As maiores cheias e secas no Amazonas e as possíveis influências dos fenômenos El Niño, La Niña, ODP E OMA.

Abstract

The aim of this study is to associate the impacts generated by the coupled ocean-atmosphere phenomena such as El Niño, La Niña, the Pacific Decadal Oscillation (PDO) and the Atlantic Multidecadal Oscillation (AMO), which can influence the atmospheric systems responsible for producing regional-scale weather conditions, and to relate these phenomena with the severe FLOODS and DROUGHTS which have stricken western Amazon. This is an original research because not only does it analyze the interannual coupled phenomena (El Niño and La Niña) and the decadal oscillations (PDO and AMO), but also presents a better understanding of the ten most severe FLOODS and DROUGHTS registered in western Amazon, including the most recent ones: the 2009 and 2012 FLOODS; and the 2005 and 2010 DROUGHTS. It was observed that variations in rainfall and river flows in western Amazon show an interannual variability and interdecadal time frame that are more important than the trends of the increase or the decrease of rivers’ water level. This variability is associated with patterns of variation in the same time scale in the tropical Pacific and tropical Atlantic oceans, as well as with the interannual variability associated with El Niño – Southern Oscillation – or the decadal variability of the Pacific and the Atlantic. The results are interesting because they are partially contrary to other studies already published. Most severe FLOODS, 80% of them, occurred in La Niña years, and 20% in El Niño years; 80% of cases with negative PDO, 20% with positive PDO, 70% with negative AMO and 30% with positive AMO. The three major severe FLOODS in Negro River were in years with positive AMO, 1953, 2009 and 2012. Most of the DROUGHTS, 60% of them, were registered with the occurrence of El Niños, 30% in years of La Niña and 10% in neutral year; 60% with positive PDO, 40% with negative PDO, 50% with positive AMO and 50% with negative AMO. It is observed the influence of interannual and decadal phenomena in the occurrence of severe FLOODS and DROUGHTS in western Amazon.