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Southeastern South America is subject to considerable precipitation variability on seasonal to decadal timescales and has undergone very heavy land‐cover changes (LCCs) since the middle of the past century. The influence of local LCC and precipitation as drivers of regional evapotranspiration (ET) long‐term trends and variability remains largely unknown in the region. Here, ensembles of stand‐alone dynamic global vegetation models (DGVMs) with different atmospheric forcings are used to disentangle the influence of those two drivers on austral summer ET from 1950 to 2010. This paper examines the influence of both the El Niño‐Southern Oscillation (ENSO) and the dipole‐like first‐mode of southeastern South American precipitation variability (EOF1) on regional ET. We found that in the lower La Plata Basin, ET was driven by precipitation variability and showed a positive summer trend. Moreover, the region showed marked seasonal anomalies during El Niño and La Niña summers but mainly during EOF1 phases. On the contrary, in the upper La Plata Basin, LCCs forced the negative summer ET trend and particularly reduced the summer anomalies of the late 1990s, a period of ENSO and EOF1‐positive phases. In the South Atlantic Convergence Zone region, the high ET uncertainty across ensemble members impeded finding robust results, which highlights the importance of using multiple DGVMs and atmospheric forcings instead of relying on single model/forcing results. [ABSTRACT FROM AUTHOR]

ABSTRACT It is known that the El Niño - Southern Oscillation ( ENSO) episodes have a great influence on South American precipitation and its extreme events during austral autumn (from March until May, MAM) and winter (from June until August, JJA) that occur after the ENSO peak (normally this happens on austral summer). Recent papers have studied the two types of ENSO and their influence on atmosphere-ocean system. This study analysed the influence of Central and East equatorial Pacific ENSO on South American seasonal/monthly mean precipitation and its extreme events during MAM and JJA. The composites of precipitation anomalies, during these two types of ENSO, show that there are different, even opposite patterns over South America. In MAM, there is an increased precipitation in southeastern South America and a decrease in the northeast South America during East El Niño ( EEN) and an increased precipitation in central Brazil during Central El Niño ( CEN). In JJA, the signs of anomaly precipitation are opposite between CEN (less precipitation) and EEN (more precipitation) over southeastern South America. The extreme precipitation events show patterns consistent with the precipitation anomaly patterns, but, normally, the changes in the frequency of extremes precipitation events affect more extensive areas than the total precipitation. If monthly or seasonal atmospheric anomalies in a certain region during one of the types of ENSO are similar (opposite) to the atmospheric anomalies associated with extreme precipitation events in this region, then there is enhancement (suppression) of the frequency of extreme events in this region during this type of ENSO. [ABSTRACT FROM AUTHOR]

This study examines the Interdecadal Pacific Oscillation (IPO) modulation of the El Niño–Southern Oscillation (ENSO) teleconnections in its decaying stages with the tropical ocean by focusing on the Indian Ocean Basin‐Wide (IOBW) mode and the precipitation over South America (SA) in the 1901–2012 period. Composite analyses revealed that the ENSO teleconnections are IPO‐modulated due to the differential ENSO decaying speed, which is slower during the positive than negative IPO phase, for both El Niño (EN) and La Niña (LN) cases. Negative precipitation anomalies related to EN persist over northeastern SA until austral winter for the positive IPO phase (POS IPO), while significant opposite sign anomalies occur in this region for the negative IPO phase (NEG IPO). These results are associated with the Walker circulation's reversal during NEG IPO which is, in turn, accompanied by negative IOBW. During the POS IPO, the positive IOBW causes upward movements over there and, by continuity, downward movements over SA. In the NEG IPO, for LN events the wave train originating in the north of Australia propagates toward subtropical SA, which, coupled with the surface circulation, causes dryness in this region. In addition, the rapid decay of LN in the NEG IPO, followed by the emergence of EN, caused changes in the Walker circulation, such that enhanced upward movements occurred over the Pacific and SA region, and downward movements over the Indian Ocean until austral winter. In turn, the slower decay of the LN in the POS IPO maintains strong subsidence over the central Pacific and weak upward motions over western SA. So, the EN (LN) and positive (negative) IOBW during the POS (NEG) IPO prolong the scarcity of precipitation over equatorial (subtropical) SA. Persistent dry periods over these regions during the ENSO decaying stage might have important implications for the seasonal forecasts. [ABSTRACT FROM AUTHOR]

El Niño–Southern Oscillation (ENSO) phenomena occur in the equatorial Pacific and differentially affect the global climate. Recently, studies have begun to analyse the influence of ENSO intensity on the global climate, but how this intensity affects South American precipitation remains unclear. This work defined the ENSO intensities each season (versus annually, as is more commonly done) because understanding this seasonal intensity is essential for seasonal forecasting. The atmospheric patterns identified in this study showed that the stronger the sea surface temperature (SST) anomalies (SSTA) in the equatorial eastern Pacific were, the stronger the atmospheric responses. The known South American precipitation pattern occurred at all ENSO intensity categories but had different intensities. However, the most important patterns in this study differed from the main pattern. Central‐eastern South America did not have a notable precipitation pattern during all El Niño (EN) years, but there was a negative pattern of strong ENs. In addition, the intensity of the precipitation anomaly during weak EN and La Niña (LN), mainly in northeastern South America, was stronger in austral autumn than in austral summer because the intensity in a previous season can influence the current season's precipitation pattern and the total SST in autumn is stronger than that in summer. Asymmetries between EN and LN events are important to consider; EN tends to be more intense than LN, and deep convection anomalies during EN are displaced eastward relative to those during LN. In this study, categories were defined based on ENSO intensities, but asymmetries appeared in atmospheric patterns, mainly in omega patterns during strong events. The intensities of SSTAs over the equatorial eastern Pacific affected the intensities of the Walker circulation and Rossby waves and, consequently, the intensity of precipitation patterns in different South American regions. [ABSTRACT FROM AUTHOR]

The Paraná River of South America is one of the largest rivers in the world. Although the connection between Paraná streamflow and El Niño–Southern Oscillation (ENSO) has been studied before, little is known about the long‐term (interdecadal) changes of this connectivity. Here we reveal these changes by analysing long instrumental records of Paraná flow, ENSO indices and other climate variables. We find that flow and ENSO were connected in 1876–1940 and 1983–2016, but disconnected in 1941–1982. Flow variability was more related to central Pacific ENSO fluctuations in 1876–1940 but more linked with eastern Pacific ones in 1983–2016, probably because the ENSO–Paraná basin teleconnection was different in the two periods. ENSO‐related Pacific climate anomalies exhibited their smallest amplitudes during the disconnection period 1941–1982, suggesting that the ENSO–flow link vanishes when ENSO is weak. We also find that the ENSO–flow disconnection coincided with the coldest phase of the Interdecadal Pacific Oscillation (IPO) in the study period. Thus, the IPO may be modulating the ENSO–flow connectivity. Interestingly, during the disconnection years (1941–1982), flow was related to climate variability observed in sectors of the southern South Atlantic and tropical North Atlantic oceans. This and the other empirical results presented here provide new insights into the Paraná response to ENSO and thus provide valuable information for future mechanistic studies on this response. [ABSTRACT FROM AUTHOR]

Oceanic heat sources disturb the atmosphere, which, to come back to its initial state, disperses waves. These waves affect the climate in remote regions, characterizing the teleconnection patterns. In this study, we describe eight teleconnection patterns that affect South America climate: the El Niño–Southern Oscillation (ENSO), the Pacific Decadal Oscillation (PDO), the Atlantic Multidecadal Oscillation (AMO), the Tropical Atlantic Dipole (TAD), the South Atlantic Dipole (SAD), the Southern Annular Mode (SAM), the Madden–Julian Oscillation (MJO), and the Indian Ocean Dipole (IOD). Precipitation and winds at 850‐hPa anomalies, considering these teleconnection patterns in ENSO neutral periods, are also presented. Overall, southeastern South America and the north sector of the North and Northeast regions of Brazil are the most affected areas by the teleconnection patterns. In general, there is a precipitation dipole pattern between these regions during each teleconnection pattern. [ABSTRACT FROM AUTHOR]

ABSTRACT Recent studies show that different types of ENSO influence the atmospheric fields differently. In this study, precipitation anomalies and extreme events over South America are analysed with relation to two types of ENSO [East (strong Sea Surface Temperature Anomalies (SSTA) on East Pacific) and Central (strong SSTA on Central Pacific)]. The composites of precipitation anomalies, during these two types of ENSO, show that there are different patterns, e.g. during austral summer of Central El Niño (CEN) there are negative precipitation anomalies in eastern Brazil that do not exist in East El Niño (EEN), whereas in southern Brazil there are positive precipitation anomalies during EEN that do not exist in CEN. Furthermore, the anomalies are mostly stronger and more extensive during EEN (Central La Niña - CLN) than in CEN (East La Niña - ELN), although there are some exceptions, such as during austral spring in southern Brazil, where anomalies during CEN (ELN) are stronger than during EEN (CLN). The anomalous frequency of extreme precipitation events shows generally patterns consistent with the anomalous precipitation behaviour, though the patterns are not always coincident, because the regions with significant increase of frequency of extreme events tend to be more extensive than those with increased seasonal precipitation. When the monthly or seasonal atmospheric anomalies associated with a type of ENSO episode are very similar (opposite) to the atmospheric anomalies associated with extreme precipitation in a certain region, then a significant enhancement (suppression) of the frequency of extreme events is observed in that region during this type of episode. [ABSTRACT FROM AUTHOR]

Sea surface temperature (SST) anomalies in the Pacific Ocean during El Niño-Southern Oscillation (ENSO) episodes exhibit different spatial patterns from year to year. In most ENSO studies, SST anomalies have been analysed in the 3.4 or 3.0 El Niño regions. Recent analyses have considered different SST anomalies areas in the Pacific, such as ENSO Modoki, which takes into account anomalies in the central Pacific which are bounded by opposite anomalies in the eastern and western Pacific. In order to analyse the influence of different Pacific spatial patterns on South American precipitation and on the Southern Hemisphere atmospheric circulation, composites obtained from Canonical ENSO were compared with those from ENSO Modoki in cases when strong anomalies were present in the Central Pacific. During the Canonical El Niño (La Niña), there tends to be a precipitation increase (decrease) in the La Plata Basin (LPB, 45°W-65°W, 15°S-35°S) and a decrease (increase) over northern South America during all seasons. In ENSO Modoki exhibiting strong anomalies in the Central Pacific, these typical patterns are not observed, and in some regions the anomalies even show opposite signs. Precipitation anomaly differences or similarities over South America between the two cases occur in different areas and different seasons. In both cases, differences in tropical South American precipitation during both ENSO types are related to differences in the Walker circulation. In extra-tropical South America, the precipitation differences are due to differences in the Pacific wavetrains and differences in moisture flux intensity over the continent. Copyright © 2012 Royal Meteorological Society [ABSTRACT FROM AUTHOR]

Predator assemblages are complex systems in which asynchrony in the dynamics of resources and consumers, and the idiosyncratic perception of environmental conditions by the predators may obscure the detection of expected patterns. We disentangle the specific effects of these variables on the guild structure of a vertebrate predatory assemblage in a semiarid ecosystem of western South America. Over 16 years, this system faced dramatic fluctuations in prey availability associated with four El Niño events. After controlling for other sources of variation, we tested if increased resource availability is associated with higher niche overlaps, as expected from the lean/fat scenario. We determined the existence of two trophic guilds of predators (specialized mammal-eaters and omnivorous species with emphasis on arthropods) and found that they responded to increased productivity both at the guild and whole assemblage levels. However, the population response of arthropod prey (almost simultaneous) and of different small mammal prey (delayed by 1 or 2 years) to productivity imposed a degree of asynchrony in prey availability and in the response of predators. This resulted in the between-guilds exchange of predator species depending on mammal prey scarcity or abundance. As a consequence, the observed pattern was an apparent lack of response at the assemblage level. Despite differences in the perception of prey levels by predators, we conclude that each one of them responded accordingly to theoretical predictions following a simple rule: if prey resources are not limiting, predators behave opportunistically converging over the most abundant resources, thus increasing niche overlap; if prey shortages occur, predators specialize on those prey resources that they gather most efficiently, thus lowering niche overlap; if resources become even scarcer, all predators converge again upon the few prey resources still available, thus increasing overlap – out of necessity. [ABSTRACT FROM AUTHOR]