Global simulation of tropospheric chemistry at 12.5 km resolution: performance and evaluation of the GEOS-Chem chemical module (v10-1) within the NASA GEOS Earth system  model (GEOS-5 ESM)

Hu, Li; Keller, Christoph A.; Long, M. S.; Sherwen, Tomás; Auer, Benjamin M.; Silva, Arlindo da; Nielsen, J. E.; Pawson, Steven; Thompson, Matthew A.; Trayanov, Atanas; Travis, Katherine R.; Grange, Stuart K.; Evans, M. J.; Jacob, Daniel J.

doi:10.5194/gmd-11-4603-2018

Cited by 81 publications

(98 citation statements)

References 68 publications

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“…earth system models with online coupled meteorology (e.g., (Hu et al, 2018;Long et al, 2015)). Further work is needed to specifically assess model treatment of PBL-FT coupling (e.g., using PAN:NOx or other diagnostic quantities) and PBL depths to improve tracer simulations in the FT.…”

Section: Discussionmentioning

confidence: 99%

On the sources and sinks of atmospheric VOCs: An integrated analysis of recent aircraft campaigns over North America

Chen¹,

Millet²,

Singh³

et al. 2019

Preprint

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Abstract. We apply a high-resolution chemical transport model (GEOS-Chem CTM) with updated treatment of volatile organic compounds (VOCs) and a comprehensive suite of airborne datasets over North America to i) characterize the VOC budget, and ii) test the ability of current models to capture the distribution and reactivity of atmospheric VOCs, over this region. Biogenic emissions dominate the North American VOC budget in the model, accounting for 70&#8201;% and 95&#8201;% of annually emitted VOC-carbon and reactivity, respectively. Based on current inventories anthropogenic emissions have declined to the point where biogenic emissions are the dominant summertime source of VOC reactivity even in most major North American cities. Methane oxidation is a 2&#215; larger source of non-methane VOCs (via production of formaldehyde and methyl hydroperoxide) over North America in the model than are anthropogenic emissions. However, anthropogenic VOCs account for over half the ambient VOC loading over the majority of the region owing to their longer aggregate lifetime. Fires can be a significant VOC source episodically but are small on average. In the planetary boundary layer (PBL), the model exhibits skill in capturing observed variability in total VOC-abundance (R2&#8201;=&#8201;0.36) and reactivity (R2&#8201;=&#8201;0.54). The same is not true in the free troposphere (FT), where skill is low and there is a persistent low model bias (~&#8201;60&#8201;%), with most (27 of 34) model VOCs underestimated by more than a factor of 2. A comparison of PBL&#8201;:&#8201;FT concentration ratios over the southeastern US points to a misrepresentation of PBL ventilation as a contributor to these model FT biases. We also find that a relatively small number of VOCs (acetone, methanol, ethane, acetaldehyde, formaldehyde, isoprene&#8201;+&#8201;oxidation products, methyl hydroperoxide) drive a large fraction of total ambient VOC reactivity and associated model biases; research to improve understanding of their budgets is thus warranted. A source tracer analysis suggests a current overestimate of biogenic sources for hydroxyacetone, methyl ethyl ketone and glyoxal, an underestimate of biogenic formic acid sources, and an underestimate of peroxyacetic acid production across biogenic and anthropogenic precursors. Future work to improve model representations of vertical transport and to address the VOC biases discussed are needed to advance predictions of ozone and SOA formation.

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Section: Discussionmentioning

confidence: 99%

On the sources and sinks of atmospheric VOCs: An integrated analysis of recent aircraft campaigns over North America

Chen¹,

Millet²,

Singh³

et al. 2019

Preprint

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“…Biogenic VOC emissions from terrestrial plants are calculated online in GEOS-Chem using the Model of Emissions of Gases and Aerosols from Nature version 2.1 (MEGAN v2.1), implemented into GEOS-Chem as described by . NO x emissions from microbial processes in soils are estimated as described in Hudman et al (2012). The annual combined global flux of formic and acetic acids from soils estimated previously by Paulot et al (2011) corresponds to approximately 10 % of this NO x source, and we therefore prescribe the formic acid and acetic acid soil fluxes as 5 % (each) of the Hudman et al (2012) molar NO x flux.…”

Section: Natural Emissionsmentioning

confidence: 99%

On the sources and sinks of atmospheric VOCs: an integrated analysis of recent aircraft campaigns over North America

et al. 2019

View full text Add to dashboard Cite

Abstract. We apply a high-resolution chemical transport model (GEOS-Chem CTM) with updated treatment of volatile organic compounds (VOCs) and a comprehensive suite of airborne datasets over North America to (i) characterize the VOC budget and (ii) test the ability of current models to capture the distribution and reactivity of atmospheric VOCs over this region. Biogenic emissions dominate the North American VOC budget in the model, accounting for 70 % and 95 % of annually emitted VOC carbon and reactivity, respectively. Based on current inventories anthropogenic emissions have declined to the point where biogenic emissions are the dominant summertime source of VOC reactivity even in most major North American cities. Methane oxidation is a 2× larger source of nonmethane VOCs (via production of formaldehyde and methyl hydroperoxide) over North America in the model than are anthropogenic emissions. However, anthropogenic VOCs account for over half of the ambient VOC loading over the majority of the region owing to their longer aggregate lifetime. Fires can be a significant VOC source episodically but are small on average. In the planetary boundary layer (PBL), the model exhibits skill in capturing observed variability in total VOC abundance (R2=0.36) and reactivity (R2=0.54). The same is not true in the free troposphere (FT), where skill is low and there is a persistent low model bias (∼ 60 %), with most (27 of 34) model VOCs underestimated by more than a factor of 2. A comparison of PBL : FT concentration ratios over the southeastern US points to a misrepresentation of PBL ventilation as a contributor to these model FT biases. We also find that a relatively small number of VOCs (acetone, methanol, ethane, acetaldehyde, formaldehyde, isoprene + oxidation products, methyl hydroperoxide) drive a large fraction of total ambient VOC reactivity and associated model biases; research to improve understanding of their budgets is thus warranted. A source tracer analysis suggests a current overestimate of biogenic sources for hydroxyacetone, methyl ethyl ketone and glyoxal, an underestimate of biogenic formic acid sources, and an underestimate of peroxyacetic acid production across biogenic and anthropogenic precursors. Future work to improve model representations of vertical transport and to address the VOC biases discussed are needed to advance predictions of ozone and SOA formation.

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“…Overestimation of oxidant levels could also result in excessive sulfate formation in the model. Indeed, previous studies suggest that the GEOS-Chem model tends to overestimate OH and H 2 O 2 compared to surface-based proxy measurements and satellite observations (Allen et al, 2013;Hu et al, 2018;Prinn et al, 2005).…”

Section: Discussionmentioning

confidence: 99%

Evaluating the Response of Summertime Surface Sulfate to Hydroclimate Variations in the Continental United States: Role of Meteorological Inputs in the GEOS‐Chem Model

et al. 2019

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Understanding the response of sulfate to climate change is crucial given tight couplings between sulfate and the hydrological cycle. As the sources and sinks of sulfate are sensitive to cloud and precipitation processes, the accuracy of model simulations depends on the accuracy of these meteorological inputs. In this study, we evaluate the GEOS‐Chem model in simulating summertime surface sulfate concentrations in the continental United States across different levels of dryness and compare the model performance based on two sets of meteorological fields: Modern Era Retrospective Analysis for Research and Applications (MERRA) and MERRA‐2. Both simulations fail to reproduce observed increases in sulfate during drought, as indicated by negative correlation slopes between surface sulfate concentrations and the standardized precipitation evapotranspiration index (SPEI). This deficiency can be largely attributed to too large a decrease in clouds and hence aqueous phase sulfate production as conditions shift from wet to dry. MERRA‐2‐driven GEOS‐Chem (M2GC) shows improvements in cloud and precipitation fields relative to the MERRA‐driven GEOS‐Chem, hence eliminating approximately half of the bias in the simulated sulfate‐SPEI slope. However, M2GC still underestimates boundary layer cloud fraction, overestimates liquid water content, and overestimates the rates of the decrease in both quantities as conditions become drier. Explicitly correcting these cloud biases in M2GC results in a 60–80% reduction of the bias in the simulated sulfate‐SPEI slope. The strong sensitivity of simulated sulfate to prescribed cloud fields suggests the need for more comprehensive assessment of cloud inputs for sulfate simulations under current and future climate change scenarios.

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Global simulation of tropospheric chemistry at 12.5 km resolution: performance and evaluation of the GEOS-Chem chemical module (v10-1) within the NASA GEOS Earth system model (GEOS-5 ESM)

Cited by 81 publications

References 68 publications

On the sources and sinks of atmospheric VOCs: An integrated analysis of recent aircraft campaigns over North America

On the sources and sinks of atmospheric VOCs: An integrated analysis of recent aircraft campaigns over North America

On the sources and sinks of atmospheric VOCs: an integrated analysis of recent aircraft campaigns over North America

Evaluating the Response of Summertime Surface Sulfate to Hydroclimate Variations in the Continental United States: Role of Meteorological Inputs in the GEOS‐Chem Model

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