Tendências observadas em extremos de precipitação sobre a região Semiárida do Nordeste do Brasil

Abstract

The frequency of extreme precipitation events has increased in recent years, with greater intensity and duration, thus favoring natural disasters such as flood and severe drought. Therefore, the expansion of knowledge about the spatial and temporal variability of these extreme events is of paramount importance to the climatic conditions of a particular region. This research aims to check the possible trends in the intensity of rain occurred during the less rainy and rainy season on the Semi-arid region of Northeast Brazil during the period 1961-2011. The study was conducted with daily precipitation data, distributed in 193 rainfall stations, provided by the ANA and the INMET. We used the percentile for definition of extreme events WRE and HRE. Subsequently, the Mann-Kendall test was applied in order to check the possible trend, whether increasing or decreasing, with statistical significance level of 5%. The results indicated that there was a negative trend in the months from October to December and positive trend from June to August, all with statistical significance of 5%. The other months trends are presented, but not significant. The higher frequency of El Niño possibly explains the downward trend in the intensity of rainfall, consequently favored for longer periods without rain. Overall, these results indicated an increase in the intensity of dryness and reduction of heavy precipitation events over the years, leaving a reduction in precipitation of around 0.16 mm/year for the rainy less season and 0.64 mm/year for the rainy season