quantile technique, the Q85% quantile (very heavy rainfall, above 37mm/24h) was selected as the reference threshold for Juazeiro do Norte. Using the precipitation maxima methodology with the FUNCEME data, reference values were determined for each intensity level (Level I: 59.2; Level II: 80.8; Level III: 102.5; Level IV: 124.1). By defining these reference values, it was possible to quantify the occurrence of events across different intensity levels, ranging from low to very high. As a result, events classified as Level IV (very high intensity) were selected for a detailed analysis of their occurrence and possible genesis. It was found that Level IV events primarily occur during the rainy season, particularly in March, and are influenced by the presence of the ITCZ.