Impact of Organic Aerosols on Air Quality and Climate
Final Report Abstract
The proposed work aimed to improve the description of OA in large-scale models by addressing the major shortcomings of the existing modelling approaches. For this purpose, the computationally efficient module for the description of organic aerosol composition and evolution in the atmosphere (ORACLE) was further developed by Dr. Tsimpidi to include all the recent findings and developments based on laboratory and field measurements allowing for the first time in a CCM both the volatility and the oxygen content of OA to be tracked during its atmospheric aging based on the 2D-VBS approach. Furthermore, the researcher developed novel methods to estimate the glass transition temperatures, and thus the phase state of OA, based on the molar mass and molecular O:C ratio of SOA components provided by the ORACLE-2D. In the context of this project, primary organic emissions from open biomass burning and from anthropogenic sources were updated and simulated using separate surrogate species for each source category. In addition, an extensive global data set of AMS measurements and factoranalysis results from field campaigns in the Northern Hemisphere was compiled and used for the model evaluation as well as for optimizing the model performance through a series of multiple sensitivity simulations. In the frame of the proposed project, the researcher applied the developed state-of-the-art OA module to investigate the effects of OA on global and regional air quality and climate, identifying gaps in our understanding of OA physics and chemistry, improving the predictive capability of OA, identifying the OA sources and formation pathways, and prioritizing the most urgent research issues so that they can be addressed in future experimental and modeling studies. The results highlight strong contributions of SOA from anthropogenic sources to global OA concentrations, supporting recent global studies that have also reported similar findings. Furthermore, they indicate that IVOCs can be major contributors to OA formation on a global scale expressing the need for more research in order to determine the parameters that control their emissions, chemistry, and atmospheric removal. In this context, an extensive sensitivity analysis conducted during the project identified that a combination of increased IVOC emissions, enhanced photochemical aging of IVOCs, and decreased hygroscopicity of the freshly emitted IVOCs can help reduce discrepancies between simulated and observed SOA concentrations. Using the extended ORACLE version we found higher concentrations of fresh SOA close to sources while aged SOA increased as the air masses were transported away from the sources and to higher altitudes. However, the particle phase state was found to depend mostly on the ambient RH and temperature, determining the spatiotemporal distributions of SOA phase state worldwide. Thus, the calculated SOA over the planetary boundary layer were mostly liquid in tropical and polar air with high relative humidity, semi-solid in the midlatitudes and solid over dry lands, while in the middle and upper troposphere, SOA were mostly in a glassy solid phase state. Overall, the ability of the new version of ORACLE to simulate the degree of OA oxidation can potentially provide valuable insights into the composition and reactivity of OA and the physicochemical evolution during atmospheric transport of OA, which can help reduce aerosolrelated uncertainties that persist in global atmospheric chemistry and climate modeling.
Publications
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Effects of mineral dust on global atmospheric nitrate concentrations, Atmos. Chem. Phys., 16, 1491-1509, 2016
Karydis, V.A., Tsimpidi, A. P., Pozzer, A., Astitha, M., and Lelieveld, J.
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Global combustion sources of organic aerosols: model comparison with 84 AMS factor-analysis data sets, Atmos. Chem. Phys., 16, 8939-8962, 2016
Tsimpidi, A. P., Karydis, V. A., Pandis, S. N., and Lelieveld, J.:
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Global distribution of particle phase state in atmospheric secondary organic aerosols, Nature comm., 8, 2017
Manabu S., Li, Y., Tsimpidi, A. P., Karydis, V.A., Berkemeier, T., Pandis, S.N., Lelieveld, J., Koop, T., and Pöschl, U.
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Global impact of mineral dust on cloud droplet number concentration, Atmos. Chem. Phys. 17, 5601-5621, 2017
Karydis, V. A., Tsimpidi, A. P., Bacer, S., Pozzer, A., Nenes, A., and Lelieveld, J.
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Global-scale combustion sources of organic aerosols: Sensitivity to formation and removal mechanisms, Atmos. Chem. Phys., 7345-73641, 2017
Tsimpidi, A. P., Karydis, V. A., Pandis, S. N., and Lelieveld, J.
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Impact of agricultural emission reductions on fine particulate matter and public health, Atmos. Chem. Phys., 17, 12813-12826, 2017
Pozzer, A., Tsimpidi, A. P., Karydis, V.A., de Meij, A., and Lelieveld, J.
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Influence of local production and vertical transport on the organic aerosol budget over Paris, J. Geophys. Res.
Janssen, R.H.H., Tsimpidi, A. P., Karydis, V. A., Pozzer, A., Lelieveld, J., Crippa, M., Prevot, A. S. H., Ait-Helal, W., Borbon, A., Sauvage, S., and Locoge, N.
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Investigation of global particulate nitrate from the AeroCom Phase III experiment, Atmos. Chem. Phys. 17, 12911-12940, 2017
Bian, H., Chin, M., Hauglustaine, D. A., Schulz, M., Myhre, G., Bauer, S. E., Lund, M. T., Karydis, V. A., Kucsera, T. L., Pan, X., Pozzer, A., Skeie, R. B., Steenrod, S. D., Sudo, K., Tsigaridis, K., Tsimpidi, A. P., and Svetlana Tsyro
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ORACLE 2-D (v2.0): an efficient module to compute the volatility and oxygen content of organic aerosol with a global chemistry-climate model, Geoscientific Model Development, 11, 3369-3389, 2018
Tsimpidi, A. P., Karydis, V. A., Pozzer, A., Pandis, S. N., and Lelieveld, J.
