Temperature Variability over South America

2009 ◽  
Vol 22 (22) ◽  
pp. 5854-5869 ◽  
Author(s):  
Jennifer M. Collins ◽  
Rosane Rodrigues Chaves ◽  
Valdo da Silva Marques
Keyword(s):  
South America ◽  
North Atlantic Ocean ◽  
Southern Oscillation ◽  
Austral Summer ◽  
Tropical Region ◽  
Supporting Evidence ◽  
Recent Period ◽  
Central Brazil ◽  
The North ◽  
Mean Temperature

Abstract The variation of air temperature at 2 m above the earth’s surface in South America (SA) between 1948 and 2007 is investigated primarily using the NCEP–NCAR reanalysis. In December–February (austral summer), the majority of SA has a mean temperature between 21° and 24°C during 1948–75, and for 1976–2007 the mean temperature is above 24°C. In June–August (austral winter), warmer temperatures are observed in the tropical region in the recent period. The results indicate that Northeast Brazil (NEB) and central Brazil are warmer in the more recent period. In the last seven years (2001–07) compared to the earlier periods, greater warming is noted in the tropical SA region, mainly in NEB and over the North Atlantic Ocean, and cooling is observed in part of the subtropical SA region. Supporting evidence for the warming in Brazil is given through analyses of station data and observational data. The results presented here indicate that the climate change over SA is likely not predominantly a result of variations in El Niño–Southern Oscillation (the most important coupled ocean–atmosphere phenomenon to produce climate variability over SA). Instead, the climate changes likely occur as a response to other natural variability of the climate and/or may be a result of human activity. However, even without ascertaining the specific causes, the most important finding in this work is to demonstrate that a change in the temperature patterns of SA occurred between 1948 and 2007.

Anomalies of continental precipitation associated with El Niño Southern Oscillation: the role of moisture contribution from oceanic and terrestrial sources 

2021 ◽  
Author(s):  
Rogert Sorí ◽  
Raquel Nieto ◽  
Margarida L.R. Liberato ◽  
Luis Gimeno
Keyword(s):  
South America ◽  
Southern Oscillation ◽  
The United States ◽  
Precipitation Pattern ◽  
Two Phase ◽  
The North ◽  
Terrestrial Origin ◽  
Precipitation Anomalies ◽  
June July

<p>The regional and global precipitation pattern is highly modulated by the influence of El Niño Southern Oscillation (ENSO), which is considered the most important mode of climate variability on the planet. In this study was investigated the asymmetry of the continental precipitation anomalies during El Niño and La Niña. To do it, a Lagrangian approach already validated was used to determine the proportion of the total Lagrangian precipitation that is of oceanic and terrestrial origin. During both, El Niño and La Niña, the Lagrangian precipitation in regions such as the northeast of South America, the east and west coast of North America, Europe, the south of West Africa, Southeast Asia, and Oceania is generally determined by the oceanic component of the precipitation, while that from terrestrial origin provides a major percentage of the average Lagrangian precipitation towards the interior of the continents. The role of the moisture contribution to precipitation from terrestrial and oceanic origin was evaluated in regions with statistically significant precipitation anomalies during El Niño and La Niña. Two-phase asymmetric behavior of the precipitation was found in regions such the northeast of South America, South Africa, the north of Mexico, and southeast of the United States, etc. principally for December-January-February and June-July-August. For some of these regions was also calculated the anomalies of the precipitation from other datasets to confirm the changes. Besides, for these regions was calculated the anomaly of the Lagrangian precipitation, which agrees in all the cases with the precipitation change. For these regions, it was determined which component of the Lagrangian precipitation, whether oceanic or terrestrial, controlled the precipitation anomalies. A schematic figure represents the extent of the most important seasonal oceanic and terrestrial sources for each subregion during El Niño and La Niña.</p>

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

2016 ◽  
Vol 29 (18) ◽  
pp. 6751-6763 ◽  
Author(s):  
Verónica Martín-Gómez ◽  
Emilio Hernández-Garcia ◽  
Marcelo Barreiro ◽  
Cristóbal López
Keyword(s):  
South America ◽  
Rainfall Variability ◽  
Austral Summer ◽  
Eastern Shore ◽  
Central Brazil ◽  
Moisture Sources ◽  
Tropical Oceans ◽  
Eastern Brazil ◽  
Central Eastern ◽  
Atmospheric Circulation Anomalies

Abstract Sea surface temperature (SST) anomalies over the tropical oceans are able to generate extratropical atmospheric circulation anomalies that can induce rainfall variability and changes in the sources of moisture. The work reported here evaluates the interdecadal changes in the moisture sources for southeastern South America (SESA) during austral summer, and it is divided into two complementary parts. In the first part the authors construct a climate network to detect synchronization periods among the tropical oceans and the precipitation over SESA. Afterward, taking into account these results, the authors select two periods with different degrees of synchronization to compare the spatial distribution of the SESA moisture sources. Results show that during the last century there were three synchronization periods among the tropical oceans and the precipitation over SESA (during the 1930s, 1970s, and 1990s) and suggest that the main moisture sources of SESA are the recycling over the region, the central-eastern shore of Brazil together with the surrounding Atlantic Ocean, and the southwestern South Atlantic surrounding the SESA domain. Comparison of SESA moisture sources for the 1980s (a period of nonsignificant synchronization) and the 1990s (a synchronized period) shows that the principal differences are in the intensity of the recycling and in the strength of the central-eastern shore of Brazil. Moreover, the authors find that a region centered at (20°S, 300°E) is a moisture source for SESA only during the 1990s. These differences can be associated with the development of a low-level anticyclonic (cyclonic) anomaly circulation over central-eastern Brazil that favors the transport of moisture from central Brazil (central-eastern shore of Brazil) toward SESA in the 1990s (1980s).

scholarly journals The Rapid Warming of the North Atlantic Ocean in the Mid-1990s in an Eddy-Permitting Ocean Reanalysis (1982–2013)

2016 ◽  
Vol 29 (15) ◽  
pp. 5417-5430 ◽  
Author(s):  
Chunxue Yang ◽  
Simona Masina ◽  
Alessio Bellucci ◽  
Andrea Storto
Keyword(s):  
Atlantic Ocean ◽  
Heat Transport ◽  
North Atlantic ◽  
North Atlantic Ocean ◽  
Ocean Reanalysis ◽  
The North ◽  
Mean Temperature ◽  
The Mean ◽  
The North Atlantic ◽  
Mean State

Abstract The rapid warming in the mid-1990s in the North Atlantic Ocean is investigated by means of an eddy-permitting ocean reanalysis. Both the mean state and variability, including the mid-1990s warming event, are well captured by the reanalysis. An ocean heat budget applied to the subpolar gyre (SPG) region (50°–66°N, 60°–10°W) shows that the 1995–99 rapid warming is primarily dictated by changes in the heat transport convergence term while the surface heat fluxes appear to play a minor role. The mean negative temperature increment suggests a warm bias in the model and data assimilation corrects the mean state of the model, but it is not crucial to reconstruct the time variability of the upper-ocean temperature. The decomposition of the heat transport across the southern edge of the SPG into time-mean and time-varying components shows that the SPG warming is mainly associated with both the anomalous advection of mean temperature and the mean advection of temperature anomalies across the 50°N zonal section. The relative contributions of the Atlantic meridional overturning circulation (AMOC) and gyre circulation to the heat transport are also analyzed. It is shown that both the overturning and gyre components are relevant to the mid-1990s warming. In particular, the fast adjustment of the barotropic circulation response to the NAO drives the anomalous transport of mean temperature at the subtropical/subpolar boundary, while the slowly evolving AMOC feeds the large-scale advection of thermal anomalies across 50°N. The persistently positive phase of the NAO during the years prior to the rapid warming likely favored the cross-gyre heat transfer and the following SPG warming.

scholarly journals Precipitação na América do Sul: Médias Climáticas e Padrões da Variabilidade no Período entre 1979 e 2008

2016 ◽  
Vol 9 (1) ◽  
pp. 032
Author(s):  
Éder Leandro Maier ◽  
Juliana Costi ◽  
Sandra Barreira ◽  
Jefferson Cardia Simões
Keyword(s):  
South America ◽  
North Atlantic ◽  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Principal Component ◽  
Monthly Precipitation ◽  
Tropical Regions ◽  
The North ◽  
North Atlantic Variability

Este artigo discute os principais padrões médios e anômalos da precipitação sobre a América do Sul no período 1979–2008. Para isso foram manipulados dados mensais da precipitação observada em 890 estações meteorológicas localizadas na Argentina, Bolívia, Brasil, Paraguai e Uruguai ao longo desse período de trinta anos. As médias climáticas foram subtraídas das amostras, originando as anomalias, as quais foram agrupadas por meio da Análise das Componentes Principais em dois modos. No modo T se identificou 6 componentes principais, que explicam 35% da variância e representam 12 padrões espaciais anômalos originados, principalmente, pelo fenômeno El Niño–Oscilação Sul (ENOS) e pela variabilidade do Atlântico Norte. No modo S foram identificadas 8 zonas em que a variabilidade temporal das séries anômalas é semelhante, sendo que o ENOS prevalece no controle das anomalias nas zonas situadas na região equatorial e extratropical, além disso, a variabilidade do Atlântico Norte pode maximizar ou minimizar os impactos do ENOS. A frequência de recorrência desses estresses hídrico variam entre 20 e 60 meses.  This article discusses mean and anomalous rainfall patterns over South America in the period 1979–2008. For that we handled monthly precipitation data observed at 890 meteorological stations located in Argentina, Bolivia, Brazil, Paraguay and Uruguay over this thirty years period. Climatic means were subtracted from the data, resulting in anomalies that were grouped by Principal Component Analysis in two modes. We identified 6 main components in the T mode, which explain 35% of the variance and represent 12 anomalous spatial patterns originated mainly by El Niño–Southern Oscillation (ENSO) phenomenon and the North Atlantic variability. In mode S, we identified eight zones where the series temporal variability is also anomalous, and the ENOS prevails as the anomalies controller in the equatorial and extra tropical regions. Further, North Atlantic variability may maximize or minimize the ENSO impact. The frequency of these recurrent water stresses range from 20 to 60 months. Keywords: Precipitation, South America, PCA  

scholarly journals El Niño effects on rainfall in South America: comparison with rainfalls in india and other parts of the world

2006 ◽  
Vol 6 ◽  
pp. 35-41 ◽  
Author(s):  
R. P. Kane
Keyword(s):  
South America ◽  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Major Effect ◽  
Eastern Coast ◽  
Western Coast ◽  
Central Brazil ◽  
The Andes ◽  
Almost All

Abstract. As a finer classification of El Niños, ENSOW were defined as years when El Niño (EN) existed on the Peru coast, Southern Oscillation Index SOI (Tahiti minus Darwin pressure) was negative (SO), and Pacific SST anomalies were positive (W). Further, Unambiguous ENSOW were defined as years when SO and W occurred in the middle of the calendar year, while Ambiguous ENSOW were defined as years when SO and W occurred in the earlier or later part of the calendar year (not in the middle). In contrast with India and some other regions where Unambiguous ENSOW were associated predominantly with droughts, in the case of South America, the association was mixed. In Chile on the western coast and Uruguay etc. on the eastern coast, the major effect was of excessive rains. In Argentina and central Brazil, the effects were unclear. In Amazon, the effects were not at all uniform, and were different (droughts or excess rains) or even absent in regions only a few hundred kilometers away from each other. Even in Peru-Ecuador, the effects were clear only in the coastal regions. In the interior and in the Andes, the effects were obscure. In NE Brazil, El Niños have been popularly known to be causing severe droughts. The fact is that during 1871–1998, there were 52 El Niño events, out of which 31 were associated with droughts in NE Brazil, while 21 had no association. The reason is that besides El Niños, another major factor affecting NE Brazil is the influx of moisture from the Atlantic. In some years, warmer Atlantic in conjunction with westward winds can bring moisture to NE Brazil, nullifying the drought effects of El Niños. A curious feature at almost all locations is the occurrence of extreme events (high floods or severe droughts) in some years, apparently without any El Niño or La Niña events. This possibility should always be borne in mind.

scholarly journals Some Factors That Influence Seasonal Precipitation in Argentinean Chaco

2012 ◽  
Vol 2012 ◽  
pp. 1-13 ◽  
Author(s):  
Marcela Hebe González ◽  
María Laura Cariaga ◽  
María de los Milagros Skansi
Keyword(s):  
Southern Oscillation ◽  
Rainfall Variability ◽  
Southern Annular Mode ◽  
Spring Precipitation ◽  
Study Region ◽  
Central Brazil ◽  
The North ◽  
Interannual Rainfall Variability ◽  
Oceanic Forcing ◽  
Main Activity

The Chaco plain region in Argentina is located in the north of the country and east of Los Andes where the main activity is the agriculture. As such activity is highly affected by interannual rainfall variability, the influence of some of the principal atmospheric and oceanic forcing is investigated in this paper. Results show that the factors which affect precipitation highly depend on the season and the subregion. The position of the South Atlantic Height and the sea surface temperature in the coast of southern Brazil and Buenos Aires seem to be the factors that affect rainfall, all over the year. The El Niño-Southern Oscillation phenomenon affects summer and spring rainfall and the Southern Annular Mode involves spring precipitation but both only in the east of the study region. Furthermore, enhanced convection in Central Brazil, mainly influences autumn and spring rainfall.

scholarly journals Seasonal Predictability of Summer Rainfall over South America

2018 ◽  
Vol 31 (20) ◽  
pp. 8181-8195 ◽  
Author(s):  
Rodrigo J. Bombardi ◽  
Laurie Trenary ◽  
Kathy Pegion ◽  
Benjamin Cash ◽  
Timothy DelSole ◽  
...  
Keyword(s):  
South America ◽  
Spatial Resolution ◽  
Large Scale ◽  
Climate Models ◽  
Southern Oscillation ◽  
Austral Summer ◽  
Summer Rainfall ◽  
Forecast Skill ◽  
Seasonal Predictability ◽  
Temporal Scales

The seasonal predictability of austral summer rainfall is evaluated in a set of retrospective forecasts (hindcasts) performed as part of the Minerva and Metis projects. Both projects use the European Centre for Medium-Range Weather Forecasts (ECMWF) Integrated Forecast System (IFS) coupled to the Nucleus for European Modelling of the Ocean (NEMO). The Minerva runs consist of three sets of hindcasts where the spatial resolution of the model’s atmospheric component is progressively increased while keeping the spatial resolution of its oceanic component constant. In the Metis runs, the spatial resolution of both the atmospheric and oceanic components are progressively increased. We find that raw model predictions show seasonal forecast skill for rainfall over northern and southeastern South America. However, predictability is difficult to detect on a local basis, but it can be detected on a large-scale pattern basis. In addition, increasing horizontal resolution does not lead to improvements in the forecast skill of rainfall over South America. A predictable component analysis shows that only the first predictable component of austral summer precipitation has forecast skill, and the source of forecast skill is El Niño–Southern Oscillation. Seasonal prediction of precipitation remains a challenge for state-of-the-art climate models. Positive benefits of increasing model resolution might be more evident in other atmospheric fields (i.e., temperature or geopotential height) and/or temporal scales (i.e., subseasonal temporal scales).

scholarly journals Assessment of ECMWF SEAS5 Seasonal Forecast Performance over South America

2019 ◽  
Vol 35 (2) ◽  
pp. 561-584 ◽  
Author(s):  
S. Gubler ◽  
K. Sedlmeier ◽  
J. Bhend ◽  
G. Avalos ◽  
C. A. S. Coelho ◽  
...  
Keyword(s):  
South America ◽  
Minimum Temperature ◽  
High Performance ◽  
Austral Summer ◽  
Prediction Performance ◽  
Dynamical Model ◽  
Maximum Temperature ◽  
Forecast Performance ◽  
Empirical Prediction ◽  
The North

Abstract Seasonal predictions have a great socioeconomic potential if they are reliable and skillful. In this study, we assess the prediction performance of SEAS5, version 5 of the seasonal prediction system of the European Centre for Medium-Range Weather Forecasts (ECMWF), over South America against homogenized station data. For temperature, we find the highest prediction performances in the tropics during austral summer, where the probability that the predictions correctly discriminate different observed outcomes is 70%. In regions lying to the east of the Andes, the predictions of maximum and minimum temperature still exhibit considerable performance, while farther to the south in Chile and Argentina the temperature prediction performance is low. Generally, the prediction performance of minimum temperature is slightly lower than for maximum temperature. The prediction performance of precipitation is generally lower and spatially and temporally more variable than for temperature. The highest prediction performance is observed at the coast and over the highlands of Colombia and Ecuador, over the northeastern part of Brazil, and over an isolated region to the north of Uruguay during DJF. In general, Niño-3.4 has a strong influence on both air temperature and precipitation in the regions where ECMWF SEAS5 shows high performance, in some regions through teleconnections (e.g., to the north of Uruguay). However, we show that SEAS5 outperforms a simple empirical prediction based on Niño-3.4 in most regions where the prediction performance of the dynamical model is high, thereby supporting the potential benefit of using a dynamical model instead of statistical relationships for predictions at the seasonal scale.

scholarly journals Tropical–Extratropical Interactions Associated with an Atlantic Tropical Plume and Subtropical Jet Streak

2005 ◽  
Vol 133 (9) ◽  
pp. 2759-2776 ◽  
Author(s):  
Peter Knippertz
Keyword(s):  
North America ◽  
South America ◽  
Atlantic Ocean ◽  
North Atlantic Ocean ◽  
Cloud Formation ◽  
Cloud Band ◽  
The North ◽  
Northwest Africa ◽  
Subtropical Jet ◽  
Upper Level

Abstract Tropical plumes (TPs) are elongated bands of upper- and midlevel clouds stretching from the Tropics poleward and eastward into the subtropics, typically accompanied by a subtropical jet (STJ) streak and a trough on their poleward side. This study uses ECMWF analyses and high-resolution University of Wisconsin–Nonhydrostatic Modeling System trajectories to analyze the multiscale complex tropical–extratropical interactions involved in the genesis of a pronounced TP and STJ over the NH Atlantic Ocean in late March 2002 that was associated with extreme precipitation in arid northwest Africa. Previous concepts for TP genesis from the literature are discussed in the light of this case study. Analysis of the upper-level flow prior to the TP formation shows a northeastward propagation and a continuous acceleration of the STJ over the Atlantic Ocean equatorward of a positively tilted upper-level trough to the west of northwest Africa. Both dynamic and advective processes contribute to the generation of the accompanying cloud band. The northern portion of the TP consists of parcels that exit a strong STJ streak over North America, enter the deep Tropics over South America, and then accelerate into the Atlantic STJ, accompanied by strong cross-jet ageostrophic motions, rising, and cloud formation. The southern portion is formed by parcels originating in the divergent outflow from strong near-equatorial convection accompanying the TP genesis. A local increase in the Hadley overturning is found over the tropical Atlantic and east Pacific/South America and appears to be related to low inertial stability at the outflow level and to low-level trade surges associated with the cold advection, sinking, and lower-level divergence underneath two strong upper-level convergence centers in the eastern portions of both a subtropical ridge over North America and an extratropical ridge over the North Atlantic Ocean. Evidence is presented that the convective response lags the trade surge by several days.

scholarly journals Pacific climate reflected in Waipuna Cave dripwater hydrochemistry

2020 ◽  
Author(s):  
Cinthya Nava-Fernandez ◽  
Adam Hartland ◽  
Fernando Gázquez ◽  
Ola Kwiecien ◽  
Norbert Marwan ◽  
...  
Keyword(s):  
Southern Oscillation ◽  
Austral Summer ◽  
Surface Air Temperature ◽  
Co2 Concentration ◽  
Isotopic Signature ◽  
Severe Drought ◽  
Response Dynamics ◽  
Calcite Precipitation ◽  
Diffuse Flow ◽  
The North

Abstract. Cave microclimatic and geochemical monitoring is vitally important for correct interpretations of proxy time series from speleothems with regard to past climatic and environmental dynamics. We present results of a comprehensive cave monitoring programme in Waipuna Cave in the North Island of New Zealand, a region that is strongly influenced by the southern Westerlies and the El Niño–Southern Oscillation (ENSO). This study aims to characterise the response of the Waipuna Cave hydrological system to atmospheric circulation dynamics in the southwestern Pacific region in order to secure the quality of ongoing palaeo-environmental reconstructions from this cave. Cave air and water temperatures, drip rates, and CO2, concentration were measured, and samples for water isotopes (δ18O, δD, d-excess, 17Oexcess) and elemental ratios (Mg / Ca, Sr / Ca), were collected continuously and/or at monthly intervals from 10 drip sites inside Waipuna Cave for a period of ca. 3 years. These datasets were compared to surface air temperature, rainfall, and potential evaporation from nearby meteorological stations to test the degree of signal transfer and expression of surface environmental conditions in Waipuna Cave hydrochemistry. Based on the drip response dynamics to rainfall and other characteristics we identify three hydrological pathways in Waipuna Cave: diffuse flow, combined flow, and fracture flow. Dripwater isotopes do not reflect seasonal variability, but show higher values during severe drought. Dripwater δ18O values display limited variability and reflect the mean isotopic signature of precipitation, testifying to rapid and thorough buffering in the epikarst. Mg / Ca and Sr / Ca ratios in dripwaters are predominantly controlled by prior calcite precipitation (PCP). Prior calcite precipitation is strongest during austral summer (December–February), reflecting drier conditions and lack of effective infiltration, and is weakest during the wet austral winter (July–September). The Sr / Ca ratio is particularly sensitive to ENSO conditions due to the interplay of congruent/incongruent host rock dissolution, which manifests itself in lower Sr / Ca in above-average warmer and wetter (La Niña-like) conditions. Our microclimatic observations at Waipuna Cave provide valuable baseline for perceptive interpretation of speleothem proxy records aiming at reconstructing the past expression of Pacific climate modes.

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