scholarly journals Description and evaluation of the UKCA stratosphere–troposphere chemistry scheme (StratTrop vn 1.0) implemented in UKESM1

2020 ◽  
Vol 13 (3) ◽  
pp. 1223-1266 ◽  
Author(s):  
Alexander T. Archibald ◽  
Fiona M. O'Connor ◽  
Nathan Luke Abraham ◽  
Scott Archer-Nicholls ◽  
Martyn P. Chipperfield ◽  
...  
Keyword(s):  
Tropospheric Ozone ◽  
General Model ◽  
Current Model ◽  
Model Performance ◽  
Chemical Mechanism ◽  
System Model ◽  
Atmospheric Composition ◽  
Earth System ◽  
Model Simulations ◽  
Overall Performance

Abstract. Here we present a description of the UKCA StratTrop chemical mechanism, which is used in the UKESM1 Earth system model for CMIP6. The StratTrop chemical mechanism is a merger of previously well-evaluated tropospheric and stratospheric mechanisms, and we provide results from a series of bespoke integrations to assess the overall performance of the model. We find that the StratTrop scheme performs well when compared to a wide array of observations. The analysis we present here focuses on key components of atmospheric composition, namely the performance of the model to simulate ozone in the stratosphere and troposphere and constituents that are important for ozone in these regions. We find that the results obtained for tropospheric ozone and its budget terms from the use of the StratTrop mechanism are sensitive to the host model; simulations with the same chemical mechanism run in an earlier version of the MetUM host model show a range of sensitivity to emissions that the current model does not fall within. Whilst the general model performance is suitable for use in the UKESM1 CMIP6 integrations, we note some shortcomings in the scheme that future targeted studies will address.

scholarly journals Description and evaluation of the UKCA stratosphere-troposphere chemistry scheme (StratTrop vn 1.0) implemented in UKESM1

2019 ◽  
Author(s):  
Alexander T. Archibald ◽  
Fiona M. O'Connor ◽  
N. Luke Abraham ◽  
Scott Archer-Nicholls ◽  
Martyn P. Chipperfield ◽  
...  
Keyword(s):  
General Model ◽  
Current Model ◽  
Model Performance ◽  
Earth System Model ◽  
Chemical Mechanism ◽  
System Model ◽  
Atmospheric Composition ◽  
Earth System ◽  
Model Simulations ◽  
Overall Performance

Abstract. Here we present a description of the UKCA StratTrop chemical mechanism which is used in the UKESM1 Earth System Model for CMIP6. The StratTrop chemical mechanism is a merger of previously well evaluated tropospheric and stratospheric mechanisms and we provide results from a series of bespoke integrations to assess the overall performance of the model. We find that the StratTrop scheme performs well when compared to a wide array of observations. The analysis we present here focuses on key components of atmospheric composition, namely the performance of the model to simulate ozone in the stratosphere and troposphere and constituents that are important for ozone in these regions. We find that the results obtained from the use of the StratTrop mechanism are sensitive to the host model; simulations with the same chemical mechanism run in an earlier version of the MetUM host model show a range of sensitivity to emissions that the current model does not fall within. Whilst the general model performance is suitable for use in the UKESM1 CMIP6 integrations, we note some shortcomings in the scheme that future targeted studies will address.

Linking Peroxy Radical Chemistry to Global Climate: The Common Representatives Intermediates Chemical Mechanism in the UK Earth System Model

2020 ◽  
Author(s):  
Scott Archer-Nicholls ◽  
James M. Weber ◽  
N. Luke Abraham ◽  
Maria R. Russo ◽  
Christoph Knote ◽  
...  
Keyword(s):  
Tropospheric Ozone ◽  
Global Climate ◽  
Peroxy Radical ◽  
Chemical Mechanism ◽  
System Model ◽  
Peroxy Radicals ◽  
Earth System ◽  
Radical Chemistry ◽  
The Common ◽  
The Uk

<p>Production of ozone and secondary organic aerosols (SOA) in the troposphere is driven by the photo-oxidation of volatile organic compounds (VOCs). Crucial intermediates in these oxidation steps are peroxy radicals, which enable ozone generation when reacting with NO. Recent pioneering studies have shown peroxy radical chemistry to have much broader impacts on the atmosphere, with many of these species undergoing autoxidation and forming highly oxidised organic molecules (HOMs), including accretion products, which can form new particles, contribute to SOA growth and influence global climate. However, explicitly simulating the full complexity of this chemistry is impractical due to the many thousands of VOC species in the atmosphere; techniques for reducing complexity are therefore necessary. The Master Chemical Mechanism (MCM) is a near-explicit scheme, with ~6,000 species and ~19,000 reactions, but is almost exclusively used in box-model applications due to its high cost. The Common Representative Intermediates (CRIv2-R5) mechanism is an effective compromise, preserving the ozone forming potential of the MCM from the emission and atmospheric degradation of isoprene, α/β-pinene, and 19 other primary VOC species whilst reducing the number of species and reactions to be feasible in a 3D model (approximately 240 species and 650 reactions, including 47 non-transported peroxy radical species and their associated reactions).</p><p>We have implemented CRIv2R5 into a global chemistry-climate model, the UK Earth System Model (UKESM1). We present results from a present-day emissions scenario for the Coupled Model Intercomparison Project (CMIP6) to enable a broad scope of model simulations with more basic chemistry and observations to evaluate the model changes against. We find significant differences to tropospheric ozone production and oxidative capacity of the atmosphere, with a strong sensitivity to magnitude and speciation of VOC emissions, highlighting the importance of accurately simulating VOC chemistry to understand trends in tropospheric ozone under changing emissions and climate.</p><p>Moving forward, having the comprehensive CRIv2R5 mechanism within UKESM1 provides the framework for investigating the impacts of recently discovered peroxy radical chemical processes on global climate. We present further work that has focused on expanding the CRI mechanism in box-model studies with a semi-explicit treatment key peroxy radical processes including (i) the autoxidation of peroxy radicals from the hydroxyl radical and ozone initiated reactions of α-pinene, (ii) the formation of multiple generations of peroxy radicals, (iii) formation of accretion products (dimers) and (iv) isoprene-driven suppression of accretion product formation as observed in experiments. This new CRI-HOM mechanism is now being implemented into the global UKESM1 model and coupled with its aerosol mechanism. This work will enable pioneering investigations linking best process-level understanding of gas-phase peroxy radical chemistry to SOA formation and thus improving our understanding of the relationship between biogenic VOC emissions and global climate.</p>

scholarly journals Evaluating simplified chemical mechanisms within present-day simulations of the Community Earth System Model version 1.2 with CAM4 (CESM1.2 CAM-chem): MOZART-4 vs. Reduced Hydrocarbon vs. Super-Fast chemistry

2018 ◽  
Vol 11 (10) ◽  
pp. 4155-4174 ◽  
Author(s):  
Benjamin Brown-Steiner ◽  
Noelle E. Selin ◽  
Ronald Prinn ◽  
Simone Tilmes ◽  
Louisa Emmons ◽  
...  
Keyword(s):  
Computational Cost ◽  
Earth System Model ◽  
Chemical Mechanism ◽  
System Model ◽  
Earth System ◽  
Chemical Mechanisms ◽  
Trade Offs ◽  
Community Earth System Model ◽  
Time Periods ◽  
Fast Mechanism

Abstract. While state-of-the-art complex chemical mechanisms expand our understanding of atmospheric chemistry, their sheer size and computational requirements often limit simulations to short lengths or ensembles to only a few members. Here we present and compare three 25-year present-day offline simulations with chemical mechanisms of different levels of complexity using the Community Earth System Model (CESM) Version 1.2 CAM-chem (CAM4): the Model for Ozone and Related Chemical Tracers, version 4 (MOZART-4) mechanism, the Reduced Hydrocarbon mechanism, and the Super-Fast mechanism. We show that, for most regions and time periods, differences in simulated ozone chemistry between these three mechanisms are smaller than the model–observation differences themselves. The MOZART-4 mechanism and the Reduced Hydrocarbon are in close agreement in their representation of ozone throughout the troposphere during all time periods (annual, seasonal, and diurnal). While the Super-Fast mechanism tends to have higher simulated ozone variability and differs from the MOZART-4 mechanism over regions of high biogenic emissions, it is surprisingly capable of simulating ozone adequately given its simplicity. We explore the trade-offs between chemical mechanism complexity and computational cost by identifying regions where the simpler mechanisms are comparable to the MOZART-4 mechanism and regions where they are not. The Super-Fast mechanism is 3 times as fast as the MOZART-4 mechanism, which allows for longer simulations or ensembles with more members that may not be feasible with the MOZART-4 mechanism given limited computational resources.

scholarly journals TOAST 1.0: Tropospheric Ozone Attribution of Sources with Tagging for CESM 1.2.2

2018 ◽  
Vol 11 (7) ◽  
pp. 2825-2840 ◽  
Author(s):  
Tim Butler ◽  
Aurelia Lupascu ◽  
Jane Coates ◽  
Shuai Zhu
Keyword(s):  
Tropospheric Ozone ◽  
Surface Ozone ◽  
Chemical Mechanism ◽  
System Model ◽  
Ozone Production ◽  
Anthropogenic Emissions ◽  
Source Attribution ◽  
Volatile Organic ◽  
Community Earth System Model ◽  
Northern Hemispheric

Abstract. A system for source attribution of tropospheric ozone produced from both NOx and volatile organic compound (VOC) precursors is described, along with its implementation in the Community Earth System Model (CESM) version 1.2.2 using CAM4. The user can specify an arbitrary number of tag identities for each NOx or VOC species in the model, and the tagging system rewrites the model chemical mechanism and source code to incorporate tagged tracers and reactions representing these tagged species, as well as ozone produced in the stratosphere. If the user supplies emission files for the corresponding tagged tracers, the model will produce tagged ozone tracers which represent the contribution of each of the tag identities to the modelled total tropospheric ozone. Our tagged tracers preserve Ox. The size of the tagged chemical mechanism scales linearly with the number of specified tag identities. Separate simulations are required for NOx and VOC tagging, which avoids the sharing of tag identities between NOx and VOC species. Results are presented and evaluated for both NOx and VOC source attribution. We show that northern hemispheric surface ozone is dominated year-round by anthropogenic emissions of NOx, but that the mix of corresponding VOC precursors changes over the course of the year; anthropogenic VOC emissions contribute significantly to surface ozone in winter–spring, while biogenic VOCs are more important in summer. The system described here can provide important diagnostic information about modelled ozone production, and could be used to construct source–receptor relationships for tropospheric ozone.

Time of Emergence of anthropogenic deoxygenation and warming in the thermocline

2020 ◽  
Author(s):  
Angélique Hameau ◽  
Thomas Frölicher ◽  
Juliette Mignot ◽  
Fortunat Joos
Keyword(s):  
Surface Waters ◽  
Anthropogenic Impacts ◽  
Internal Variability ◽  
Oxygen Depletion ◽  
System Model ◽  
Earth System ◽  
Model Simulations ◽  
Adverse Impacts ◽  
Delayed Emergence ◽  
Lines Of Evidence

<div>Multiple lines of evidence from observation- and model-based studies show that anthropogenic greenhouse gas emissions cause ocean warming and oxygen depletion, with adverse impacts on marine organisms and ecosystems.</div><div>Temperatures increase is a primary indicator for climate change. However, in the thermocline, changes in oxygen and other biogeochemical tracers might be detectable before warming (Hameau et al., 2019a).</div><div>Here, we compare the local time of emergence (ToE) of anthropogenic temperature and oxygen changes in the thermocline within an ensemble of Earth system model simulations from the CMIP5 dataset (Hameau et al., 2019b).</div><div>Generally, warming emerges from internal variability prior to changes in oxygen.</div><div>Yet, in 35$\pm$11\% of the global thermocline, anthropogenic deoxygenation is detectable before warming.</div><div>Earlier emergence of oxygen changes is typically related to decreasing trends in ventilation, which reduce the supply of oxygen-rich surface waters to the thermocline.</div><div>In addition, reduced ventilation slows the propagation of anthropogenic warming from the surface into the ocean interior, further contributing to the delayed emergence of warming compared to deoxygenation.</div><div>As the magnitude of simulated interval variability and of simulated anthropogenic changes vary considerably across models, we introduce the relative ToE metric. This reduces the inter-model spread, allowing for a better comparison among models.</div><div>Our results underline the importance of an ocean biogeochemical observing system and that the detection of anthropogenic impacts becomes more likely when using multi-tracer observations.</div>

scholarly journals Development of Observation-based Global Multi-layer Soil Moisture Products for 1970 to 2016

2021 ◽  
Author(s):  
Yaoping Wang ◽  
Jiafu Mao ◽  
Mingzhou Jin ◽  
Forrest M. Hoffman ◽  
Xiaoying Shi ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Earth System Model ◽  
System Model ◽  
Surface Model ◽  
Earth System ◽  
Model Simulations ◽  
The Earth ◽  
Wide Range ◽  
In Situ Observations

Abstract. Soil moisture (SM) datasets are critical to understanding the global water, energy, and biogeochemical cycles and benefit extensive societal applications. However, individual sources of SM data (e.g., in situ and satellite observations, reanalysis, offline land surface model simulations, Earth system model simulations) have source-specific limitations and biases related to the spatiotemporal continuity, resolutions, and modeling/retrieval assumptions. Here, we developed seven global, gap-free, long-term (1970–2016), multi-layer (0–10, 10–30, 30–50, and 50–100 cm) SM products at monthly 0.5° resolution (available at https://doi.org/10.6084/m9.figshare.13661312.v1) by synthesizing a wide range of SM datasets using three statistical methods (unweighted averaging, optimal linear combination, and emergent constraint). The merged products outperformed their source datasets when evaluated with in situ observations and the latest gridded datasets that did not enter merging because of insufficient spatial, temporal, or soil layer coverage. Assessed against in situ observations, the global mean bias of the synthesized SM data ranged from −0.044 to 0.033 m3/m3, root mean squared error from 0.076 to 0.104 m3/m3, and Pearson correlation from 0.35 to 0.67. The merged SM datasets also showed the ability to capture historical large-scale drought events and physically plausible global sensitivities to observed meteorological factors. Three of the new SM products, produced by applying any of the three merging methods onto the source datasets excluding the Earth system models, were finally recommended for future applications because of their better performances than the Earth system model–dependent merged estimates. Despite uncertainties in the raw SM datasets and fusion methods, these hybrid products create added value over existing SM datasets because of the performance improvement and harmonized spatial, temporal, and vertical coverages, and they provide a new foundation for scientific investigation and resource management.

scholarly journals Hackathon Speeds Progress Toward Climate Model Collaboration

Eos ◽  
2019 ◽  
Vol 100 ◽  
Author(s):  
Wilbert Weijer ◽  
Forrest Hoffman ◽  
Paul Ullrich ◽  
Michael Wehner ◽  
Jialin Liu
Keyword(s):  
Climate Change ◽  
Climate Model ◽  
Earth System Model ◽  
System Model ◽  
Earth System ◽  
Model Simulations

Climate scientists collaborated in a nationwide event to analyze and compare archived Earth system model simulations and to generate input for the IPCC's upcoming climate change report.

scholarly journals Multiphase processes in the EC-Earth Earth System model and their relevance to the atmospheric oxalate, sulfate, and iron cycles

2021 ◽  
Author(s):  
Stelios Myriokefalitakis ◽  
Elisa Bergas-Massó ◽  
María Gonçalves-Ageitos ◽  
Carlos Pérez García-Pando ◽  
Twan van Noije ◽  
...  
Keyword(s):  
Oxalic Acid ◽  
Aqueous Phase ◽  
Earth System Model ◽  
System Model ◽  
Atmospheric Composition ◽  
Global Ocean ◽  
Deposition Flux ◽  
Earth System ◽  
Sulfate Production ◽  
Phase Chemistry

Abstract. Understanding how multiphase processes affect the iron-containing aerosol cycle is key to predict ocean biogeochemistry changes and hence the feedback effects on climate. For this work, the EC-Earth Earth system model in its climate-chemistry configuration is used to simulate the global atmospheric oxalate (OXL), sulfate (SO42−), and iron (Fe) cycles, after incorporating a comprehensive representation of the multiphase chemistry in cloud droplets and aerosol water. The model considers a detailed gas-phase chemistry scheme, all major aerosol components, and the partitioning of gases in aerosol and atmospheric water phases. The dissolution of Fe-containing aerosols accounts kinetically for the solution’s acidity, oxalic acid, and irradiation. Aerosol acidity is explicitly calculated in the model, both for accumulation and coarse modes, accounting for thermodynamic processes involving inorganic and crustal species from sea salt and dust. Simulations for present-day conditions (2000–2014) have been carried out with both EC-Earth and the atmospheric composition component of the model in standalone mode driven by meteorological fields from ECMWF’s ERA-Interim reanalysis. The calculated global budgets are presented and the links between the 1) aqueous-phase processes, 2) aerosol dissolution, and 3) atmospheric composition, are demonstrated and quantified. The model results are supported by comparison to available observations. We obtain an average global OXL net chemical production of 12.61 ± 0.06 Tg yr−1 in EC-Earth, with glyoxal being by far the most important precursor of oxalic acid. In comparison to the ERA-Interim simulation, differences in atmospheric dynamics as well as the simulated weaker oxidizing capacity in EC-Earth result overall in a ~30 % lower OXL source. On the other hand, the more explicit representation of the aqueous-phase chemistry in EC-Earth compared to the previous versions of the model leads to an overall ~20 % higher sulfate production, but still well correlated with atmospheric observations. The total Fe dissolution rate in EC-Earth is calculated at 0.806 ± 0.014 Tg Fe yr−1 and is added to the primary dissolved Fe (DFe) sources from dust and combustion aerosols in the model (0.072 ± 0.001 Tg Fe yr−1). The simulated DFe concentrations show a satisfactory comparison with available observations, indicating an atmospheric burden of ∼0.007 Tg Fe, and overall resulting in an atmospheric deposition flux into the global ocean of 0.376 ± 0.005 Tg Fe yr−1, well within the range reported in the literature. All in all, this work is a first step towards the development of EC-Earth into an Earth System Model with fully interactive bioavailable atmospheric Fe inputs to the marine biogeochemistry component of the model.

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