Evolution of Extreme Madden-Julian Oscillation Events and their Impact on South America

• Autores: Minjares, Mónica; Barreiro, Marcelo; Corral, Álvaro
• Año de publicación: 2025
• Idioma: inglés
• Tipo de recurso: documento de conferencia
• Materia: Meteorología; Madden-Julian Oscillation; Extreme events
• Institución: Universidad Nacional de La Plata

The Madden-Julian Oscillation is the leading mode of intraseasonal variability in the tropics, having large influence on the tropical circulation and precipitation within the time band of 30-60 days (Wheeler and Hendon, 2004; Kiladis et al., 2014) and is the most important source of predictability on subseasonal time scales (Ling et al., 2019). The influence of MJO is not limited to the tropics, it also impacts the extratropics through atmospheric teleconnection patterns. During austral summer the MJO influences the South American Dipole (SAD), a rainfall pattern characterized by opposite rainfall anomalies in the South Atlantic Convergence Zone (SACZ) and southeastern South America (SESA). ENSO is the most important source of interannual climate variability, is originated in the equatorial Pacific but has a strong influence around the globe. In particular in South America during austral summer the El Niño phase influences the rainy season in the coast of Peru, northeastern Brazil, southeastern Brazil, Uruguay, Argentina and Chile (e.g. Ambrizzi et al. 2004; Barreiro 2010, Barreiro 2024). Both, MJO and ENSO are known to influence the SAD through different mechanisms. In a recent work (Corral et al. 2023), we studied the statistics of the size and duration of MJO events and found that there is increased probability of extinction after about 27 days, roughly half the characteristic period. Moreover, this analysis allows us to distinguish between weak MJO and extreme MJO events, which would be expected to have different impacts worldwide and particularly over South America. Hence in this study we focus characterizing the evolution of extreme MJO events and their impact in tropical and extratropical South America depending on the initiation phase. Following our previous work (Corral et al. 2023), MJO events are considered extremes when they exceed a certain threshold, based on the distribution of events. We further analyze whether ENSO influences MJO and its impacts over South America.
Facultad de Ciencias Astronómicas y Geofísicas