Classification of precipitation anomalies in the Rio Grande do Sul in ENSO events in the 20th century

This study investigated the intensity and spatial distribution of precipitation anomalies in Rio Grande do Sul state (RS) during 20th century by analyzing influence El Niño – Southern Oscillation (ENSO) its three phases. Reanalyzes from University Delaware (V5) were used. Precipitation divided into zones (Campaign, Plateau, Coast) to investigate possible differences under ENSO influence. Alexandersson's Standard Normal Homogeneity Test was applied verify structural breaks. Wavelets used rate periodicity Anomalies that occurred La Niña phases classified contingency tables as weak, average, strong evaluate qualitative behavior these anomalies. It found presented a break 1955 when tendency positive increased. From 1955, increased at least 0.5 standard deviation while frequency decreased 85 60 months. Peaks higher than 200 mm. In neutral cases, intensified since 1970. Negative did not show specific any phase. Contingency indicated events present visible pattern. could intensify episodes negative (-0.5) deviation. Therefore, increase or decrease monthly anomaly but Weak Niños tends contribute cases are associated with an average 2 deviations concluded RS is stronger Niña. Still, both may induce anomalies, depending on each case. Wavelet analysis revealed cycles coincide Niño/La showed (decrease) (negative) The other climatic variability modes meteorological 25 43 months RS.