scholarly journals Impacts of Atmospheric Rivers on Precipitation in Southern South America

2018 ◽  
Vol 19 (10) ◽  
pp. 1671-1687 ◽  
Author(s):  
Maximiliano Viale ◽  
Raúl Valenzuela ◽  
René D. Garreaud ◽  
F. Martin Ralph
Keyword(s):  
South America ◽  
West Coast ◽  
Detection Algorithm ◽  
Water Vapor Transport ◽  
The South ◽  
Southern South America ◽  
Atmospheric Rivers ◽  
The Andes ◽  
Hourly Data ◽  
The Impact

Abstract This study quantifies the impact of atmospheric rivers (ARs) on precipitation in southern South America. An AR detection algorithm was developed based on integrated water vapor transport (IVT) from 6-hourly CFSR reanalysis data over a 16-yr period (2001–16). AR landfalls were linked to precipitation using a comprehensive observing network that spanned large variations in terrain along and across the Andes from 27° to 55°S, including some sites with hourly data. Along the Pacific (west) coast, AR landfalls are most frequent between 38° and 50°S, averaging 35–40 days yr−1. This decreases rapidly to the south and north of this maximum, as well as to the east of the Andes. Landfalling ARs are more frequent in winter/spring (summer/fall) to the north (south) of ~43°S. ARs contribute 45%–60% of the annual precipitation in subtropical Chile (37°–32°S) and 40%–55% along the midlatitude west coast (37°–47°S). These values significantly exceed those in western North America, likely due to the Andes being taller. In subtropical and midlatitude regions, roughly half of all events with top-quartile precipitation rates occur under AR conditions. Median daily and hourly precipitation in ARs is 2–3 times that of other storms. The results of this study extend knowledge of the key roles of ARs on precipitation, weather, and climate in the South American region. They enable comparisons with other areas globally, provide context for specific events, and support local nowcasting and forecasting.

scholarly journals Impact of enriched analyses on regional numerical forecasts over southeastern South America during SALLJEX

2014 ◽  
Vol 29 (3) ◽  
pp. 315-330
Author(s):  
Yanina García Skabar ◽  
Matilde Nicolini
Keyword(s):  
Data Assimilation ◽  
South America ◽  
Atmospheric Modeling ◽  
South American ◽  
The South ◽  
Low Level ◽  
Positive Effects ◽  
Accumulated Rainfall ◽  
Low Level Jet ◽  
The Impact

During the warm season 2002-2003, the South American Low-Level Jet Experiment (SALLJEX) was carried out in southeastern South America. Taking advantage of the unique database collected in the region, a set of analyses is generated for the SALLJEX period assimilating all available data. The spatial and temporal resolution of this new set of analyses is higher than that of analyses available up to present for southeastern South America. The aim of this paper is to determine the impact of assimilating data into initial fields on mesoscale forecasts in the region, using the Brazilian Regional Atmospheric Modeling System (BRAMS) with particular emphasis on the South American Low-Level Jet (SALLJ) structure and on rainfall forecasts. For most variables, using analyses with data assimilated as initial fields has positive effects on short term forecast. Such effect is greater in wind variables, but not significant in forecasts longer than 24 hours. In particular, data assimilation does not improve forecasts of 24-hour accumulated rainfall, but it has slight positive effects on accumulated rainfall between 6 and 12 forecast hours. As the main focus is on the representation of the SALLJ, the effect of data assimilation in its forecast was explored. Results show that SALLJ is fairly predictable however assimilating additional observation data has small impact on the forecast of SALLJ timing and intensity. The strength of the SALLJ is underestimated independently of data assimilation. However, Root mean square error (RMSE) and BIAS values reveal the positive effect of data assimilation up to 18-hours forecasts with a greater impact near higher topography.

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 The impact of the subtropical South Atlantic SST on South American precipitation

2008 ◽  
Vol 26 (11) ◽  
pp. 3457-3476 ◽  
Author(s):  
A. S. Taschetto ◽  
I. Wainer
Keyword(s):  
South America ◽  
Southern Oscillation ◽  
South Atlantic ◽  
Empirical Orthogonal Functions ◽  
Convergence Zone ◽  
South American ◽  
The South ◽  
Inter Tropical Convergence Zone ◽  
The Impact ◽  
Sst Anomalies

Abstract. The Community Climate Model (CCM3) from the National Center for Atmospheric Research (NCAR) is used to investigate the effect of the South Atlantic sea surface temperature (SST) anomalies on interannual to decadal variability of South American precipitation. Two ensembles composed of multidecadal simulations forced with monthly SST data from the Hadley Centre for the period 1949 to 2001 are analysed. A statistical treatment based on signal-to-noise ratio and Empirical Orthogonal Functions (EOF) is applied to the ensembles in order to reduce the internal variability among the integrations. The ensemble treatment shows a spatial and temporal dependence of reproducibility. High degree of reproducibility is found in the tropics while the extratropics is apparently less reproducible. Austral autumn (MAM) and spring (SON) precipitation appears to be more reproducible over the South America-South Atlantic region than the summer (DJF) and winter (JJA) rainfall. While the Inter-tropical Convergence Zone (ITCZ) region is dominated by external variance, the South Atlantic Convergence Zone (SACZ) over South America is predominantly determined by internal variance, which makes it a difficult phenomenon to predict. Alternatively, the SACZ over western South Atlantic appears to be more sensitive to the subtropical SST anomalies than over the continent. An attempt is made to separate the atmospheric response forced by the South Atlantic SST anomalies from that associated with the El Niño – Southern Oscillation (ENSO). Results show that both the South Atlantic and Pacific SSTs modulate the intensity and position of the SACZ during DJF. Particularly, the subtropical South Atlantic SSTs are more important than ENSO in determining the position of the SACZ over the southeast Brazilian coast during DJF. On the other hand, the ENSO signal seems to influence the intensity of the SACZ not only in DJF but especially its oceanic branch during MAM. Both local and remote influences, however, are confounded by the large internal variance in the region. During MAM and JJA, the South Atlantic SST anomalies affect the magnitude and the meridional displacement of the ITCZ. In JJA, the ENSO has relatively little influence on the interannual variability of the simulated rainfall. During SON, however, the ENSO seems to counteract the effect of the subtropical South Atlantic SST variations on convection over South America.

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.

Size and Locomotion in Teratorns (Aves: Teratornithidae)

The Auk ◽  
1983 ◽  
Vol 100 (2) ◽  
pp. 390-403 ◽  
Author(s):  
Kenneth E. Campbell ◽  
Eduardo P. Tonni
Keyword(s):  
South America ◽  
New World ◽  
Pelvic Girdle ◽  
Andes Mountains ◽  
New Method ◽  
Southern South America ◽  
The Andes ◽  
Body Weights ◽  
Westerly Winds

Abstract The extinct family Teratornithidae contains the world's largest known flying birds. A new method of determining body weights of extinct birds, based on the size of their tibiotarsi, facilitates the estimation of the wing dimensions of these giant birds. An analysis of the bones of the teratorn wing shows that they closely resemble those of condors, suggesting that teratorns flew in a manner similar to these large New World vultures. The bones of the pelvic girdle and hindlimbs indicate that teratorns were probably agile on the ground, though better adapted for walking and stalking than running. We estimate that the largest teratorn, Argentavis magnificens, weighed 80 kg and had a wingspan of 6-8 m. It probably became airborne by spreading its huge wings into the strong, continuous, westerly winds that blew across southern South America before the elevation of the Andes Mountains and, once aloft, flew in the manner of condors.

scholarly journals Precipitation and Water Vapor Transport in the Southern Hemisphere with Emphasis on the South American Region

2009 ◽  
Vol 48 (9) ◽  
pp. 1902-1912 ◽  
Author(s):  
Josefina Moraes Arraut ◽  
Prakki Satyamurty
Keyword(s):  
Water Vapor ◽  
South America ◽  
North Atlantic ◽  
Vapor Transport ◽  
Water Vapor Transport ◽  
The South ◽  
Meridional Transport ◽  
Moisture Flow ◽  
The North ◽  
The North Atlantic

Abstract December–March climatologies of precipitation and vertically integrated water vapor transport were analyzed and compared to find the main paths by which moisture is fed to high-rainfall regions in the Southern Hemisphere in this season. The southern tropics (20°S–0°) exhibit high rainfall and receive ample moisture from the northern trades, except in the eastern Pacific and the Atlantic Oceans. This interhemispheric flow is particularly important for Amazonian rainfall, establishing the North Atlantic as the main source of moisture for the forest during its main rainy season. In the subtropics the rainfall distribution is very heterogeneous. The meridional average of precipitation between 35° and 25°S is well modulated by the meridional water vapor transport through the 25°S latitude circle, being greater where this transport is from the north and smaller where it is from the south. In South America, to the east of the Andes, the moisture that fuels precipitation between 20° and 30°S comes from both the tropical South and North Atlantic Oceans whereas between 30° and 40°S it comes mostly from the North Atlantic after passing over the Amazonian rain forest. The meridional transport (across 25°S) curve exhibits a double peak over South America and the adjacent Atlantic, which is closely reproduced in the mean rainfall curve. This corresponds to two local maxima in the two-dimensional field of meridional transport: the moisture corridor from Amazonia into the continental subtropics and the moisture flow coming from the southern tropical Atlantic into the subtropical portion of the South Atlantic convergence zone. These two narrow pathways of intense moisture flow could be suitably called “aerial rivers.” Their longitudinal positions are well defined. The yearly deviations from climatology for moisture flow and rainfall correlate well (0.75) for the continental peak but not for the oceanic peak (0.23). The structure of two maxima is produced by the effect of transients in the time scale of days.

Unraveling South American spatial precipitation patterns, intensity and variability through a multi-proxy approach for the past 2 kyr

2020 ◽  
Author(s):  
Francisco J. Briceño-Zuluaga ◽  
Juliana Nogueira ◽  
Heitor Evangelista ◽  
James Apaéstegui ◽  
Abdelfettah Sifeddine ◽  
...  
Keyword(s):  
South America ◽  
Hydrological Cycle ◽  
Climatic Variability ◽  
Ice Cores ◽  
High Standard ◽  
Water Vapor Transport ◽  
South American ◽  
Equatorial Atlantic ◽  
The South ◽  
Mountainous Regions

<p>South America hydrological cycle is highly dependent on the water vapor transport advected from tropical-equatorial Atlantic, Southern Pacific as well as the polar advections. While the Pacific contribution in the continental water budget is basically restricted to the western Andes region, the Atlantic Ocean and others mechanism – as advection in Amazonas basin – play a great role in modulating precipitation over the continent. Besides, modes of climatic variability, such as ENSO, have an important role in pluviosity distribution patterns and respectively intensity, influencing the availability of water resources from mountainous regions, vital to ecosystems and to economy and human wellbeing. Intense droughts and floods observed continentally during the modern epoch have pointed to the need of better understanding the regional climate related issue. Recent paleoclimate advances, especially the creation of high-standard regional proxy record databases, allow describing the South American climate from a new perspective. Here we present an effort of the South American PAGES 2k paleo-community LOTRED-SA to build a South America hydrology robust and unique multiproxy database. We present a spatial and temporal approach of the South American hydro-climate reconstruction based on more than 360 available databases in an attempt to unravel their changes and impacts. Following a multi-proxy approach, we expect to better describe duration and location of wet and dryer climate regimes at most important climate spatial domains, and modes patterns on South America, during each period; as well as their predominant variability base on high resolution records (tree rings, speleothems, lake, marine and ice cores). we combine here the use of different proxy records and spatial-temporal approach, owing to consolidate interpretations of the hydrological cycles in South America.</p>

Darwin the geologist in southern South America

2016 ◽  
Vol 35 (2) ◽  
pp. 303-345 ◽  
Author(s):  
Robert H. Dott ◽  
Ian W. D. Dalziel
Keyword(s):  
South America ◽  
Charles Darwin ◽  
Lateral Compression ◽  
Central Chile ◽  
Southern South America ◽  
The Andes ◽  
Andean Cordillera ◽  
Marine Terraces ◽  
Four Books ◽  
Geological Map

Charles Darwin was a reputable geologist before he achieved biological fame. Most of his geological research was accomplished in southern South America during the voyage of H.M.S. Beagle (1831–1836). Afterward he published four books and several articles about geology and coral atolls and became active in the Geological Society of London. We have followed Darwin's footsteps during our own researches and have been very impressed with his keen observations and inferences. He made some mistakes, however, such as appealing to iceberg rafting to explain erratic boulders and to inundations of the sea to carve valleys. Darwin prepared an important hand-colored geological map of southern South America, which for unknown reasons he did not publish. The distributions of seven map units are shown. These were described in his books wherein he also documented multiple elevated marine terraces on both coasts of South America. While exploring the Andean Cordillera in central Chile and Argentina, he discovered two fossil forests. Darwin developed a tectonic theory involving vertical uplift of the entire continent, which was greatest in the Andes where magma leaked up from a hypothetical subterranean sea of magma to form volcanoes and earthquakes. The theory had little impact and was soon eclipsed by theories involving lateral compression of strata. His and other contemporary theories suffered from a lack of knowledge about the earth's interior. Finally with modern plate tectonic theory involving intense lateral compression across the Andean Cordillera we can explain satisfactorily the geology so carefully documented by Darwin.

Ecogeography and the Great American Interchange

Paleobiology ◽  
1991 ◽  
Vol 17 (3) ◽  
pp. 266-280 ◽  
Author(s):  
S. David Webb
Keyword(s):  
North America ◽  
South America ◽  
North American ◽  
Mammalian Fauna ◽  
The South ◽  
Land Bridge ◽  
Southern Mexico ◽  
The North ◽  
Land Mammal ◽  
The Impact

When the isthmian land bridge triggered the Great American Interchange, a large majority of land-mammal families crossed reciprocally between North and South America at about 2.5 Ma (i.e., Late Pliocene). Initially land-mammal dynamics proceeded as predicted by equilibrium theory, with roughly equal reciprocal mingling on both continents. Also as predicted, the impact of the interchange faded in North America after about 1 m.y. In South America, contrary to such predictions, the interchange became decidedly unbalanced: during the Pleistocene, groups of North American origin continued to diversify at exponential rates. Whereas only about 10% of North American genera are derived from southern immigrants, more than half of the modern mammalian fauna of South America, measured at the generic level, stems from northern immigrants. In addition, extinctions more severely decimated interchange taxa in North America, where six families were lost, than in South America, where only two immigrant families became extinct.This paper presents a two-phase ecogeographic model to explain the asymmetrical results of the land-mammal interchange. During the humid interglacial phase, the tropics were dominated by rain forests, and the principal biotic movement was from Amazonia to Central America and southern Mexico. During the more arid glacial phase, savanna habitats extended broadly right through tropical latitudes. Because the source area in the temperate north was six times as large as that in the south, immigrants from the north outnumbered those from the south. One prediction of this hypothesis is that immigrants from the north generally should reach higher latitudes in South America than the opposing contingent of land-mammal taxa in North America. Another prediction is that successful interchange families from the north should experience much of their phylogenetic diversification in low latitudes of North America before the interchange. Insofar as these predictions can be tested, they appear to be upheld.

Bomarea rinconii (Alstroemeriaceae), a new species from the Talamanca Mountains in Chiriqui Province, Panama

Phytotaxa ◽  
2013 ◽  
Vol 105 (1) ◽  
pp. 21
Author(s):  
DANIEL ADOLFO CÁCERES GONZÁLEZ
Keyword(s):  
New Species ◽  
South America ◽  
Greater Antilles ◽  
Southern South America ◽  
The Andes ◽  
A New Species

Bomarea Mirbel (1804: 71; Alstroemeriaceae) includes 122 species (Govaerts 2013) and is divided into four subgenera (Hofreiter & Tillich 2002): Baccata (five species), Bomarea (ca. seventy species), Sphaerine(twelve species) and Wichuraea (eighteen species). Bomarea is distributed from Mexico and the Greater Antilles to southern South America (Gereau 1994). The centre of distribution of the genus is along the Andes from Colombia to Bolivia (Hofreiter 2008).

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