Rivers of the Andes and the Amazon Basin: Deciphering global change from the hydroclimatic variability in the critical zone

Abstract. Phosphorus (P) availability decreases with soil age and potentially limits the productivity of ecosystems growing on old and weathered soils. Despite growing on ancient soils, ecosystems of lowland Amazonia are highly productive and are among the most biodiverse on Earth. P eroded and weathered in the Andes is transported by the rivers and deposited in floodplains of the lowland Amazon basin creating hotspots of P fertility. We hypothesize that animals feeding on vegetation and detritus in these hotspots may redistribute P to P-depleted areas, thus contributing to dissipate the P gradient across the landscape. Using a mathematical model, we show that animal-driven spatial redistribution of P from rivers to land and from seasonally flooded to terra firme (upland) ecosystems may sustain the P cycle of Amazonian lowlands. Our results show how P imported to land by terrestrial piscivores in combination with spatial redistribution of herbivores and detritivores can significantly enhance the P content in terra firme ecosystems, thereby highlighting the importance of food webs for the biogeochemical cycling of Amazonia.

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Sensitivity of precipitation in the highlands and lowlands of Peru to physics parameterization options in WRFV3.8.1

10.5194/gmd-2021-307 ◽

2021 ◽

Author(s):

Santos J. González-Rojí ◽

Martina Messmer ◽

Christoph C. Raible ◽

Thomas F. Stocker

Keyword(s):

Observational Data ◽

Amazon Basin ◽

Cumulus Parameterization ◽

Data Sets ◽

Monthly Precipitation ◽

Microphysics Scheme ◽

The Andes ◽

Station Data ◽

Pattern Correlation ◽

Simulated Precipitation

Abstract. The performance of the Weather Research and Forecasting (WRF) model version 3.8.1 at convection-permitting scale is evaluated by means of several sensitivity simulations over southern Peru down to a grid resolution of 1 km, whereby the main focus is on the domain with 5 km horizontal resolution. Different configurations of microphysics, cumulus, longwave radiation and planetary boundary layer schemes are tested. For the year 2008, the simulated precipitation amounts and patterns are compared to gridded observational data sets and weather station data gathered from Peru, Bolivia and Brazil. The temporal correlation of simulated monthly precipitation sums against in-situ and gridded observational data show that the most challenging regions for WRF are the slopes along both sides of the Andes, i.e., elevations between 1000 and 3000 m above sea level. The pattern correlation analysis between simulated precipitation and station data suggests that all tested WRF setups perform rather poorly along the northeastern slopes of the Andes during the entire year. In the southwestern region of the domain the performance of all setups is better except for the driest period (May–September). The results of the pattern correlation to the gridded observational data sets show that all setups perform reasonably well except along both slopes during the dry season. The precipitation patterns reveal that the typical setup used over Europe is too dry throughout the entire year, and that the experiment with the combination of the single-moment 6-class microphysics scheme and the Grell–Freitas cumulus parameterization in the domains with resolutions larger than 5 km, suitable for East Africa, does not perfectly apply to other equatorial regions such as the Amazon basin in southeastern Peru. The experiment with the Stony–Brook University microphysics scheme and the Grell-Freitas cumulus parameterization tends to overestimate precipitation over the northeastern slopes of the Andes, but allows to enforce a positive feedback between the soil moisture, air temperature, relative humidity, mid-level cloud cover and finally, also precipitation. Hence, this setup is the one providing the most accurate results over the Peruvian Amazon, and particularly over the department of Madre de Dios, which is a region of interest because it is considered the biodiversity hotspot of Peru. The robustness of this particular parameterization option is backed up by similar results obtained during wet climate conditions observed in 2012.

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Synoptic and Mesoscale atmospheric features associated with an extreme Snowstorm over the Central Andes in August 2013

10.5194/nhess-2019-286 ◽

2019 ◽

Author(s):

Marcelo Zamuriano ◽

Paul Froidevaux ◽

Isabel Moreno ◽

Mathias Vuille ◽

Stefan Brönnimann

Keyword(s):

Spatial Distribution ◽

Snow Cover ◽

Rossby Wave ◽

Moisture Transport ◽

Large Scale ◽

Amazon Basin ◽

Cold Front ◽

Wave Train ◽

Pressure System ◽

The Andes

Abstract. We study the synoptic and mesoscale characteristics of a snowfall event over the Bolivian Altiplano in August 2013 that caused severe damage to people, infrastructure and livestock. This event was associated with a cold front episode following the eastern slope of the Andes-Amazon interface and a cut-off low pressure system (COL) over the Pacific Ocean. Large scale analyses suggest a two-stage mechanism: The first phase consisted of a strong cold surge to the east of the Andes inducing low level blocking of southward moisture transport over the SW Amazon basin due to post-frontal high-pressure up to 500 hPa synchronized to a Rossby wave train. The second stage was initiated by the displacement of 500 hPa anticyclone over the Andes due to a Rossby wave passage and a subsequent increase in north-easterly moisture transport, while another cold front along the eastern Andes provided additional lifting. We analyse an analog event (July 2010) to confirm the influence of these large-scale features on snow formation. We conduct a mesoscale analysis using the Weather Research and Forecasting (WRF-ARW) model. For this purpose, we perform a series of high-resolution numerical experiments that include sensitivity studies where we apply orographic and lake Titicaca temperature modifications. We compare our findings to MODIS snow cover estimates and in-situ measurements. The control simulation is able to capture the snow cover spatial distribution and sheds light over several aspects of the snowfall dynamics. In our WRF simulations, daytime snowfall mainly occurs around complex orography whereas nocturnal snowfall is concentrated over the plateau due to a combination of nocturnal winds and complex orography inside the plateau. The sensitivity experiments indicate the importance of the lake and mountain for thermal wind circulation affecting the spatial distribution of snowfall by shifting the position of the convergence zones. The influence of the lake's thermal effect is not evident around the regions surrounding the lake.

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Likely Ranges of Climate Change in Bolivia

Journal of Applied Meteorology and Climatology ◽

10.1175/jamc-d-12-0224.1 ◽

2013 ◽

Vol 52 (6) ◽

pp. 1303-1317 ◽

Cited By ~ 25

Author(s):

Christian Seiler ◽

Ronald W. A. Hutjes ◽

Pavel Kabat

Keyword(s):

Climate Change ◽

Amazon Basin ◽

Rainfall Variability ◽

Annual Rainfall ◽

Amazon Forest ◽

Climate Change Scenarios ◽

Wet Season ◽

Global Circulation Models ◽

The Andes ◽

Interannual Rainfall Variability

AbstractBolivia is facing numerous climate-related threats, ranging from water scarcity due to rapidly retreating glaciers in the Andes to a partial loss of the Amazon forest in the lowlands. To assess what changes in climate may be expected in the future, 35 global circulation models (GCMs) from the third and fifth phases of the Coupled Model Intercomparison Project (CMIP3/5) were analyzed for the Bolivian case. GCMs were validated against observed surface air temperature, precipitation, and incoming shortwave (SW) radiation for the period 1961–90. Weighted ensembles were developed, and climate change projections for five emission scenarios were assessed for 2070–99. GCMs revealed an overall cold, wet, and positive-SW-radiation bias and showed no substantial improvement from the CMIP3 to the CMIP5 ensemble for the Bolivian case. Models projected an increase in temperature (2.5°–5.9°C) and SW radiation (1%–5%), with seasonal and regional differences. In the lowlands, changes in annual rainfall remained uncertain for CMIP3 whereas CMIP5 GCMs were more inclined to project decreases (−9%). This pattern also applied to most of the Amazon basin, suggesting a higher risk of partial biomass loss for the CMIP5 ensemble. Both ensembles agreed on less rainfall (−19%) during drier months (June–August and September–November), with significant changes in interannual rainfall variability, but disagreed on changes during wetter months (January–March). In the Andes, CMIP3 GCMs tended toward less rainfall (−9%) whereas CMIP5 tended toward more (+20%) rainfall during parts of the wet season. The findings presented here may provide inputs for studies of climate change impact that assess how resilient human and natural systems are under different climate change scenarios.

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Soil versus Biological Controls on Nutrient Cycling in Terra Firme Forests

The Biogeochemistry of the Amazon Basin ◽

10.1093/oso/9780195114317.003.0007 ◽

2001 ◽

Author(s):

Elvira Cuevas

Keyword(s):

Amazon Basin ◽

Evergreen Forest ◽

Water Retention Capacity ◽

Terra Firme ◽

Retention Capacity ◽

Seasonally Dry ◽

The Andes ◽

Rio Negro ◽

Blackwater Rivers ◽

Seasonally Flooded

Terra firme forests are those that by definition are not permanently or seasonally flooded (terra firme meaning “firm terrain”). This type of forest encompasses the Amazon and Orinoco basins, stretching from the lower slopes of the Andes, east to the Guianas, and south to about 15°S in western Brazil and northern Bolivia (Richards 1996). Structural and compositional variability in these forests in the Amazon basin is very wide as a result of climate differences and geomorphological position. The region is not climatically uniform; the central and much of the southern parts have less and more seasonal rainfall than the eastern and western parts (Walsh 1996). These differences have direct and indirect ecological significance, as phenology and biological processes related to nutrient availability will be strongly influenced by both factors (Cuevas and Medina 1986, 1988, 1990, Medina and Cuevas 1989). Periods of two or more consecutive dry days are ecologically significant in a humid area such as San Carlos de Río Negro, in the northern part of the Amazon, because of low water retention capacity in the widespread sandy soils. In lower geomorphological positions, dry spells of 5-10 days may result in fluctuations of the water table from 0.4-1.0 m (Herrera 1977, Bongers et al. 1985). In areas with a more strongly seasonal climate, roots have been found extending to 18 m depth (Nepstad et al. 1995). This may explain the presence of evergreen forest in the seasonally dry eastern Amazon. Structure and physiognomy of terra firme forests is very similar throughout Amazonia, but floristically it is quite variable due to different compositions in the subbasins of the Amazon’s major tributaries. These subbasins are located within geochemical regions that can be differentiated based on the physicochemical properties of drainage waters (Sioli 1975, Fittkau 1971, Fittkau et al. 1975). Blackwater rivers, such as the Río Negro, drain mostly sandy podsolized soils low in most essential nutrients for plant growth. They are characterized by a high content of humic acids, which remain dissolved because of the predominant low concentrations of polyvalent cations, mainly Ca2+ and Mg2+.

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The Andean Cultural Frontier

Journal of Inter-American Studies ◽

10.2307/165167 ◽

1963 ◽

Vol 5 (4) ◽

pp. 431-436 ◽

Cited By ~ 2

Author(s):

Edmund E. Hegen

Keyword(s):

Amazon Basin ◽

Eastern Region ◽

Physical Barrier ◽

The North ◽

The Andes ◽

Inca Empire ◽

Cultural Boundary ◽

Western Border ◽

Forest Line

From the Sierra Macarena in the north to the Sierra Divisor east of the Río Ucayali, the eastern ranges of the Andes form an amphitheater along the western border of the Upper Amazon Basin. This Andean arc was for centuries a combined physical and cultural boundary. The noman's land of the Ceja and the hostility of the Montaña with its rough relief, short lateral valleys, turbulent rivers, and with the “conservatism of the forest” represented a rigid and formidable physical barrier.The eastern region of the Inca Empire, Anti-Suyo, certainly never reached far beyond the forest line along the eastern ranges. The deepest penetration into the Selva took place probably under Inca Túpac Yupanqui, during the wars against the Shiris, who settled around “Chachapuyas and Muyupampas.”

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A Climatology of Extreme South American Andean Cold Surges

Journal of Applied Meteorology and Climatology ◽

10.1175/jamc-d-18-0146.1 ◽

2018 ◽

Vol 57 (10) ◽

pp. 2297-2315 ◽

Cited By ~ 2

Author(s):

Kevin C. Prince ◽

Clark Evans

Keyword(s):

Spatial Variation ◽

Amazon Basin ◽

Meridional Wind ◽

Andes Mountains ◽

South American ◽

Austral Winter ◽

Cold Surge ◽

The Andes ◽

Cold Surges ◽

The Tropics

AbstractCold surges represent one of several phenomena by which midlatitude features can modulate the atmosphere, both dynamically and thermodynamically, deep into the tropics. This study involves the construction of a climatology of the strongest South American cold surges that follow along the Andes Mountains to quantify the extent to which these surges modulate the atmosphere from the midlatitudes to the tropics. Cold surges occurring during June–September (austral winter) from 1980 to 2017 are considered. In this study, cold-surge events are identified using standardized anomalies of 925-hPa meridional wind and 925-hPa temperature. As compared with previous cold-surge investigations, the use of standardized anomalies better enables spatial variation in cold-surge intensity and impacts to be quantified. A strong cold surge is defined as one in which the 925-hPa temperature is at least 3 standardized anomalies below 0 and the 925-hPa meridional wind is at least 3 standardized anomalies above 0 on the meso-α scale or larger. Using these criteria, 67 events are identified. The composite cold surge is characterized by highly anomalous cold, southerly flow that originates in northern Argentina and progresses northward, significantly modulating lower-tropospheric kinematic and thermodynamic fields across the entire Amazon basin over a period of 2 to as many as 8 days.

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Atmospheric Circulation and Climatic Variability

The Physical Geography of South America ◽

10.1093/oso/9780195313413.003.0010 ◽

2007 ◽

Cited By ~ 2

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.

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Pre-Columbian geometric earthworks in the upper Purús: a complex society in western Amazonia

Antiquity ◽

10.1017/s0003598x00099373 ◽

2009 ◽

Vol 83 (322) ◽

pp. 1084-1095 ◽

Cited By ~ 74

Author(s):

Martti Pärssinen ◽

Denise Schaan ◽

Alceu Ranzi

Keyword(s):

Amazon Basin ◽

East Side ◽

Complex Society ◽

Building Society ◽

The Andes

It's an ill wind that blows nobody any good. The combination of land cleared of its rainforest for grazing and satellite survey have revealed a sophisticated pre-Columbian monument-building society in the upper Amazon Basin on the east side of the Andes. This hitherto unknown people constructed earthworks of precise geometric plan connected by straight orthogonal roads. Introducing us to this new civilisation, the authors show that the ‘geoglyph culture’ stretches over a region more than 250km across, and exploits both the floodplains and the uplands. They also suggest that we have so far seen no more than a tenth of it.

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Extreme Summer Convection in South America

Journal of Climate ◽

10.1175/2010jcli3465.1 ◽

2010 ◽

Vol 23 (14) ◽

pp. 3761-3791 ◽

Cited By ~ 111

Author(s):

Ulrike Romatschke ◽

Robert A. Houze

Keyword(s):

South America ◽

Amazon Basin ◽

Three Dimensional ◽

Tropical Rainfall Measuring Mission ◽

Central Andes ◽

South Atlantic Convergence Zone ◽

Reanalysis Data ◽

The North ◽

The Andes ◽

Environmental Prediction

Abstract Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR) and National Centers for Environmental Prediction–National Center for Atmospheric Research (NCEP–NCAR) reanalysis data are used to indicate mechanisms responsible for extreme summer convection over South America. The three-dimensional reflectivity field is analyzed to define three types of extreme echo, deep convective cores, wide convective cores, and broad stratiform regions. The location and timing of these echoes are sensitive to midlatitude synoptic disturbances crossing the Andes. At the leading edges of these disturbances the nocturnal South American low-level jet (SALLJ) transports moisture along the eastern edge of the Andes from the tropical to the subtropical part of the continent. Where the SALLJ rises over lower but steep mountains on the east side of the southern central Andes, deep and wide convective cores are triggered in the evening. When the SALLJ withdraws to the north as the disturbance passes, nocturnal triggering occurs in the northeastern foothills of the central Andes. Extreme convection over the Amazon basin takes the form of broad stratiform regions that evolve from systems with wide convective cores moving into the center of the region from both the southwest and northeast. The systems from the northeast form at the northeast coast and are likely squall lines. Along the coast of the Brazilian Highlands, diurnal/topographic forcing leads to daytime maxima of deep convective cores followed a few hours later by wide convective cores. Wide convective cores and broad stratiform regions form in the South Atlantic convergence zone (SACZ) with a diurnal cycle related to continental heating.

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