Jingqiu Mao

University of Alaska Fairbanks

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Co-Authors

W. H. Brune

Pennsylvania State University

R. C. Cohen

Planetary Science Institute

Xinrong Ren

University of Maryland, College Park

Larry W. Horowitz

NOAA Geophysical Fluid Dynamics Laboratory

Glenn M. Wolfe

University of Maryland, Baltimore County

J. D. Crounse

California Institute of Technology

Joel A. Thornton

University of Washington

P. O. Wennberg

California Institute of Technology

J. L. Jiménez

Cooperative Institute for Research in Environmental Sciences

William R. Simpson

University of Alaska Fairbanks

Cooperative Institutions

University of Colorado Boulder

135

Cooperative Institute for Research in Environmental Sciences

110

National Oceanic and Atmospheric Administration

NOAA Earth System Research Laboratory

NSF National Center for Atmospheric Research

Centre National de la Recherche Scientifique

California Institute of Technology

University of California, Berkeley

Georgia Institute of Technology

Harvard University

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HO_x chemistry during INTEX‐A 2004: Observation, model calculation, and comparison with previous studies

Journal of Geophysical Research Atmospheres (2008)

Xinrong Ren J. R. Olson J. H. Crawford W. H. Brune Jingqiu Mao

OH and HO 2 were measured with the Airborne Tropospheric Hydrogen Oxides Sensor (ATHOS) as part of a large measurement suite from the NASA DC‐8 aircraft during the Intercontinental Chemical Transport Experiment‐A (INTEX‐A). This mission, which was conducted mainly over North America and the western Atlantic Ocean in summer 2004, was an excellent test of atmospheric oxidation chemistry. The HOx results from INTEX‐A are compared to those from previous campaigns and to results for other related measurements from INTEX‐A. Throughout the troposphere, observed OH was generally 0.95 of modeled OH; below 8 km, observed HO 2 was generally 1.20 of modeled HO 2 . This observed‐to‐modeled comparison is similar to that for TRACE‐P, another midlatitude study for which the median observed‐to‐modeled ratio was 1.08 for OH and 1.34 for HO 2 , and to that for PEM‐TB, a tropical study for which the median observed‐to‐modeled ratio was 1.17 for OH and 0.97 for HO 2 . HO 2 behavior above 8 km was markedly different. The observed‐to‐modeled HO 2 ratio increased from ∼1.2 at 8 km to ∼3 at 11 km with the observed‐to‐modeled ratio correlating with NO. Above 8 km, the observed‐to‐modeled HO 2 and observed NO were both considerably greater than observations from previous campaigns. In addition, the observed‐to‐modeled HO 2 /OH, which is sensitive to cycling reactions between OH and HO 2 , increased from ∼1.5 at 8 km to almost 3.5 at 11 km. These discrepancies suggest a large unknown HO x source and additional reactants that cycle HO x from OH to HO 2 . In the continental planetary boundary layer, the observed‐to‐modeled OH ratio increased from 1 when isoprene was less than 0.1 ppbv to over 4 when isoprene was greater than 2 ppbv, suggesting that forests throughout the United States are emitting unknown HO x sources. Progress in resolving these discrepancies requires a focused research activity devoted to further examination of possible unknown OH sinks and HO x sources.

Atmospheric chemistry

Middle latitudes

10.1029/2007jd009166

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Citations (220)

Global and regional effects of the photochemistry of CH3O2NO2: evidence from ARCTAS

Atmospheric chemistry and physics (2011)

E. C. Browne A. E. Perring P. J. Wooldridge E. C. Apel Samuel R. Hall

Abstract. Using measurements from the NASA Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) experiment, we show that methyl peroxy nitrate (CH3O2NO2) is present in concentrations of ~5–15 pptv in the springtime arctic upper troposphere. We investigate the regional and global effects of CH3O2NO2 by including its chemistry in the GEOS-Chem 3-D global chemical transport model. We find that at temperatures below 240 K inclusion of CH3O2NO2 chemistry results in decreases of up to ~20 % in NOx, ~20 % in N2O5, ~5 % in HNO3, ~2 % in ozone, and increases in methyl hydrogen peroxide of up to ~14 %. Larger changes are observed in biomass burning plumes lofted to high altitude. Additionally, by sequestering NOx at low temperatures, CH3O2NO2 decreases the cycling of HO2 to OH, resulting in a larger upper tropospheric HO2 to OH ratio. These results may impact some estimates of lightning NOx sources as well as help explain differences between models and measurements of upper tropospheric composition.

Atmospheric chemistry

Atmospheric Composition

Tropospheric ozone

10.5194/acp-11-4209-2011

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Citations (73)

Brownness of Organic Aerosol over the United States: Evidence for Seasonal Biomass Burning and Photobleaching Effects

Environmental Science & Technology (2021)

L.‐W. Antony Chen Judith C. Chow Xiaoliang Wang Junji Cao Jingqiu Mao

Light-absorptivity of organic aerosol may play an important role in visibility and climate forcing, but it has not been assessed as extensively as black carbon (BC) aerosol. Based on multiwavelength thermal/optical analysis and spectral mass balance, this study quantifies BC for the U.S. Interagency Monitoring of Protected Visual Environments (IMPROVE) network while developing a brownness index (γBr) for non-BC organic carbon (OC*) to illustrate the spatiotemporal trends of light-absorbing brown carbon (BrC) content. OC* light absorption efficiencies range from 0 to 3.1 m2 gC-1 at 405 nm, corresponding to the lowest and highest BrC content of 0 and 100%, respectively. BC, OC*, and γBr explain >97% of the variability of measured spectral light absorption (405-980 nm) across 158 IMPROVE sites. Network-average OC* light absorptions at 405 nm are 50 and 28% those for BC over rural and urban areas, respectively. Larger organic fractions of light absorption occur in winter, partially due to higher organic brownness. Winter γBr exhibits a dramatic regional/urban-rural contrast consistent with anthropogenic BrC emissions from residential wood combustion. The spatial differences diminish to uniformly low γBr in summer, suggesting effective BrC photobleaching over the midlatitudes. An empirical relationship between BC, ambient temperature, and γBr is established, which can facilitate the incorporation of organic aerosol absorptivity into climate and visibility models that currently assume either zero or static organic light absorption efficiencies.

Molar absorptivity

Photobleaching

10.1021/acs.est.0c08706

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Citations (50)

Global Atmospheric Chemistry – Which Air Matters

Michael J. Prather Zhu Xin Clare M. Flynn Sarah A. Strode José María Álvarez Rodríguez

Abstract. An approach for analysis and modeling of global atmospheric chemistry is developed for application to measurements that provide a tropospheric climatology of those heterogeneously distributed, reactive species that control the loss of methane and the production and loss of ozone. We identify key species (e.g., O3, NOx, HNO3, HNO4, C2H3NO5, H2O, HOOH, CH3OOH, HCHO, CO, CH4, C2H6, acetaldehyde, acetone), and presume that they can be measured simultaneously in air parcels on the scale of a few km horizontally and a few tenths vertically. Six global models have prepared such climatologies (at model resolution) for August with emphasis on the vast central Pacific and Atlantic Ocean basins. We show clear differences in model generated reactivities as well as species covariances that could readily be discriminated with an unbiased climatology. A primary tool is comparison of multi-dimensional probability densities of key species weighted by frequency of occurrence as well as by the reactivity of the parcels with respect to methane and ozone. The reactivity-weighted probabilities tell us which parcels matter in this case. Testing 100-km scale models with 2-km measurements using these tools also addresses a core question about model resolution and whether fine-scale atmospheric structures matter to the overall ozone and methane budget. A new method enabling these six global chemistry-climate models to ingest an externally-sourced climatology and then compute air parcel reactivity is demonstrated. Such an observed climatology is anticipated from the NASA Atmospheric Tomography (ATom) aircraft mission (2015–2020), measuring the key species, executing profiles over the Pacific and Atlantic Ocean basins. This work is a core part of the design of ATom.

Atmospheric chemistry

Tropospheric ozone

Atmospheric models

10.5194/acp-2016-1105

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Anthropogenic amplification of biogenic secondary organic aerosol production

Yiqi Zheng Larry W. Horowitz Raymond Menzel David Paynter Vaishali Naïk

Abstract. Biogenic secondary organic aerosols (SOA) contribute to a large fraction of fine aerosols globally, impacting air quality and climate. The formation of biogenic SOA depends on not only emissions of biogenic volatile organic compounds (BVOCs) but also anthropogenic pollutants including primary organic aerosol, sulfur dioxide (SO2), and nitrogen oxides (NOx). However, the anthropogenic impact on biogenic SOA production (AIBS) remains unclear. Here we use the decadal trend and variability of observed OA in the southeast US, combined with a global chemistry-climate model, to better constrain AIBS. We show that the reduction in SO2 emissions can only explain 40 % of the decreasing decadal trend of OA in this region, constrained by the low summertime month-to-month variability of surface OA. We hypothesize that the rest of OA decreasing trend is largely due to reduction in NOx emissions. By implementing a scheme for monoterpene SOA with enhanced sensitivity to NOx, our model can reproduce the decadal trend and variability of OA in this region. Extending to centennial scale, our model shows that global SOA production increases by 36 % despite BVOC reductions from preindustrial period to present day, largely amplified by AIBS. Our work suggests a strong coupling between anthropogenic and biogenic emissions in biogenic SOA production that is missing from current climate models.

Isoprene

10.5194/egusphere-2023-372

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Citations (1)

Comment on egusphere-2023-372

Yiqi Zheng Larry W. Horowitz Raymond Menzel David Paynter Vaishali Naïk

Abstract. Biogenic secondary organic aerosols (SOA) contribute to a large fraction of fine aerosols globally, impacting air quality and climate. The formation of biogenic SOA depends on not only emissions of biogenic volatile organic compounds (BVOCs) but also anthropogenic pollutants including primary organic aerosol, sulfur dioxide (SO₂), and nitrogen oxides (NO_x). However, the anthropogenic impact on biogenic SOA production (AIBS) remains unclear. Here we use the decadal trend and variability of observed OA in the southeast US, combined with a global chemistry-climate model, to better constrain AIBS. We show that the reduction in SO₂ emissions can only explain 40 % of the decreasing decadal trend of OA in this region, constrained by the low summertime month-to-month variability of surface OA. We hypothesize that the rest of OA decreasing trend is largely due to reduction in NO_x emissions. By implementing a scheme for monoterpene SOA with enhanced sensitivity to NO_x, our model can reproduce the decadal trend and variability of OA in this region. Extending to centennial scale, our model shows that global SOA production increases by 36 % despite BVOC reductions from preindustrial period to present day, largely amplified by AIBS. Our work suggests a strong coupling between anthropogenic and biogenic emissions in biogenic SOA production that is missing from current climate models.

Isoprene

Centennial

10.5194/egusphere-2023-372-rc1

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Citations (0)

Global atmospheric model for mercury including oxidation by bromine atoms

Atmospheric chemistry and physics (2010)

Christopher D. Holmes Daniel Jacob Elizabeth S. Corbitt Jingqiu Mao Xin Yang

Abstract. Global models of atmospheric mercury generally assume that gas-phase OH and ozone are the main oxidants converting Hg0 to HgII and thus driving mercury deposition to ecosystems. However, thermodynamic considerations argue against the importance of these reactions. We demonstrate here the viability of atomic bromine (Br) as an alternative Hg0 oxidant. We conduct a global 3-D simulation with the GEOS-Chem model assuming gas-phase Br to be the sole Hg0 oxidant (Hg + Br model) and compare to the previous version of the model with OH and ozone as the sole oxidants (Hg + OH/O3 model). We specify global 3-D Br concentration fields based on our best understanding of tropospheric and stratospheric Br chemistry. In both the Hg + Br and Hg + OH/O3 models, we add an aqueous photochemical reduction of HgII in cloud to impose a tropospheric lifetime for mercury of 6.5 months against deposition, as needed to reconcile observed total gaseous mercury (TGM) concentrations with current estimates of anthropogenic emissions. This added reduction would not be necessary in the Hg + Br model if we adjusted the Br oxidation kinetics downward within their range of uncertainty. We find that the Hg + Br and Hg + OH/O3 models are equally capable of reproducing the spatial distribution of TGM and its seasonal cycle at northern mid-latitudes. The Hg + Br model shows a steeper decline of TGM concentrations from the tropics to southern mid-latitudes. Only the Hg + Br model can reproduce the springtime depletion and summer rebound of TGM observed at polar sites; the snowpack component of GEOS-Chem suggests that 40% of HgII deposited to snow in the Arctic is transferred to the ocean and land reservoirs, amounting to a net deposition flux to the Arctic of 60 Mg a−1. Summertime events of depleted Hg0 at Antarctic sites due to subsidence are much better simulated by the Hg + Br model. Model comparisons to observed wet deposition fluxes of mercury in the US and Europe show general consistency. However the Hg + Br model does not capture the summer maximum over the southeast US because of low subtropical Br concentrations while the Hg + OH/O3 model does. Vertical profiles measured from aircraft show a decline of Hg0 above the tropopause that can be captured by both the Hg + Br and Hg + OH/O3 models, except in Arctic spring where the observed decline is much steeper than simulated by either model; we speculate that oxidation by Cl species might be responsible. The Hg + Br and Hg + OH/O3 models yield similar global budgets for the cycling of mercury between the atmosphere and surface reservoirs, but the Hg + Br model results in a much larger fraction of mercury deposited to the Southern Hemisphere oceans.

Mercury

Ozone Depletion

Atmospheric chemistry

Tropospheric ozone

10.5194/acp-10-12037-2010

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Citations (480)

Observational constraints on ambient brown carbon with IMPROVE network observations

AGUFM (2019)

Jingqiu Mao Nicole A. June X. Wang L. W. A. Chen Judith C. Chow

Source

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Citations (0)

Sensitivity of nitrate aerosols to ammonia emissions and to nitrate chemistry: implications for present and future nitrate optical depth

Atmospheric chemistry and physics (2016)

Fabien Paulot Paul Ginoux William Cooke Leo J. Donner Songmiao Fan

Abstract. We update and evaluate the treatment of nitrate aerosols in the Geophysical Fluid Dynamics Laboratory (GFDL) atmospheric model (AM3). Accounting for the radiative effects of nitrate aerosols generally improves the simulated aerosol optical depth, although nitrate concentrations at the surface are biased high. This bias can be reduced by increasing the deposition of nitrate to account for the near-surface volatilization of ammonium nitrate or by neglecting the heterogeneous production of nitric acid to account for the inhibition of N2O5 reactive uptake at high nitrate concentrations. Globally, uncertainties in these processes can impact the simulated nitrate optical depth by up to 25 %, much more than the impact of uncertainties in the seasonality of ammonia emissions (6 %) or in the uptake of nitric acid on dust (13 %). Our best estimate for fine nitrate optical depth at 550 nm in 2010 is 0.006 (0.005–0.008). In wintertime, nitrate aerosols are simulated to account for over 30 % of the aerosol optical depth over western Europe and North America. Simulated nitrate optical depth increases by less than 30 % (0.0061–0.010) in response to projected changes in anthropogenic emissions from 2010 to 2050 (e.g., −40 % for SO2 and +38 % for ammonia). This increase is primarily driven by greater concentrations of nitrate in the free troposphere, while surface nitrate concentrations decrease in the midlatitudes following lower concentrations of nitric acid. With the projected increase of ammonia emissions, we show that better constraints on the vertical distribution of ammonia (e.g., convective transport and biomass burning injection) and on the sources and sinks of nitric acid (e.g., heterogeneous reaction on dust) are needed to improve estimates of future nitrate optical depth.

Nitric acid

Deposition

Ammonium nitrate

Reactive nitrogen

10.5194/acp-16-1459-2016

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Citations (105)

Ozone and organic nitrates over the eastern United States: Sensitivity to isoprene chemistry

Journal of Geophysical Research Atmospheres (2013)

Jingqiu Mao Fabien Paulot Daniel J. Jacob R. C. Cohen J. D. Crounse

Abstract We implement a new isoprene oxidation mechanism in a global 3‐D chemical transport model (GEOS‐Chem). Model results are evaluated with observations for ozone, isoprene oxidation products, and related species from the International Consortium for Atmospheric Research on Transport and Transformation aircraft campaign over the eastern United States in summer 2004. The model achieves an unbiased simulation of ozone in the boundary layer and the free troposphere, reflecting canceling effects from recent model updates for isoprene chemistry, bromine chemistry, and HO 2 loss to aerosols. Simulation of the ozone‐CO correlation is improved relative to previous versions of the model, and this is attributed to a lower and reversible yield of isoprene nitrates, increasing the ozone production efficiency per unit of nitrogen oxides (NO x ≡ NO + NO 2 ). The model successfully reproduces the observed concentrations of organic nitrates (∑ANs) and their correlations with HCHO and ozone. ∑ANs in the model is principally composed of secondary isoprene nitrates, including a major contribution from nighttime isoprene oxidation. The correlations of ∑ANs with HCHO and ozone then provide sensitive tests of isoprene chemistry and argue in particular against a fast isomerization channel for isoprene peroxy radicals. ∑ANs can provide an important reservoir for exporting NO x from the U.S. boundary layer. We find that the dependence of surface ozone on isoprene emission is positive throughout the U.S., even if NO x emissions are reduced by a factor of 4. Previous models showed negative dependences that we attribute to erroneous titration of OH by isoprene.

Isoprene

Chemical Transport Model

Atmospheric chemistry

Tropospheric ozone

10.1002/jgrd.50817

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Citations (336)