South American rainfall variations induced by changes in atmospheric circulations during reintensified and persistent El Niño-Southern Oscillation events

• Published in: Theoretical and applied climatology Vol. 155; no. 6; pp. 5499 - 5514
• Main Authors: Jimenez, Leonardo M., Andreoli, Rita V., de Souza, Itamara Parente, de Souza, Rodrigo Augusto Ferreira, Kayano, Mary Toshie, Ceron, Wilmar L.
• Format: Journal Article
• Language: English
• Published: Vienna Springer Vienna 01-06-2024; Springer Nature B.V
• Subjects: Anomalies; Aquatic Pollution; Atmospheric circulation; Atmospheric circulation anomalies; Atmospheric circulation patterns; Atmospheric Protection/Air Quality Control/Air Pollution; Atmospheric Sciences; Circulation; Climate; Climate models; Climate prediction; Climate variability; Climatology; Earth and Environmental Science; Earth Sciences; El Nino; El Nino phenomena; El Nino-Southern Oscillation event; La Nina; Oceans; Planetary waves; Precipitation; Precipitation anomalies; Rainfall; Rainfall variations; Rossby waves; Sea surface temperature; Seasonal precipitation; Southern Oscillation; Spatial variability; Spatial variations; Summer; Surface temperature; Trade winds; Variability; Walker circulation; Waste Water Technology; Water Management; Water Pollution Control; Wave packets; Wave trains
• ISSN: 0177-798X; 1434-4483
• DOI: 10.1007/s00704-024-04943-5

The seasonal precipitation contrasts in South America (SA) associated with two types of multiyear El Niño–Southern Oscillation (ENSO) events – reintensified and persistent – during the period 1901–2012 were investigated. These multiyear events differ in the timing of the maximum anomalies in Sea Surface Temperature (SST) in the central tropical Pacific Ocean during the austral summer of the first year (Y1) relative to the second year (Y2). These SST differences drive or couple with other modes of climate variability in the adjacent oceans, modifying in different ways the Walker circulation. For El Niño (EN), intensification [persistence] starts in the winter [autumn] following Y1 summer, when the strengthened [weakened] northeast [east] trade winds couple with the Walker circulation leading to the strengthening of subsidence in Indonesia and the intensification [persistence] of warming in the central Pacific until Y2 summer. In response, precipitation anomalies in SA during Y1 seasons exhibit different [similar] positioning and are more intense compared to the Y2 seasons during reintensified [persistent] events. For both events, dry conditions in northern and northeastern SA are modulated by the position and intensity of the descending branch of the Walker circulation. The most severe dry conditions occur in the Y1 summer, but they are more intense and with larger coverage during persistent events when EN is more intense. Wet conditions show substantial spatial variability in central eastern and southern SA and are associated with changes in regional atmospheric circulation and Rossby wave trains. Considering the linearity of ENSO, in the sense that EN and La Niña (LN) have nearly opposite effects, our results are also valid for LN events, but with reversed sign of the above-described precipitation and atmospheric circulation anomaly patterns. So, the results can be valuable for climate modeling, prediction, and monitoring.