Analysis of extreme climate events and their climate causes for risks reduction in aguapeí and peixe hydrographic basins, são paulo, Brazil

Abstract

In order to improve our understanding on the extreme events of the hydrographic basins of river Aguapeí and river Peixe, using a variety of statistical analyzes, the objective of this work was to detect oscillations, systems or dominant phenomena that influence rainfall and the occurrence of extreme events in these hydrographic basins, to identify cli- matic trends, and groups with similar rainfall behavior using the Cluster analysis. In addition, SPI was used to analyze local extreme events, the variations of which were associated with the El Niño- South Oscillation (ENSO) Canonico or Modoki, and the Prp index was subjected to Wave Analysis to identify the climatic causes of rainfall variability. The wavelet analyses identified significant peaks at the 0.25 and 0.5 years although a 22-year time scale predominates during almost all years. Years with high rainfall rates are due to the association of different time scale phenomena, whereas their absences cause low rainfall years. A higher frequency of drought events was found, however, the occurrence of rainy events was more intense. Extreme rainy events occur mainly in canonical El Niño years, and light drought events in canonical La Niña years.