Publication Abstracts

Hodzic et al. 2020

Hodzic, A., P. Campuzano-Jost, H. Bian, M. Chin, P.R. Colarco, D.A. Day, K.D. Froyd, B. Heinold, D.S. Jo, J.M. Katich, J.K. Kodros, B.A. Nault, J.R. Pierce, E. Ray, J. Schacht, G.P. Schill, J.C. Schroder, J.P. Schwarz, D.T. Sueper, I. Tegen, S. Tilmes, K. Tsigaridis, P. Yu, and J.L. Jimenez, 2020: Characterization of organic aerosol across the global remote troposphere: A comparison of ATom measurements and global chemistry models. Atmos. Chem. Phys., 20, 4607-4635, doi:10.5194/acp-20-4607-2020.

The spatial distribution and properties of submicron organic aerosol (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 few data have been available and where OA predictions from AeroCom Phase II global models span 2 to 3 orders of magnitude, 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 DC-8 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 lower troposphere in the summer and over the regions influenced by biomass burning from Africa (up to 10 µg/sm3). Lower concentrations (∼0.1-0.3 µg/sm3) are observed in the northern middle and high latitudes and very low concentrations (<0.1 µg/sm3) in the southern middle and high latitudes. The ATom dataset is used to evaluate predictions of eight current global chemistry models that implement a variety of commonly used representations of OA sources and chemistry, as well as of the AeroCom-II ensemble. The current model ensemble captures the average vertical and spatial distribution of measured OA concentrations, and the spread of the individual models remains within a factor of 5. These results are significantly improved over the AeroCom-II model ensemble, which shows large overestimations over these regions. However, some of the improved agreement with observations occurs for the wrong reasons, as models have the tendency to greatly overestimate the primary OA fraction and underestimate the secondary fraction. Measured OA in the remote free troposphere is highly oxygenated, with organic aerosol to organic carbon (OA/OC) ratios of ∼2.2-2.8, and is 30%-60% more oxygenated than in current models, which can lead to significant errors in OA concentrations. The model-measurement comparisons presented here support the concept of a more dynamic OA system as proposed by Hodzic et al. (2016), with enhanced removal of primary OA and a stronger production of secondary OA in global models needed to provide better agreement with observations.

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BibTeX Citation

  author={Hodzic, A. and Campuzano-Jost, P. and Bian, H. and Chin, M. and Colarco, P. R. and Day, D. A. and Froyd, K. D. and Heinold, B. and Jo, D. S. and Katich, J. M. and Kodros, J. K. and Nault, B. A. and Pierce, J. R. and Ray, E. and Schacht, J. and Schill, G. P. and Schroder, J. C. and Schwarz, J. P. and Sueper, D. T. and Tegen, I. and Tilmes, S. and Tsigaridis, K. and Yu, P. and Jimenez, J. L.},
  title={Characterization of organic aerosol across the global remote troposphere: A comparison of ATom measurements and global chemistry models},
  journal={Atmos. Chem. Phys.},

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RIS Citation

ID  - ho00700s
AU  - Hodzic, A.
AU  - Campuzano-Jost, P.
AU  - Bian, H.
AU  - Chin, M.
AU  - Colarco, P. R.
AU  - Day, D. A.
AU  - Froyd, K. D.
AU  - Heinold, B.
AU  - Jo, D. S.
AU  - Katich, J. M.
AU  - Kodros, J. K.
AU  - Nault, B. A.
AU  - Pierce, J. R.
AU  - Ray, E.
AU  - Schacht, J.
AU  - Schill, G. P.
AU  - Schroder, J. C.
AU  - Schwarz, J. P.
AU  - Sueper, D. T.
AU  - Tegen, I.
AU  - Tilmes, S.
AU  - Tsigaridis, K.
AU  - Yu, P.
AU  - Jimenez, J. L.
PY  - 2020
TI  - Characterization of organic aerosol across the global remote troposphere: A comparison of ATom measurements and global chemistry models
JA  - Atmos. Chem. Phys.
VL  - 20
SP  - 4607
EP  - 4635
DO  - 10.5194/acp-20-4607-2020
ER  -

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