Interdecadal Variability of Southeastern South America Rainfall and Moisture Sources during the Austral Summertime

Martín-Gómez, Verónica; Hernández-Garcı́a, Emilio; Barreiro, Marcelo; López, Cristóbal

doi:10.1175/jcli-d-15-0803.1

Cited by 28 publications

(8 citation statements)

References 45 publications

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“…The one‐year lagged SASD–ENSO relationship weakened in the 1960s and 1980s, exhibited a high correlation in the 1970s and 1990s, and decreased gradually after the 2000s. The observations made as part of this study are consistent with those of a previous study which showed that relative precipitation over the SESA region increased in the 1990s compared to the 1980s (Martín‐Gómez et al., 2016). However, this relationship was quite different from the interdecadal relationship between the JJA Atlantic Niño index (i.e., Atl3) and the Nino3.4 index that increased after the 1970s (Kucharski et al., 2016; Martín‐Rey et al., 2012, 2014).…”

Section: Discussionsupporting

confidence: 92%

Inter‐Basin Interaction Between Variability in the South Atlantic Ocean and the El Niño/Southern Oscillation

Ham

Lee

et al. 2021

Geophysical Research Letters

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events are known to affect global climate and weather and are closely associated with substantial year-to-year changes in global ecosystems and food production (Cai et al., 2020). In the 1980s and 1990s, intensive observation programs conducted over the tropical Pacific have fundamentally enhanced the understanding of El Niño and La Niña events and the associated basin-scale atmospheric fluctuations that are collectively referred to as the El Niño-Southern Oscillation (ENSO) (McPhaden et al., 2010).Changes in sea surface temperature (SST) anomalies in the tropical Pacific during the ENSO are caused by variations within the Pacific. El Niño events are preceded by an increased warm water volume in the western Pacific (Jin, 1997;Timmermann et al., 2018), and tropical weather noise over the western Pacific can either lead to irregularities in the ENSO through abrupt decay or trigger the ENSO (Hu & Fedorov, 2016;Vecchi & Harrison, 2000). Therefore, the ENSO-related climate variations outside the equatorial Pacific are thought to be part of its influence on the global climate. However, since the mid-2000s, this Pacific-confined view of ENSO dynamics has been supplemented by the discovery of interactions between the ENSO and other ocean basins (

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Section: Discussionsupporting

confidence: 92%

Inter‐Basin Interaction Between Variability in the South Atlantic Ocean and the El Niño/Southern Oscillation

Ham

Lee

et al. 2021

Geophysical Research Letters

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“…(2017); Martín‐Gómez et al . (2016); Muñoz et al . (2015, 2016) focus on summer, which is the rainy season in a large area of the continent, but not in Uruguay.…”

Section: Introductionmentioning

confidence: 99%

Influence of Madden–Julian Oscillation on extreme rainfall events in Spring in southern Uruguay

Ungerovich¹,

Barreiro

Masoller

2021

Intl Journal of Climatology

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The influence of Madden–Julian Oscillation (MJO) on the dynamics of extreme rainfall events during austral Spring in Uruguay is investigated. The research is focused on the southern region of the country, which includes 15 weather stations. Extreme events are defined as days in which accumulated rainfall exceeds the 90 percentile of rainy days, and MJO is classified according to the Real‐time Multivariate MJO series 1 (RMM1) and 2 (RMM2) indices. Given that the extratropical teleconnections associated with MJO take at least 1 week to set up, we explore the influence of MJO up to 11 days prior to extreme events. A nonlinear time series analysis is performed (using symbolic patterns known as ordinal patterns) in order to consider the effects of the persistence of particular phases of MJO on the dynamic of extreme rainfall events. We find that MJO has the highest influence on extreme rainfall events in the region when it shows a persistence in phases 4 and 5 for more than 5 days, which intensifies the polar jet, influencing the trajectories of the transient waves that propagate in high latitudes, favouring geopotential disturbances over Uruguay. In other cases, the atmospheric pattern that leads to extreme rainfall events is characterized by a blocking episode that prevents transient activity from high latitudes to reach Uruguay, and the disturbances associated with the extreme events propagate along the subtropics.

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“…Specifically, for DJF, the changes in circulation imposed a northern NLLJ, and the humidity comes from TSA and local sources (Figure 7C). Except in SON (Supplementary Figure 1I), the north-south extension of the TSA moisture source for the NLLJ in Brazil-SE occupies a broad latitudinal band (Martín-Gómez et al, 2016), from the equator to subtropical latitudes (35 • S).…”

Section: Moisture Transport Associated To Nlljsmentioning

confidence: 99%

Assessing the Moisture Transports Associated With Nocturnal Low-Level Jets in Continental South America

Braz

Ambrizzi

Rocha

et al. 2021

Front. Environ. Sci.

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Given the crucial role of low-level circulation in convective events, this study presents a climatological characterization of the moisture sources and sinks associated with the occurrence of nocturnal low-level jets (NLLJs) in South America. Six selected NLLJ cores are identified according to the jet index that considers a vertical wind speed shear of the lower troposphere at 00:00 local time (LT). The Lagrangian FLEXible PARTicle (FLEXPART) model was used to provide the outputs for tracking atmospheric air masses to determine the moisture sources and sinks for the NLLJ cores (Argentina, Venezuela, and the regions of Brazil: south—Brazil-S, southeast—Brazil-SE, north—Brazil-N, and northeast—Brazil-NE). The analysis is based on 37 years (1980–2016) of the ERA-Interim reanalysis. We found that the NLLJ index is stronger in the warm periods of a year (austral spring and summer) for the six selected regions. The NLLJ frequency is also higher in the warm months of the year, except in Brazil-NE where it is very frequent in all months. In Brazil-NE, the NLLJ also persists for 8 or more days, while the other NLLJs frequently persist for 1–2 days. The NLLJs occupy a broad low-level layer (from 1000 to 700 hPa) and exhibit a mean speed between 7 and 12 ms–1, which peaks mostly at 900 hPa. The moisture transport for each NLLJ shows that in addition to the intense local moisture sources, the NLLJs in Argentina and Brazil-S receive moisture from the tropical-subtropical South Atlantic Ocean and the Amazon basin, while the tropical-subtropical South Atlantic Ocean is the main moisture source for the NLLJ in Brazil-SE. Both moisture sources and sinks are stronger in the austral summer and fall. The NLLJ in Brazil receives moisture from the tropical South Atlantic (TSA) Ocean, which has weak seasonality. The moisture sources for the NLLJs in Brazil-N and Venezuela come from the tropical North Atlantic (TNA) Ocean in the austral summer and fall, while the TSA Ocean appears as an additional moisture source in the austral winter. This research contributes to improving our understanding of the NLLJs and their role in transporting moisture and controlling precipitation over the continent according to the seasons of a year, helping to improve seasonal climate forecasting.

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Interdecadal Variability of Southeastern South America Rainfall and Moisture Sources during the Austral Summertime

Cited by 28 publications

References 45 publications

Inter‐Basin Interaction Between Variability in the South Atlantic Ocean and the El Niño/Southern Oscillation

Inter‐Basin Interaction Between Variability in the South Atlantic Ocean and the El Niño/Southern Oscillation

Influence of Madden–Julian Oscillation on extreme rainfall events in Spring in southern Uruguay

Assessing the Moisture Transports Associated With Nocturnal Low-Level Jets in Continental South America

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