Extreme precipitation events and their relationship with ENSO and MJO phases over northern South America

Abstract

Several droughts and floods in Amazonia and Northeast Brazil have occurred in recent years and projections from Intergovernmental Panel on Climate Change indicate an increase of these extreme events. El Niño Southern Oscillation (ENSO) is one of the phenomena associated with extreme rainfall events in the Amazon. However, recent studies have indicated that the basic response of ENSO is dependent on the Madden-Julian Oscillation (MJO) phase. Hence, this study analyses the MJO influence on precipitation extreme events over northern South America in El Niño and La Niña years. Extreme precipitation events over northern South America for the rainy season (December-May) were obtained through a composite analysis of the combinations of ENSO and MJO phases. Most of the dry extreme events occurred during El Niño periods, while wet extreme events were more recurrent during La Niña or neutral years. However, the results showed that the MJO convection could enhance or weaken the basic response of ENSO on extreme precipitation events. Moreover, dry/wet extreme events over both Amazon and Northeast Brazil are favoured when MJO convection over Indonesia is enhanced (MJO phases 4 and 5)/suppressed (MJO phase 2). Additionally, the interannual variability of the extreme events showed an increasing linear trend for dry extreme events and a decreasing linear trend for wet extreme events. The results presented here contribute to a better understanding of the climate variability and will be helpful for the forecast of ENSO effects on extreme events over northern South America. KEY WORDS extreme events; ENSO and MJO interaction; northern South America

Meteorological context of the onset and end of the rainy season in Central Amazonia during the GoAmazon2014/5

“…The results indicated that combined responses showed that precipitation is strongly influenced by the MJO phases rather than by ENSO conditions, especially during the austral summer. Thus, our results corroborate those of Shimizu et al (2016), who observed the highest percentages of days with active MJO and increased rainfall occurring during El Niño and neutral year. Figure 6 shows the daily variation of air temperature at 850 hPa, relative humidity and Bowen ratio at the T3 Manacapuru site.…”

“…These studies also show significantly lagged correlations between MJO and ENSO indices. Despite this, Shimizu et al (2016) recently examined the regional relationship between ENSO and MJO phases in climatological patterns of precipitation over South America. The results indicated that combined responses showed that precipitation is strongly influenced by the MJO phases rather than by ENSO conditions, especially during the austral summer.…”

“…Various studies have discussed observational and modeled aspects of the onset and demise of the rainy season in Amazonia using a variety of climatic indicators, such as rainfall, outgoing long-wave radiation or dynamic fields (e.g., Kousky, 1988;Marengo et al, 2001Marengo et al, , 2012Fu et al, 1999;Liebmann and Marengo, 2001;Gan et al, 2004;Wang and Fu, 2002;Silva and Carvalho, 2007;Raia and Cavalcanti, 2008;Marengo and Espinoza, 2015). However, modeling work still shows uncertainties in the representation of the onset of the rainy season.…”

Strongest MJO on Record Triggers Extreme Atacama Rainfall and Warmth in Antarctica

“…The MJO is the major mode of intraseasonal variability in the tropics. Many studies have pointed to a MJO role on the South American climate through the activation of the main Pacific teleconnection modes (Grimm & Ambrizzi, 2009;Shimizu et al, 2017). It impacts weather and climate over most of the regions of the planet (Zhang, 2005), although a full understanding of the physical mechanism of the wave remains incomplete.…”

“…It impacts weather and climate over most of the regions of the planet (Zhang, 2005), although a full understanding of the physical mechanism of the wave remains incomplete. Many studies have pointed to a MJO role on the South American climate through the activation of the main Pacific teleconnection modes (Grimm & Ambrizzi, 2009;Shimizu et al, 2017). Only recently, the MJO has been linked to an increase in rainfall in Northern and Central Chile during phases 7, 8, and 1 (Barrett et al, 2012;Juliá et al, 2012).…”