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  • 1
    Online Resource
    Online Resource
    Implications of three-dimensional chemical transport in hot Jupiter atmospheres: Results from a consistently coupled chemistry-radiation-hydrodynamics model
    EDP Sciences ; 2020
    In:  Astronomy & Astrophysics Vol. 636 ( 2020-4), p. A68-
    Details
    In: Astronomy & Astrophysics, EDP Sciences, Vol. 636 ( 2020-4), p. A68-
    Abstract: We present results from a set of simulations using a fully coupled three-dimensional (3D) chemistry-radiation-hydrodynamics model and investigate the effect of transport of chemical species by the large-scale atmospheric flow in hot Jupiter atmospheres. We coupled a flexible chemical kinetics scheme to the Met Office Unified Model, which enables the study of the interaction of chemistry, radiative transfer, and fluid dynamics. We used a newly-released “reduced” chemical network, comprising 30 chemical species, that was specifically developed for its application in 3D atmosphere models. We simulated the atmospheres of the well-studied hot Jupiters HD 209458b and HD 189733b which both have dayside–nightside temperature contrasts of several hundred Kelvin and superrotating equatorial jets. We find qualitatively quite different chemical structures between the two planets, particularly for methane (CH 4 ), when advection of chemical species is included. Our results show that consideration of 3D chemical transport is vital in understanding the chemical composition of hot Jupiter atmospheres. Three-dimensional mixing leads to significant changes in the abundances of absorbing gas-phase species compared with what would be expected by assuming local chemical equilibrium, or from models including 1D – and even 2D – chemical mixing. We find that CH 4 , carbon dioxide (CO 2 ), and ammonia (NH 3 ) are particularly interesting as 3D mixing of these species leads to prominent signatures of out-of-equilibrium chemistry in the transmission and emission spectra, which are detectable with near-future instruments.
    Type of Medium: Online Resource
    ISSN: 0004-6361 , 1432-0746
    URL: Article
    DOI: 10.1051/0004-6361/201937153
    RVK:
    UA 1000
    RVK:
    US 1090
    Language: English
    Publisher: EDP Sciences
    Publication Date: 2020
    detail.hit.zdb_id: 1458466-9
    SSG: 16,12
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  • 2
    Online Resource
    Online Resource
    Non‐additive response of the high‐latitude Southern Hemisphere climate to aerosol forcing in a climate model with interactive chemistry
    Wiley ; 2020
    In:  Atmospheric Science Letters Vol. 21, No. 12 ( 2020-12)
    Details
    In: Atmospheric Science Letters, Wiley, Vol. 21, No. 12 ( 2020-12)
    Abstract: A suite of chemistry‐climate model simulations, forced by pairs of anthropogenic forcings [comprising greenhouse gases (GHGs), ozone depleting substances (ODSs), or aerosols], were employed to investigate whether the high‐latitude Southern Hemisphere (SH) circulation response to these forcings is linearly additive, a common assumption in attribution studies. We find that the geographical pattern of sea‐level pressure (SLP) response to a combination of GHGs and ODSs is linearly additive. However, we find significant differences in the SLP response when combining GHGs and aerosols compared to the sum of the individual forcings, a non‐additivity that is currently masked by the dominance of the ODSs forcing. This non‐linearity also results in changes to the SH split jet. These results were obtained using a coupled chemistry‐climate model, indicating that the non‐linear response is due to chemical interactions between the forcing agents. As such, future simulations investigating a post‐ozone hole Southern Hemisphere climate should consider this chemical interaction.
    Type of Medium: Online Resource
    ISSN: 1530-261X , 1530-261X
    URL: Issue
    URL: Article
    DOI: 10.1002/asl2.v21.12
    DOI: 10.1002/asl.1004
    Language: English
    Publisher: Wiley
    Publication Date: 2020
    detail.hit.zdb_id: 2025884-7
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  • 3
    Online Resource
    Online Resource
    Responses of Arctic sea ice to stratospheric ozone depletion
    Elsevier BV ; 2022
    In:  Science Bulletin Vol. 67, No. 11 ( 2022-06), p. 1182-1190
    Details
    In: Science Bulletin, Elsevier BV, Vol. 67, No. 11 ( 2022-06), p. 1182-1190
    Type of Medium: Online Resource
    ISSN: 2095-9273
    URL: Article
    DOI: 10.1016/j.scib.2022.03.015
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2022
    detail.hit.zdb_id: 2069521-4
    detail.hit.zdb_id: 2816140-3
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  • 4
    Online Resource
    Online Resource
    Climate Projections Very Likely Underestimate Future Volcanic Forcing and Its Climatic Effects
    American Geophysical Union (AGU) ; 2023
    In:  Geophysical Research Letters Vol. 50, No. 12 ( 2023-06-28)
    Details
    In: Geophysical Research Letters, American Geophysical Union (AGU), Vol. 50, No. 12 ( 2023-06-28)
    Abstract: There is a 95% chance that the time‐averaged 2015–2100 volcanic SO 2 flux from explosive eruptions exceeds the time‐averaged 1850–2014 flux Standard climate projections very likely underestimate the 2015–2100 stratospheric aerosol optical depth and volcanic climate effects Small‐magnitude eruptions ( 〈 3 Tg SO 2 ) contribute 30%–50% of the volcanic climate effects in a median future eruption scenario
    Type of Medium: Online Resource
    ISSN: 0094-8276 , 1944-8007
    URL: Article
    DOI: 10.1029/2023GL103743
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2023
    detail.hit.zdb_id: 2021599-X
    detail.hit.zdb_id: 7403-2
    SSG: 16,13
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  • 5
    Online Resource
    Online Resource
    Using machine learning to build temperature-based ozone parameterizations for climate sensitivity simulations
    IOP Publishing ; 2018
    In:  Environmental Research Letters Vol. 13, No. 10 ( 2018-10-09), p. 104016-
    Details
    In: Environmental Research Letters, IOP Publishing, Vol. 13, No. 10 ( 2018-10-09), p. 104016-
    Type of Medium: Online Resource
    ISSN: 1748-9326
    URL: Article
    DOI: 10.1088/1748-9326/aae2be
    Language: Unknown
    Publisher: IOP Publishing
    Publication Date: 2018
    detail.hit.zdb_id: 2255379-4
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  • 6
    Online Resource
    Online Resource
    Implementation of U.K. Earth System Models for CMIP6
    American Geophysical Union (AGU) ; 2020
    In:  Journal of Advances in Modeling Earth Systems Vol. 12, No. 4 ( 2020-04)
    Details
    In: Journal of Advances in Modeling Earth Systems, American Geophysical Union (AGU), Vol. 12, No. 4 ( 2020-04)
    Abstract: We describe the implementation of U.K. Earth system models for CMIP6 experiments We document the assumptions made in implementing the external forcing in line with experiment protocols Special attention was paid to ensuring that these expensive simulations were reproducible
    Type of Medium: Online Resource
    ISSN: 1942-2466 , 1942-2466
    URL: Article
    DOI: 10.1029/2019MS001946
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2020
    detail.hit.zdb_id: 2462132-8
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  • 7
    Online Resource
    Online Resource
    Quasi-Newton methods for atmospheric chemistry simulations: implementation in UKCA UM vn10.8
    Copernicus GmbH ; 2018
    In:  Geoscientific Model Development Vol. 11, No. 8 ( 2018-08-01), p. 3089-3108
    Details
    In: Geoscientific Model Development, Copernicus GmbH, Vol. 11, No. 8 ( 2018-08-01), p. 3089-3108
    Abstract: Abstract. A key and expensive part of coupled atmospheric chemistry–climate model simulations is the integration of gas-phase chemistry, which involves dozens of species and hundreds of reactions. These species and reactions form a highly coupled network of differential equations (DEs). There exist orders of magnitude variability in the lifetimes of the different species present in the atmosphere, and so solving these DEs to obtain robust numerical solutions poses a stiff problem. With newer models having more species and increased complexity, it is now becoming increasingly important to have chemistry solving schemes that reduce time but maintain accuracy. While a sound way to handle stiff systems is by using implicit DE solvers, the computational costs for such solvers are high due to internal iterative algorithms (e.g. Newton–Raphson methods). Here, we propose an approach for implicit DE solvers that improves their convergence speed and robustness with relatively small modification in the code. We achieve this by blending the existing Newton–Raphson (NR) method with quasi-Newton (QN) methods, whereby the QN routine is called only on selected iterations of the solver. We test our approach with numerical experiments on the UK Chemistry and Aerosol (UKCA) model, part of the UK Met Office Unified Model suite, run in both an idealised box-model environment and under realistic 3-D atmospheric conditions. The box-model tests reveal that the proposed method reduces the time spent in the solver routines significantly, with each QN call costing 27 % of a call to the full NR routine. A series of experiments over a range of chemical environments was conducted with the box model to find the optimal iteration steps to call the QN routine which result in the greatest reduction in the total number of NR iterations whilst minimising the chance of causing instabilities and maintaining solver accuracy. The 3-D simulations show that our moderate modification, by means of using a blended method for the chemistry solver, speeds up the chemistry routines by around 13 %, resulting in a net improvement in overall runtime of the full model by approximately 3 % with negligible loss in the accuracy. The blended QN method also improves the robustness of the solver, reducing the number of grid cells which fail to converge after 50 iterations by 40 %. The relative differences in chemical concentrations between the control run and that using the blended QN method are of order  ∼  10−7 for longer-lived species, such as ozone, and below the threshold for solver convergence (10−4) almost everywhere for shorter-lived species such as the hydroxyl radical.
    Type of Medium: Online Resource
    ISSN: 1991-9603
    URL: Article
    URL: Article
    DOI: 10.5194/gmd-11-3089-2018
    DOI: 10.5194/gmd-11-3089-2018-supplement
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2018
    detail.hit.zdb_id: 2456725-5
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  • 8
    Online Resource
    Online Resource
    Simulating the climate response to atmospheric oxygen variability in the Phanerozoic: a focus on the Holocene, Cretaceous and Permian
    Copernicus GmbH ; 2019
    In:  Climate of the Past Vol. 15, No. 4 ( 2019-08-05), p. 1463-1483
    Details
    In: Climate of the Past, Copernicus GmbH, Vol. 15, No. 4 ( 2019-08-05), p. 1463-1483
    Abstract: Abstract. The amount of dioxygen (O2) in the atmosphere may have varied from as little as 5 % to as much as 35 % during the Phanerozoic eon (54 Ma–present). These changes in the amount of O2 are large enough to have led to changes in atmospheric mass, which may alter the radiative budget of the atmosphere, leading to this mechanism being invoked to explain discrepancies between climate model simulations and proxy reconstructions of past climates. Here, we present the first fully 3-D numerical model simulations to investigate the climate impacts of changes in O2 under different climate states using the coupled atmosphere–ocean Hadley Centre Global Environmental Model version 3 (HadGEM3-AO) and Hadley Centre Coupled Model version 3 (HadCM3-BL) models. We show that simulations with an increase in O2 content result in increased global-mean surface air temperature under conditions of a pre-industrial Holocene climate state, in agreement with idealised 1-D and 2-D modelling studies. We demonstrate the mechanism behind the warming is complex and involves a trade-off between a number of factors. Increasing atmospheric O2 leads to a reduction in incident shortwave radiation at the Earth's surface due to Rayleigh scattering, a cooling effect. However, there is a competing warming effect due to an increase in the pressure broadening of greenhouse gas absorption lines and dynamical feedbacks, which alter the meridional heat transport of the ocean, warming polar regions and cooling tropical regions. Case studies from past climates are investigated using HadCM3-BL and show that, in the warmest climate states in the Maastrichtian (72.1–66.0 Ma), increasing oxygen may lead to a temperature decrease, as the equilibrium climate sensitivity is lower. For the Asselian (298.9–295.0 Ma), increasing oxygen content leads to a warmer global-mean surface temperature and reduced carbon storage on land, suggesting that high oxygen content may have been a contributing factor in preventing a “Snowball Earth” during this period of the early Permian. These climate model simulations reconcile the surface temperature response to oxygen content changes across the hierarchy of model complexity and highlight the broad range of Earth system feedbacks that need to be accounted for when considering the climate response to changes in atmospheric oxygen content.
    Type of Medium: Online Resource
    ISSN: 1814-9332
    URL: Article
    URL: Article
    DOI: 10.5194/cp-15-1463-2019
    DOI: 10.5194/cp-15-1463-2019-supplement
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2019
    detail.hit.zdb_id: 2217985-9
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  • 9
    Online Resource
    Online Resource
    Improvements to the representation of BVOC chemistry–climate interactions in UKCA (v11.5) with the CRI-Strat 2 mechanism: incorporation and evaluation
    Copernicus GmbH ; 2021
    In:  Geoscientific Model Development Vol. 14, No. 8 ( 2021-08-20), p. 5239-5268
    Details
    In: Geoscientific Model Development, Copernicus GmbH, Vol. 14, No. 8 ( 2021-08-20), p. 5239-5268
    Abstract: Abstract. We present the first incorporation of the Common Representative Intermediates version 2.2 tropospheric chemistry mechanism, CRI v2.2, combined with stratospheric chemistry, into the global chemistry–climate United Kingdom Chemistry and Aerosols (UKCA) model to give the CRI-Strat 2 mechanism. A rigorous comparison of CRI-Strat 2 with the earlier version, CRI-Strat, is performed in UKCA in addition to an evaluation of three mechanisms, CRI-Strat 2, CRI-Strat and the standard UKCA chemical mechanism, StratTrop v1.0, against a wide array of surface and airborne chemical data. CRI-Strat 2 comprises a state-of-the-art isoprene scheme, optimized against the Master Chemical Mechanism v3.3.1, which includes isoprene peroxy radical isomerization, HOx recycling through the addition of photolabile hydroperoxy aldehydes (HPALDs), and isoprene epoxy diol (IEPOX) formation. CRI-Strat 2 also features updates to several rate constants for the inorganic chemistry, including the reactions of inorganic nitrogen and O(1D). The update to the isoprene chemistry in CRI-Strat 2 increases OH over the lowest 500 m in tropical forested regions by 30 %–50 % relative to CRI-Strat, leading to an improvement in model–observation comparisons for surface OH and isoprene relative to CRI-Strat and StratTrop. Enhanced oxidants also cause a 25 % reduction in isoprene burden and an increase in oxidation fluxes of isoprene and other biogenic volatile organic compounds (BVOCs) at low altitudes with likely impacts on subsequent aerosol formation, atmospheric lifetime, and climate. By contrast, updates to the rate constants of O(1D) with its main reactants relative to CRI-Strat reduces OH in much of the free troposphere, producing a 2 % increase in the methane lifetime, and increases the tropospheric ozone burden by 8 %, primarily from reduced loss via O(1D)+H2O. The changes to inorganic nitrogen reaction rate constants increase the NOx burden by 4 % and shift the distribution of nitrated species closer to that simulated by StratTrop. CRI-Strat 2 is suitable for multi-decadal model integrations and the improved representation of isoprene chemistry provides an opportunity to explore the consequences of HOx recycling in the United Kingdom Earth System Model (UKESM1). This new mechanism will enable a re-evaluation of the impact of BVOCs on the chemical composition of the atmosphere and further probe the feedback between the biosphere and the climate.
    Type of Medium: Online Resource
    ISSN: 1991-9603
    URL: Article
    URL: Article
    DOI: 10.5194/gmd-14-5239-2021
    DOI: 10.5194/gmd-14-5239-2021-supplement
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2021
    detail.hit.zdb_id: 2456725-5
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  • 10
    Online Resource
    Online Resource
    Chemistry-driven changes strongly influence climate forcing from vegetation emissions
    Springer Science and Business Media LLC ; 2022
    In:  Nature Communications Vol. 13, No. 1 ( 2022-11-23)
    Details
    In: Nature Communications, Springer Science and Business Media LLC, Vol. 13, No. 1 ( 2022-11-23)
    Abstract: Biogenic volatile organic compounds (BVOCs) affect climate via changes to aerosols, aerosol-cloud interactions (ACI), ozone and methane. BVOCs exhibit dependence on climate (causing a feedback) and land use but there remains uncertainty in their net climatic impact. One factor is the description of BVOC chemistry. Here, using the earth-system model UKESM1, we quantify chemistry’s influence by comparing the response to doubling BVOC emissions in the pre-industrial with standard and state-of-science chemistry. The net forcing (feedback) is positive: ozone and methane increases and ACI changes outweigh enhanced aerosol scattering. Contrary to prior studies, the ACI response is driven by cloud droplet number concentration (CDNC) reductions from suppression of gas-phase SO 2 oxidation. With state-of-science chemistry the feedback is 43% smaller as lower oxidant depletion yields smaller methane increases and CDNC decreases. This illustrates chemistry’s significant influence on BVOC’s climatic impact and the more complex pathways by which BVOCs influence climate than currently recognised.
    Type of Medium: Online Resource
    ISSN: 2041-1723
    URL: Article
    DOI: 10.1038/s41467-022-34944-9
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2022
    detail.hit.zdb_id: 2553671-0
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