MJO influence on ENSO effects in precipitation and temperature over South America

Abstract

Researches on the effects of the El Nino Southern Oscillation (ENSO) over precipitation and temperature, such as drought, flood, and anomalous high or cold temperatures, have large importance because of the impacts on the environment, society, and economy. Some recent studies, focusing on the Northern Hemisphere, have indicated that the basic response of ENSO is dependent on the phase of the Madden-Julian Oscillation (MJO). The present work investigates the combined response of the phases of these two distinct phenomena, ENSO and MJO, over South America. Our goal is to explore the relative importance of the MJO to precipitation and temperature anomalies during each ENSO phase. A composite analysis with each combination of the phases of ENSO and MJO was performed to obtain the mean patterns of temperature and precipitation over South America for the months of November to March (austral summer) and May to September (austral winter). The results showed that the precipitation and temperature anomaly patterns observed during the ENSO phases, without the concurrent occurrence of the MJO, can be strengthened or weakened during events where ENSO and MJO occur simultaneously. Moreover, the effect on the anomaly patterns in these events depends on the MJO phase.