Simulation of radon-222 with the GEOS-Chem global model: emissions, seasonality, and convective transport

Abstract. Radon-222 (222Rn) is a short-lived radioactive gas naturally emitted from land surfaces and has long been used to assess convective transport in atmospheric models. In this study, we simulate 222Rn using the GEOS-Chem chemical transport model to improve our understanding of 222Rn emissions and surface concentration seasonality and characterize convective transport associated with two Goddard Earth Observing System (GEOS) meteorological products, the Modern-Era Retrospective analysis for Research and Applications (MERRA) and GEOS Forward Processing (GEOS-FP). We evaluate four global 222Rn emission scenarios by comparing model results with observations at 51 surface sites. The default emission scenario in GEOS-Chem yields a moderate agreement with surface observations globally (68.9 % of data within a factor of 2) and a large underestimate of winter surface 222Rn concentrations at Northern Hemisphere midlatitudes and high latitudes due to an oversimplified formulation of 222Rn emission fluxes (1 atom cm−2 s−1 over land with a reduction by a factor of 3 under freezing conditions). We compose a new global 222Rn emission scenario based on Zhang et al. (2011) and demonstrate its potential to improve simulated surface 222Rn concentrations and seasonality. The regional components of this scenario include spatially and temporally varying emission fluxes derived from previous measurements of soil radium content and soil exhalation models, which are key factors in determining 222Rn emission flux rates. However, large model underestimates of surface 222Rn concentrations still exist in Asia, suggesting unusually high regional 222Rn emissions. We therefore propose a conservative upscaling factor of 1.2 for 222Rn emission fluxes in China, which was also constrained by observed deposition fluxes of 210Pb (a progeny of 222Rn). With this modification, the model shows better agreement with observations in Europe and North America (> 80 % of data within a factor of 2) and reasonable agreement in Asia (close to 70 %). Further constraints on 222Rn emissions would require additional concentration and emission flux observations in the central United States, Canada, Africa, and Asia. We also compare and assess convective transport in model simulations driven by MERRA and GEOS-FP using observed 222Rn vertical profiles in northern midlatitude summer and from three short-term airborne campaigns. While simulations with both GEOS products are able to capture the observed vertical gradient of 222Rn concentrations in the lower troposphere (0–4 km), neither correctly represents the level of convective detrainment, resulting in biases in the middle and upper troposphere. Compared with GEOS-FP, MERRA leads to stronger convective transport of 222Rn, which is partially compensated for by its weaker large-scale vertical advection, resulting in similar global vertical distributions of 222Rn concentrations between the two simulations. This has important implications for using chemical transport models to interpret the transport of other trace species when these GEOS products are used as driving meteorology.

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Simulation of radon-222 with the GEOS-Chem global model: Emissions, seasonality, and convective transport

10.5194/acp-2020-804 ◽

2020 ◽

Author(s):

Bo Zhang ◽

Hongyu Liu ◽

James H. Crawford ◽

Gao Chen ◽

T. Duncan Fairlie ◽

...

Keyword(s):

Large Scale ◽

Transport Model ◽

Lower Troposphere ◽

Chemical Transport ◽

Surface Concentration ◽

Vertical Gradient ◽

Convective Transport ◽

Chemical Transport Model ◽

Earth Observing System ◽

Land Surfaces

Abstract. Radon-222 (222Rn) is a short-lived radioactive gas naturally emitted from land surfaces, and has long been used to assess convective transport in atmospheric models. In this study, we simulate 222Rn using the GEOS-Chem chemical transport model to improve our understanding of 222Rn emissions and surface concentration seasonality, and characterize convective transport associated with two Goddard Earth Observing System (GEOS) meteorological products, MERRA and GEOS-FP. We evaluate four global 222Rn emission scenarios by comparing model results with observations at 51 surface sites. The default emission scenario in GEOS-Chem yields a moderate agreement with surface observations globally ( 80 % data within a factor of 2), and reasonable agreement in Asia (close to 70 %). Further constraints on 222Rn emissions would require additional concentration and emission flux observations in the central U.S., Canada, Africa, and Asia. We also compare and assess convective transport in model simulations driven by MERRA and GEOS-FP using observed 222Rn vertical profiles in northern mid-latitude summer, and from three short-term airborne campaigns. While simulations with both GEOS products are able to capture the observed vertical gradient of 222Rn concentrations in the lower troposphere (0–4 km), neither correctly represents the level of convective detrainment, resulting in biases in the middle and upper troposphere. Compared with GEOS-FP, MERRA leads to stronger convective transport of 222Rn, which is partially compensated by its weaker large-scale vertical advection, resulting in similar global vertical distributions of 222Rn concentrations between the two simulations. This has important implications for using chemical transport models to interpret the transport of other trace species when these GEOS products are used as driving meteorology.

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Evaluation of cloud convection and tracer transport in a three-dimensional chemical transport model

Atmospheric Chemistry and Physics ◽

10.5194/acp-11-5783-2011 ◽

2011 ◽

Vol 11 (12) ◽

pp. 5783-5803 ◽

Cited By ~ 21

Author(s):

W. Feng ◽

M. P. Chipperfield ◽

S. Dhomse ◽

B. M. Monge-Sanz ◽

X. Yang ◽

...

Keyword(s):

Mass Flux ◽

Large Scale ◽

Transport Model ◽

Chemical Transport ◽

Convective Transport ◽

Convective Precipitation ◽

Tracer Transport ◽

Chemical Transport Model ◽

Mass Fluxes ◽

Spatial And Seasonal Variation

Abstract. We investigate the performance of cloud convection and tracer transport in a global off-line 3-D chemical transport model. Various model simulations are performed using different meteorological (re)analyses (ERA-40, ECMWF operational and ECMWF Interim) to diagnose the updraft mass flux, convective precipitation and cloud top height. The diagnosed upward mass flux distribution from TOMCAT agrees quite well with the ECMWF reanalysis data (ERA-40 and ERA-Interim) below 200 hPa. Inclusion of midlevel convection improves the agreement at mid-high latitudes. However, the reanalyses show strong convective transport up to 100 hPa, well into the tropical tropopause layer (TTL), which is not captured by TOMCAT. Similarly, the model captures the spatial and seasonal variation of convective cloud top height although the mean modelled value is about 2 km lower than observed. The ERA-Interim reanalyses have smaller archived upward convective mass fluxes than ERA-40, and smaller convective precipitation, which is in better agreement with satellite-based data. TOMCAT captures these relative differences when diagnosing convection from the large-scale fields. The model also shows differences in diagnosed convection with the version of the operational analyses used, which cautions against using results of the model from one specific time period as a general evaluation. We have tested the effect of resolution on the diagnosed modelled convection with simulations ranging from 5.6° × 5.6° to 1° × 1°. Overall, in the off-line model, the higher model resolution gives stronger vertical tracer transport, however, it does not make a large change to the diagnosed convective updraft mass flux (i.e., the model results using the convection scheme fail to capture the strong convection transport up to 100 hPa as seen in the archived convective mass fluxes). Similarly, the resolution of the forcing winds in the higher resolution CTM does not make a large improvement compared to the archived mass fluxes. Including a radon tracer in the model confirms the importance of convection for reproducing observed midlatitude profiles. The model run using archived mass fluxes transports significantly more radon to the upper troposphere but the available data does not strongly discriminate between the different model versions.

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Evaluation of cloud convection and tracer transport in a three-dimensional chemical transport model

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-10-22953-2010 ◽

2010 ◽

Vol 10 (10) ◽

pp. 22953-22991 ◽

Cited By ~ 4

Author(s):

W. Feng ◽

M. P. Chipperfield ◽

S. Dhomse ◽

B. M. Monge-Sanz ◽

X. Yang ◽

...

Keyword(s):

Mass Flux ◽

Large Scale ◽

Transport Model ◽

Chemical Transport ◽

Convective Transport ◽

Convective Precipitation ◽

Tracer Transport ◽

Chemical Transport Model ◽

Mass Fluxes ◽

Spatial And Seasonal Variation

Abstract. We investigate the performance of cloud convection and tracer transport in a global off-line 3-D chemical transport model. Various model simulations are performed using different meteorological (re)analyses (ERA-40, ECMWF operational and ECMWF Interim) to diagnose the updraft mass flux, convective precipitation and cloud top height. The diagnosed upward mass flux distribution from TOMCAT agrees quite well with the ECMWF reanalysis data (ERA-40 and ERA-Interim) below 200 hPa. Inclusion of midlevel convection improves the agreement at mid-high latitudes. However, the reanalyses show strong convective transport up to 100 hPa, well into the tropical tropopause layer (TTL), which is not captured by TOMCAT. Similarly, the model captures the spatial and seasonal variation of convective cloud top height although the mean modelled value is about 2 km lower than observed. The ERA-Interim reanalyses have smaller archived upward convective mass fluxes than ERA-40, and smaller convective precipitation, which is in better agreement with satellite-based data. TOMCAT captures these relative differences when diagnosing convection from the large-scale fields. The model also shows differences in diagnosed convection with the version of the operational analyses used, which cautions against using results of the model from one specific time period as a general evaluation. We have tested the effect of resolution on the diagnosed modelled convection with simulations ranging from 5.6° × 5.6° to 1° × 1°. Overall, in the off-line model, the higher model resolution does not make a large change to the diagnosed convective tracer transport. Similarly, the resolution of the forcing winds in the higher resolution CTM does not make a large improvement compared to the archived mass fluxes. Including a radon tracer in the model confirms the importance of convection for reproducing observed midlatitude profiles. The model run using archived mass fluxes transports significantly more radon to the upper troposphere but the available data does not strongly discriminate between the different model versions.

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Multi-species inversion of CH4, CO and H2 emissions from surface measurements

Atmospheric Chemistry and Physics ◽

10.5194/acp-9-5281-2009 ◽

2009 ◽

Vol 9 (14) ◽

pp. 5281-5297 ◽

Cited By ~ 83

Author(s):

I. Pison ◽

P. Bousquet ◽

F. Chevallier ◽

S. Szopa ◽

D. Hauglustaine

Keyword(s):

Transport Model ◽

Regional Scale ◽

Surface Concentration ◽

Temporal Variations ◽

Global Scale ◽

Chemical Transport Model ◽

Methyl Chloroform ◽

Emission Fluxes ◽

Surface Measurements ◽

One Year

Abstract. In order to study the spatial and temporal variations of the emissions of greenhouse gases and of their precursors, we developed a data assimilation system and applied it to infer emissions of CH4, CO and H2 for one year. It is based on an atmospheric chemical transport model and on a simplified scheme for the oxidation chain of hydrocarbons, including methane, formaldehyde, carbon monoxide and molecular hydrogen together with methyl chloroform. The methodology is exposed and a first attempt at evaluating the inverted fluxes is made. Inversions of the emission fluxes of CO, CH4 and H2 and concentrations of HCHO and OH were performed for the year 2004, using surface concentration measurements of CO, CH4, H2 and CH3CCl3 as constraints. Independent data from ship and aircraft measurements and satellite retrievals are used to evaluate the results. The total emitted mass of CO is 30% higher after the inversion, due to increased fluxes by up to 35% in the Northern Hemisphere. The spatial distribution of emissions of CH4 is modified by a decrease of fluxes in boreal areas up to 60%. The comparison between mono- and multi-species inversions shows that the results are close at a global scale but may significantly differ at a regional scale because of the interactions between the various tracers during the inversion.

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The role of horizontal model resolution in assessing the transport of CO in a middle latitude cyclone using WRF-Chem

Atmospheric Chemistry and Physics ◽

10.5194/acp-14-609-2014 ◽

2014 ◽

Vol 14 (2) ◽

pp. 609-627 ◽

Cited By ~ 12

Author(s):

C. A. Klich ◽

H. E. Fuelberg

Keyword(s):

Large Scale ◽

Transport Model ◽

Deep Convection ◽

Middle Latitude ◽

Convective Transport ◽

Vertical Transport ◽

Squall Line ◽

Grid Spacing ◽

Chemical Transport Model ◽

Hysplit Model

Abstract. We use the Weather Research and Forecasting with Chemistry (WRF-Chem) online chemical transport model to simulate a middle latitude cyclone in East Asia at three different horizontal resolutions (45, 15, and 5 km grid spacing). The cyclone contains a typical warm conveyor belt (WCB) with an embedded squall line that passes through an area having large surface concentrations (> 400 ppbv) of carbon monoxide (CO). Model output from WRF-Chem is used to compare differences between the large-scale CO vertical transport by the WCB (the 45 km simulation) with the smaller-scale transport due to its convection (the 5 km simulation). Forward trajectories are calculated from WRF-Chem output using the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model. At 45 km grid spacing, the WCB exhibits gradual ascent, lofting surface CO to 6–7 km. Upon reaching the warm front, the WCB and associated CO ascend more rapidly and later turn eastward over the Pacific Ocean. Convective transport at 5 km resolution with explicitly resolved convection occurs much more rapidly, with surface CO lofted to altitudes greater than 10 km in 1 h or less. We also compute CO vertical mass fluxes over specified areas and times to compare differences in transport due to the different grid spacings. Upward CO flux exceeds 110 000 t h−1 in the domain with explicit convection when the squall line is at peak intensity, while fluxes from the two coarser resolutions are an order of magnitude smaller. Specific areas of interest within the 5 km domain are defined to compare the magnitude of convective transport to that within the entire 5 km region. Although convection encompasses only a small portion of the 5 km domain, it is responsible for ~40% of the upward CO transport. We also examine the vertical transport due to a short wave trough and its associated area of convection, not related to the cyclone, that lofts CO to the upper troposphere. Results indicate that fine-scale resolution with explicitly resolved convection is important when assessing the vertical transport of surface emissions in areas of deep convection.

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Inversion of long-lived trace gas emissions using combined Eulerian and Lagrangian chemical transport models

Atmospheric Chemistry and Physics ◽

10.5194/acp-11-9887-2011 ◽

2011 ◽

Vol 11 (18) ◽

pp. 9887-9898 ◽

Cited By ~ 49

Author(s):

M. Rigby ◽

A. J. Manning ◽

R. G. Prinn

Keyword(s):

High Resolution ◽

Large Scale ◽

Transport Model ◽

Initial Conditions ◽

Dispersion Model ◽

Chemical Transport ◽

Particle Dispersion ◽

Global Network ◽

Lagrangian Model ◽

Chemical Transport Model

Abstract. We present a method for estimating emissions of long-lived trace gases from a sparse global network of high-frequency observatories, using both a global Eulerian chemical transport model and Lagrangian particle dispersion model. Emissions are derived in a single step after determining sensitivities of the observations to initial conditions, the high-resolution emissions field close to observation points, and larger regions further from the measurements. This method has the several advantages over inversions using one type of model alone, in that: high-resolution simulations can be carried out in limited domains close to the measurement sites, with lower resolution being used further from them; the influence of errors due to aggregation of emissions close to the measurement sites can be minimized; assumptions about boundary conditions to the Lagrangian model do not need to be made, since the entire emissions field is estimated; any combination of appropriate models can be used, with no code modification. Because the sensitivity to the entire emissions field is derived, the estimation can be carried out using traditional statistical methods without the need for multiple steps in the inversion. We demonstrate the utility of this approach by determining global SF6 emissions using measurements from the Advanced Global Atmospheric Gases Experiment (AGAGE) between 2007 and 2009. The global total and large-scale patterns of the derived emissions agree well with previous studies, whilst allowing emissions to be determined at higher resolution than has previously been possible, and improving the agreement between the modeled and observed mole fractions at some sites.

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Vehicle induced turbulence and atmospheric pollution

10.5194/acp-2020-1243 ◽

2021 ◽

Author(s):

Paul A. Makar ◽

Craig Stroud ◽

Ayodeji Akingunola ◽

Junhua Zhang ◽

Shuzhan Ren ◽

...

Keyword(s):

Radiative Transfer ◽

Nitrogen Dioxide ◽

Transport Model ◽

Lower Troposphere ◽

Chemical Transport ◽

Vertical Transport ◽

Anthropogenic Sources ◽

Chemical Transport Model ◽

Human Environment ◽

Mean Square Errors

Abstract. Theoretical models of the Earth's atmosphere adhere to an underlying concept of flow driven by radiative transfer and the nature of the surface over which the flow is taking place: heat from the sun and/or anthropogenic sources are the sole sources of energy driving atmospheric constituent transport. However, another source of energy is prevalent in the human environment at the very local scale – the transfer of kinetic energy from moving vehicles to the atmosphere. We show that this source of energy, due to being co-located with combustion emissions, can influence their vertical distribution to the extent of having a significant influence on lower troposphere pollutant concentrations throughout North America. The effect of vehicle-induced turbulence on freshly emitted chemicals remains notable even when taking into account more complex urban radiative transfer-driven turbulence theories at high resolution. We have designed a parameterization to account for the at-source vertical transport of freshly emitted pollutants from mobile emissions resulting from vehicle-induced turbulence, in analogy to sub-grid-scale parameterizations for plume rise emissions from large stacks. This parameterization allows vehicle-induced turbulence to be represented at the scales inherent 3D chemical transport models, allowing its impact over large regions to be represented, without the need for the computational resources and much higher resolution of large eddy simulation models. Including this sub-grid-scale parameterization for the vertical transport of emitted pollutants due to vehicle-induced turbulence into a 3D chemical transport model of the atmosphere reduces pre-existing North American nitrogen dioxide biases by a factor of eight, and improves most model performance scores for nitrogen dioxide, particulate matter and ozone (for example, reductions in root mean square errors of 20, 9 and 0.5 percent, respectively).

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Modeling lightning-NOx chemistry at sub-grid scale in a global chemical transport model

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-15-34091-2015 ◽

2015 ◽

Vol 15 (23) ◽

pp. 34091-34147 ◽

Cited By ~ 1

Author(s):

A. Gressent ◽

B. Sauvage ◽

D. Cariolle ◽

M. Evans ◽

M. Leriche ◽

...

Keyword(s):

Large Scale ◽

Transport Model ◽

Chemical Transport ◽

Horizontal Resolution ◽

Parameter Estimates ◽

Plume Dispersion ◽

Chemical Transport Model ◽

Tropical Regions ◽

The Impact ◽

Lightning Nox

Abstract. For the first time, a plume-in-grid approach is implemented in a chemical transport model (CTM) to parameterize the effects of the non-linear reactions occurring within high concentrated NOx plumes from lightning NOx emissions (LNOx) in the upper troposphere. It is characterized by a set of parameters including the plume lifetime, the effective reaction rate constant related to NOx-O3 chemical interactions and the fractions of NOx conversion into HNO3 within the plume. Parameter estimates were made using the DSMACC chemical box model, simple plume dispersion simulations and the mesoscale 3-D Meso-NH model. In order to assess the impact of the LNOx plume approach on the NOx and O3 distributions at large scale, simulations for the year 2006 were performed using the GEOS-Chem global model with a horizontal resolution of 2° × 2.5°. The implementation of the LNOx parameterization implies NOx and O3 decrease at large scale over the region characterized by a strong lightning activity (up to 25 and 8 %, respectively, over Central Africa in July) and a relative increase downwind of LNOx emissions (up to 18 and 2 % for NOx and O3, respectively, in July) are derived. The calculated variability of NOx and O3 mixing ratios around the mean value according to the known uncertainties on the parameter estimates is maximum over continental tropical regions with ΔNOx [−33.1; +29.7] ppt and ΔO3 [−1.56; +2.16] ppb, in January, and ΔNOx [−14.3; +21] ppt and ΔO3 [−1.18; +1.93] ppb, in July, mainly depending on the determination of the diffusion properties of the atmosphere and the initial NO mixing ratio injected by lightning. This approach allows (i) to reproduce a more realistic lightning NOx chemistry leading to better NOx and O3 distributions at the large scale and (ii) focus on other improvements to reduce remaining uncertainties from processes related to NOx chemistry in CTM.

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Methanol from TES global observations: retrieval algorithm and seasonal and spatial variability

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-12-11823-2012 ◽

2012 ◽

Vol 12 (5) ◽

pp. 11823-11859 ◽

Cited By ~ 1

Author(s):

K. E. Cady-Pereira ◽

M. W. Shephard ◽

D. B. Millet ◽

M. Luo ◽

K. C. Wells ◽

...

Keyword(s):

Large Scale ◽

Transport Model ◽

A Priori ◽

Lower Troposphere ◽

Initial Guess ◽

Retrieval Algorithm ◽

Atmospheric Conditions ◽

Chemical Transport Model ◽

Model Retrieval ◽

Peak Sensitivity

Abstract. We present a detailed description of the TES methanol (CH3OH) retrieval algorithm, along with initial global results showing the seasonal and spatial distribution of methanol in the lower troposphere. The full development of the TES methanol retrieval is described, including microwindow selection, error analysis, and the utilization of a priori and initial guess information provided by the GEOS-Chem chemical transport model. Retrieval simulations and a sensitivity analysis using the developed retrieval strategy show that TES: (i) generally provides between 0.5 and 1.0 pieces of information, (ii) is sensitive in the lower troposphere with peak sensitivity typically occurring between ~900–700 hPa (~1–3 km) at a vertical resolution of ~5 km, (iii) has a limit of detectability between 0.5 and 1.0 ppbv Representative Volume Mixing Ratio (RVMR) depending on the atmospheric conditions, corresponding roughly to a profile with a maximum concentration of at least 1 to 2 ppbv, and (iv) in a simulation environment has a mean bias of 0.16 ppbv and a standard deviation of 0.34 ppbv. Applying the newly-derived TES retrieval globally and comparing the results with corresponding GEOS-Chem output, we find generally consistent large-scale patterns between the two. However, TES often reveals higher methanol concentrations than predicted in the Northern Hemisphere spring, summer and fall. In the Southern Hemisphere, the TES methanol observations indicate a model overestimate over the bulk of South America from December through July, and a model underestimate during the biomass burning season.

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The chemical transport model Oslo CTM3

Geoscientific Model Development Discussions ◽

10.5194/gmdd-5-1561-2012 ◽

2012 ◽

Vol 5 (2) ◽

pp. 1561-1626 ◽

Cited By ~ 1

Author(s):

O. A. Søvde ◽

M. J. Prather ◽

I. S. A. Isaksen ◽

T. K. Berntsen ◽

F. Stordal ◽

...

Keyword(s):

Large Scale ◽

Transport Model ◽

Chemical Transport ◽

Horizontal Distribution ◽

Chemical Transport Model ◽

Polar Cap ◽

Time Step ◽

Transport Time ◽

Photolysis Rates ◽

Vertical Distributions

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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Simulation of radon-222 with the GEOS-Chem global model: emissions, seasonality, and convective transport