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 Increased climate pressure on the agricultural frontier in the Eastern Amazonia–Cerrado transition zone

2022 ◽  
Vol 12 (1) ◽  
Author(s):  
José A. Marengo ◽  
Juan C. Jimenez ◽  
Jhan-Carlo Espinoza ◽  
Ana Paula Cunha ◽  
Luiz E. O. Aragão
Keyword(s):  
Transition Zone ◽  
Large Scale ◽  
Vapor Pressure Deficit ◽  
Environmental Changes ◽  
Severe Drought ◽  
Wet Season ◽  
Agricultural Frontier ◽  
Global Food Security ◽  
Drought Conditions ◽  
Global Food

AbstractSeveral 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 another 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. 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, where they induce delayed wet-season and worsen 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.

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>

scholarly journals Consistent regional fluxes of CH<sub>4</sub> and CO<sub>2</sub> inferred from GOSAT proxy XCH<sub>4</sub> : XCO<sub>2</sub> retrievals, 2010–2014

2017 ◽  
Vol 17 (7) ◽  
pp. 4781-4797 ◽  
Author(s):  
Liang Feng ◽  
Paul I. Palmer ◽  
Hartmut Bösch ◽  
Robert J. Parker ◽  
Alex J. Webb ◽  
...  
Keyword(s):  
South America ◽  
Large Scale ◽  
A Priori ◽  
Co2 Fluxes ◽  
A Posteriori ◽  
Data Products ◽  
The Tropics ◽  
Regional Fluxes ◽  
Tropical South America

Abstract. We use the GEOS-Chem global 3-D model of atmospheric chemistry and transport and an ensemble Kalman filter to simultaneously infer regional fluxes of methane (CH4) and carbon dioxide (CO2) directly from GOSAT retrievals of XCH4 : XCO2, using sparse ground-based CH4 and CO2 mole fraction data to anchor the ratio. This work builds on the previously reported theory that takes into account that (1) these ratios are less prone to systematic error than either the full-physics data products or the proxy CH4 data products; and (2) the resulting CH4 and CO2 fluxes are self-consistent. We show that a posteriori fluxes inferred from the GOSAT data generally outperform the fluxes inferred only from in situ data, as expected. GOSAT CH4 and CO2 fluxes are consistent with global growth rates for CO2 and CH4 reported by NOAA and have a range of independent data including new profile measurements (0–7 km) over the Amazon Basin that were collected specifically to help validate GOSAT over this geographical region. We find that large-scale multi-year annual a posteriori CO2 fluxes inferred from GOSAT data are similar to those inferred from the in situ surface data but with smaller uncertainties, particularly over the tropics. GOSAT data are consistent with smaller peak-to-peak seasonal amplitudes of CO2 than either the a priori or in situ inversion, particularly over the tropics and the southern extratropics. Over the northern extratropics, GOSAT data show larger uptake than the a priori but less than the in situ inversion, resulting in small net emissions over the year. We also find evidence that the carbon balance of tropical South America was perturbed following the droughts of 2010 and 2012 with net annual fluxes not returning to an approximate annual balance until 2013. In contrast, GOSAT data significantly changed the a priori spatial distribution of CH4 emission with a 40 % increase over tropical South America and tropical Asia and a smaller decrease over Eurasia and temperate South America. We find no evidence from GOSAT that tropical South American CH4 fluxes were dramatically affected by the two large-scale Amazon droughts. However, we find that GOSAT data are consistent with double seasonal peaks in Amazonian fluxes that are reproduced over the 5 years we studied: a small peak from January to April and a larger peak from June to October, which are likely due to superimposed emissions from different geographical regions.

scholarly journals Towards understanding hydroclimatic change in Victoria, Australia – why was the last decade so dry?

2009 ◽  
Vol 6 (5) ◽  
pp. 6181-6206 ◽  
Author(s):  
A. S. Kiem ◽  
D. C. Verdon-Kidd
Keyword(s):  
Climate Change ◽  
Water Resources ◽  
Large Scale ◽  
Regional Scale ◽  
Seasonal Rainfall ◽  
Severe Drought ◽  
Physical Mechanisms ◽  
Drought Conditions ◽  
Hydroclimatic Change ◽  
Impacts Of Climate Change

Abstract. Since the mid-1990s Victoria, located in southeast Australia, has experienced severe drought conditions characterized by streamflow that is the lowest on record in many areas. While severe decreases in annual and seasonal rainfall totals have also been observed, this alone does not seem to explain the observed reduction in flow. In this study, we investigate the large-scale climate drivers for Victoria and demonstrate how these modulate the regional scale synoptic patterns, which in turn alter the way seasonal rainfall totals are compiled and the amount of runoff per unit rainfall that is produced. The hydrological implications are significant and illustrate the need for robust hydrological modelling, which takes into account insights into physical mechanisms that drive regional hydroclimatology, in order to properly understand and quantify the impacts of climate change (natural and/or anthropogenic) on water resources.

scholarly journals Trends and Extremes of Drought Episodes in Vietnam Sub-Regions during 1980–2017 at Different Timescales

Water ◽  
2020 ◽  
Vol 12 (3) ◽  
pp. 813 ◽  
Author(s):  
Milica Stojanovic ◽  
Margarida L.R. Liberato ◽  
Rogert Sorí ◽  
Marta Vázquez ◽  
Tan Phan-Van ◽  
...  
Keyword(s):  
Large Scale ◽  
Root Zone ◽  
Southern Oscillation ◽  
Standardized Precipitation Index ◽  
Lower Troposphere ◽  
Severe Drought ◽  
Positive Trend ◽  
Drought Conditions ◽  
Northern Regions ◽  
Dry Conditions

This study investigated the temporal occurrence of dry conditions in the seven climatic sub-regions of Vietnam during the 1980–2017 period. This assessment was performed using the Standardized Precipitation Evapotranspiration Index (SPEI) and the Standardized Precipitation Index (SPI) at 1 to 24 months timescales. Results show that the main periods of extreme drought occurred simultaneously throughout the country in 1992–1993 and 2003–2004, except for 2015–2016, when it was not identified in the southern region. In addition, a slight temporal lag was identified latitudinally (north–south) at the beginning of dry conditions, revealing the largest difference between the northern and southern regions. A positive trend in the time series of both indices (SPEI and SPI) prevailed in all sub-regions, with the SPEI minus SPI difference always being negative, suggesting the importance of temperature and evapotranspiration for this trend. Further detailed analyses were then performed using SPEI at 1-month and 12-months timescales for all climate sub-regions, as well as the main indicators to characterize duration and severity. Results show that the number of drought episodes did not vary much between regions, but they did vary in duration and severity at the annual scale. Moreover, changes in the soil root zone are largely associated with dry and wet conditions not only from season to season, but also in longer accumulation periods and more strongly in the northern regions of Vietnam. Indeed, a study of the most severe drought episodes also revealed the occurrence of negative anomalies of the root-soil moisture in the subsequent four or more months. Dynamic atmospheric conditions associated with the peak of most severe drought episodes show the crucial role of subsidence of dry air in the middle and high atmosphere, which prevents convection in the lower troposphere. Finally, the linkages between drought conditions in Vietnam and large-scale atmospheric and oceanic teleconnection patterns were revealed to be quite different among northern and southern sub-regions. During the positive phase of El Niño–Southern Oscillation (ENSO), drought episodes at different timescales were identified in the southern climate sub-regions, while the negative phase was associated with drought conditions in the northern regions.

scholarly journals Daily Precipitation Statistics for South America: An Intercomparison between NCEP Reanalyses and Observations

2011 ◽  
Vol 12 (1) ◽  
pp. 101-117 ◽  
Author(s):  
Viviane B. S. Silva ◽  
Vernon E. Kousky ◽  
R. Wayne Higgins
Keyword(s):  
South America ◽  
Large Scale ◽  
Atmospheric Model ◽  
Northeastern Brazil ◽  
South American ◽  
The South ◽  
Wet Season ◽  
Central Brazil ◽  
Monsoon System ◽  
Dry Bias

Abstract In this study, the authors document the extent to which the precipitation statistics of the new CFS reanalysis (CFSR) represent an improvement over the earlier reanalyses: the NCEP–NCAR reanalysis (R1) and the NCEP–DOE Second Atmospheric Model Intercomparison Project (AMIP-II) reanalysis (R2). An intercomparison between the CFSR, R1, R2, and observations over South America was made for the period 1979–2006. The CFSR shows notable improvements in the large-scale precipitation patterns compared with the previous reanalyses (R1 and R2). In spite of these improvements, the CFSR has substantial biases in intensity and frequency of occurrence of rainfall events. Over west-central Brazil, the core region of the South American monsoon system (SAMS), the CFSR displays a dry bias during the onset phase of the SAMS wet season and a wet bias during the peak and decay phases of the SAMS wet season. The CFSR also displays a dry bias along the South American coast near the mouth of the Amazon and along the east coast of northeastern Brazil. A wet bias exists in all seasons over southeast Brazil and over the Andes Mountains.

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.

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.

scholarly journals Mitigating Drought Conditions under Climate and Land Use Changes by Applying Hedging Rules for the Multi-Reservoir System

Water ◽  
2021 ◽  
Vol 13 (21) ◽  
pp. 3095
Author(s):  
Zejun Li ◽  
Bensheng Huang ◽  
Zhifeng Yang ◽  
Jing Qiu ◽  
Bikui Zhao ◽  
...  
Keyword(s):  
Land Use ◽  
Environmental Changes ◽  
Land Use Changes ◽  
Hydrologic Model ◽  
Future Climate ◽  
Severe Drought ◽  
Reservoir System ◽  
Operating Rules ◽  
Drought Conditions ◽  
Hedging Rules

Climate and land use changes have substantially affected hydrologic cycles and increased the risk of drought. Reservoirs are one of the important means to provide resilience against hydrologic variability and achieve sustainable water management. Therefore, adaptive reservoir operating rules are needed to mitigate their adverse effects. In this study, the Hanjiang River Basin in southeast China was selected as the study area. Future climate and land use projections were produced by the Delta method and CA-Markov model, respectively. Future climate forcings and land use patterns were then incorporated into a distributed hydrologic model to evaluate river flow regime shifts. Results revealed that climate and land use changes may lead to severe drought conditions in the future. Lower flows are shown to be more sensitive to environmental changes and a decline of monthly flows could reach up to nearly 30% in the dry season. To address the threat of increasing drought uncertainties in the water supply system, the aggregation-decomposition method incorporated with hedging rules was applied to guide the multi-reservoir operation. Parameters of optimal hedging rules were obtained by a multi-objective optimization algorithm. The performance of hedging rules was evaluated by comparison to standard operating policies and conventional operating rules with respect to reliability, resiliency, vulnerability, and sustainability indices. Results showed that the multi-reservoir system guided by hedging rules can be more adaptive to the environmental changes.

scholarly journals Vegetation and environmental changes in tropical South America from the last glacial to the Holocene documented by multiple cave sediment proxies

2019 ◽  
Vol 524 ◽  
pp. 115717 ◽  
Author(s):  
Valdir F. Novello ◽  
Francisco W. Cruz ◽  
Michael M. McGlue ◽  
Corinne I. Wong ◽  
Brittany M. Ward ◽  
...  
Keyword(s):  
South America ◽  
Environmental Changes ◽  
The Holocene ◽  
Last Glacial ◽  
Cave Sediment ◽  
The Last Glacial ◽  
Tropical South America
Sign in / Sign up

Export Citation Format

Share Document