scholarly journals Eastern Patagonia Seasonal Precipitation: Influence of Southern Hemisphere Circulation and Links with Subtropical South American Precipitation

2012 ◽  
Vol 25 (19) ◽  
pp. 6781-6795 ◽  
Author(s):  
Ana Laura Berman ◽  
Gabriel Silvestri ◽  
Rosa Compagnucci
Keyword(s):  
South America ◽  
Atmospheric Circulation ◽  
Southern Hemisphere ◽  
South American ◽  
Seasonal Precipitation ◽  
The Andes ◽  
Four Seasons ◽  
Westerly Flow ◽  
Continental Area ◽  
Frontal Systems

Abstract Some aspects of the seasonal precipitation over eastern Patagonia, the southernmost area of South America east of the Andes Cordillera, are examined in this paper. Results indicate that the central-north areas, the southern continental region, and the southernmost islands are three independent regions of seasonal precipitation, and that each of them is associated with specific patterns of atmospheric circulation. Precipitation over the central-north region is significantly related to the precipitation over a wide area of southern South America east of the Andes during the four seasons. Enhanced (reduced) precipitation over this area is associated with weakened (intensified) westerly flow in the region. Precipitation over the southern continental area has a close connection with the dipolar pattern of precipitation over subtropical South America during spring, summer, and autumn. The anomalies of atmospheric circulation at low and upper levels associated with the subtropical dipole are also able to modulate the intensity of the westerlies over the south of eastern Patagonia, affecting the regional precipitation. Precipitation over the islands of the southernmost part of eastern Patagonia is connected with subtropical precipitation in summer and winter. The activity of frontal systems associated with migratory perturbations moving to the east along the Southern Hemisphere storm tracks modulates the variability of seasonal precipitation over this region.

Temperate Forests of the Southern Andean Region

2007 ◽  
Author(s):  
Thomas T. Veblen
Keyword(s):  
South America ◽  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
Boreal Forests ◽  
Temperate Forests ◽  
High Latitudes ◽  
Andean Region ◽  
Southern South America ◽  
The Andes ◽  
Evergreen Conifers

Although most of the continent of South America is characterized by tropical vegetation, south of the tropic of Capricorn there is a full range of temperate-latitude vegetation types including Mediterranean-type sclerophyll shrublands, grasslands, steppe, xeric woodlands, deciduous forests, and temperate rain forests. Southward along the west coast of South America the vast Atacama desert gives way to the Mediterranean-type shrublands and woodlands of central Chile, and then to increasingly wet forests all the way to Tierra del Fuego at 55°S. To the east of the Andes, these forests are bordered by the vast Patagonian steppe of bunch grasses and short shrubs. The focus of this chapter is on the region of temperate forests occurring along the western side of the southernmost part of South America, south of 33°S. The forests of the southern Andean region, including the coastal mountains as well as the Andes, are presently surrounded by physiognomically and taxonomically distinct vegetation types and have long been isolated from other forest regions. Although small in comparison with the extent of temperate forests of the Northern Hemisphere, this region is one of the largest areas of temperate forest in the Southern Hemisphere and is rich in endemic species. For readers familiar with temperate forests of the Northern Hemisphere, it is difficult to place the temper temperate forests of southern South America into a comparable ecological framework owing both to important differences in the histories of the biotas and to contrasts between the broad climatic patterns of the two hemispheres. There is no forest biome in the Southern Hemisphere that is comparable to the boreal forests of the high latitudes of the Northern Hemisphere. The boreal forests of the latter are dominated by evergreen conifers of needle-leaved trees, mostly in the Pinaceae family, and occur in an extremely continental climate. In contrast, at high latitudes in southern South America, forests are dominated mostly by broadleaved trees such as the southern beech genus (Nothofagus). Evergreen conifers with needle or scaleleaves (from families other than the Pinaceae) are a relatively minor component of these forests.

scholarly journals Comparison of 20th century and pre-industrial climate over South America in regional model simulations

2012 ◽  
Vol 8 (5) ◽  
pp. 1599-1620 ◽  
Author(s):  
S. Wagner ◽  
I. Fast ◽  
F. Kaspar
Keyword(s):  
South America ◽  
Greenhouse Gas ◽  
Atmospheric Circulation ◽  
20Th Century ◽  
Climate Model ◽  
Regional Climate ◽  
Regional Model ◽  
Andes Mountains ◽  
Southern South America ◽  
The Andes

Abstract. In this study, we assess how the anthropogenically induced increase in greenhouse gas concentrations affects the climate of central and southern South America. We utilise two regional climate simulations for present day (PD) and pre-industrial (PI) times. These simulations are compared to historical reconstructions in order to investigate the driving processes responsible for climatic changes between the different periods. The regional climate model is validated against observations for both re-analysis data and GCM-driven regional simulations for the second half of the 20th century. Model biases are also taken into account for the interpretation of the model results. The added value of the regional simulation over global-scale modelling relates to a better representation of hydrological processes that are particularly evident in the proximity of the Andes Mountains. Climatic differences between the simulated PD minus PI period agree qualitatively well with proxy-based temperature reconstructions, albeit the regional model overestimates the amplitude of the temperature increase. For precipitation the most important changes between the PD and PI simulation relate to a dipole pattern along the Andes Mountains with increased precipitation over the southern parts and reduced precipitation over the central parts. Here only a few regions show robust similarity with studies based on empirical evidence. However, from a dynamical point-of-view, atmospheric circulation changes related to an increase in high-latitude zonal wind speed simulated by the regional climate model are consistent with numerical modelling studies addressing changes in greenhouse gas concentrations. Our results indicate that besides the direct effect of greenhouse gas changes, large-scale changes in atmospheric circulation and sea surface temperatures also exert an influence on temperature and precipitation changes in southern South America. These combined changes in turn affect the relationship between climate and atmospheric circulation between PD and PI times and should be considered for the statistical reconstruction of climate indices calibrated within present-day climate data.

scholarly journals Migration in South America: an overview of the austral system

1994 ◽  
Vol 4 (2-3) ◽  
pp. 91-107 ◽  
Author(s):  
R. Terry Chesser
Keyword(s):  
South America ◽  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
Resource Availability ◽  
South American ◽  
Global Migration ◽  
Migration System ◽  
East West ◽  
Passerine Migration ◽  
Tyrant Flycatchers

SummaryAustral migrants are species that breed in temperate areas of South America and migrate north, towards or into Amazonia, for the southern winter. Migrations among these species are the most extensive of Southern Hemisphere migrations, and the austral system represents a third major migration system, in the sense that the term has been applied to Northern Hemisphere temperate-tropical migration. The geography of South America greatly influences the austral system. Lack of east-west geographical barriers and the shape of the continent promote a pattern of partially overlapping breeding and wintering ranges. The suboscine family Tyrannidae, the tyrant-flycatchers, is the largest group of austral migrants, with other major families including Emberizidae, Anatidae, Furnariidae, Accipitridae and Hirundinidae. Tyrant-flycatchers constitute more than one-half of the passerine austral migrants and roughly one-third of total austral migrants, a taxonomic domination seen in no other global migration system. Parallels exist, however, between austral migration and the Nearctic and Palearctic systems. Many of the same families, including Hirundinidae, Anatidae and Charadriidae, exhibit similarly high degrees of migratory behavi-our in each system. Passerine migration in the austral system is similar in numbers to that of the Nearctic-Neotropical system, but species migrate shorter distances and breed in more open and scrubby habitats. Possible differences in year-round resource availability between South American and North American temperate forests, in addition to differing availability of these habitats, may contribute to the low numbers of forest-dwelling austral migrants.

Floristics of the South American Páramo Moss Flora

1990 ◽  
Vol 2 (1) ◽  
pp. 127-132
Author(s):  
Dana Griffin III
Keyword(s):  
South America ◽  
Southern Hemisphere ◽  
Cloud Forest ◽  
South American ◽  
Long Distance Dispersal ◽  
The South ◽  
Long Distance ◽  
Late Pliocene ◽  
Northern Andes ◽  
The Past

The South American paramos appeared in Pliocene times and persist to the present day. The moss flora of this habitat consists of an estimated 400 species that comprise 8 floristic groups. In Venezuela these groups and their percent representation are as follows: neotropical 37%, Andean 26%, cosmopolitan 18%, Andean-African 8%, neotropical-Asiatic 3%, neotropical-Australasian 2%, temperate Southern Hemisphere 2% and northern boreal-temperate 2%. Acrocarpous taxa outnumber pleurocarps by nearly 3:1. The neotropical and Andean floristic stocks likely were present prior to late Pliocene orogenies that elevated the cordillera above climatic timberlines. These species may have existed in open, marshy areas (paramillos) or may have evolved from cloud forest ancestors. Taxa of northern boreal- temperate affinities, including those with Asiatic distributions, probably arrived in the paramos during the Pleistocene, a period which may also have seen the establishment in the Northern Andes of some cosmopolitan elements. Species with temperate Southern Hemisphere and Australasian affinities likely spread first to austral South America thence migrated northward during a cool, moist interval sometime over the past 2.5-3 million years or may have become established in the paramos as a result of long- distance dispersal.

Teleconnection patterns in the Southern Hemisphere in subseasonal to seasonal models hindcasts and influences on South America

2020 ◽  
Author(s):  
Iracema Cavalcanti ◽  
Naurinete Barreto
Keyword(s):  
South America ◽  
Atmospheric Circulation ◽  
Southern Hemisphere ◽  
Austral Summer ◽  
Polar Vortex ◽  
Southern Annular Mode ◽  
Atmospheric Teleconnection ◽  
Teleconnection Patterns ◽  
South Pacific Ocean ◽  
Precipitation Anomalies

<p>The main atmospheric teleconnection patterns in the Southern Hemisphere are the Southern Annular Mode (SAM) and the Pacific South American (PSA). The SAM has opposite atmospheric anomalies between high and middle latitudes and it is linked with the polar vortex intensity and jet streams. PSA shows a wavetrain pattern from tropical to the extratropical atmosphere over the South Pacific Ocean triggered by convection in the tropical Indian, Maritime Continent and tropical Pacific. These modes modulate the atmospheric circulation variability and have an influence on the precipitation over Southern Hemisphere continents, mainly in South America (SA). Global models are able to represent these modes in climate simulations of seasonal timescale. The objective of this study is to analyse these teleconnections in hindcasts of subseasonal timescale and the relations to precipitation anomalies over South America. Predictions in the subseasonal time scale of austral summer are very important for several sectors of Southeastern and Southern regions of SA, as these are very populated regions and have agriculture and the largest hydropower,  which are very much affected by precipitation extremes, both excess and lack of rain. Two models of the S2S project (ECMWF and NCEP) are used for the summer seasons of 1999 to 2011 and the patterns are compared to ERA5 reanalyses and GPCP data. EOF analyses of geopotential at 200 hPa and regression analyses against precipitation show the patterns and the influences over South America. The SAM pattern is represented in predictions of 1 to 4 weeks in advance, and PSA pattern, from 1 to 3 weeks in advance. Then, the atmospheric circulation and meteorological variables composites of extreme positive and negative amplitudes of SAM and PSA are analysed to interpret precipitation anomalies during these specific periods for predictions of weeks 2 and 3.</p>

Atmospheric Circulation and Climatic Variability

2007 ◽  
Author(s):  
René D. Garreaud ◽  
Patricio Aceituno
Keyword(s):  
South America ◽  
Atmospheric Circulation ◽  
Amazon Basin ◽  
Southern Oscillation ◽  
Climatic Variability ◽  
Climatic Conditions ◽  
The West ◽  
The Andes ◽  
Weather And Climate ◽  
Atmospheric Phenomena

Regional variations in South America’s weather and climate reflect the atmospheric circulation over the continent and adjacent oceans, involving mean climatic conditions and regular cycles, as well as their variability on timescales ranging from less than a few months to longer than a year. Rather than surveying mean climatic conditions and variability over different parts of South America, as provided by Schwerdtfeger and Landsberg (1976) and Hobbs et al. (1998), this chapter presents a physical understanding of the atmospheric phenomena and precipitation patterns that explain the continent’s weather and climate. These atmospheric phenomena are strongly affected by the topographic features and vegetation patterns over the continent, as well as by the slowly varying boundary conditions provided by the adjacent oceans. The diverse patterns of weather, climate, and climatic variability over South America, including tropical, subtropical, and midlatitude features, arise from the long meridional span of the continent, from north of the equator south to 55°S. The Andes cordillera, running continuously along the west coast of the continent, reaches elevations in excess of 4 km from the equator to about 40°S and, therefore, represents a formidable obstacle for tropospheric flow. As shown later, the Andes not only acts as a “climatic wall” with dry conditions to the west and moist conditions to the east in the subtropics (the pattern is reversed in midlatitudes), but it also fosters tropical-extratropical interactions, especially along its eastern side. The Brazilian plateau also tends to block the low-level circulation over subtropical South America. Another important feature is the large area of continental landmass at low latitudes (10°N–20°S), conducive to the development of intense convective activity that supports the world’s largest rain forest in the Amazon basin. The El Niño–Southern Oscillation phenomenon, rooted in the ocean-atmosphere system of the tropical Pacific, has a direct strong influence over most of tropical and subtropical South America. Similarly, sea surface temperature anomalies over the Atlantic Ocean have a profound impact on the climate and weather along the eastern coast of the continent. In this section we describe the long-term annual and monthly mean fields of several meteorological variables.

Latitude does not influence cavity entrance orientation of South American avian excavators

The Auk ◽  
2021 ◽  
Author(s):  
Valeria Ojeda ◽  
Alejandro Schaaf ◽  
Tomás A Altamirano ◽  
Bianca Bonaparte ◽  
Laura Bragagnolo ◽  
...  
Keyword(s):  
South America ◽  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
Spatial Scales ◽  
Probability Model ◽  
Selection Procedure ◽  
Circular Data ◽  
South American ◽  
Key Driver

Abstract In the Northern Hemisphere, several avian cavity excavators (e.g., woodpeckers) orient their cavities increasingly toward the equator as latitude increases (i.e. farther north), and it is proposed that they do so to take advantage of incident solar radiation at their nests. If latitude is a key driver of cavity orientations globally, this pattern should extend to the Southern Hemisphere. Here, we test the prediction that cavities are oriented increasingly northward at higher (i.e. colder) latitudes in the Southern Hemisphere and describe the preferred entrance direction(s) of 1,501 cavities excavated by 25 avian species (n = 22 Picidae, 2 Trogonidae, 1 Furnariidae) across 12 terrestrial ecoregions (15°S to 55°S) in South America. We used Bayesian projected normal mixed-effects models for circular data to examine the influence of latitude, and potential confounding factors, on cavity orientation. Also, a probability model-selection procedure was used to simultaneously examine multiple orientation hypotheses in each ecoregion to explore underlying cavity-orientation patterns. Contrary to predictions, and patterns from the Northern Hemisphere, birds did not orient their cavities more toward the equator with increasing latitude, suggesting that latitude may not be an important underlying selective force shaping excavation behavior in South America. Moreover, unimodal cavity-entrance orientations were not frequent among the ecoregions analyzed (only in 4 ecoregions), whereas bimodal (in 5 ecoregions) or uniform (in 3 ecoregions) orientations were also present, although many of these patterns were not very clear. Our results highlight the need to include data from under-studied biotas and regions to improve inferences at macroecological scales. Furthermore, we suggest a re-analysis of Northern Hemisphere cavity orientation patterns using a multi-model approach, and a more comprehensive assessment of the role of environmental factors as drivers of cavity orientation at different spatial scales in both hemispheres.

scholarly journals Observational evidences on the modulation of the South American Low Level Jet east of the Andes according the ENSO variability

2009 ◽  
Vol 27 (2) ◽  
pp. 645-657 ◽  
Author(s):  
G. A. M. Silva ◽  
T. Ambrizzi ◽  
J. A. Marengo
Keyword(s):  
South America ◽  
South American ◽  
The South ◽  
Trade Winds ◽  
La Plata ◽  
The Andes ◽  
La Plata Basin ◽  
Normal Frequency ◽  
Rainfall Anomalies ◽  
Low Level Jet

Abstract. The differences on the phase and wavelength of the quasi-stationary waves over the South America generated by El Niño (EN) and La Niña (LN) events seem to affect the daily evolution of the South American Low Level Jet east of the Andes (SALLJ). For the austral summer period of 1977–2004 the SALLJ episodes detected according to Bonner criterion 1 show normal to above-normal frequency in EN years, and in LN years the episodes show normal to below-normal frequency. During EN and LN years the SALLJ episodes were associated with positive rainfall anomalies over the La Plata Basin, but more intense during LN years. During EN years the increase in the SALLJ cases were associated to intensification of the Subtropical Jet (SJ) around 30° S and positive Sea Level Pressure (SLP) anomalies over the western equatorial Atlantic and tropical South America, particularly over central Brazil. This favored the intensification of the northeasterly trade winds over the northern continent and it channeled by the Andes mountain to the La Plata Basin region where negative SLP are found. The SALLJ cases identified during the LN events were weaker and less frequent when compared to those for EN years. In this case the SJ was weaker than in EN years and the negative SLP anomalies over the tropical continent contributed to the inversion of the northeasterly trade winds. Also a southerly flow anomaly was generated by the geostrophic balance due to the anomalous blocking over southeast Pacific and the intense cyclonic transient over the southern tip of South America. As result the warm tropical air brought by the SALLJ encounters the cold extratropical air from the southerly winds over the La Plata basin. This configuration can increase the conditional instability over the La Plata basin and may explain the more intense positive rainfall anomalies in SALLJ cases during LN years than in EN years.

A model for paleobiogeography of South American cricetine rodents

Paleobiology ◽  
1979 ◽  
Vol 5 (2) ◽  
pp. 126-132 ◽  
Author(s):  
Larry G. Marshall
Keyword(s):  
South America ◽  
Central America ◽  
South American ◽  
Land Bridge ◽  
The Andes ◽  
History Of ◽  
Grassland Habitats ◽  
The Guianas ◽  
Forest Habitats ◽  
Glacial Advance

A model for the paleobiogeographic history of South American cricetine rodents is proposed based on new and/or recently published fossil, geological, paleobotanical and radioisotope data. Cricetine rodents of the tribe Sigmodontini evolved in North America before 7.0 Myr BP. They got to South America by waif dispersal across the Bolivar Trough marine barrier from Central America during a world wide drop in sea level (the “Messinian Low”) between 7.0 and 5.0 Myr BP. The basal stock was probably a sylvan (forest) form, from which evolved pastoral (grazing) forms in the savanna-grassland area of Venezuela, Colombia and the Guianas. The pastoral forms in the northern savanna-grassland area were restricted there until about 3.5 Myr BP. At that time there occurred the first glaciation in South America and consonant with glacial advance was a retraction of forest habitats and an expansion of savanna-grassland habitats. At that time the pastoral forms were able to disperse southward through a savanna-grassland corridor along the eastern foothills of the Andes and spread throughout the previously disjunct savanna-grasslands of Bolivia and Argentina. Cricetines are first recorded as fossil in the Monte Hermoso Fm. of Argentina which is about 3.5 Myr BP in age. The Panamanian land bridge came into existence about 3.0 Myr BP as indicated by the beginning of a major interchange of terrestrial faunas between the Americas, which was well underway by 2.7 Myr BP.

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