Climate Forcing and Trends of Organic Aerosols in the Community Earth System Model (CESM2)

Tilmes, Simone; Hodzic, Alma; Emmons, L. K.; Mills, Michael J.; Gettelman, Andrew; Kinnison, Douglas E.; Park, Mi-Jeong; Lamarque, Jean‐François; Vitt, Francis; Shrivastava, Manish; Campuzano‐Jost, P.; Jimenez, José L.; Liu, X.

doi:10.1029/2019ms001827

Cited by 128 publications

(176 citation statements)

References 69 publications

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“…Field campaigns like Studies of Emissions and Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys (SEAC 4 RS), whose goals included investigating oxidation chemistry of biogenic VOCs and measuring ozone, ozone precursors, and NO x reservoir species, are critical for evaluating whether models are accurately repre-senting ozone. The SEAC 4 RS field campaign was conducted during August through September of 2013 (Toon et al, 2016) with many of the flights centered over the southeastern US. In SEAC 4 RS and in many other past field campaigns, terpene oxidation products were not quantitatively measured.…”

Section: Evaluation Against Field Campaign Datamentioning

confidence: 99%

Comprehensive isoprene and terpene gas-phase chemistry improves simulated surface ozone in the southeastern US

et al. 2020

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Abstract. Ozone is a greenhouse gas and air pollutant that is harmful to human health and plants. During the summer in the southeastern US, many regional and global models are biased high for surface ozone compared to observations. Past studies have suggested different solutions including the need for updates to model representation of clouds, chemistry, ozone deposition, and emissions of nitrogen oxides (NOx) or biogenic hydrocarbons. Here, due to the high biogenic emissions in the southeastern US, more comprehensive and updated isoprene and terpene chemistry is added into CESM/CAM-chem (Community Earth System Model/Community Atmosphere Model with full chemistry) to evaluate the impact of chemistry on simulated ozone. Comparisons of the model results with data collected during the Studies of Emissions Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys (SEAC4RS) field campaign and from the US EPA (Environmental Protection Agency) CASTNET (Clean Air Status and Trends Network) monitoring stations confirm the updated chemistry improves simulated surface ozone, ozone precursors, and NOx reservoir compounds. The isoprene and terpene chemistry updates reduce the bias in the daily maximum 8 h average (MDA8) surface ozone by up to 7 ppb. In the past, terpene oxidation in particular has been ignored or heavily reduced in chemical schemes used in many regional and global models, and this study demonstrates that comprehensive isoprene and terpene chemistry is needed to reduce surface ozone model biases. Sensitivity tests were performed in order to evaluate the impact of lingering uncertainties in isoprene and terpene oxidation on ozone. Results suggest that even though isoprene emissions are higher than terpene emissions in the southeastern US, remaining uncertainties in isoprene and terpene oxidation have similar impacts on ozone due to lower uncertainties in isoprene oxidation. Additionally, this study identifies the need for further constraints on the aerosol uptake of organic nitrates derived from isoprene and terpenes in order to reduce uncertainty in simulated ozone. Although the updates to isoprene and terpene chemistry greatly reduce the ozone bias in CAM-chem, a large bias remains. Evaluation against SEAC4RS field campaign results suggests future improvements to horizontal resolution and cloud parameterizations in CAM-chem may be particularly important for further reducing this bias.

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Section: Evaluation Against Field Campaign Datamentioning

confidence: 99%

Comprehensive isoprene and terpene gas-phase chemistry improves simulated surface ozone in the southeastern US

et al. 2020

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“…This version of MAM4 is modified to allow for the simulation of stratospheric aerosols from volcanic eruptions (from their SO2 emissions) and oxidation of OCS (Mills et al, 2016). The representation of secondary organic aerosols follows the Volatility Basis Set approached (Tilmes et al, 2019).…”

Section: Modelsmentioning

confidence: 99%

Effective Radiative forcing from emissions of reactive gases and aerosols – a multimodel comparison

Thornhill¹,

Collins²,

Kramer³

et al. 2020

Preprint

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Abstract. This paper quantifies the effective radiative forcing from CMIP6 models of the present-day anthropogenic emissions of NOx, CO, VOCs, SO2, NH3, black carbon and primary organic carbon. Effective radiative forcing from pre-industrial to present-day changes in the concentrations of methane, N2O and halocarbons are quantified and attributed to their anthropogenic emissions. Emissions of reactive species can cause multiple changes in the composition of radiatively active species: tropospheric ozone, stratospheric ozone, secondary inorganic and organic aerosol and methane. We therefore break down the ERFs from each emitted species into the contributions from the composition changes. The 1850 to 2014 mean ERFs are 1.1 ± 0.07 W m−2 for sulfate, −0.24 ± 0.01 W m−2 for organic carbon (OC), and 0.15 ± 0.04 W m−2 for black carbon (BC), and for the aerosols combined it is −0.95 ± 0.03 W m−2. The means for the reactive gases are 0.69 ± 0.04 W m−2 for methane (CH4), 0.06 ± 0.04 W m−2 for NOx, −0.09 ± 0.03 W m−2 for volatile organic carbons (VOC), 0.16 ± 0.03 W m−2 for ozone (O3), 0.27 W m−2 for nitrous oxide (N2O) and −0.02 ± 0.06 W m−2 for hydrocarbon (HC). Differences in ERFs calculated for the different models reflect differences in the complexity of their aerosol and chemistry schemes, especially in the case of methane where tropospheric chemistry captures increased forcing from ozone production.

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“…Simulations based on the CESM2.0 Earth system model use the Whole Atmosphere Community Climate Model (WACCM6, Gettelman et al, 2019.…”

Section: Gc10-tomas Is Based On the Geos-chem Version 1001 Coupled Wmentioning

confidence: 99%

Characterization of Organic Aerosol across the Global Remote Troposphere: A comparison of ATom measurements and global chemistry models

Hodžić¹,

Campuzano‐Jost²,

Bian³

et al. 2019

Preprint

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Abstract. The spatial distribution and properties of submicron organic aerosols (OA) are among the key sources of uncertainty in our understanding of aerosol effects on climate. Uncertainties are particularly large over remote regions of the free troposphere and Southern Ocean, where very little data has been available, and where OA predictions from AeroCom Phase II global models span a factor of 400–1000, greatly exceeding the model spread over source regions. The (nearly) pole-to-pole vertical distribution of non-refractory aerosols was measured with an aerosol mass spectrometer onboard the NASA DC8 aircraft as part of the Atmospheric Tomography (ATom) mission during the northern hemisphere summer (August 2016) and winter (February 2017). This study presents the first extensive characterization of OA mass concentrations and their level of oxidation in the remote atmosphere. OA and sulfate are the major contributors by mass to submicron aerosols in the remote troposphere, together with sea salt in the marine boundary layer. Sulfate was dominant in the lower stratosphere. OA concentrations have a strong seasonal and zonal variability, with the highest levels measured in the summer and over the regions influenced by the biomass burning from Africa (up to 10 μg sm−3). Lower concentrations (~ 0.1–0.3 μg sm−3) are observed in the northern mid- and high-latitudes and very low concentrations (

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Climate Forcing and Trends of Organic Aerosols in the Community Earth System Model (CESM2)

Cited by 128 publications

References 69 publications

Comprehensive isoprene and terpene gas-phase chemistry improves simulated surface ozone in the southeastern US

Comprehensive isoprene and terpene gas-phase chemistry improves simulated surface ozone in the southeastern US

Effective Radiative forcing from emissions of reactive gases and aerosols – a multimodel comparison

Characterization of Organic Aerosol across the Global Remote Troposphere: A comparison of ATom measurements and global chemistry models

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