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1
Wohltmann, I., and M. Rex. "The Lagrangian chemistry and transport model ATLAS: validation of transport and mixing." Geoscientific Model Development Discussions 2, no. 2 (July 3, 2009): 709–62. http://dx.doi.org/10.5194/gmdd-2-709-2009.
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Abstract. We present a new global Chemical Transport Model (CTM) with full stratospheric chemistry and Lagrangian transport and mixing called ATLAS (Alfred Wegener InsTitute LAgrangian Chemistry/Transport System). Lagrangian (trajectory-based) models have several important advantages over conventional Eulerian (grid-based) models, including the absence of spurious numerical diffusion, efficient code parallelization and no limitation of the largest time step by the Courant-Friedrichs-Lewy criterion. The basic concept of transport and mixing is similar to the approach in the commonly used CLaMS model. Several aspects of the model are different from CLaMS and are introduced and validated here, including a different mixing algorithm which is less diffusive and agrees better with observations with the same mixing parameters. In addition, values for the vertical and horizontal stratospheric bulk diffusion coefficients are inferred and compared to other studies. This work focusses on the description of the dynamical part of the model and the validation of the mixing algorithm. The overall model including the chemistry module, which contains 49 species, 170 reactions and a detailed treatment of heterogeneous chemistry, will be presented in a separate paper.
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Wohltmann, I., and M. Rex. "The Lagrangian chemistry and transport model ATLAS: validation of advective transport and mixing." Geoscientific Model Development 2, no. 2 (November 2, 2009): 153–73. http://dx.doi.org/10.5194/gmd-2-153-2009.
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Abstract. We present a new global Chemical Transport Model (CTM) with full stratospheric chemistry and Lagrangian transport and mixing called ATLAS (Alfred Wegener InsTitute LAgrangian Chemistry/Transport System). Lagrangian (trajectory-based) models have several important advantages over conventional Eulerian (grid-based) models, including the absence of spurious numerical diffusion, efficient code parallelization and no limitation of the largest time step by the Courant-Friedrichs-Lewy criterion. The basic concept of transport and mixing is similar to the approach in the commonly used CLaMS model. Several aspects of the model are different from CLaMS and are introduced and validated here, including a different mixing algorithm for lower resolutions which is less diffusive and agrees better with observations with the same mixing parameters. In addition, values for the vertical and horizontal stratospheric bulk diffusion coefficients are inferred and compared to other studies. This work focusses on the description of the dynamical part of the model and the validation of the mixing algorithm. The chemistry module, which contains 49 species, 170 reactions and a detailed treatment of heterogeneous chemistry, will be presented in a separate paper.
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Riede, H., P. Jöckel, and R. Sander. "Quantifying atmospheric transport, chemistry, and mixing using a new trajectory-box model and a global atmospheric-chemistry GCM." Geoscientific Model Development 2, no. 2 (December 15, 2009): 267–80. http://dx.doi.org/10.5194/gmd-2-267-2009.
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Abstract. We present a novel method for the quantification of transport, chemistry, and mixing along atmospheric trajectories based on a consistent model hierarchy. The hierarchy consists of the new atmospheric-chemistry trajectory-box model CAABA/MJT and the three-dimensional (3-D) global ECHAM/MESSy atmospheric-chemistry (EMAC) general circulation model. CAABA/MJT employs the atmospheric box model CAABA in a configuration using the atmospheric-chemistry submodel MECCA (M), the photochemistry submodel JVAL (J), and the new trajectory submodel TRAJECT (T), to simulate chemistry along atmospheric trajectories, which are provided offline. With the same chemistry submodels coupled to the 3-D EMAC model and consistent initial conditions and physical parameters, a unique consistency between the two models is achieved. Since only mixing processes within the 3-D model are excluded from the model consistency, comparisons of results from the two models allow to separate and quantify contributions of transport, chemistry, and mixing along the trajectory pathways. Consistency of transport between the trajectory-box model CAABA/MJT and the 3-D EMAC model is achieved via calculation of kinematic trajectories based on 3-D wind fields from EMAC using the trajectory model LAGRANTO. The combination of the trajectory-box model CAABA/MJT and the trajectory model LAGRANTO can be considered as a Lagrangian chemistry-transport model (CTM) moving isolated air parcels. The procedure for obtaining the necessary statistical basis for the quantification method is described as well as the comprehensive diagnostics with respect to chemistry. The quantification method presented here allows to investigate the characteristics of transport, chemistry, and mixing in a grid-based 3-D model. The analysis of chemical processes within the trajectory-box model CAABA/MJT is easily extendable to include, for example, the impact of different transport pathways or of mixing processes onto chemistry. Under certain prerequisites described here, the results can be used to complement observations with detailed information about the history of observed air masses.
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Deckert, R., P. Jöckel, V. Grewe, K. D. Gottschaldt, and P. Hoor. "A quasi chemistry-transport model mode for EMAC." Geoscientific Model Development Discussions 3, no. 4 (November 19, 2010): 2189–220. http://dx.doi.org/10.5194/gmdd-3-2189-2010.
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Abstract. A quasi chemistry-transport model mode (QCTM) is presented for the numerical chemistry-climate simulation system ECHAM/MESSy Atmospheric Chemistry (EMAC). It allows for a quantification of chemical signals through suppression of any feedback between chemistry and dynamics. Noise would otherwise interfere too strongly. The signal follows from the difference of two QCTM simulations, reference and sensitivity. These are fed with offline chemical fields as a substitute of the feedbacks between chemistry and dynamics: offline mixing ratios of radiatively active substances enter the radiation scheme (a), offline mixing ratios of nitric acid enter the scheme for re-partitioning and sedimentation from polar stratospheric clouds (b). Offline methane oxidation is the exclusive source of chemical water-vapor tendencies (c). Any set of offline fields suffices to suppress the feedbacks, though may be inconsistent with the simulation setup. An adequate set of offline climatologies can be produced from a non-QCTM simulation of the reference setup. Test simulations reveal the particular importance of adequate offline fields associated with (a). Inconsistencies from (b) are negligible when using adequate fields of nitric acid. Acceptably small inconsistencies come from (c), but should vanish for an adequate prescription of water vapor tendencies. Toggling between QCTM and non-QCTM is done via namelist switches and does not require a source code re-compilation.
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Menut, Laurent, Bertrand Bessagnet, Régis Briant, Arineh Cholakian, Florian Couvidat, Sylvain Mailler, Romain Pennel, et al. "The CHIMERE v2020r1 online chemistry-transport model." Geoscientific Model Development 14, no. 11 (November 5, 2021): 6781–811. http://dx.doi.org/10.5194/gmd-14-6781-2021.
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Abstract. The CHIMERE chemistry-transport model v2020r1 replaces the v2017r5 version and provides numerous novelties. The most important of these is the online coupling with the Weather Research and Forecasting (WRF) meteorological model via the OASIS3 – Model Coupling Toolkit (MCT) external coupler. The model can still be used in offline mode; the online mode enables us to take into account the direct and indirect effects of aerosols on meteorology. This coupling also enables using the meteorological parameters with sub-hourly time steps. Some new parameterizations are implemented to increase the model performance and the user's choices: dimethyl sulfide (DMS) emissions, additional schemes for secondary organic aerosol (SOA) formation with volatility basis set (VBS) and H2O, improved schemes for mineral dust, biomass burning, and sea-salt emissions. The NOx emissions from lightning are added. The model also includes the possibility to use the operator-splitting integration technique. The subgrid-scale variability calculation of concentrations due to emission activity sectors is now possible. Finally, a new vertical advection scheme has been implemented, which is able to simulate more correctly long-range transport of thin pollutant plumes.
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Deckert, R., P. Jöckel, V. Grewe, K. D. Gottschaldt, and P. Hoor. "A quasi chemistry-transport model mode for EMAC." Geoscientific Model Development 4, no. 1 (March 16, 2011): 195–206. http://dx.doi.org/10.5194/gmd-4-195-2011.
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Abstract. A quasi chemistry-transport model mode (QCTM) is presented for the numerical chemistry-climate simulation system ECHAM/MESSy Atmospheric Chemistry (EMAC). It allows for a quantification of chemical signals through suppression of any feedback between chemistry and dynamics. Noise would otherwise interfere too strongly. The signal is calculated from the difference of two QCTM simulations, a reference simulation and a sensitivity simulation. In order to avoid the feedbacks, the simulations adopt the following offline chemical fields: (a) offline mixing ratios of radiatively active substances enter the radiation scheme, (b) offline mixing ratios of nitric acid enter the scheme for re-partitioning and sedimentation from polar stratospheric clouds, (c) and offline methane oxidation is the exclusive source of chemical water-vapor tendencies. Any set of offline fields suffices to suppress the feedbacks, though may be inconsistent with the simulation setup. An adequate set of offline climatologies can be produced from a non-QCTM simulation using the setup of the reference simulation. Test simulations reveal the particular importance of adequate offline fields associated with (a). Inconsistencies from (b) are negligible when using adequate fields of nitric acid. Acceptably small inconsistencies come from (c), but should vanish for an adequate prescription of chemical water vapor tendencies. Toggling between QCTM and non-QCTM is done via namelist switches and does not require a source code re-compilation.
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Jung, G., I. M. Hedgecock, and N. Pirrone. "ECHMERIT V1.0 – a new global fully coupled mercury-chemistry and transport model." Geoscientific Model Development Discussions 2, no. 1 (May 7, 2009): 385–453. http://dx.doi.org/10.5194/gmdd-2-385-2009.
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Abstract. Mercury is a global pollutant due to its long lifetime in the atmosphere. Its hemispheric transport patterns and eventual deposition are therefore of major concern. For the purpose of global atmospheric mercury chemistry and transport modelling the ECHMERIT model was developed. ECHMERIT, based on the global circulation model ECHAM5 differs from most global mercury models in that the emissions, chemistry (including general tropospheric chemistry and mercury chemistry), transport and deposition are coupled on-line to the GCM. The chemistry mechanism includes an online calculation of photolysis rate constants using the Fast-J photolysis mechanism, the CBM-Z tropospheric gas-phase mechanism and aqueous-phase chemistry based on the MECCA mechanism. Additionally, a mercury chemistry mechanism that incorporates gas and aqueous phase mercury chemistry is included. A detailed description of the model, including the wet and dry deposition modules, and the implemented emissions is given in this technical report. First model testing and evaluation show a satisfactory model performance for surface ozone and mercury concentrations (with a mean bias of 1.46 ppb for ozone and a mean bias of 13.55 ppq for TGM when compared with EMEP station data). Requirements regarding measurement data and emission inventories which could considerably improve model skill are discussed.
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Jung, G., I. M. Hedgecock, and N. Pirrone. "ECHMERIT V1.0 – a new global fully coupled mercury-chemistry and transport model." Geoscientific Model Development 2, no. 2 (November 4, 2009): 175–95. http://dx.doi.org/10.5194/gmd-2-175-2009.
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Abstract. Mercury is a global pollutant due to its long lifetime in the atmosphere. Its hemispheric transport patterns and eventual deposition are therefore of major concern. For the purpose of global atmospheric mercury chemistry and transport modelling the ECHMERIT model was developed. ECHMERIT, based on the global circulation model ECHAM5 differs from most global mercury models in that the emissions, chemistry (including general tropospheric chemistry and mercury chemistry), transport and deposition are coupled on-line to the GCM. The chemistry mechanism includes an online calculation of photolysis rate constants using the Fast-J photolysis mechanism, the CBM-Z tropospheric gas-phase mechanism and aqueous-phase chemistry based on the MECCA mechanism. Additionally, a mercury chemistry mechanism that incorporates gas and aqueous phase mercury chemistry is included. A detailed description of the model, including the wet and dry deposition modules, and the implemented emissions is given in this technical report. First model testing and evaluation show a satisfactory model performance for surface ozone and mercury mixing ratios (with a mean bias of 1.46 nmol/mol for ozone and a mean bias of 13.55 fmol/mol for TGM when compared with EMEP station data). Requirements regarding measurement data and emission inventories which could considerably improve model skill are discussed.
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Riede, H., P. Jöckel, and R. Sander. "Quantifying atmospheric transport, chemistry, and mixing using a new trajectory-box model and a global atmospheric-chemistry GCM." Geoscientific Model Development Discussions 2, no. 1 (May 8, 2009): 455–84. http://dx.doi.org/10.5194/gmdd-2-455-2009.
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Abstract. We present a novel method for the quantification of transport, chemistry, and mixing along atmospheric trajectories based on a consistent model hierarchy. The hierarchy consists of the new atmospheric-chemistry trajectory-box model CAABA/MJT and the three-dimensional (3-D) global ECHAM/MESSy atmospheric-chemistry (EMAC) general circulation model (GCM). CAABA/MJT employs the atmospheric box model CAABA together with the atmospheric-chemistry submodel MECCA (M), the photochemistry submodel JVAL (J), and the new trajectory submodel TRAJECT (T), to simulate atmospheric chemistry along atmospheric trajectories which are provided offline. With the same submodels coupled to the EMAC model, a unique consistency is achieved, which allows to separate contributions of transport, chemistry, and mixing along the trajectory pathways through comparison of results from the two models. Consistency of transport between the trajectory-box model CAABA/MJT and the 3-D EMAC model is achieved via calculation of trajectories based on 3-D wind fields from EMAC. The procedure to obtain the necessary statistical basis for the quantification analysis is described as well as the comprehensive diagnostics with respect to chemistry. The quantification method is applied to 3-D model data as a diagnostic tool with the focus on the transfer of results to observational data.
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Wang, ChangJian, Jennifer Wen, ShouXiang Lu, and Jin Guo. "Single-step chemistry model and transport coefficient model for hydrogen combustion." Science China Technological Sciences 55, no. 8 (June 29, 2012): 2163–68. http://dx.doi.org/10.1007/s11431-012-4932-4.
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Wohltmann, Ingo, Daniel Kreyling, and Ralph Lehmann. "Transport parameterization of the Polar SWIFT model (version 2)." Geoscientific Model Development 15, no. 18 (September 27, 2022): 7243–55. http://dx.doi.org/10.5194/gmd-15-7243-2022.
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Abstract. The Polar SWIFT model is a fast scheme for calculating the chemistry of stratospheric ozone depletion in the polar vortex in winter. It is intended for use in general circulation models (GCMs) and earth system models (ESMs) to enable the simulation of interactions between the ozone layer and climate when a full stratospheric chemistry scheme is computationally too expensive. In addition to the simulation of chemistry, ozone has to be transported in the GCM. As an alternative to the general schemes for the transport and mixing of tracers in the GCMs, a parameterization of the transport of ozone can be used in order to obtain the total change of ozone as the sum of the change by transport and by chemistry. One of the benefits of this approach is the easy and self-contained coupling to a GCM. Another potential advantage is that a transport parameterization based on reanalysis data and measurements can avoid deficiencies in the representation of transport in the GCMs, such as deficits in the representation of the Brewer–Dobson circulation caused by the gravity wave parameterization. Hence, we present a transport parameterization for the Polar SWIFT model that simulates the change in vortex-averaged ozone by transport in a fast and simple way without the need for a complex transport scheme in the GCM.
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Manders, Astrid M. M., Peter J. H. Builtjes, Lyana Curier, Hugo A. C. Denier van der Gon, Carlijn Hendriks, Sander Jonkers, Richard Kranenburg, et al. "Curriculum vitae of the LOTOS–EUROS (v2.0) chemistry transport model." Geoscientific Model Development 10, no. 11 (November 16, 2017): 4145–73. http://dx.doi.org/10.5194/gmd-10-4145-2017.
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Abstract. The development and application of chemistry transport models has a long tradition. Within the Netherlands the LOTOS–EUROS model has been developed by a consortium of institutes, after combining its independently developed predecessors in 2005. Recently, version 2.0 of the model was released as an open-source version. This paper presents the curriculum vitae of the model system, describing the model's history, model philosophy, basic features and a validation with EMEP stations for the new benchmark year 2012, and presents cases with the model's most recent and key developments. By setting the model developments in context and providing an outlook for directions for further development, the paper goes beyond the common model description.With an origin in ozone and sulfur modelling for the models LOTOS and EUROS, the application areas were gradually extended with persistent organic pollutants, reactive nitrogen, and primary and secondary particulate matter. After the combination of the models to LOTOS–EUROS in 2005, the model was further developed to include new source parametrizations (e.g. road resuspension, desert dust, wildfires), applied for operational smog forecasts in the Netherlands and Europe, and has been used for emission scenarios, source apportionment, and long-term hindcast and climate change scenarios. LOTOS–EUROS has been a front-runner in data assimilation of ground-based and satellite observations and has participated in many model intercomparison studies. The model is no longer confined to applications over Europe but is also applied to other regions of the world, e.g. China. The increasing interaction with emission experts has also contributed to the improvement of the model's performance. The philosophy for model development has always been to use knowledge that is state of the art and proven, to keep a good balance in the level of detail of process description and accuracy of input and output, and to keep a good record on the effect of model changes using benchmarking and validation. The performance of v2.0 with respect to EMEP observations is good, with spatial correlations around 0.8 or higher for concentrations and wet deposition. Temporal correlations are around 0.5 or higher. Recent innovative applications include source apportionment and data assimilation, particle number modelling, and energy transition scenarios including corresponding land use changes as well as Saharan dust forecasting. Future developments would enable more flexibility with respect to model horizontal and vertical resolution and further detailing of model input data. This includes the use of different sources of land use characterization (roughness length and vegetation), detailing of emissions in space and time, and efficient coupling to meteorology from different meteorological models.
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Emmerson, K. M., and M. J. Evans. "Comparison of tropospheric gas-phase chemistry schemes for use within global models." Atmospheric Chemistry and Physics 9, no. 5 (March 12, 2009): 1831–45. http://dx.doi.org/10.5194/acp-9-1831-2009.
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Abstract. Methane and ozone are two important climate gases with significant tropospheric chemistry. Within chemistry-climate and transport models this chemistry is simplified for computational expediency. We compare the state of the art Master Chemical Mechanism (MCM) with six tropospheric chemistry schemes (CRI-reduced, GEOS-CHEM and a GEOS-CHEM adduct, MOZART-2, TOMCAT and CBM-IV) that could be used within composition transport models. We test the schemes within a box model framework under conditions derived from a composition transport model and from field observations from a regional scale pollution event. We find that CRI-reduced provides much skill in simulating the full chemistry, yet with greatly reduced complexity. We find significant variations between the other chemical schemes, and reach the following conclusions. 1) The inclusion of a gas phase N2O5+H2O reaction in one scheme and not others is a large source of uncertainty in the inorganic chemistry. 2) There are significant variations in the calculated concentration of PAN between the schemes, which will affect the long range transport of reactive nitrogen in global models. 3) The representation of isoprene chemistry differs hugely between the schemes, leading to significant uncertainties on the impact of isoprene on composition. 4) Differences are found in NO3 concentrations in the nighttime chemistry. Resolving these four issues through further investigative laboratory studies will reduce the uncertainties within the chemical schemes of global tropospheric models.
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Menut, Laurent, Sylvain Mailler, Bertrand Bessagnet, Guillaume Siour, Augustin Colette, Florian Couvidat, and Frédérik Meleux. "An alternative way to evaluate chemistry-transport model variability." Geoscientific Model Development 10, no. 3 (March 17, 2017): 1199–208. http://dx.doi.org/10.5194/gmd-10-1199-2017.
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Abstract. A simple and complementary model evaluation technique for regional chemistry transport is discussed. The methodology is based on the concept that we can learn about model performance by comparing the simulation results with observational data available for time periods other than the period originally targeted. First, the statistical indicators selected in this study (spatial and temporal correlations) are computed for a given time period, using colocated observation and simulation data in time and space. Second, the same indicators are used to calculate scores for several other years while conserving the spatial locations and Julian days of the year. The difference between the results provides useful insights on the model capability to reproduce the observed day-to-day and spatial variability. In order to synthesize the large amount of results, a new indicator is proposed, designed to compare several error statistics between all the years of validation and to quantify whether the period and area being studied were well captured by the model for the correct reasons.
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Strahan, S. E., and B. C. Polansky. "Implementation issues in chemistry and transport models." Atmospheric Chemistry and Physics Discussions 5, no. 5 (October 21, 2005): 10217–58. http://dx.doi.org/10.5194/acpd-5-10217-2005.
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Abstract. Offline chemistry and transport models (CTMs) are versatile tools for studying composition and climate issues requiring multi-decadal simulations. They are computationally fast compared to coupled chemistry climate models, making them well-suited for integrating sensitivity experiments necessary for understanding model performance and interpreting results. The archived meteorological fields used by CTMs can be implemented with lower horizontal or vertical resolution than the original meteorological fields in order to shorten integration time, but the effects of these shortcuts on transport processes must be understood if the CTM is to have credibility. In this paper we present a series of CTM experiments, each differing from another by a single feature of the implementation. Transport effects arising from changes in resolution and model lid height are evaluated using process-oriented diagnostics that intercompare CH4, O3, and age tracer carried in the simulations. Some of the diagnostics used are derived from observations and are shown as a reality check for the model. Processes evaluated include the tropical ascent, tropical-midlatitude exchange, the poleward circulation in the upper stratosphere, and the development of the Antarctic vortex. We find that faithful representation of stratospheric transport in this CTM using Lin and Rood advection is possible with a full mesosphere, ~1 km resolution in the lower stratosphere, and relatively low vertical resolution (>4 km spacing) in the middle stratosphere and above, but lowering the lid from the upper to lower mesosphere leads to less realistic constituent distributions in the upper stratosphere. Ultimately, this affects the polar lower stratosphere, but the effects are greater for the Antarctic than the Arctic. The fidelity of lower stratospheric transport requires realistic tropical and high latitude mixing barriers which are produced at 2°×2.5°, but not lower resolution. At 2°×2.5° resolution, the CTM produces a vortex capable of isolating perturbed chemistry (e.g. high Cly and low NOy) required for simulating polar ozone loss.
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Emmerson, K. M., and M. J. Evans. "Comparison of tropospheric chemistry schemes for use within global models." Atmospheric Chemistry and Physics Discussions 8, no. 6 (November 28, 2008): 19957–87. http://dx.doi.org/10.5194/acpd-8-19957-2008.
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Abstract. Methane and ozone are two important climate gases with significant tropospheric chemistry. Within chemistry-climate and transport models this chemistry is simplified for computational expediency. We compare the state of the art Master Chemical Mechanism (MCM) with six tropospheric chemistry schemes (CRI-reduced, GEOS-CHEM and a GEOS-CHEM adduct, MOZART, TOMCAT and CBM-IV) that could be used within composition transport models. We test the schemes within a box model framework under conditions derived from a composition transport model and from field observations from a regional scale pollution event. We find that CRI-reduced provides much skill in simulating the full chemistry, yet with greatly reduced complexity. We find significant variations between the other chemical schemes, and reach the following conclusions. 1) The inclusion of a gas phase N2O5+H2O reaction in some schemes and not others is a large source of uncertainty in the inorganic chemistry. 2) There are significant variations in the calculated concentration of PAN between the schemes, which will affect the long range transport of reactive nitrogen in global models. 3) The representation of isoprene chemistry differs hugely between the schemes, leading to significant uncertainties on the impact of isoprene on composition. 4) Night-time chemistry is badly represented with significant disagreements in the ratio of NO3 to NOx. Resolving these four issues through further investigative laboratory studies will reduce the uncertainties within the chemical schemes of global tropospheric models.
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Borisov, D. V., and I. U. Shalygina. "Refinement of land use data for emission calculations in the CHIMERE chemistry-transport model: A case study for the Nizhny Novgorod region ." Hydrometeorological research and forecasting 3 (September 2021): 150–61. http://dx.doi.org/10.37162/2618-9631-2021-3-150-161.
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Refinement of land use data for emission calculations in the CHIMERE chemistry-transport model: A case study for the Nizhny Novgorod region / Borisov D.V., Shalygina I.U. // Hydrometeorological Research and Forecasting, 2021, no. 3 (381), pp. 150-161. The quality of calculating the concentration of pollutants in the chemistry-transport model largely depends on the reliability of used emission data. The possibility of updating the EMEP (European Monitoring and Evaluation Program) emission data using OpenStreetMap geodata for the CHIMERE chemistry-transport model calculations is discussed on the example of the Nizhny Novgorod region. The GlobCover land-use data refinement procedure based on OpenStreetMap information provides a 3.3% increase in the urban area and a more accurate configuration of the emission field as compared to the real distribution of sources of atmospheric emissions. Experimental CHIMERE chemistry-transport model calculations of pollutant concentrations based on the initial and updated emission fields demonstrated the efficiency of the proposed approach. Keywords: emissions, EMEP, land use, OpenStreetMap, CHIMERE chemistry-transport model, air quality
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Philip, Sajeev, Randall V. Martin, and Christoph A. Keller. "Sensitivity of chemistry-transport model simulations to the duration of chemical and transport operators: a case study with GEOS-Chem v10-01." Geoscientific Model Development 9, no. 5 (May 3, 2016): 1683–95. http://dx.doi.org/10.5194/gmd-9-1683-2016.
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Abstract. Chemistry-transport models involve considerable computational expense. Fine temporal resolution offers accuracy at the expense of computation time. Assessment is needed of the sensitivity of simulation accuracy to the duration of chemical and transport operators. We conduct a series of simulations with the GEOS-Chem chemistry-transport model at different temporal and spatial resolutions to examine the sensitivity of simulated atmospheric composition to operator duration. Subsequently, we compare the species simulated with operator durations from 10 to 60 min as typically used by global chemistry-transport models, and identify the operator durations that optimize both computational expense and simulation accuracy. We find that longer continuous transport operator duration increases concentrations of emitted species such as nitrogen oxides and carbon monoxide since a more homogeneous distribution reduces loss through chemical reactions and dry deposition. The increased concentrations of ozone precursors increase ozone production with longer transport operator duration. Longer chemical operator duration decreases sulfate and ammonium but increases nitrate due to feedbacks with in-cloud sulfur dioxide oxidation and aerosol thermodynamics. The simulation duration decreases by up to a factor of 5 from fine (5 min) to coarse (60 min) operator duration. We assess the change in simulation accuracy with resolution by comparing the root mean square difference in ground-level concentrations of nitrogen oxides, secondary inorganic aerosols, ozone and carbon monoxide with a finer temporal or spatial resolution taken as “truth”. Relative simulation error for these species increases by more than a factor of 5 from the shortest (5 min) to longest (60 min) operator duration. Chemical operator duration twice that of the transport operator duration offers more simulation accuracy per unit computation. However, the relative simulation error from coarser spatial resolution generally exceeds that from longer operator duration; e.g., degrading from 2° × 2.5° to 4° × 5° increases error by an order of magnitude. We recommend prioritizing fine spatial resolution before considering different operator durations in offline chemistry-transport models. We encourage chemistry-transport model users to specify in publications the durations of operators due to their effects on simulation accuracy.
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Schraner, M., E. Rozanov, C. Schnadt Poberaj, P. Kenzelmann, A. M. Fischer, V. Zubov, B. P. Luo, et al. "Technical Note: Chemistry-climate model SOCOL: version 2.0 with improved transport and chemistry/microphysics schemes." Atmospheric Chemistry and Physics Discussions 8, no. 3 (June 9, 2008): 11103–47. http://dx.doi.org/10.5194/acpd-8-11103-2008.
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Abstract. We describe version 2.0 of the chemistry-climate model (CCM) SOCOL. The new version includes fundamental changes of the transport scheme such as transporting all chemical species of the model individually and applying a family-based correction scheme for mass conservation for species of the nitrogen, chlorine and bromine groups, a revised transport scheme for ozone, furthermore more detailed halogen reaction and deposition schemes, and a new cirrus parameterisation in the tropical tropopause region. By means of these changes the model manages to overcome or considerably reduce deficiencies recently identified in SOCOL version 1.1 within the CCM Validation activity of SPARC (CCMVal). In particular, as a consequence of these changes, regional mass loss or accumulation artificially caused by the semi-Lagrangian transport scheme can be significantly reduced, leading to much more realistic distributions of the modelled chemical species, most notably of the halogens and ozone.
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Schraner, M., E. Rozanov, C. Schnadt Poberaj, P. Kenzelmann, A. M. Fischer, V. Zubov, B. P. Luo, et al. "Technical Note: Chemistry-climate model SOCOL: version 2.0 with improved transport and chemistry/microphysics schemes." Atmospheric Chemistry and Physics 8, no. 19 (October 15, 2008): 5957–74. http://dx.doi.org/10.5194/acp-8-5957-2008.
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Abstract. We describe version 2.0 of the chemistry-climate model (CCM) SOCOL. The new version includes fundamental changes of the transport scheme such as transporting all chemical species of the model individually and applying a family-based correction scheme for mass conservation for species of the nitrogen, chlorine and bromine groups, a revised transport scheme for ozone, furthermore more detailed halogen reaction and deposition schemes, and a new cirrus parameterisation in the tropical tropopause region. By means of these changes the model manages to overcome or considerably reduce deficiencies recently identified in SOCOL version 1.1 within the CCM Validation activity of SPARC (CCMVal). In particular, as a consequence of these changes, regional mass loss or accumulation artificially caused by the semi-Lagrangian transport scheme can be significantly reduced, leading to much more realistic distributions of the modelled chemical species, most notably of the halogens and ozone.
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Allen, Dale J., Prasad Kasibhatla, Anne M. Thompson, Richard B. Rood, Bruce G. Doddridge, Kenneth E. Pickering, Robert D. Hudson, and Shian-Jiann Lin. "Transport-induced interannual variability of carbon monoxide determined using a chemistry and transport model." Journal of Geophysical Research: Atmospheres 101, no. D22 (December 1, 1996): 28655–69. http://dx.doi.org/10.1029/96jd02984.
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Strahan, S. E., B. N. Duncan, and P. Hoor. "Observationally derived transport diagnostics for the lowermost stratosphere and their application to the GMI chemistry and transport model." Atmospheric Chemistry and Physics Discussions 7, no. 1 (January 29, 2007): 1449–77. http://dx.doi.org/10.5194/acpd-7-1449-2007.
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Abstract. Transport from the surface to the lowermost stratosphere can occur on timescales of a few months or less, making it possible for short-lived tropospheric pollutants to influence stratospheric composition and chemistry. Models used to study this influence must demonstrate the credibility of their chemistry and transport in the upper troposphere and lower stratosphere (UT/LS). Data sets from satellite and aircraft instruments measuring CO, O3, N2O, and CO2 in the UT/LS are used to create a suite of diagnostics of the seasonally-varying transport into and within the lowermost stratosphere, and of the coupling between the troposphere and stratosphere in the extratropics. The diagnostics are used to evaluate a version of the Global Modeling Initiative (GMI) Chemistry and Transport Model that uses a combined tropospheric and stratospheric chemical mechanism and meteorological fields from the GEOS-4 general circulation model. The diagnostics derived from N2O and O3 show that the model lowermost stratosphere (LMS) has realistic input from the overlying high latitude stratosphere in all seasons. Diagnostics for the LMS show two distinct layers. The upper layer (~350 K–380 K) has a strong annual cycle in its composition, while the lower layer, just above the tropopause, shows no seasonal variation in the degree of tropospheric coupling or composition. The GMI CTM agrees closely with the observations in both layers and is realistically coupled to the UT in all seasons. This study demonstrates the credibility of the GMI CTM for the study of the impact of tropospheric emissions on the stratosphere.
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Asim Mushtaq, Asim Mushtaq, and Hilmi Mukhtar and Azmi Mohd Shariff Hilmi Mukhtar and Azmi Mohd Shariff. "Modelling for Gas Transport in Enhanced Polymeric Blend Membrane." Journal of the chemical society of pakistan 41, no. 4 (2019): 613. http://dx.doi.org/10.52568/000772/jcsp/41.04.2019.
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The main aim of this research work is to develop a model of carbon dioxide (CO2) separation from natural gas by using membrane separation technology. This study includes the transport mechanism of the porous membrane. The fundamental theories of diffusion, poiseuille (viscous) flow, Knudsen diffusion and surface diffusion are used. The developed model of incorporating three diffusion mechanisms to be modified for modeling of polymeric blends towards membrane selectivity and permeability. For the purpose of assessing the gas permeance using the theoretical models, the experimental data taken from CO2 permeance in the PSU/PVAc (85/15) wt. % /DEA enhanced polymeric blend membrane was considered. The results obtained from modified Cho Empirical model of total gas permeance showed the least error as compared to other models. The modified Cho Empirical mathematical models were extended by blending factor to predict CO2 gas molecule transport in Enhanced Polymeric Blend Membrane (EPBM) to obtain precise theoretical values that are close to the experimental values. The Extended modified Cho Empirical model validation demonstrated the ability to predict CO2 permeance with reasonable accuracy.
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Menut, L., B. Bessagnet, D. Khvorostyanov, M. Beekmann, N. Blond, A. Colette, I. Coll, et al. "CHIMERE 2013: a model for regional atmospheric composition modelling." Geoscientific Model Development 6, no. 4 (July 22, 2013): 981–1028. http://dx.doi.org/10.5194/gmd-6-981-2013.
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Abstract. Tropospheric trace gas and aerosol pollutants have adverse effects on health, environment and climate. In order to quantify and mitigate such effects, a wide range of processes leading to the formation and transport of pollutants must be considered, understood and represented in numerical models. Regional scale pollution episodes result from the combination of several factors: high emissions (from anthropogenic or natural sources), stagnant meteorological conditions, kinetics and efficiency of the chemistry and the deposition. All these processes are highly variable in time and space, and their relative contribution to the pollutants budgets can be quantified with chemistry-transport models. The CHIMERE chemistry-transport model is dedicated to regional atmospheric pollution event studies. Since it has now reached a certain level a maturity, the new stable version, CHIMERE 2013, is described to provide a reference model paper. The successive developments of the model are reviewed on the basis of published investigations that are referenced in order to discuss the scientific choices and to provide an overview of the main results.
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Strahan, S. E., and B. C. Polansky. "Meteorological implementation issues in chemistry and transport models." Atmospheric Chemistry and Physics 6, no. 10 (July 12, 2006): 2895–910. http://dx.doi.org/10.5194/acp-6-2895-2006.
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Abstract. Offline chemistry and transport models (CTMs) are versatile tools for studying composition and climate issues requiring multi-decadal simulations. They are computationally fast compared to coupled chemistry climate models, making them well-suited for integrating sensitivity experiments necessary for understanding model performance and interpreting results. The archived meteorological fields used by CTMs can be implemented with lower horizontal or vertical resolution than the original meteorological fields in order to shorten integration time, but the effects of these shortcuts on transport processes must be understood if the CTM is to have credibility. In this paper we present a series of sensitivity experiments on a CTM using the Lin and Rood advection scheme, each differing from another by a single feature of the wind field implementation. Transport effects arising from changes in resolution and model lid height are evaluated using process-oriented diagnostics that intercompare CH4, O3, and age tracer carried in the simulations. Some of the diagnostics used are derived from observations and are shown as a reality check for the model. Processes evaluated include tropical ascent, tropical-midlatitude exchange, poleward circulation in the upper stratosphere, and the development of the Antarctic vortex. We find that faithful representation of stratospheric transport in this CTM is possible with a full mesosphere, ~1 km resolution in the lower stratosphere, and relatively low vertical resolution (>4 km spacing) in the middle stratosphere and above, but lowering the lid from the upper to lower mesosphere leads to less realistic constituent distributions in the upper stratosphere. Ultimately, this affects the polar lower stratosphere, but the effects are greater for the Antarctic than the Arctic. The fidelity of lower stratospheric transport requires realistic tropical and high latitude mixing barriers which are produced at 2°×2.5°, but not lower resolution. At 2°×2.5° resolution, the CTM produces a vortex capable of isolating perturbed chemistry (e.g. high Cly and low NOy) required for simulating polar ozone loss.
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Solazzo, Efisio, and Stefano Galmarini. "Error apportionment for atmospheric chemistry-transport models – a new approach to model evaluation." Atmospheric Chemistry and Physics 16, no. 10 (May 24, 2016): 6263–83. http://dx.doi.org/10.5194/acp-16-6263-2016.
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Abstract. In this study, methods are proposed to diagnose the causes of errors in air quality (AQ) modelling systems. We investigate the deviation between modelled and observed time series of surface ozone through a revised formulation for breaking down the mean square error (MSE) into bias, variance and the minimum achievable MSE (mMSE). The bias measures the accuracy and implies the existence of systematic errors and poor representation of data complexity, the variance measures the precision and provides an estimate of the variability of the modelling results in relation to the observed data, and the mMSE reflects unsystematic errors and provides a measure of the associativity between the modelled and the observed fields through the correlation coefficient. Each of the error components is analysed independently and apportioned to resolved processes based on the corresponding timescale (long scale, synoptic, diurnal, and intra-day) and as a function of model complexity.The apportionment of the error is applied to the AQMEII (Air Quality Model Evaluation International Initiative) group of models, which embrace the majority of regional AQ modelling systems currently used in Europe and North America.The proposed technique has proven to be a compact estimator of the operational metrics commonly used for model evaluation (bias, variance, and correlation coefficient), and has the further benefit of apportioning the error to the originating timescale, thus allowing for a clearer diagnosis of the processes that caused the error.
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Jorba, Oriol, Thomas Loridan, Pedro Jiménez-Guerrero, Carlos Pérez, and José María Baldasano. "Linking the advanced research WRF meteorological model with the CHIMERE chemistry-transport model." Environmental Modelling & Software 23, no. 8 (August 2008): 1092–94. http://dx.doi.org/10.1016/j.envsoft.2008.02.002.
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Richardson, John D. "A new model for plasma transport and chemistry at Saturn." Journal of Geophysical Research 97, A9 (1992): 13705. http://dx.doi.org/10.1029/92ja00920.
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Carmichael, Gregory R., and Leonard K. Peters. "A second generation model for regional-scale transport/chemistry/deposition." Atmospheric Environment (1967) 20, no. 1 (January 1986): 173–88. http://dx.doi.org/10.1016/0004-6981(86)90218-0.
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Strahan, S. E., B. N. Duncan, and P. Hoor. "Observationally derived transport diagnostics for the lowermost stratosphere and their application to the GMI chemistry and transport model." Atmospheric Chemistry and Physics 7, no. 9 (May 11, 2007): 2435–45. http://dx.doi.org/10.5194/acp-7-2435-2007.
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Abstract. Transport from the surface to the lowermost stratosphere (LMS) can occur on timescales of a few months or less, making it possible for short-lived tropospheric pollutants to influence stratospheric composition and chemistry. Models used to study this influence must demonstrate the credibility of their chemistry and transport in the upper troposphere and lower stratosphere (UT/LS). Data sets from satellite and aircraft instruments measuring CO, O3, N2O, and CO2 in the UT/LS are used to create a suite of diagnostics for the seasonally-varying transport into and within the lowermost stratosphere, and of the coupling between the troposphere and stratosphere in the extratropics. The diagnostics are used to evaluate a version of the Global Modeling Initiative (GMI) Chemistry and Transport Model (CTM) that uses a combined tropospheric and stratospheric chemical mechanism and meteorological fields from the GEOS-4 general circulation model. The diagnostics derived from N2O and O3 show that the model lowermost stratosphere has realistic input from the overlying high latitude stratosphere in all seasons. Diagnostics for the LMS show two distinct layers. The upper layer begins ~30 K potential temperature above the tropopause and has a strong annual cycle in its composition. The lower layer is a mixed region ~30 K thick near the tropopause that shows no clear seasonal variation in the degree of tropospheric coupling. Diagnostics applied to the GMI CTM show credible seasonally-varying transport in the LMS and a tropopause layer that is realistically coupled to the UT in all seasons. The vertical resolution of the GMI CTM in the UT/LS, ~1 km, is sufficient to realistically represent the extratropical tropopause layer. This study demonstrates that the GMI CTM has the transport credibility required to study the impact of tropospheric emissions on the stratosphere.
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Bregman, B., A. Segers, M. Krol, E. Meijer, and P. van Velthoven. "On the use of mass-conserving wind fields in chemistry-transport models." Atmospheric Chemistry and Physics Discussions 2, no. 5 (October 28, 2002): 1765–90. http://dx.doi.org/10.5194/acpd-2-1765-2002.
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Abstract. A new method has been developed that provides mass-conserving wind fields for global chemistry-transport models. In previous global Eulerian modeling studies a mass-imbalance was found between the model mass transport and the surface pressure tendencies. Several methods have been suggested to correct for this imbalance, but so far no satisfactory solution has been found. Our new method solves these problems by using the wind fields in a spherical harmonical form (divergence and vorticity) by mimicing the physics of the weather forecast model as closely as possible. A 3-D chemistry-transport model was used to show that the calculated ozone fields with the new processing method agree remarkably better with ozone observations in the upper troposphere and lower stratosphere. In addition, the calculated age of air in the lower stratosphere show better agreement with observations, although the air remains still too young in the extra tropical stratosphere.
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Bregman, B., A. Segers, M. Krol, E. Meijer, and P. van Velthoven. "On the use of mass-conserving wind fields in chemistry-transport models." Atmospheric Chemistry and Physics 3, no. 2 (April 15, 2003): 447–57. http://dx.doi.org/10.5194/acp-3-447-2003.
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Abstract. A new method has been developed that provides mass-conserving wind fields for global chemistry-transport models. In previous global Eulerian modeling studies a mass-imbalance was found between the model mass transport and the surface pressure tendencies. Several methods have been suggested to correct for this imbalance, but so far no satisfactory solution has been found. Our new method solves these problems by using the wind fields in a spherical harmonical form (divergence and vorticity) by mimicing the physics of the weather forecast model as closely as possible. A 3-D chemistry-transport model was used to show that the calculated ozone fields with the new processing method agree remarkably better with ozone observations in the upper troposphere and lower stratosphere. In addition, the calculated age of air in the lower stratosphere show better agreement with observations, although the air remains still too young in the extra-tropical stratosphere.
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Orbe, Clara, Huang Yang, Darryn W. Waugh, Guang Zeng, Olaf Morgenstern, Douglas E. Kinnison, Jean-Francois Lamarque, et al. "Large-scale tropospheric transport in the Chemistry–Climate Model Initiative (CCMI) simulations." Atmospheric Chemistry and Physics 18, no. 10 (May 25, 2018): 7217–35. http://dx.doi.org/10.5194/acp-18-7217-2018.
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Abstract. Understanding and modeling the large-scale transport of trace gases and aerosols is important for interpreting past (and projecting future) changes in atmospheric composition. Here we show that there are large differences in the global-scale atmospheric transport properties among the models participating in the IGAC SPARC Chemistry–Climate Model Initiative (CCMI). Specifically, we find up to 40 % differences in the transport timescales connecting the Northern Hemisphere (NH) midlatitude surface to the Arctic and to Southern Hemisphere high latitudes, where the mean age ranges between 1.7 and 2.6 years. We show that these differences are related to large differences in vertical transport among the simulations, in particular to differences in parameterized convection over the oceans. While stronger convection over NH midlatitudes is associated with slower transport to the Arctic, stronger convection in the tropics and subtropics is associated with faster interhemispheric transport. We also show that the differences among simulations constrained with fields derived from the same reanalysis products are as large as (and in some cases larger than) the differences among free-running simulations, most likely due to larger differences in parameterized convection. Our results indicate that care must be taken when using simulations constrained with analyzed winds to interpret the influence of meteorology on tropospheric composition.
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Lugon, Lya, Karine Sartelet, Youngseob Kim, Jérémy Vigneron, and Olivier Chrétien. "Nonstationary modeling of NO<sub>2</sub>, NO and NO<sub><i>x</i></sub> in Paris using the Street-in-Grid model: coupling local and regional scales with a two-way dynamic approach." Atmospheric Chemistry and Physics 20, no. 13 (July 3, 2020): 7717–40. http://dx.doi.org/10.5194/acp-20-7717-2020.
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Abstract. Regional-scale chemistry-transport models have coarse spatial resolution (coarser than 1 km ×1 km) and can thus only simulate background concentrations. They fail to simulate the high concentrations observed close to roads and in streets, where a large part of the urban population lives. Local-scale models may be used to simulate concentrations in streets. They often assume that background concentrations are constant and/or use simplified chemistry. Recently developed, the multi-scale model Street-in-Grid (SinG) estimates gaseous pollutant concentrations simultaneously at local and regional scales by coupling them dynamically. This coupling combines the regional-scale chemistry-transport model Polair3D and a street-network model, the Model of Urban Network of Intersecting Canyons and Highway (MUNICH), with a two-way feedback. MUNICH explicitly models street canyons and intersections, and it is coupled to the first vertical level of the chemical-transport model, enabling the transfer of pollutant mass between the street-canyon roof and the atmosphere. The original versions of SinG and MUNICH adopt a stationary hypothesis to estimate pollutant concentrations in streets. Although the computation of the NOx concentration is numerically stable with the stationary approach, the partitioning between NO and NO2 is highly dependent on the time step of coupling between transport and chemistry processes. In this study, a new nonstationary approach is presented with a fine coupling between transport and chemistry, leading to numerically stable partitioning between NO and NO2. Simulations of NO, NO2 and NOx concentrations over Paris with SinG, MUNICH and Polair3D are compared to observations at traffic and urban stations to estimate the added value of multi-scale modeling with a two-way dynamical coupling between the regional and local scales. As expected, the regional chemical-transport model underestimates NO and NO2 concentrations in the streets. However, there is good agreement between the measurements and the concentrations simulated with MUNICH and SinG. The two-way dynamic coupling between the local and regional scales tends to be important for streets with an intermediate aspect ratio and with high traffic emissions.
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Barth, M. C., S. W. Kim, C. Wang, K. E. Pickering, L. E. Ott, G. Stenchikov, M. Leriche, et al. "Cloud-scale model intercomparison of chemical constituent transport in deep convection." Atmospheric Chemistry and Physics Discussions 7, no. 3 (June 8, 2007): 8035–85. http://dx.doi.org/10.5194/acpd-7-8035-2007.
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Abstract. Transport and scavenging of chemical constituents in deep convection is important to understanding the composition of the troposphere and therefore chemistry-climate and air quality issues. High resolution cloud chemistry models have been shown to represent convective processing of trace gases quite well. To improve the representation of sub-grid convective transport and wet deposition in large-scale models, general characteristics, such as species mass flux, from the high resolution cloud chemistry models can be used. However, it is important to understand how these models behave when simulating the same storm. The intercomparison described here examines transport of six species. CO and O3, which are primarily transported, show good agreement among models and compare well with observations. Models that included lightning production of NOx reasonably predict NOx mixing ratios in the anvil compared with observations, but the NOx variability is much larger than that seen for CO and O3. Predicted anvil mixing ratios of the soluble species, HNO3, H2O2, and CH2O, exhibit significant differences among models, attributed to different schemes in these models of cloud processing including the role of the ice phase, the impact of cloud-modified photolysis rates on the chemistry, and the representation of the species chemical reactivity. The lack of measurements of these species in the convective outflow region does not allow us to evaluate the model results with observations.
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Barth, M. C., S. W. Kim, C. Wang, K. E. Pickering, L. E. Ott, G. Stenchikov, M. Leriche, et al. "Cloud-scale model intercomparison of chemical constituent transport in deep convection." Atmospheric Chemistry and Physics 7, no. 18 (September 18, 2007): 4709–31. http://dx.doi.org/10.5194/acp-7-4709-2007.
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Abstract. Transport and scavenging of chemical constituents in deep convection is important to understanding the composition of the troposphere and therefore chemistry-climate and air quality issues. High resolution cloud chemistry models have been shown to represent convective processing of trace gases quite well. To improve the representation of sub-grid convective transport and wet deposition in large-scale models, general characteristics, such as species mass flux, from the high resolution cloud chemistry models can be used. However, it is important to understand how these models behave when simulating the same storm. The intercomparison described here examines transport of six species. CO and O3, which are primarily transported, show good agreement among models and compare well with observations. Models that included lightning production of NOx reasonably predict NOx mixing ratios in the anvil compared with observations, but the NOx variability is much larger than that seen for CO and O3. Predicted anvil mixing ratios of the soluble species, HNO3, H2O2, and CH2O, exhibit significant differences among models, attributed to different schemes in these models of cloud processing including the role of the ice phase, the impact of cloud-modified photolysis rates on the chemistry, and the representation of the species chemical reactivity. The lack of measurements of these species in the convective outflow region does not allow us to evaluate the model results with observations.
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Charlesworth, Edward J., Ann-Kristin Dugstad, Frauke Fritsch, Patrick Jöckel, and Felix Plöger. "Impact of Lagrangian transport on lower-stratospheric transport timescales in a climate model." Atmospheric Chemistry and Physics 20, no. 23 (December 8, 2020): 15227–45. http://dx.doi.org/10.5194/acp-20-15227-2020.
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Abstract. We investigate the impact of model trace gas transport schemes on the representation of transport processes in the upper troposphere and lower stratosphere. Towards this end, the Chemical Lagrangian Model of the Stratosphere (CLaMS) was coupled to the ECHAM/MESSy Atmospheric Chemistry (EMAC) model and results from the two transport schemes (Lagrangian critical Lyapunov scheme and flux-form semi-Lagrangian, respectively) were compared. Advection in CLaMS was driven by the EMAC simulation winds, and thereby the only differences in transport between the two sets of results were caused by differences in the transport schemes. To analyze the timescales of large-scale transport, multiple tropical-surface-emitted tracer pulses were performed to calculate age of air spectra, while smaller-scale transport was analyzed via idealized, radioactively decaying tracers emitted in smaller regions (nine grid cells) within the stratosphere. The results show that stratospheric transport barriers are significantly stronger for Lagrangian EMAC-CLaMS transport due to reduced numerical diffusion. In particular, stronger tracer gradients emerge around the polar vortex, at the subtropical jets, and at the edge of the tropical pipe. Inside the polar vortex, the more diffusive EMAC flux-form semi-Lagrangian transport scheme results in a substantially higher amount of air with ages from 0 to 2 years (up to a factor of 5 higher). In the lowermost stratosphere, mean age of air is much smaller in EMAC, owing to stronger diffusive cross-tropopause transport. Conversely, EMAC-CLaMS shows a summertime lowermost stratosphere age inversion – a layer of older air residing below younger air (an “eave”). This pattern is caused by strong poleward transport above the subtropical jet and is entirely blurred by diffusive cross-tropopause transport in EMAC. Potential consequences from the choice of the transport scheme on chemistry–climate and geoengineering simulations are discussed.
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Yudin, Valery A., Sergey P. Smyshlyaev, Marvin A. Geller, and Victor L. Dvortsov. "Transport Diagnostics of GCMs and Implications for 2D Chemistry-Transport Model of Troposphere and Stratosphere." Journal of the Atmospheric Sciences 57, no. 5 (March 2000): 673–99. http://dx.doi.org/10.1175/1520-0469(2000)057<0673:tdogai>2.0.co;2.
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Douglass, Anne R., Mark R. Schoeberl, Richard B. Rood, and Steven Pawson. "Evaluation of transport in the lower tropical stratosphere in a global chemistry and transport model." Journal of Geophysical Research: Atmospheres 108, no. D9 (May 2, 2003): n/a. http://dx.doi.org/10.1029/2002jd002696.
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Makino, Kimiko, Hiroyuki Ohshima, and Tamotsu Kondo. "Kinetic model for membrane transport." Biophysical Chemistry 35, no. 1 (January 1990): 85–95. http://dx.doi.org/10.1016/0301-4622(90)80063-d.
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Makino, Kimiko, Hiroyuki Ohshima, and Tamotsu Kondo. "Kinetic model for membrane transport." Biophysical Chemistry 38, no. 3 (November 1990): 231–39. http://dx.doi.org/10.1016/0301-4622(90)87005-6.
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Hamer, P. D., V. Marécal, R. Hossaini, M. Pirre, N. Warwick, M. Chipperfield, A. A. Samah, et al. "Modelling the chemistry and transport of bromoform within a sea breeze driven convective system during the SHIVA Campaign." Atmospheric Chemistry and Physics Discussions 13, no. 8 (August 7, 2013): 20611–76. http://dx.doi.org/10.5194/acpd-13-20611-2013.
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Abstract. We carry out a case study of the transport and chemistry of bromoform and its product gases (PGs) in a sea breeze driven convective episode on 19 November 2011 along the North West coast of Borneo during the "Stratospheric ozone: Halogen Impacts in a Varying Atmosphere" (SHIVA) campaign. We use ground based, ship, aircraft and balloon sonde observations made during the campaign, and a 3-D regional online transport and chemistry model capable of resolving clouds and convection explicitly that includes detailed bromine chemistry. The model simulates the temperature, wind speed, wind direction fairly well for the most part, and adequately captures the convection location, timing, and intensity. The simulated transport of bromoform from the boundary layer up to 12 km compares well to aircraft observations to support our conclusions. The model makes several predictions regarding bromine transport from the boundary layer to the level of convective detrainment (11 to 12 km). First, the majority of bromine undergoes this transport as bromoform. Second, insoluble organic bromine carbonyl species are transported to between 11 and 12 km, but only form a small proportion of the transported bromine. Third, soluble bromine species, which include bromine organic peroxides, hydrobromic acid (HBr), and hypobromous acid (HOBr), are washed out efficiently within the core of the convective column. Fourth, insoluble inorganic bromine species (principally Br2) are not washed out of the convective column, but are also not transported to the altitude of detrainment in large quantities. We expect that Br2 will make a larger relative contribution to the total vertical transport of bromine atoms in scenarios with higher CHBr3 mixing ratios in the boundary layer, which have been observed in other regions. Finally, given the highly detailed description of the chemistry, transport and washout of bromine compounds within our simulations, we make a series of recommendations about the physical and chemical processes that should be represented in 3-D chemical transport models (CTMs) and chemistry climate models (CCMs), which are the primary theoretical means of estimating the contribution made by CHBr3 and other very short-lived substances (VSLS) to the stratospheric bromine budget.
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Grellier, L., V. Marécal, B. Josse, P. D. Hamer, T. J. Roberts, A. Aiuppa, and M. Pirre. "Towards a representation of halogen chemistry within volcanic plumes in a chemistry transport model." Geoscientific Model Development Discussions 7, no. 2 (April 28, 2014): 2581–650. http://dx.doi.org/10.5194/gmdd-7-2581-2014.
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Abstract. Volcanoes are a known source of halogens to the atmosphere. HBr volcanic emissions lead rapidly to the formation of BrO within volcanic plumes as shown by recent work based on observations and models. BrO, having a longer residence time in the atmosphere than HBr, is expected to have a significant impact on tropospheric chemistry, at least at the local and regional scales. The objective of this paper is to prepare a framework that will allow 3-D modelling of volcanic halogen emissions in order to determine their fate within the volcanic plume and then in the atmosphere at the regional and global scales. This work is based on a 1-D configuration of the chemistry transport model MOCAGE whose low computational cost allows us to perform a large set of sensitivity studies. This paper studies the Etna eruption on the 10 May 2008 that took place just before night time. Adaptations are made to MOCAGE to be able to produce the chemistry occurring within the volcanic plume. A simple sub-grid scale parameterization of the volcanic plume is implemented and tested. The use of this parameterization in a 0.5° × 0.5° configuration (typical regional resolution) has an influence on the partitioning between the various bromine compounds both during the eruption period and also during the night period immediately afterwards. During the day after the eruption, simulations both with and without parameterizations give very similar results that are consistent with the tropospheric column of BrO and SO2 in the volcanic plume derived from GOME-2 observations. Tests have been performed to evaluate the sensitivity of the results to the mixing between ambient air and the magmatic air at very high temperature at the crater vent that modifies the composition of the emission, and in particular the sulphate aerosol content that is key compound in the BrO production. Simulations show that the plume chemistry is not very sensitive to the assumptions used for the mixing parameter (relative quantity of ambient air mixed with magmatic air in the mixture) that is not well known. This is because there is no large change in the compounds limiting/favouring the BrO production in the plume. The impact of the model grid resolution is also tested in view of future 3-D-simulations at the global scale. A dilution of the emitted gases and aerosols is observed when using the typical global resolution (2°) as compared to a typical regional resolution (0.5°), as expected. Taking this into account, the results of the 2° resolution simulations are consistent with the GOME-2 observations. In general the simulations at 2° resolution are less efficient at producing BrO after the emission both with and without the subgrid-scale parameterization. The differences are mainly due to an interaction between concentration effects than stem from using a reduced volume in the 0.5° resolution combined with second order rate kinetics. The last series of tests were on the mean radius assumed for the sulphate aerosols that indirectly impacts the production of BrO by heterogeneous reactions. The simulations show that the BrO production is sensitive to this parameter with a stronger production when smaller aerosols are assumed. These results will be used to guide the implementation of volcanic halogen emissions in the 3-D configuration of MOCAGE.
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Bregman, B., E. Meijer, and R. Scheele. "Key aspects of stratospheric tracer modeling." Atmospheric Chemistry and Physics Discussions 6, no. 3 (June 6, 2006): 4375–414. http://dx.doi.org/10.5194/acpd-6-4375-2006.
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Abstract. This study describes key aspects of global chemistry-transport models and the impact on stratospheric tracer transport. We concentrate on global models that use assimilated winds from numerical weather predictions, but the results also apply to tracer transport in general circulation models. We examined grid resolution, numerical diffusion and dispersion of the winds fields, the meteorology update time intervals, update frequency, and time interpolation. For this study we applied the three-dimensional chemistry-transport Tracer Model version 5 (TM5) and a trajectory model and performed several diagnoses focusing on different transport regimes. Covering different time and spatial scales, we examined (1) polar vortex dynamics during the Arctic winter, (2) the large-scale stratospheric meridional circulation, and (3) air parcel dispersion in the tropical lower stratosphere. Tracer distributions inside the Arctic polar vortex show considerably worse agreement with observations when the model grid resolution in the polar region is reduced to avoid numerical instability. Using time interpolated winds improve the tracer distributions only marginally. Considerable improvement is found when the update frequency of the assimilated winds is increased from 6 to 3h, both in the large-scale tracer distribution and the polar regions. It further reduces in particular the vertical dispersion of air parcels in the tropical lower stratosphere. The results in this study demonstrates significant progress in the use of assimilated meteorology in chemistry-transport models, which is important for both short- and long-term integrations.
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Mailler, Sylvain, Laurent Menut, Dmitry Khvorostyanov, Myrto Valari, Florian Couvidat, Guillaume Siour, Solène Turquety, et al. "CHIMERE-2017: from urban to hemispheric chemistry-transport modeling." Geoscientific Model Development 10, no. 6 (June 28, 2017): 2397–423. http://dx.doi.org/10.5194/gmd-10-2397-2017.
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Abstract. CHIMERE is a chemistry-transport model designed for regional atmospheric composition. It can be used at a variety of scales from local to continental domains. However, due to the model design and its historical use as a regional model, major limitations had remained, hampering its use at hemispheric scale, due to the coordinate system used for transport as well as to missing processes that are important in regions outside Europe. Most of these limitations have been removed in the CHIMERE-2017 version, allowing its use in any region of the world and at any scale, from the scale of a single urban area up to hemispheric scale, with or without polar regions included. Other important improvements have been made in the treatment of the physical processes affecting aerosols and the emissions of mineral dust. From a computational point of view, the parallelization strategy of the model has also been updated in order to improve model numerical performance and reduce the code complexity. The present article describes all these changes. Statistical scores for a model simulation over continental Europe are presented, and a simulation of the circumpolar transport of volcanic ash plume from the Puyehue volcanic eruption in June 2011 in Chile provides a test case for the new model version at hemispheric scale.
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Søvde, O. A., M. J. Prather, I. S. A. Isaksen, T. K. Berntsen, F. Stordal, X. Zhu, C. D. Holmes, and J. Hsu. "The chemical transport model Oslo CTM3." Geoscientific Model Development Discussions 5, no. 2 (June 19, 2012): 1561–626. http://dx.doi.org/10.5194/gmdd-5-1561-2012.
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Abstract. We present here the global chemical transport model Oslo CTM3, an update of the Oslo CTM2. The update comprises a faster transport scheme, an improved wet scavenging scheme for large scale rain, updated photolysis rates and a new lightning parameterization. Oslo CTM3 is better parallelized and allows for stable, large time steps for advection, enabling more complex or high resolution simulations. Thorough comparisons between the Oslo CTM3, Oslo CTM2 and measurements are performed, and in general the Oslo CTM3 is found to reproduce measurements well. Inclusion of tropospheric sulfur chemistry and nitrate aerosols in CTM3 is shown to be important to reproduce tropospheric O3, OH and the CH4 lifetime well. Using the same meteorology to drive the two models, shows that some features related to transport are better resolved by the CTM3, such as polar cap transport, while features like transport close to the vortex edge are resolved better in the Oslo CTM2 due to its required shorter transport time step. The longer transport time steps in CTM3 result in larger errors e.g. near the jets, and when necessary, this can be remedied by using a shorter time step. An additional, more accurate and time consuming, treatment of polar cap transport is presented, however, both perform acceptably. A new treatment of the horizontal distribution of lightning is presented and found to compare well with measurements. Vertical distributions of lighting are updated, and tested against the old vertical distribution. The new profiles are found to produce more NOx in the tropical middle troposphere, and less at the surface and at high altitudes.
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Wohltmann, I., R. Lehmann, and M. Rex. "The Lagrangian chemistry and transport model ATLAS: simulation and validation of stratospheric chemistry and ozone loss in the winter 1999/2000." Geoscientific Model Development 3, no. 2 (November 1, 2010): 585–601. http://dx.doi.org/10.5194/gmd-3-585-2010.
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Abstract. ATLAS is a new global Lagrangian Chemistry and Transport Model (CTM), which includes a stratospheric chemistry scheme with 46 active species, 171 reactions, heterogeneous chemistry on polar stratospheric clouds and a Lagrangian denitrification module. Lagrangian (trajectory-based) models have several important advantages over conventional Eulerian models, including the absence of spurious numerical diffusion, efficient code parallelization and no limitation of the largest time step by the Courant-Friedrichs-Lewy criterion. This work describes and validates the stratospheric chemistry scheme of the model. Stratospheric chemistry is simulated with ATLAS for the Arctic winter 1999/2000, with a focus on polar ozone depletion and denitrification. The simulations are used to validate the chemistry module in comparison with measurements of the SOLVE/THESEO 2000 campaign. A Lagrangian denitrification module, which is based on the simulation of the nucleation, sedimentation and growth of a large number of polar stratospheric cloud particles, is used to model the substantial denitrification that occured in this winter.
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Wohltmann, I., R. Lehmann, and M. Rex. "The Lagrangian chemistry and transport model ATLAS: simulation and validation of stratospheric chemistry and ozone loss in the winter 1999/2000." Geoscientific Model Development Discussions 3, no. 2 (June 1, 2010): 769–817. http://dx.doi.org/10.5194/gmdd-3-769-2010.
Full textAbstract:
Abstract. ATLAS is a new global Lagrangian Chemistry and Transport Model (CTM), which includes a stratospheric chemistry scheme with 46 active species, 171 reactions, heterogeneous chemistry on polar stratospheric clouds and a Lagrangian denitrification module. Lagrangian (trajectory-based) models have several important advantages over conventional Eulerian models, including the absence of spurious numerical diffusion, efficient code parallelization and no limitation of the largest time step by the Courant-Friedrichs-Lewy criterion. This work describes and validates the stratospheric chemistry scheme of the model. Stratospheric chemistry is simulated with ATLAS for the Arctic winter 1999/2000, with a focus on polar ozone depletion and denitrification. The simulations are used to validate the chemistry module in comparison with measurements of the SOLVE/THESEO 2000 campaign. A Lagrangian denitrification module, which is based on the simulation of the nucleation, sedimentation and growth of a large number of polar stratospheric cloud particles, is used to model the substantial denitrification that occured in this winter.
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Pirovano, G., A. Balzarini, B. Bessagnet, C. Emery, G. Kallos, F. Meleux, C. Mitsakou, U. Nopmongcol, G. M. Riva, and G. Yarwood. "Investigating impacts of chemistry and transport model formulation on model performance at European scale." Atmospheric Environment 53 (June 2012): 93–109. http://dx.doi.org/10.1016/j.atmosenv.2011.12.052.
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Siddiqi, Fasih A., and Naved Iqbal Alvi. "Transport studies with model membrane." Journal of Polymer Science Part B: Polymer Physics 27, no. 7 (June 1989): 1499–517. http://dx.doi.org/10.1002/polb.1989.090270711.
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