scholarly journals The South American Water Balance: The Influence of Low-Level Jets

2016 ◽  
Vol 29 (4) ◽  
pp. 1429-1449 ◽  
Author(s):  
Marília Guedes do Nascimento ◽  
Dirceu Luis Herdies ◽  
Diego Oliveira de Souza
Keyword(s):  
Water Balance ◽  
Amazon Basin ◽  
Important Variable ◽  
Moisture Convergence ◽  
South American ◽  
Low Level ◽  
La Plata Basin ◽  
Low Level Jets ◽  
Main Components ◽  
Main Pattern

Abstract To study the climatology of the water balance over South America and analyze the influence of low-level jets (LLJs), a climate study of the water balance and its main components was performed, specifically in the Amazon and La Plata basin (LPB) region, from 1979 to 2008. The results showed that on average for the analysis period, the Amazon basin and LPB performed as a sink of moisture (ET < P) and as a moisture convergence for the regions, which accounted for approximately 62% and 43% of the precipitation, respectively. During the study period, 884 days with an occurrence of LLJs were observed, occurring most frequently during the winter and around 0000 and 0600 UTC. When considering the water balance for the days with LLJs, it was observed that the Amazon acts as a source of moisture, especially in the dry season, and that the LPB behaves as a sink during all months. The influence of the LLJ as a modulator for precipitation on the LPB is clear, as the precipitation is 32% higher during the LLJ events compared with days without LLJs. This main pattern shows that the moisture convergence trough of the LLJs is crucial for the water balance on the LPB, whereas evapotranspiration is a more important variable of the water balance on the Amazon basin with or without the LLJs.

INTER-SEASONAL AND INTER-BASINS HYDROLOGICAL COUPLING IN SOUTH AMERICA

2021 ◽  
Author(s):  
Paulo Rodrigo Zanin ◽  
Prakki Satyamurty
Keyword(s):  
Soil Moisture ◽  
Amazon Basin ◽  
Winter Season ◽  
Western Region ◽  
South American ◽  
La Plata ◽  
La Plata Basin ◽  
Precipitation Recycling ◽  
Source Sink ◽  
Southeastern Region

AbstractThe inter-seasonal and inter-basins hydrological couplings between the Amazon and the La Plata basins are obtained with the help of ERA-5 atmospheric reanalysis, MERGE/CPTEC precipitation, GLEAM evapotranspiration and the GLDAS/Noah soil moisture datasets. The hypotheses formulated by Zanin and Satyamurty (2020a) about the hydrological processes interconnecting the Amazon Basin and the La Plata Basin are tested. A new method for finding the source-sink relationships among the boxes (regions) is presented. The precipitation recycling, frequency of source-sink behaviors, the soil moisture memory and the continental moisture transport between remote regions are evaluated. The main result of this study is that the amount of water precipitated over the Southeastern region of the Amazon Basin at the end of the South American Monsoon during autumn season, influences the amount of precipitation during winter season over the Central-western region of the La Plata Basin.

The Physical Geography of South America

2007 ◽  
Author(s):  
Thomas Veblen ◽  
Kenneth Young ◽  
Antony Orme
Keyword(s):  
South America ◽  
Amazon Basin ◽  
Physical Geography ◽  
Environmental Literature ◽  
South American ◽  
High Mountains ◽  
Natural Landscape ◽  
Modern Agriculture ◽  
Body Of Knowledge ◽  
Main Components

The Physical Geography of South America, the eighth volume in the Oxford Regional Environments series, presents an enduring statement on the physical and biogeographic conditions of this remarkable continent and their relationships to human activity. It fills a void in recent environmental literature by assembling a team of specialists from within and beyond South America in order to provide an integrated, cross-disciplinary body of knowledge about this mostly tropical continent, together with its high mountains and temperate southern cone. The authors systematically cover the main components of the South American environment - tectonism, climate, glaciation, natural landscape changes, rivers, vegetation, animals, and soils. The book then presents more specific treatments of regions with special attributes from the tropical forests of the Amazon basin to the Atacama Desert and Patagonian steppe, and from the Atlantic, Caribbean, and Pacific coasts to the high Andes. Additionally, the continents environments are given a human face by evaluating the roles played by people over time, from pre-European and European colonial impacts to the effects of modern agriculture and urbanization, and from interactions with El Niño events to prognoses for the future environments of the continent.

scholarly journals A New Look at the Identification of Low-Level Jets in South America

2018 ◽  
Vol 146 (7) ◽  
pp. 2315-2334 ◽  
Author(s):  
Maurício I. Oliveira ◽  
Ernani L. Nascimento ◽  
Carolina Kannenberg
Keyword(s):  
South America ◽  
Numerical Data ◽  
Southeastern Brazil ◽  
La Plata ◽  
Low Level ◽  
La Plata Basin ◽  
Low Level Jets ◽  
Forcing Mechanisms ◽  
Definition Of ◽  
Environmental Prediction

Abstract Criteria currently employed in algorithms that identify low-level jets (LLJs) in South America utilizing rawinsonde and gridded model data fail to detect an important number of LLJ events. This study discusses shortcomings in the existing approaches for LLJ identification in South America and proposes modifications to the criteria regarding layer depth for LLJ identification and wind direction. Episodes of southerly LLJs, which have received less attention in the La Plata basin, are also included in the investigation. A sensitivity analysis of LLJ detection in South America upon the choice of the criteria applied to a sample period of 15 years (1996–2010) of gridded numerical data from the National Centers for Environmental Prediction (NCEP) Climate Forecast System Reanalysis (CFSR), and to a 20-yr dataset (1996–2015) of actual rawinsondes for the La Plata basin, reveals the benefits of revising the criteria. The modified criteria allow for the characterization of a wider spectrum of LLJs over key regions of South America, such as over the Bolivian–Paraguayan border, Sierras de Córdoba in Argentina, and southern-southeastern Brazil. This wider range of events includes elevated LLJs, mostly with strong zonal components, that account for approximately 20% of the full sample of LLJs identified in the rawinsonde dataset investigated here. The revised criteria have the advantage of retaining the identification of episodes that meet the consecrated definition of the South American LLJ, while at the same time providing an augmented sample of such wind systems. Our results provide further insights into the forcing mechanisms of distinct types of LLJs in South America, ranging from topographic to baroclinic effects.

scholarly journals On the importance of cascading moisture recycling in South America

2014 ◽  
Vol 14 (23) ◽  
pp. 13337-13359 ◽  
Author(s):  
D. C. Zemp ◽  
C.-F. Schleussner ◽  
H. M. J. Barbosa ◽  
R. J. van der Ent ◽  
J. F. Donges ◽  
...  
Keyword(s):  
Land Use ◽  
South America ◽  
Complex Network ◽  
Amazon Basin ◽  
South American ◽  
Total Precipitation ◽  
Wet Season ◽  
La Plata ◽  
Moisture Recycling ◽  
La Plata Basin

Abstract. Continental moisture recycling is a crucial process of the South American climate system. In particular, evapotranspiration from the Amazon basin contributes substantially to precipitation regionally as well as over other remote regions such as the La Plata basin. Here we present an in-depth analysis of South American moisture recycling mechanisms. In particular, we quantify the importance of cascading moisture recycling (CMR), which describes moisture transport between two locations on the continent that involves re-evaporation cycles along the way. Using an Eulerian atmospheric moisture tracking model forced by a combination of several historical climate data sets, we were able to construct a complex network of moisture recycling for South America. Our results show that CMR contributes about 9–10% to the total precipitation over South America and 17–18% over the La Plata basin. CMR increases the fraction of total precipitation over the La Plata basin that originates from the Amazon basin from 18–23 to 24–29% during the wet season. We also show that the south-western part of the Amazon basin is not only a direct source of rainfall over the La Plata basin, but also a key intermediary region that distributes moisture originating from the entire Amazon basin towards the La Plata basin during the wet season. Our results suggest that land use change in this region might have a stronger impact on downwind rainfall than previously thought. Using complex network analysis techniques, we find the eastern side of the sub-tropical Andes to be a key region where CMR pathways are channeled. This study offers a better understanding of the interactions between the vegetation and the atmosphere on the water cycle, which is needed in a context of land use and climate change in South America.

scholarly journals A Theory of Topographically Bound Balanced Motions and Application to Atmospheric Low-Level Jets

2012 ◽  
Vol 69 (9) ◽  
pp. 2878-2891 ◽  
Author(s):  
Levi G. Silvers ◽  
Wayne H. Schubert
Keyword(s):  
Potential Vorticity ◽  
Wave Train ◽  
South American ◽  
Topographic Feature ◽  
Low Level ◽  
The Andes ◽  
Low Level Jets ◽  
Low Level Jet ◽  
Western Side ◽  
Isentropic Coordinates

Abstract The subject of this study is topographically bound low-level jets, such as the South American summertime low-level jet on the eastern side of the Andes and its companion, the Chilean low-level jet on the western side of the Andes. These jets are interpreted as balanced flows that obey the potential vorticity invertibility principle. This invertibility principle is expressed in isentropic coordinates, and the mathematical issue of isentropes that intersect the topography is treated by the method of a massless layer. In this way, the low-level jets on the western and eastern sides of the Andes can both be attributed to the infinite potential vorticity that lies in the infinitesimally thin massless layer on the topographic feature. To obtain a cyclonic flow centered on the topographic feature, the mountain crest must have been heated enough to draw down the overlying isentropic surfaces; otherwise, isentropic surfaces bend upward at the mountain crest and an anticyclonic flow is produced. Both anticyclonic and cyclonic solutions are obtained here using analytical and numerical methods to solve the invertibility principle. The summertime topographically bound flows discussed here are quite distinct from the wintertime Rossby wave train patterns that occur when strong westerlies impinge on the topography.

scholarly journals Estimation of the Surface Water Budget of the La Plata Basin

2009 ◽  
Vol 10 (4) ◽  
pp. 981-998 ◽  
Author(s):  
Fengge Su ◽  
Dennis P. Lettenmaier
Keyword(s):  
Surface Water ◽  
Water Balance ◽  
River Basin ◽  
Land Surface ◽  
Moisture Convergence ◽  
Spatiotemporal Variability ◽  
Atmospheric Moisture ◽  
La Plata ◽  
La Plata Basin

Abstract The Variable Infiltration Capacity (VIC) land surface hydrology model forced by gridded observed precipitation and temperature for the period 1979–99 is used to simulate the land surface water balance of the La Plata basin (LPB). The modeled water balance is evaluated with streamflow observations from the major tributaries of the LPB. The spatiotemporal variability of the water balance terms of the LPB are then evaluated using offline VIC model simulations, the 40-yr European Centre for Medium-Range Weather Forecasts Re-Analysis (ERA-40), and inferences obtained from a combination of these two. The seasonality and interannual variability of the water balance terms vary across the basin. Over the Uruguay River basin and the entire LPB, precipitation (P) exceeds evapotranspiration (E) and the basins act as a moisture sink. However, the Paraguay River basin acts as a net source of moisture in dry seasons (strong negative P − E). The annual means and monthly time series of ERA-40 P are in good agreement with gauge observations over the entire LPB and its subbasins, except for the Uruguay basin. The E estimates from VIC and inferred from the ERA-40 atmospheric moisture budget are consistent in both seasonal and interannual variations over the entire LPB, but large discrepancies exist between the two E estimates over the subbasins. The long-term mean of atmospheric moisture convergence P − E agrees well with observed runoff R for the upper Paraná River basin, whereas the imbalance is large (28%) for the Uruguay basin—possibly because of its small size. Major problems appear over the Paraguay basin with negative long-term mean of atmospheric moisture convergence P − E, which is not physically realistic. The computed precipitation recycling in the LPB (for L = 500 km) exhibits strong seasonal and spatial variations with ratios of 0%–3% during the cold season and 5%–7% during the warm season.

Future projections in the climatology of five low-level jets across different CORDEX domains

2020 ◽  
Author(s):  
Sushant Das ◽  
Abraham Torres ◽  
Arturo Corrales ◽  
Erika Coppola ◽  
Filippo Giorgi ◽  
...  
Keyword(s):  
Global Warming ◽  
Lower Boundary ◽  
West African ◽  
Global Climate Models ◽  
Historical Period ◽  
South American ◽  
Low Level ◽  
Future Global Warming ◽  
Low Level Jets ◽  
Low Level Jet

<p>Five of the most prominent low-level jets (LLJs) around the world – the Monsoon Low-Level Jet, Caribbean Low-Level Jet, West African Westerly Jet, Great Plains Low-Level Jet and South American Low-Level Jet – are examined for future climate conditions relative to the present using an ensemble of Regional Climate Model (RCM) simulations under the Coordinated Regional Downscaling Experiment (CORDEX) initiative. The simulations were conducted on a 25 km horizontal grid spacing using lateral and lower boundary forcing from three Coupled Model Inter-comparison Project 5 (CMIP5) global climate models (GCMs) for a near-present historical period (1995–2014) and two future periods (2041–2060 and 2080–2099) under the Representative Concentration Pathway 8.5 (RCP8.5). The RCM is capable of capturing most of the observed climatological features of the LLJs and exhibits a much greater capacity to represent their positioning and core strength compared to the driving GCMs. Analysis of the influence of global warming on the LLJs shows a consistent strengthening of the jets and a shift in their location under both future scenarios. The Monsoon and West African LLJs exhibit a northward shift, while the Caribbean and South American LLJs undergo a westward expansion. The use of an ensemble of high-resolution simulations provides a key element in a robust assessment of changes in LLJs associated with future global-warming scenarios.</p>

scholarly journals On the importance of cascading moisture recycling in South America

2014 ◽  
Vol 14 (11) ◽  
pp. 17479-17526 ◽  
Author(s):  
D. C. Zemp ◽  
C.-F. Schleussner ◽  
H. M. J. Barbosa ◽  
R. J. Van der Ent ◽  
J. F. Donges ◽  
...  
Keyword(s):  
South America ◽  
River Basin ◽  
Amazon Basin ◽  
South American ◽  
The South ◽  
Wet Season ◽  
La Plata ◽  
Moisture Recycling ◽  
La Plata Basin ◽  
Recycling Networks

Abstract. Continental moisture recycling is a crucial process of the South American climate system. Evapotranspiration from the Amazon river basin contributes to precipitation regionally and in the La Plata river basin. Here we present an in-depth analysis of South American moisture recycling. We quantify the importance of "cascading moisture recycling", which describes the exchange of moisture between the vegetation and the atmosphere through precipitation and re-evaporation cycles on its way between two locations on the continent. We use the Water Accounting Model 2-layers (WAM-2layers) forced by precipitation from TRMM and evapotranspiration from MODIS for the period 2001 until 2010 to construct moisture recycling networks. These networks describe the direction and amount of moisture transported from its source (evapotranspiration) to its destination (precipitation) in South America. Model-based calculations of continental and regional recycling ratios in the Amazon basin compare well with other existing studies using different datasets and methodologies. Our results show that cascading moisture recycling contributes about 10% to the total precipitation over South America and 17% over the La Plata basin. Considering cascading moisture recycling increases the total dependency of the La Plata basin on moisture from the Amazon basin by about 25% from 23 to 29% during the wet season. Using tools from complex network analysis, we reveal the importance of the south-western part of the Amazon basin as a key intermediary region for continental moisture transport in South America during the wet season. Our results suggest that land use change in this region might have a stronger impact on downwind rainfed agriculture and ecosystem stability than previously thought.

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