scholarly journals The Continuum of Drought in Southwestern North America

2018 ◽  
Vol 31 (20) ◽  
pp. 8627-8643 ◽  
Author(s):  
Luke A. Parsons ◽  
Sloan Coats ◽  
Jonathan T. Overpeck
Keyword(s):  
North America ◽  
Full Range ◽  
Earth System Model ◽  
System Model ◽  
Cmip5 Models ◽  
Last Millennium ◽  
Earth System ◽  
Potential Predictability ◽  
Ocean Atmosphere ◽  
The Continuum

Drought has severe consequences for humans and their environment, yet we have a limited understanding of the drivers of drought across the full range of time scales on which it occurs. Here, the atmosphere and ocean conditions that drive this continuum of drought variability in southwestern North America (SWNA) are studied using the latest observationally based products, paleoclimate reconstructions, and state-of-the-art Earth system model simulations of the last millennium. A novel application of the self-organizing maps (SOM) methodology allows for a visualization of the continuum of climate states coinciding with thousands of droughts of varying lengths in last millennium simulations from the Community Earth System Model (CESM), the Goddard Institute for Space Studies Model E2-R (GISS E2-R), and eight other members from phase 5 of the Coupled Model Intercomparison Project (CMIP5). It is found that most droughts are associated with a cool Pacific decadal oscillation (PDO) pattern, but persistent droughts can coincide with a variety of ocean–atmosphere states, including time periods showing a warm PDO or weak ocean–atmosphere anomalies. Many CMIP5 models simulate similar SWNA teleconnection patterns, but the SOM analysis demonstrates that models simulate different continuums of ocean–atmosphere states coinciding with droughts of different lengths, suggesting fundamental differences in their drought dynamics. These findings have important implications for our understanding and simulation of the drivers of persistent drought, and for their potential predictability.

scholarly journals Tropical climate variability in the Community Earth System Model: Data Assimilation Research Testbed

2019 ◽  
Vol 54 (1-2) ◽  
pp. 793-806 ◽  
Author(s):  
Jonathan Eliashiv ◽  
Aneesh C. Subramanian ◽  
Arthur J. Miller
Keyword(s):  
Data Assimilation ◽  
Climate Variability ◽  
Tropical Climate ◽  
Earth System Model ◽  
The Other ◽  
System Model ◽  
Earth System ◽  
Ocean Atmosphere ◽  
Community Earth System Model ◽  
Free Running

AbstractA new prototype coupled ocean–atmosphere Ensemble Kalman Filter reanalysis product, the Community Earth System Model using the Data Assimilation Research Testbed (CESM-DART), is studied by comparing its tropical climate variability to other reanalysis products, available observations, and a free-running version of the model. The results reveal that CESM-DART produces fields that are comparable in overall performance with those of four other uncoupled and coupled reanalyses. The clearest signature of differences in CESM-DART is in the analysis of the Madden–Julian Oscillation (MJO) and other tropical atmospheric waves. MJO energy is enhanced over the free-running CESM as well as compared to the other products, suggesting the importance of the surface flux coupling at the ocean–atmosphere interface in organizing convective activity. In addition, high-frequency Kelvin waves in CESM-DART are reduced in amplitude compared to the free-running CESM run and the other products, again supportive of the oceanic coupling playing a role in this difference. CESM-DART also exhibits a relatively low bias in the mean tropical precipitation field and mean sensible heat flux field. Conclusive evidence of the importance of coupling on data assimilation performance will require additional detailed direct comparisons with identically formulated, uncoupled data assimilation runs.

scholarly journals Implementation of methane cycling for deep time, global warming simulations with the DCESS Earth System Model (Version 1.2)

2017 ◽  
Author(s):  
Gary Shaffer ◽  
Esteban Fernández Villanueva ◽  
Roberto Rondanelli ◽  
Jens Olaf Pepke Pedersen ◽  
Steffen Malskær Olsen ◽  
...  
Keyword(s):  
Global Warming ◽  
Time Scales ◽  
Sediment Cores ◽  
Earth System Model ◽  
System Model ◽  
Earth System ◽  
Deep Time ◽  
Methane Cycling ◽  
Model Version ◽  
Ocean Atmosphere

Abstract. Geological records reveal a number of ancient, large and rapid negative excursions of carbon-13 isotope. Such excursions can only be explained by massive injections of depleted carbon to the Earth System over a short duration. These injections may have forced strong global warming events, sometimes accompanied by mass extinctions, for example the Triassic-Jurassic and End-Permian extinctions, 201 and 252 million years ago. In many cases evidence points to methane as the dominant form of injected carbon, whether as thermogenic methane, formed by magma intrusions through overlying carbon-rich sediment, or from warming-induced dissociation of methane hydrate, a solid compound of methane and water found in ocean sediments. As a consequence of the ubiquity and importance of methane in major Earth events, Earth System models should include a comprehensive treatment of methane cycling but such a treatment has often been lacking. Here we implement methane cycling in the Danish Center for Earth System Science (DCESS) model, a simplified but well-tested Earth System Model of Intermediate Complexity. We use a generic methane input function that allows variation of input type, size, time scale and ocean-atmosphere partition. To be able to treat such massive inputs more correctly, we extend the model to deal with ocean suboxic/anoxic conditions and with radiative forcing and methane lifetimes appropriate for high atmospheric methane concentrations. With this new model version, we carried out an extensive set of simulations for methane inputs of various sizes, time scales and ocean-atmosphere partitions to probe model behaviour. We find that larger methane inputs over shorter time scales with more methane dissolving in the ocean lead to ever-increasing ocean anoxia with consequences for ocean life and global carbon cycling. Greater methane input directly to the atmosphere leads to more warming and, for example, greater carbon dioxide release from land soils. Analysis of synthetic sediment cores from the simulations provides guidelines for the interpretation of real sediment cores spanning the warming events. With this improved DCESS model version and paleo-reconstructions, we are now better armed to gauge the amounts, types, time scales and locations of methane injections driving specific, observed deep time, global warming events.

scholarly journals Introducing the new Regional Community Earth System Model, R-CESM

2021 ◽  
pp. 1-53
Author(s):  
Dan Fu ◽  
Justin Small ◽  
Jaison Kurian ◽  
Yun Liu ◽  
Brian Kauffman ◽  
...  
Keyword(s):  
High Resolution ◽  
Earth System Model ◽  
Model Systems ◽  
System Model ◽  
Earth System ◽  
Regional Ocean Modeling System ◽  
Ocean Atmosphere ◽  
Community Earth System Model ◽  
Regional Community ◽  
The Impact

AbstractThe development of high-resolution, fully-coupled, regional Earth system model systems is important for improving our understanding of climate variability, future projections, and extreme events at regional scales. Here we introduce and present an overview of the newly-developed Regional Community Earth System Model (R-CESM). Different from other existing regional climate models, R-CESM is based on the Community Earth System Model version 2 (CESM2) framework. We have incorporated the Weather Research and Forecasting (WRF) model and Regional Ocean Modeling System (ROMS) into CESM2 as additional components. As such, R-CESM can be conveniently used as a regional dynamical downscaling tool for the global CESM solutions or/and as a standalone high-resolution regional coupled model. The user interface of R-CESM follows that of CESM, making it readily accessible to the broader community. Among countless potential applications of R-CESM, we showcase here a few preliminary studies that illustrate its novel aspects and value. These include: 1) assessing the skill of R-CESM in a multi-year, high-resolution, regional coupled simulation of the Gulf of Mexico; 2) examining the impact of WRF and CESM ocean-atmosphere coupling physics on tropical cyclone simulations; and 3) a convection-permitting simulation of submesoscale ocean-atmosphere interactions. We also discuss capabilities under development such as i) regional refinement using a high-resolution ROMS nested within global CESM; and ii) “online” coupled data assimilation. Our open-source framework (publicly available at https://github.com/ihesp/rcesm1) can be easily adapted to a broad range of applications that are of interest to the users of CESM, WRF, and ROMS.

scholarly journals Avaliação dos Impactos das Mudanças na Cobertura da Terra e Cenário de Emissões (RCP 8.5) no Balanço de água na Bacia do Rio Madeira

2020 ◽  
Vol 35 (4) ◽  
pp. 689-702
Author(s):  
Weslley de Brito Gomes ◽  
Francis Wagner Silva Correia ◽  
Vinicius Capistrano ◽  
José Augusto Paixão Veiga ◽  
Leonardo Alves Vergasta ◽  
...  
Keyword(s):  
Earth System Model ◽  
System Model ◽  
Earth System ◽  
Ocean Atmosphere ◽  
Rcp 8.5 ◽  
Model Ocean ◽  
Rio Madeira

Resumo Nesse estudo avaliou-se os impactos do aumento dos GEE's (cenário RCP 8.5) e dos desflorestamentos no ciclo da água na bacia do rio Madeira, utilizando o Modelo Regional Eta e o Modelo Hidrológico de Grandes Bacias (MGB), forçado com o Brazilian Earth System Model Ocean-Atmosphere versão 2.5 (BESM-OA 2.5). No cenário RCP 8.5, o modelo apresentou sensibilidade sobre toda a bacia do Madeira, com aumento da ordem de 4.0 °C na temperatura. O aumento foi intensificado com os cenários de desflorestamentos de 2050 (4.8 °C) e 2100 (6.2 °C). Nos cenários de desflorestamento predominou-se o Mecanismo de Retroalimentação Negativo, pois embora haja reduções na precipitação e evapotranspiração, a convergência de umidade aumentou em todos os cenários. Observou-se aumento das descargas na maioria das estações para todos os cenários futuros RCP 8.5 e desflorestamento. O aumento da precipitação na estação seca explicou em parte o aumento das vazões e na área de inundação sobre a bacia do Madeira. O aumento na precipitação à montante da bacia e a mudança nos parâmetros do solo, associada às alterações no uso da terra, contribuíram para o aumento da vazão e área de inundação sobre a bacia do Madeira. As alterações nas descargas e na área de inundação podem ter efeitos negativos, com prejuízos e danos ao meio ambiente, nos recursos hídricos, nos principais setores da economia, afetando de forma direta as comunidades que vivem às margens dos rios, principalmente as populações vulneráveis da bacia do Madeira.

Characteristics, precursors, and potential predictability of Amu Darya Drought in an Earth system model large ensemble

2020 ◽  
Vol 55 (7-8) ◽  
pp. 2185-2206
Author(s):  
Andrew Hoell ◽  
Jon Eischeid ◽  
Mathew Barlow ◽  
Amy McNally
Keyword(s):  
Earth System Model ◽  
System Model ◽  
Earth System ◽  
Large Ensemble ◽  
Potential Predictability ◽  
Amu Darya
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