Impacts of boundary layer mixing on pollutant vertical profiles in the lower troposphere: Implications to satellite remote sensing

Lin, Jintai; Chen, Xinyu

doi:10.1016/j.atmosenv.2010.02.009

Cited by 265 publications

(244 citation statements)

References 58 publications

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“…Schmidt et al (2016) simulated tropospheric BrO concentrations (global daytime mean of 0.96 ppt) with observations from satellite and aircraft and found no systematic bias. GEOS-Chem concentrations of NO 2 and H 2 O 2 (proxy for HO 2 ) have been evaluated successfully in a number of aircraft campaigns (Martin et al, 2006;Hudman et al, 2007;Singh et al, 2007;Lin and McElroy, 2010;Mao et al, 2010;Travis et al, 2016). GEOS-Chem NO 2 columns have also been evaluated against satellite observations over China (Lin et al, 2012), North America (e.g., Lamsal et al, 2014), and Africa (Marais et al, 2012).…”

Section: Atmospheric Chemistrymentioning

confidence: 99%

A new mechanism for atmospheric mercury redox chemistry: implications for the global mercury budget

et al. 2017

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Abstract. Mercury (Hg) is emitted to the atmosphere mainly as volatile elemental Hg 0 . Oxidation to water-soluble Hg II plays a major role in Hg deposition to ecosystems. Here, we implement a new mechanism for atmospheric Hg 0 / Hg II redox chemistry in the GEOS-Chem global model and examine the implications for the global atmospheric Hg budget and deposition patterns. Our simulation includes a new coupling of GEOS-Chem to an ocean general circulation model (MITgcm), enabling a global 3-D representation of atmosphereocean Hg 0 / Hg II cycling. We find that atomic bromine (Br) of marine organobromine origin is the main atmospheric Hg 0 oxidant and that second-stage HgBr oxidation is mainly by the NO 2 and HO 2 radicals. The resulting chemical lifetime of tropospheric Hg 0 against oxidation is 2.7 months, shorter than in previous models. Fast Hg II atmospheric reduction must occur in order to match the ∼ 6-month lifetime of Hg against deposition implied by the observed atmospheric variability of total gaseous mercury (TGM ≡ Hg 0 + Hg II (g)). We implement this reduction in GEOS-Chem as photolysis of aqueous-phase Hg II -organic complexes in aerosols and clouds, resulting in a TGM lifetime of 5.2 months against deposition and matching both mean observed TGM and its variability. Model sensitivity analysis shows that the interhemispheric gradient of TGM, previously used to infer a longer Hg lifetime against deposition, is misleading because Southern Hemisphere Hg mainly originates from oceanic emissions rather than transport from the Northern Hemisphere.The model reproduces the observed seasonal TGM variation at northern midlatitudes (maximum in February, minimum in September) driven by chemistry and oceanic evasion, but it does not reproduce the lack of seasonality observed at southern hemispheric marine sites. Aircraft observations in the lowermost stratosphere show a strong TGM-ozone relationship indicative of fast Hg 0 oxidation, but we show that this relationship provides only a weak test of Hg chemistry because it is also influenced by mixing. The model reproduces observed Hg wet deposition fluxes over North America, Europe, and China with little bias (0-30 %). It reproduces qualitatively the observed maximum in US deposition around the Gulf of Mexico, reflecting a combination of deep convection and availability of NO 2 and HO 2 radicals for second-stage HgBr oxidation. However, the magnitude of this maximum is underestimated. The relatively low observed Hg wet deposition over rural China is attributed to fast Hg II reduction in the presence of high organic aerosol concentrations. We find that 80 % of Hg II deposition is to the global oceans, reflecting the marine origin of Br and low concentrations of organic aerosols for Hg II reduction. Most of that deposition takes place to the tropical oceans due to the availability of HO 2 and NO 2 for second-stage HgBr oxidation.

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Section: Atmospheric Chemistrymentioning

confidence: 99%

A new mechanism for atmospheric mercury redox chemistry: implications for the global mercury budget

et al. 2017

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“…Shallow and deep moist convection processes are carried out using the relaxed Arakawa-Schubert scheme (Moorthi and Suarez, 1991). Mixing in the lower atmospheric layers is represented by a nonlocal scheme of the planetary boundary layer described by Lin and McElroy (2010). The wet deposition for water-soluble aerosols and for gases follows Liu et al (2001) and Amos et al (2012).…”

Section: A Gressent Et Al: Modeling Lightning-no X Chemistry On a Smentioning

confidence: 99%

Modeling lightning-NO<sub><i>x</i></sub> chemistry on a sub-grid scale in a global chemical transport model

et al. 2016

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Abstract. For the first time, a plume-in-grid approach is implemented in a chemical transport model (CTM) to parameterize the effects of the nonlinear reactions occurring within high concentrated NO x plumes from lightning NO x emissions (LNO x ) in the upper troposphere. It is characterized by a set of parameters including the plume lifetime, the effective reaction rate constant related to NO x -O 3 chemical interactions, and the fractions of NO x conversion into HNO 3 within the plume. Parameter estimates were made using the Dynamical Simple Model of Atmospheric Chemical Complexity (DSMACC) box model, simple plume dispersion simulations, and the 3-D Meso-NH (non-hydrostatic mesoscale atmospheric model). In order to assess the impact of the LNO x plume approach on the NO x and O 3 distributions on a 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 LNO x parameterization implies an NO x and O 3 decrease on a 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 LNO x emissions (up to 18 and 2 % for NO x and O 3 , respectively, in July). The calculated variability in NO x and O 3 mixing ratios around the mean value according to the known uncertainties in the parameter estimates is at a maximum over continental tropical regions with NO [−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 us (i) to reproduce a more realistic lightning NO x chemistry leading to better NO x and O 3 distributions on the large scale and (ii) to focus on other improvements to reduce remaining uncertainties from processes related to NO x chemistry in CTM.

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“…This bias causes GEOS-5 driven GEOS-Chem simulations to predict an artificially large build up of aerosols at night and corresponding high biases in predicted daily and monthly average concentrations. To correct this issue, we have modified the model to define a minimum mechanical mixing depth, calculated based on the local friction velocity (Lin and McElroy, 2010;Koracin and Berkowicz, 1988;Heald et al, 2012); any GEOS-5 mixed layer depths below this value are set to the minimum mechanical mixing depth. This modification yields nighttime mixed layer depths that are more consistent with observations (Liu and Liang, 2010), and more realistic diurnal variations in predicted aerosol concentrations.…”

Section: Geos-chem Modelmentioning

confidence: 99%

Simulation of nitrate, sulfate, and ammonium aerosols over the United States

et al. 2012

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Abstract. Atmospheric concentrations of inorganic gases and aerosols (nitrate, sulfate, and ammonium) are simulated for 2009 over the United States using the chemical transport model GEOS-Chem. Predicted aerosol concentrations are compared with surface-level measurement data from the Interagency Monitoring of Protected Visual Environments (IMPROVE), the Clean Air Status and Trends Network (CASTNET), and the California Air Resources Board (CARB). Sulfate predictions nationwide are in reasonably good agreement with observations, while nitrate and ammonium are over-predicted in the East and Midwest, but underpredicted in California, where observed concentrations are the highest in the country. Over-prediction of nitrate in the East and Midwest is consistent with results of recent studies, which suggest that nighttime nitric acid formation by heterogeneous hydrolysis of N 2 O 5 is over-predicted based on current values of the N 2 O 5 uptake coefficient, γ , onto aerosols. After reducing the value of γ by a factor of 10, predicted nitrate levels in the US Midwest and East still remain higher than those measured, and over-prediction of nitrate in this region remains unexplained. Comparison of model predictions with satellite measurements of ammonia from the Tropospheric Emissions Spectrometer (TES) indicates that ammonia emissions in GEOS-Chem are underestimated in California and that the nationwide seasonality applied to ammonia emissions in GEOS-Chem does not represent California very well, particularly underestimating winter emissions. An ammonia sensitivity study indicates that GEOS-Chem simulation of nitrate is ammonia-limited in southern California and much of the state, suggesting that an underestimate of ammonia emissions is likely the main cause for the underprediction of nitrate aerosol in many areas of California. An approximate doubling of ammonia emissions is needed to reproduce observed nitrate concentrations in southern California and in other ammonia sensitive areas of California. However, even a tenfold increase in ammonia emissions yields predicted nitrate concentrations that are still biased low in the central valley of California. The under-prediction of nitrate aerosol in the central valley of California may arise in part from an under-prediction of both ammonia and nitric acid in this region. Since nitrate aerosols are particularly sensitive to mixed layer depths, owing to the gas-particle equilibrium, the nitrate under-prediction could also arise in part from a potential regional overestimate of GEOS-5 mixed layer depths in the central valley due to unresolved topography in this region.

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Impacts of boundary layer mixing on pollutant vertical profiles in the lower troposphere: Implications to satellite remote sensing

Cited by 265 publications

References 58 publications

A new mechanism for atmospheric mercury redox chemistry: implications for the global mercury budget

A new mechanism for atmospheric mercury redox chemistry: implications for the global mercury budget

Modeling lightning-NO<sub><i>x</i></sub> chemistry on a sub-grid scale in a global chemical transport model

Simulation of nitrate, sulfate, and ammonium aerosols over the United States

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Impacts of boundary layer mixing on pollutant vertical profiles in the lower troposphere: Implications to satellite remote sensing

Cited by 265 publications

References 58 publications

A new mechanism for atmospheric mercury redox chemistry: implications for the global mercury budget

A new mechanism for atmospheric mercury redox chemistry: implications for the global mercury budget

Modeling lightning-NO&lt;sub&gt;&lt;i&gt;x&lt;/i&gt;&lt;/sub&gt; chemistry on a sub-grid scale in a global chemical transport model

Simulation of nitrate, sulfate, and ammonium aerosols over the United States

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Modeling lightning-NO<sub><i>x</i></sub> chemistry on a sub-grid scale in a global chemical transport model