Assessment of South America summer rainfall climatology and trends in a set of global climate models large ensembles

2020 ◽  
Author(s):  
Leandro B. Díaz ◽  
Ramiro I. Saurral ◽  
Carolina S. Vera
Keyword(s):  
South America ◽  
Climate Models ◽  
Global Climate ◽  
Summer Rainfall ◽  
Global Climate Models ◽  
Large Ensembles ◽  
Rainfall Climatology

scholarly journals ENSO Teleconnection to Eastern African Summer Rainfall in Global Climate Models: Role of the Tropical Easterly Jet

2021 ◽  
Vol 34 (1) ◽  
pp. 293-312
Author(s):  
Amandeep Vashisht ◽  
Benjamin Zaitchik ◽  
Anand Gnanadesikan
Keyword(s):  
Climate Variability ◽  
Climate Models ◽  
Southern Oscillation ◽  
Global Climate ◽  
Summer Rainfall ◽  
Global Climate Models ◽  
Eastern Africa ◽  
Climate Variability And Change ◽  
Tropical Easterly Jet ◽  
Interannual Rainfall Variability

AbstractGlobal climate models (GCMs) are critical tools for understanding and projecting climate variability and change, yet the performance of these models is notoriously weak over much of tropical Africa. To improve this situation, process-based studies of African climate dynamics and their representation in GCMs are required. Here, we focus on summer rainfall of eastern Africa (SREA), which is crucial to the Ethiopian Highlands and feeds the flow of the Blue Nile River. The SREA region is highly vulnerable to droughts, with El Niño–Southern Oscillation (ENSO) being a leading cause of interannual rainfall variability. Adequate understanding and accurate representation of climate features that influence regional variability is an important but often neglected issue when evaluating models. We perform a process-based evaluation of GCMs, focusing on the upper-troposphere tropical easterly jet (TEJ), which has been hypothesized to link ENSO to SREA. We find that most models have an ENSO–TEJ coupling similar to observed, but the models diverge in their representation of TEJ–SREA coupling. Differences in the latter explain the majority (80%) of variability in ENSO teleconnection simulation across the models. This is higher than the variance explained by rainfall coupling with the Somali jet (44%) and African easterly jet (55%). However, our diagnostics of the leading hypothesized mechanism in the models—variability in divergence in the TEJ exit region—are not consistent across models and suggest that a deeper understanding of the mechanisms of TEJ–precipitation coupling should be a priority for studies of climate variability and change in the region.

Climate engineering to mitigate the projected 21st-century terrestrial drying of the Americas: a direct comparison of carbon capture and sulfur injection

2021 ◽  
Author(s):  
Yangyang Xu ◽  
Lei Lin ◽  
Simone Tilmes ◽  
Katherine Dagon ◽  
Lili Xia ◽  
...  
Keyword(s):  
Global Warming ◽  
South America ◽  
21St Century ◽  
Carbon Capture ◽  
Model Comparison ◽  
Climate Models ◽  
Global Climate ◽  
Low Cost ◽  
Amazon Region ◽  
Global Climate Models

<p>To mitigate the projected global warming in the 21st century, it is well-recognized that society needs to cut CO2 emissions and other short-lived warming agents aggressively. However, to stabilize the climate at a warming level closer to the present day, such as the “well below 2 ◦C” aspiration in the Paris Agreement, a net-zero carbon emission by 2050 is still insufficient. The recent IPCC special report calls for a massive scheme to extract CO2 directly from the atmosphere, in addition to decarbonization, to reach negative net emissions at the mid-century mark. Another ambitious proposal is solar-radiation-based geoengineering schemes, including injecting sulfur gas into the stratosphere. Despite being in public debate for years, these two leading geoengineering schemes have not been directly compared under a consistent analytical framework using global climate models.</p><p>Here we present the first explicit analysis of the hydroclimate impacts of these two geoengineering approaches using two recently available large-ensemble model experiments conducted by a family of state-of-the-art Earth system models. Our analysis focuses on the projected aridity conditions over the Americas in the 21st century in detailed terms of the potential mitigation benefits, the temporal evolution, the spatial distribution (within North and South America), the relative efficiency, and the physical mechanisms. We show that sulfur injection, in contrast to previous notions of leading to excessive terrestrial drying (in terms of precipitation reduction) while offsetting the global mean greenhouse gas (GHG) warming, will instead mitigate the projected drying tendency under RCP8.5. The surface energy balance change induced by sulfur injection, in addition to the well-known response in temperature and precipitation, plays a crucial role in determining the overall terrestrial hydroclimate response. However, when normalized by the same amount of avoided global warming in these simulations, sulfur injection is less effective in curbing the worsening trend of regional land aridity in the Americas under RCP8.5 when compared with carbon capture. Temporally, the climate benefit of sulfur injection will emerge more quickly, even when both schemes are hypothetically started in the same year of 2020. Spatially, both schemes are effective in curbing the drying trend over North America. However, for South America, the sulfur injection scheme is particularly more effective for the sub-Amazon region (southern Brazil), while the carbon capture scheme is more effective for the Amazon region. We conclude that despite the apparent limitations (such as an inability to address ocean acidification) and potential side effects (such as changes to the ozone layer), innovative means of sulfur injection should continue to be explored as a potential low-cost option in the climate solution toolbox, complementing other mitigation approaches such as emission cuts and carbon capture (Cao et al., 2017). Our results demonstrate the urgent need for multi-model comparison studies and detailed regional assessments in other parts of the world.</p>

scholarly journals Multi-model ensemble of statistically downscaled GCMs over southeastern South America: historical evaluation and future projections of daily precipitation with focus on extremes

2021 ◽  
Author(s):  
Matias Ezequiel Olmo ◽  
Rocio Balmaceda-Huarte ◽  
Maria Laura Bettolli
Keyword(s):  
South America ◽  
Climate Models ◽  
Linear Models ◽  
Dynamical Downscaling ◽  
Daily Precipitation ◽  
Global Climate ◽  
Warm Season ◽  
Global Climate Models ◽  
Added Value ◽  
Model Ensemble

Abstract High-resolution climate information is required over southeastern South America (SESA) for a better understanding of the observed and projected climate changes due to their strong socio-economic and hydrological impacts. Thereby, this work focuses on the construction of an unprecedented multi-model ensemble of statistically downscaled global climate models (GCMs) for daily precipitation, considering different statistical techniques - including analogs, generalized linear models and neural networks - and a variety of CMIP5 and CMIP6 models. The skills and shortcomings of the different downscaled models were identified. Most of the methods added value in the representation of the main features of daily precipitation, especially in the spatial and intra-annual variability of extremes. The statistical methods showed to be sensitive to the driver GCMs, although the ESD family choice also introduced differences in the simulations. The statistically downscaled projections depicted increases in mean precipitation associated with a rising frequency of extreme events - mostly during the warm season - following the registered trends over SESA. Change rates were consistent among downscaled models up to the middle 21st century when model spread started to emerge. Furthermore, these projections were compared to the available CORDEX-CORE RCM simulations, evidencing a consistent agreement between statistical and dynamical downscaling procedures in terms of the sign of the changes, presenting some differences in their intensity. Overall, this study evidences the potential of statistical downscaling in a changing climate and contributes to its undergoing development over SESA.

scholarly journals An Assessment of Land–Atmosphere Interactions over South America Using Satellites, Reanalysis, and Two Global Climate Models

2021 ◽  
Vol 22 (4) ◽  
pp. 905-922
Author(s):  
Jessica C. A. Baker ◽  
Dayana Castilho de Souza ◽  
Paulo Y. Kubota ◽  
Wolfgang Buermann ◽  
Caio A. S. Coelho ◽  
...  
Keyword(s):  
South America ◽  
Large Scale ◽  
Climate Models ◽  
Hydrological Cycle ◽  
Global Climate ◽  
Atlantic Coast ◽  
Global Climate Models ◽  
Climate Projections ◽  
Median Response ◽  
Model Version

AbstractIn South America, land–atmosphere interactions have an important impact on climate, particularly the regional hydrological cycle, but detailed evaluation of these processes in global climate models has been limited. Focusing on the satellite-era period of 2003–14, we assess land–atmosphere interactions on annual to seasonal time scales over South America in satellite products, a novel reanalysis (ERA5-Land), and two global climate models: the Brazilian Global Atmospheric Model version 1.2 (BAM-1.2) and the U.K. Hadley Centre Global Environment Model version 3 (HadGEM3). We identify key features of South American land–atmosphere interactions represented in satellite and model datasets, including seasonal variation in coupling strength, large-scale spatial variation in the sensitivity of evapotranspiration to surface moisture, and a dipole in evaporative regime across the continent. Differences between products are also identified, with ERA5-Land, HadGEM3, and BAM-1.2 showing opposite interactions to satellites over parts of the Amazon and the Cerrado and stronger land–atmosphere coupling along the North Atlantic coast. Where models and satellites disagree on the strength and direction of land–atmosphere interactions, precipitation biases and misrepresentation of processes controlling surface soil moisture are implicated as likely drivers. These results show where improvement of model processes could reduce uncertainty in the modeled climate response to land-use change, and highlight where model biases could unrealistically amplify drying or wetting trends in future climate projections. Finally, HadGEM3 and BAM-1.2 are consistent with the median response of an ensemble of nine CMIP6 models, showing they are broadly representative of the latest generation of climate models.

Regional signatures of future fire weather over eastern Australia from global climate models

2011 ◽  
Vol 20 (4) ◽  
pp. 550 ◽  
Author(s):  
Hamish G. Clarke ◽  
Peter L. Smith ◽  
Andrew J. Pitman
Keyword(s):  
20Th Century ◽  
Climate Models ◽  
Global Climate ◽  
Summer Rainfall ◽  
Global Climate Models ◽  
Fire Season ◽  
Future Climate Change ◽  
Fire Weather ◽  
Winter Rainfall ◽  
Eastern Australia

Skill-selected global climate models were used to explore the effect of future climate change on regional bushfire weather in eastern Australia. Daily Forest Fire Danger Index (FFDI) was calculated in four regions of differing rainfall seasonality for the 20th century, 2050 and 2100 using the A2 scenario from the Special Report on Emissions Scenarios. Projected changes in FFDI vary along a latitudinal gradient. In summer rainfall-dominated tropical north-east Australia, mean and extreme FFDI are projected to decrease or remain close to 20th century levels. In the uniform and winter rainfall regions, which occupy south-east continental Australia, FFDI is projected to increase strongly by 2100. Projections fall between these two extremes for the summer rainfall region, which lies between the uniform and summer tropical rainfall zones. Based on these changes in fire weather, the fire season is projected to start earlier in the uniform and winter rainfall regions, potentially leading to a longer overall fire season.

scholarly journals Destreza de dois modelos climáticos globais em prever a circulação geral da atmosfera (Skill of two global climate models in forecasting the general circulation of the atmosphere)

2017 ◽  
Vol 10 (4) ◽  
pp. 1090
Author(s):  
Cássia Gabriele Dias ◽  
Michelle Simões Reboita ◽  
Lívia Márcia M. Dutra ◽  
Rosmeri Porfírio Da Rocha
Keyword(s):  
South America ◽  
Atmospheric Circulation ◽  
General Circulation ◽  
Climate Models ◽  
Global Climate ◽  
Global Climate Models ◽  
Trade Winds ◽  
Subtropical Anticyclone ◽  
The Andes ◽  
Wind Intensity

O presente estudo avaliou a destreza de dois modelos climáticos globais (CFSv2 e AGCM-CPTEC) em prever a circulação atmosférica sazonal sobre a América do Sul (AS). As previsões entre os anos de 2013 e início de 2014 foram comparadas com os dados da reanálise ERA-Interim. No nível de 250 hPa, o CFSv2 previu o jato subtropical mais fraco do que o observado na reanálise, enquanto o AGCM-CPTEC o previu mais intenso durante o inverno e primavera. Nos meses de Setembro, Outubro e Novembro (SON) de 2013, a Alta da Bolívia (AB) esteve bem configurada no AGCM-CPTEC, concordando com a reanálise. No entanto, com o modelo CFSv2 a AB não se configurou. Já entre os meses de Janeiro, Fevereiro e Março (JFM) de 2014, os modelos deslocaram a AB para sudoeste de sua posição climatológica. No nível de 850 hPa, os jatos de baixos níveis a leste dos Andes foram subestimados nos meses de Março, Abril e Maio (MAM) com o AGCM-CPTEC e em SON/JFM por ambos os modelos. Em MAM, o CFSv2 previu os ventos alísios de sudeste mais similar à reanálise do que o AGCM-CPTEC. O Anticiclone Subtropical do Atlântico Sul (ASAS) foi previsto em ambos os modelos, entretanto, o AGCM-CPTEC previu a intensidade e a posição desse sistema com mais acurácia. Embora os modelos CFSv2 e AGCM-CPTEC apresentem vieses na intensidade do vento e, às vezes, na direção, pode-se afirmar que esses representaram as principais características da circulação atmosférica na AS. A B S T R A C TThe present study evaluated the ability of two global climate models (CFSv2 and AGCM-CPTEC) in predicting the seasonal atmospheric circulation over South America (SA). Predictions between the years 2013 and early 2014 were compared with ERA-Interim reanalysis. At 250 hPa level, CFSv2 predicted the subtropical jet weaker than observed in the reanalysis, while AGCM-CPTEC predicted it more intense during winter and spring. In the months of September, October and November (SON) of 2013, the Bolivian High (BH) was well configured in the AGCM-CPTEC, and this was in agreement with the reanalysis. However, with the CFSv2 the BH was not predicted. Between the months of January, February and March (JFM) of 2014, the models displaced the BH to the southwest of its climatologic position. At the 850 hPa level, the low level jet eastern of the Andes was underestimated in the months of March, April and May (MAM) by AGCM-CPTEC and in SON/JFM by both models. In MAM, CFSv2 predicted better the southeast trade winds than AGCM-CPTEC. The South Atlantic Subtropical Anticyclone (SASA) was predicted by both models, however, the AGCM-CPTEC predicted the intensity and position of this system more accurately. Although the models show biases in the wind intensity and, sometimes, in the direction, it can be affirmed that in general the CFSv2 and AGCM-CPTEC models represented the main characteristics of the atmospheric circulation in the AS.Keywords: AGCM-CPTEC. CFSv2. General circulation of the atmosphere. Seasonal forecast. South America. 

Assessment of CMIP6 global climate models in reconstructing rainfall climatology of Bangladesh

2021 ◽  
Author(s):  
Mohammad Kamruzzaman ◽  
Shamsuddin Shahid ◽  
Dilip Kumar Roy ◽  
ARM Towfiqul Islam ◽  
Syewoon Hwang ◽  
...  
Keyword(s):  
Climate Models ◽  
Global Climate ◽  
Global Climate Models ◽  
Rainfall Climatology

scholarly journals Performance Evaluation of Global Climate Models (MCGs) from the IPCC-AR4, in climatic data simulation of air temperature and pluviometric precipitation for South America

2020 ◽  
Vol 6 (5) ◽  
pp. 31241-31260
Author(s):  
Fábio da Silveira Castro ◽  
Alexandre Cândido Xavier ◽  
Roberto Avelino Cecílio ◽  
Luciano Roncetti Pimenta ◽  
Valéria Hollunder Klippel ◽  
...  
Keyword(s):  
Performance Evaluation ◽  
South America ◽  
Air Temperature ◽  
Climate Models ◽  
Global Climate ◽  
Global Climate Models ◽  
Climatic Data ◽  
Data Simulation ◽  
Ipcc Ar4
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