scholarly journals The Role of Latent and Sensible Heat Fluxes in an Explosive Cyclogenesis over the South American East Coast

2011 ◽  
Vol 89 (6) ◽  
pp. 637-663 ◽  
Author(s):  
Everson DAL PIVA ◽  
Manoel Alonso GAN ◽  
Marley Cavalcante de Lima MOSCATI
Keyword(s):  
East Coast ◽  
Heat Fluxes ◽  
South American ◽  
Sensible Heat ◽  
The South ◽  
American East Coast

scholarly journals Role of Land Surface Processes in South American Monsoon Development

2006 ◽  
Vol 19 (5) ◽  
pp. 741-762 ◽  
Author(s):  
Yongkang Xue ◽  
F. de Sales ◽  
W-P. Li ◽  
C. R. Mechoso ◽  
C. A. Nobre ◽  
...  
Keyword(s):  
Surface Water ◽  
Land Surface ◽  
General Circulation ◽  
Austral Summer ◽  
Mature Stage ◽  
South American ◽  
Sensible Heat ◽  
The South ◽  
South American Monsoon

Abstract This study explores the role of vegetation biophysical processes (VBPs) in the structure and evolution of the South American monsoon system (SAMS) with an emphasis on the precipitation field. The approach is based on comparing ensemble simulations by the National Centers for Environmental Prediction general circulation model (GCM) in which the land surface parameterization in one ensemble includes an explicit representation of vegetation processes in the calculation of surface fluxes while the other does not [GCM/Simplified Simple Biosphere Model (SSiB) and GCM/Soil, respectively], but with similar monthly mean surface albedo and initial soil moisture. The ensembles consist of five pairs of 1-yr integrations differing in the initial conditions for the atmosphere. The results show that, during the austral summer, consideration of explicit vegetation processes does not alter the monthly mean precipitation at the planetary scale. However, at continental scales, GCM/SSiB produces a more successful simulation of SAMS than GCM/Soil. The improvement is particularly clear in reference to the seasonal southward displacement of precipitation during the onset of the SAMS and its northward merging with the intertropical convergence zone during the monsoon mature stage, as well as better monthly mean austral summer precipitation over the South American continent. The changes in surface water and energy balances and circulation in October (monsoon onset) and December (the start of the monsoon mature stage) were analyzed for a better understanding of the results and mechanisms involved. It was found that the major difference between the simulations is in the partitioning of latent heat and sensible heat fluxes (i.e., different Bowen ratio), which produced different latitudinal and longitudinal thermal gradients at the surface. A stronger sensible heat flux gradient between continent and ocean in the GCM/SSiB simulation helped generate an enhanced ventilation effect, which lowered moist static energy (MSE) over the northeast coast of South America leading to stronger counterclockwise turning of the low-level wind from the Atlantic Ocean toward the continent during the premonsoon and early monsoon stages, modifying moisture flux convergence (MFC). It was further identified that the seasonality of savanna and shrublands to the south and east of the Amazon rain forest contributed to the variability of heating gradients and influenced the SAMS onset and its northward merge with the ITCZ at the early monsoon mature stage. The comparison of the differences between precipitation, evaporation, advection of MSE, and MFC based on simulations using two different land parameterizations suggested that the VBP modulated the surface water budget, but its impact on precipitation was determined by the changes in circulation via changes in heat gradient and MSE.

The role of SST on the South American atmospheric circulation during January, February and March 2001

2005 ◽  
Vol 24 (7-8) ◽  
pp. 781-791 ◽  
Author(s):  
Anita Rodrigues de Moraes Drumond ◽  
Tércio Ambrizzi
Keyword(s):  
Atmospheric Circulation ◽  
South American ◽  
The South

Dust deposition tracks late-Holocene shifts in monsoon activity and the increasing role of human disturbance in the Puna-Altiplano, northwest Argentina

The Holocene ◽  
2020 ◽  
Vol 30 (4) ◽  
pp. 519-536 ◽  
Author(s):  
James Hooper ◽  
Samuel K Marx ◽  
Jan-Hendrik May ◽  
Liliana C Lupo ◽  
Julio J Kulemeyer ◽  
...  
Keyword(s):  
Late Holocene ◽  
Human Impacts ◽  
South American ◽  
Dust Deposition ◽  
The South ◽  
Dust Source ◽  
Dust Emissions ◽  
Dust Flux ◽  
Dry Conditions

The Puna-Altiplano plateau represents a regionally significant dust source, which is critically located at the nexus between the tropical and sub-polar synoptic systems that dominate the South American climate. Dust emissions in this region would therefore be expected to be sensitive to changes in these systems, in particular the strength and position of the South American Summer Monsoon (SASM). Here, we present a late-Holocene multi-proxy study where changes in dust flux, reconstructed from a high-altitude peat mire, are examined in light of climate variability and human impacts. Results show that for most the 4300 cal. yr BP record, dust flux sensitively tracked changes in SASM activity. Prior to 2600 cal. yr BP relatively high dust flux implies dry conditions prevailed across the Puna-Altiplao in association with reduced SASM activity. The chemistry of dust deposited at this time matched the large endorheic basins on the Puna, which host ephemeral lakes and terminal fans, indicating these were actively supplying dust to the airstream. After 2600 cal. yr BP, SASM activity increased while dust flux decreased and the dust chemistry changed, collectively implying the shutting down of the Puna-Altiplano as a significant dust source. Dust flux increased after 1000 cal. yr BP during the ‘Medieval Warm Period’, associated with a return to drier conditions and reactivation of dust sources across the endorheic basins of the Puna. Natural variability in dust flux was dwarfed, however, by the very significant increase in flux after 400 cal. yr BP following Spanish Colonisation and associated changing landuse practices. This finding attests to the globally significant role of humans on dust emissions.

Interannual variability of latent and sensible heat fluxes in the South China Sea

2010 ◽  
Vol 28 (1) ◽  
pp. 153-159 ◽  
Author(s):  
Haibo Zong ◽  
Yuguang Liu ◽  
Peng Xiu ◽  
Qing Xu ◽  
Zengrui Rong
Keyword(s):  
South China Sea ◽  
Interannual Variability ◽  
South China ◽  
Heat Fluxes ◽  
The South China Sea ◽  
Sensible Heat ◽  
The South ◽  
China Sea

Israeli penetration in South America (1973-1947)

2021 ◽  
Vol 26 ◽  
pp. 1-23
Keyword(s):  
South America ◽  
Key Words ◽  
Decision Makers ◽  
The Political ◽  
South American ◽  
American Continent ◽  
The South ◽  
Political Decision ◽  
South American Continent

This research is an attempt to uncover the reality and method of Israeli penetration in the South American continent, and aims to draw attention to the weaknesses and mistakes in the role of Arab communities that they had to play in South America, and the position of Arab governments towards that continent. The research was divided into two main axes, as the first dealt with the means of Israeli penetration in South America until 1947, providing a brief overview of the roots of the penetration in the South American continent and the methods it adopted in achieving this. While the second axis focused on the stance of the South American countries on the Arab-Israeli conflict (1947-1973). However, the Israeli infiltration was affecting the political decision-makers in that continent towards the decision to partition Palestine up to the October 1973 war. Key words: the penetration, Palestine, Israel, immigration, Arabs, America

The role of the vascular endothelium in arenavirus haemorrhagic fevers

2009 ◽  
Vol 102 (12) ◽  
pp. 1024-1029 ◽  
Author(s):  
Stefan Kunz
Keyword(s):  
Vascular Endothelium ◽  
Cell Function ◽  
Experimental Studies ◽  
Lassa Fever ◽  
Vascular Involvement ◽  
Lassa Virus ◽  
South American ◽  
The South ◽  
Endothelial Cell Function

SummaryViral haemorrhagic fevers (VHF) caused by arenaviruses are among the most devastating emerging human diseases.The most important pathogen among the arenaviruses is Lassa virus (LASV), the causative agent of Lassa fever that is endemic to West Africa. On the South American continent, the New World arenavirus Junin virus (JUNV), Machupo (MACV), Guanarito (GTOV), and Sabia virus (SABV) have emerged as causative agents of severe VHFs. Clinical and experimental studies on arenavirus VHF have revealed a crucial role of the endothelium in their pathogenesis. However, in contrast to other VHFs, haemorrhages are not a salient feature of Lassa fever and fatal cases do not show overt destruction of vascular tissue.The functional alteration of the vascular endothelium that precede shock and death in fatal Lassa fever may be due to more subtle direct or indirect effects of the virus on endothelial cells. Haemorrhagic disease manifestations and vascular involvement are more pronounced in the VHF caused by the South American haemorrhagic fever viruses. Recent studies on JUNV revealed perturbation of specific endothelial cell function, including expression of cell adhesion molecules, coagulation factors, and vasoactive mediators as a consequence of productive viral infection.These studies provided first possible links to some of the vascular abnormalities observed in patients; however, their relevance in vivo remains to be investigated.

scholarly journals How Does Soil Moisture Influence the Early Stages of the South American Monsoon?

2008 ◽  
Vol 21 (2) ◽  
pp. 195-213 ◽  
Author(s):  
Estela A. Collini ◽  
Ernesto H. Berbery ◽  
Vicente R. Barros ◽  
Matthew E. Pyle
Keyword(s):  
Boundary Layer ◽  
Heat Flux ◽  
Soil Moisture ◽  
Latent Heat ◽  
Sensible Heat Flux ◽  
South American ◽  
Sensible Heat ◽  
The South ◽  
Early Stages ◽  
Initial Soil

Abstract This article discusses the feedbacks between soil moisture and precipitation during the early stages of the South American monsoon. The system achieves maximum precipitation over the southern Amazon basin and the Brazilian highlands during the austral summer. Monsoon changes are associated with the large-scale dynamics, but during its early stages, when the surface is not sufficiently wet, soil moisture anomalies may also modulate the development of precipitation. To investigate this, sensitivity experiments to initial soil moisture conditions were performed using month-long simulations with the regional mesoscale Eta model. Examination of the control simulations shows that they reproduce all major features and magnitudes of the South American circulation and precipitation patterns, particularly those of the monsoon. The surface sensible and latent heat fluxes, as well as precipitation, have a diurnal cycle whose phase is consistent with previous observational studies. The convective inhibition is smallest at the time of the precipitation maximum, but the convective available potential energy exhibits an unrealistic morning maximum that may result from an early boundary layer mixing. The sensitivity experiments show that precipitation is more responsive to reductions of soil moisture than to increases, suggesting that although the soil is not too wet, it is sufficiently humid to easily reach levels where soil moisture anomalies stop being effective in altering the evapotranspiration and other surface and boundary layer variables. Two mechanisms by which soil moisture has a positive feedback with precipitation are discussed. First, the reduction of initial soil moisture leads to a smaller latent heat flux and a larger sensible heat flux, and both contribute to a larger Bowen ratio. The smaller evapotranspiration and increased sensible heat flux lead to a drier and warmer boundary layer, which in turn reduces the atmospheric instability. Second, the deeper (and drier) boundary layer is related to a stronger and higher South American low-level jet (SALLJ). However, because of the lesser moisture content, the SALLJ carries less moisture to the monsoon region, as evidenced by the reduced moisture fluxes and their convergence. The two mechanisms—reduced convective instability and reduced moisture flux convergence—act concurrently to diminish the core monsoon precipitation.

scholarly journals Ameryka Łacińska w polityce zagranicznej Brazylii – niedokończony projekt przywództwa regionalnego

2020 ◽  
Vol 2020 (55) ◽  
pp. 425-439
Author(s):  
Anita Oberda Monkiewicz
Keyword(s):  
Foreign Policy ◽  
Latin America ◽  
South American ◽  
The South ◽  
Important Place ◽  
Regional Leadership

The purpose of the article is to discuss the place and role of Latin America in Brazil’s foreign policy. The article leads to the conclusion that, starting from the 1990s, Latin America, a region that was marginalized for many years, gained an important place in Brazilian policy. The construction of the South American community has become an instrument of strengthening regional leadership, although due to the lack of a coherent strategy towards the direct neighbourhood, it proved to be short-lived.

EVOLUÇÃO DA ICTIOFAUNA DE RIACHOS SUL-AMERICANOS (CASTRO, 1999) REVISITADO APÓS MAIS DE DUAS DÉCADAS

2021 ◽  
Vol 25 (02) ◽  
pp. 231-245
Author(s):  
Ricardo Macedo Corrêa e Castro ◽  
Keyword(s):  
Maximum Size ◽  
Taxonomic Diversity ◽  
Respiratory Physiology ◽  
South American ◽  
Adult Size ◽  
The South ◽  
Evolutionary Pattern ◽  
The Family ◽  
Respective Species

A little more than 20 years after the first publication of Castro (1999), the knowledge of the South American freshwater ichthyofauna, especially that of Brazil, has increased dramatically. This increase occurred both in terms of knowledge of its taxonomic diversity - in 1999, based on various sources in the scientific literature, a total of 2,800 species of South American freshwater fish was estimated, and a total of near 3,500 species it is currently known from Brazil alone - as to the knowledge of its evolution and also ecology. Consequently, all the hypotheses originally proposed in that paper are reexamined and critically discussed here considering this new knowledge accumulated in the past nearly two decades. Although the original 1999 hypothesis that the small adult size of their respective species is a general evolutionary pattern shared by the South American stream ichthyofauna has been firmly corroborated by several studies carried out in many regions of Brazil, the different patterns associated with most of the species of stream fish originally proposed are discussed in this chapter in the light of the new accumulated knowledge about their biology and ecology. Likewise, the possible role of heterochrony in their respective evolution is critically analyzed in the context of the great advance that has occurred in understanding the phylogenetic relationships of component taxa of freshwater neotropical ichthyofauna, using mainly the family Characidae as a possible model. Finally, a recent intriguing idea of the role of respiratory physiology in determining both the maximum size of teleost fish and their patterns of environmental occupation is examined in relation to its possible effect in the evolution of South American stream ichthyofauna.

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