scholarly journals Two Contrasting Severe Seasonal Extremes in Tropical South America in 2012: Flood in Amazonia and Drought in Northeast Brazil

2013 ◽  
Vol 26 (22) ◽  
pp. 9137-9154 ◽  
Author(s):  
Jose A. Marengo ◽  
Lincoln M. Alves ◽  
Wagner R. Soares ◽  
Daniel A. Rodriguez ◽  
Helio Camargo ◽  
...  
Keyword(s):  
South America ◽  
Atmospheric Circulation ◽  
Rainy Season ◽  
Austral Summer ◽  
Active Role ◽  
Severe Drought ◽  
Northeast Brazil ◽  
Normal Surface ◽  
Dry Conditions ◽  
Tropical South America

Abstract Two simultaneous extreme events affected tropical South America to the east of the Andes during the austral summer and fall of 2012: a severe drought in Northeast Brazil and intense rainfall and floods in Amazonia, both considered records for the last 50 years. Changes in atmospheric circulation and rainfall were consistent with the notion of an active role of colder-than-normal surface waters in the equatorial Pacific, with above-normal upward motion and rainfall in western Amazonia and increased subsidence over Northeast Brazil. Atmospheric circulation and soil moisture anomalies in the region contributed to an intensified transport of Atlantic moisture into the western part of Amazonia then turning southward to the southern Amazonia region, where the Chaco low was intensified. This was favored by the intensification of subtropical high pressure over the region, associated with an anomalously intense and northward-displaced Atlantic high over a relatively colder subtropical South Atlantic Ocean. This pattern observed in 2012 was not found during other wet years in Amazonia such as 1989, 1999, and 2009. This suggests La Niña as the main cause of the abundant rainfall in western Amazonia from October to December, with wet conditions starting earlier and remaining until March 2012, mostly in northwestern Amazonia. The anomalously high river levels during the following May–July were a consequence of this early and abundant rainy season during the previous summer. In Northeast Brazil, dry conditions started to appear in December 2011 in the northern sector and then extended to the entire region by the peak of the rainy season of February–May 2012.

Deforestation impacts on Amazon-Andes hydroclimatic connectivity

2021 ◽  
Author(s):  
Juan Sierra ◽  
Jhan Carlo Espinoza ◽  
Clementine Junquas ◽  
Jan Polcher ◽  
Miguel Saavedra ◽  
...  
Keyword(s):  
South America ◽  
Transition Region ◽  
Amazon Basin ◽  
Climate Models ◽  
Regional Climate ◽  
Austral Summer ◽  
Regional Climate Models ◽  
Horizontal Resolution ◽  
Deforestation Rates ◽  
Tropical South America

<p>The Amazon rainforest is a key component of the climate system and one of the main planetary evapotranspiration sources. Over the entire Amazon basin, strong land-atmosphere feedbacks cause almost one third of the regional rainfall to be transpired by the local rainforest. Maximum precipitation recycling ratio takes place on the southwestern edge of the Amazon basin (a.k.a. Amazon-Andes transition region), an area recognized as the rainiest and biologically richest of the whole watershed. Here, high precipitation rates lead to large values of runoff per unit area providing most of the sediment load to Amazon rivers. As a consequence, the transition region can potentially be very sensitive to Amazonian forest loss. In fact, recent acceleration in deforestation rates has been reported over tropical South America. These sustained land-cover changes can alter the regional water and energy balances, as well as the regional circulation and rainfall patterns. In this sense, the use of regional climate models can help to understand the possible impacts of deforestation on the Amazon-Andes zone.</p><p>This work aims to assess the projected Amazonian deforestation effects on the moisture transport and rainfall behavior over tropical South America and the Amazon-Andes transition region. We perform 10-year austral summer simulations with the Weather Research and Forecasting model (WRF) using 3 one-way nested domains. Our finest domain is located over the south-western part of the basin, comprising two instrumented Andean Valleys (Zongo and Coroico river Valleys). Convective permitting high horizontal resolution (1km) is used over this domain. The outcomes presented here enhance the understanding of biosphere-atmosphere coupling and its deforestation induced disturbances.</p>

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>

scholarly journals The drought of the century in the Amazon Basin: an analysis of the regional variation of rainfall in South America in 1926

2005 ◽  
Vol 35 (2) ◽  
pp. 231-238 ◽  
Author(s):  
Earle Williams ◽  
Alaor Dall' Antonia ◽  
Vitoria Dall' Antonia ◽  
Jorge Mathias de Almeida ◽  
Francisco Suarez ◽  
...  
Keyword(s):  
South America ◽  
Regional Variation ◽  
Amazon Basin ◽  
Rainfall Anomaly ◽  
Annual Rainfall ◽  
Severe Drought ◽  
The West ◽  
East West ◽  
Extreme El Niño ◽  
Tropical South America

The most severe drought in tropical South America during the 20th century occurred in 1926. This extreme El Nino year is further documented anecdotally, in an update of the river stage observations at Manaus, and in annual rainfall records. The annual rainfall anomaly is an east-west dipole over tropical South America, with drought to the west over the Amazon basin whose discharge is documented at Manaus, and with a surplus to the east and including the Nordeste region of Brazil. Speculations about a role for aerosol in aggravating the drought are discussed.

Recent changes in the atmospheric circulation patterns during the dry-to-wet transition season in south tropical South America (1979-2020): Impacts on precipitation and fire season

2021 ◽  
pp. 1-56
Author(s):  
Jhan-Carlo Espinoza ◽  
Paola A. Arias ◽  
Vincent Moron ◽  
Clementine Junquas ◽  
Hans Segura ◽  
...  
Keyword(s):  
South America ◽  
Atmospheric Circulation ◽  
Low Frequency ◽  
Fire Season ◽  
South American ◽  
Low Level ◽  
Atmospheric Circulation Patterns ◽  
Transition Season ◽  
Circulation Patterns ◽  
Tropical South America

AbstractWe analyze the characteristics of atmospheric variations over tropical South America using the pattern recognition framework of weather typing or atmospheric circulation patterns (CPs). During 1979-2020, nine CPs are defined in the region, using a k-means algorithm based on daily unfiltered 850 hPa winds over 0035°N-30°S, 90°W-30°W. CPs are primarily interpreted as stages of the annual cycle of the low-level circulation. We identified three “winter” CPs (CP7, CP8 and CP9), three “summer” CPs (CP3, CP4 and CP5) and three “transitional” CPs (CP1, CP2 and CP6). Significant long-term changes are detected during the dry-to-wet transition season (July-October) over south tropical South America (STSA). One of the wintertime patterns (CP9) increases from 20% in the 1980s to 35% in the last decade while the “transitional” CP2 decreases from 13% to 7%. CP9 is characterized by enhancement of the South American Low-Level Jet and increasing atmospheric subsidence over STSA. CP2 is characterized by southerly cold-air incursions and anomalous convective activity over STSA. The years characterized by high (low) frequency of CP9 (CP2) during the dry-to-wet transition season are associated with a delayed South American Monsoon onset and anomalous dry conditions over STSA. Consistently, a higher frequency of CP9 intensifies the fire season over STSA (1999-2020). Over the Brazilian states of Maranhão, Tocantins, Goiás and São Paulo, the seasonal frequency of CP9 explains around 35%-44% of the interannual variations of fire counts.

scholarly journals Assessment of Seasonal Soil Moisture Forecasts over Southern South America with Emphasis on Dry and Wet Events

2017 ◽  
Vol 18 (8) ◽  
pp. 2297-2311 ◽  
Author(s):  
Pablo C. Spennemann ◽  
Juan A. Rivera ◽  
Marisol Osman ◽  
A. Celeste Saulo ◽  
Olga C. Penalba
Keyword(s):  
Soil Moisture ◽  
South America ◽  
Standardized Precipitation Index ◽  
Added Value ◽  
Lead Times ◽  
Severe Drought ◽  
Drought Event ◽  
Southern South America ◽  
Large Populations ◽  
Dry Conditions

Abstract The importance of forecasting extreme wet and dry conditions from weeks to months in advance relies on the need to prevent considerable socioeconomic losses, mainly in regions of large populations and where agriculture is a key value for the economies, such as southern South America (SSA). To improve the understanding of the performance and uncertainties of seasonal soil moisture and precipitation forecasts over SSA, this study aims to 1) perform a general assessment of the Climate Forecast System, version 2 (CFSv2), soil moisture and precipitation forecasts against observations and soil moisture simulations based on GLDAS, version 2.0; 2) evaluate the ability of CFSv2 to represent wet and dry events through the forecasted standardized precipitation index (SPI) and standardized soil moisture anomalies (SSMA); and 3) analyze the capability of a statistical methodology (merging observations and forecasts) in representing a severe drought event. Results show that both SPI and SSMA forecast skill are regionally and seasonally dependent. In general, a fast degradation of the forecasts skill is observed as the lead time increases, resulting in almost no added value with regard to climatology at lead times longer than 3 months. Additionally, a better performance of the SSMA forecasts is observed compared to SPI calculated using three months of precipitation (SPI3), with a higher skill for dry events against wet events. The CFSv2 forecasts are able to represent the spatial patterns of the 2008/09 severe drought event, although it shows crucial limitations regarding the identification of drought onset, duration, severity, and demise, considering both meteorological (SPI) and agricultural (SSMA) drought conditions.

Effects of Amazon basin deforestation on regional atmospheric circulation and water vapor transport towards tropical South America

2020 ◽  
Vol 54 (9-10) ◽  
pp. 4169-4189 ◽  
Author(s):  
Melissa Ruiz-Vásquez ◽  
Paola A. Arias ◽  
J. Alejandro Martínez ◽  
Jhan Carlo Espinoza
Keyword(s):  
Water Vapor ◽  
South America ◽  
Atmospheric Circulation ◽  
Amazon Basin ◽  
Vapor Transport ◽  
Water Vapor Transport ◽  
Tropical South America

Austral summer precipitation biases over tropical South America in five CMIP5 earth system models

2020 ◽  
Vol 40 (15) ◽  
pp. 6506-6525 ◽  
Author(s):  
Fernanda Cerqueira Vasconcellos ◽  
Yi Deng ◽  
Henian Zhang ◽  
Guilherme Martins
Keyword(s):  
South America ◽  
Austral Summer ◽  
Summer Precipitation ◽  
Earth System ◽  
System Models ◽  
Earth System Models ◽  
Tropical South America

scholarly journals Piacenzian Environmental Change and the Onset of Cool and Dry Conditions in Tropical South America

2020 ◽  
Vol 35 (11) ◽  
Author(s):  
Friederike Grimmer ◽  
Lydie M. Dupont ◽  
Gerlinde Jung ◽  
Gerold Wefer
Keyword(s):  
South America ◽  
Environmental Change ◽  
Dry Conditions ◽  
Tropical South America

scholarly journals Increased Climate Pressure on the New Agricultural Frontier in the Eastern Amazonia-Cerrado Transition Zone

2021 ◽  
Author(s):  
José A. Marengo ◽  
Juan C. Jimenez ◽  
Jhan-Carlo Espinoza ◽  
Ana Paula Cunha ◽  
Luiz E. O. Aragão
Keyword(s):  
South America ◽  
Transition Region ◽  
Transition Zone ◽  
Large Scale ◽  
Environmental Changes ◽  
Severe Drought ◽  
Wet Season ◽  
Agricultural Frontier ◽  
Drought Conditions ◽  
Tropical South America

Abstract Several large-scale drivers of both anthropogenic and natural environmental changes are interacting nonlinearly in the transition zone between eastern Amazonia and the adjacent Cerrado, considered to be the new Brazilian agricultural frontier. Land-use change for agrobusiness expansion together with climate change in the transition zone between eastern Amazonia and the adjacent Cerrado may have induced a worsening of severe drought conditions over the last decade. The largest warming and drying trends observed over tropical South America during the last four decades are found to be precisely in this eastern Amazonia-Cerrado transition region, where they induce delayed wet-season onset. Here we show that the largest warming and drying trends over tropical South America during the last four decades are observed to be precisely in the eastern Amazonia-Cerrado transition region, with a worsening of severe drought conditions over the last decade. Our results evidence an increase in temperature, vapor pressure deficit, subsidence, dry-day frequency, and a decrease in precipitation, humidity, and evaporation, plus a delay in the onset of the wet season, inducing a higher risk of fire during the dry-to-wet transition season. These findings provide observational evidence of the increasing climatic pressure in this area, which is sensitive for global food security, and the need to reconcile agricultural expansion and protection of natural tropical biomes.

scholarly journals Regional Climate Model–Simulated Timing and Character of Seasonal Rains in South America

2007 ◽  
Vol 135 (7) ◽  
pp. 2642-2657 ◽  
Author(s):  
Sara A. Rauscher ◽  
Anji Seth ◽  
Brant Liebmann ◽  
Jian-Hua Qian ◽  
Suzana J. Camargo
Keyword(s):  
South America ◽  
Regional Climate Model ◽  
Rainy Season ◽  
Climate Model ◽  
Regional Climate ◽  
Regional Model ◽  
Northeast Brazil ◽  
Monsoon Region ◽  
Enso Events ◽  
Dry Spells

Abstract The potential of an experimental nested prediction system to improve the simulation of subseasonal rainfall statistics including daily precipitation intensity, rainy season onset and withdrawal, and the frequency and duration of dry spells is evaluated by examining a four-member ensemble of regional climate model simulations performed for the period 1982–2002 over South America. The study employs the International Centre for Theoretical Physics (ICTP) regional climate model, version 3 (RegCM3), driven with the NCEP–NCAR reanalysis and the European Centre–Hamburg GCM, version 4.5. Statistics were examined for five regions: the northern Amazon, southern Amazon, the monsoon region, Northeast Brazil, and southeastern South America. RegCM3 and the GCM are able to replicate the distribution of daily rainfall intensity in most regions. The analysis of the rainy season timing shows the observed onset occurring first over the monsoon region and then spreading northward into the southern Amazon, in contrast to some previous studies. Correlations between the onset and withdrawal date and SSTs reveal a strong relationship between the withdrawal date in the monsoon region and SSTs in the equatorial Pacific, with above-average SSTs associated with late withdrawal. Over Northeast Brazil, the regional model errors are smaller than those shown by the GCM, and the strong interannual variability in the timing of the rainy season is better simulated by RegCM3. However, the regional model displays an early bias in onset and withdrawal over the southern Amazon and the monsoon regions. Both RegCM3 and the GCM tend to underestimate (overestimate) the frequency of shorter (longer) dry spells, although the differences in dry spell frequency during warm and cold ENSO events are well simulated. The results presented here show that there is potential for added value from the regional model in simulating subseasonal statistics; however, improvements in the physical parameterizations are needed for this tropical region.

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