Analysis of El Niño Southern Oscillation (ENOS) episodes and interannual rainfall variability in Rio Branco, Acre, 1971-2010 interval

Abstract

This study aimed to evaluate the influence of the El Niño Southern Oscillation (ENOS) phenomenon on rainfall in the municipality of Rio Branco, Acre, based on data from a conventional meteorological station from the National Institute of Meteorology (INMET), 1971-2010 interval. The randomness of the data was evaluated using the non-parametric Run test. In the analysis of the influence of the ENSO phenomenon on annual rainfall, the Rain Anomaly Index (IAC) was used, as well as information on the occurrence of ENSO episodes, available on the National Weather Service Climate Prediction Center (NOAA) website. The results showed a considerable interannual variability of rainfall, with an average of 1,947 mm, and standard deviation of 216 mm, predominantly dry years-S (12 years) and very dry-MS (12 years), due to negative rainfall anomalies (23 years), which are mostly associated with the El Niño event (11 years), generating rainfall volumes below the climatological average.