10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
Abstract View
How to Make Organic Molecules for New Particle Formation in Atmospheric Models: Recipes from the CERN CLOUD Experiment
HAMISH GORDON, Simone Schuchmann, Roy Lee III Mauldin, Matti Rissanen, Chao Yan, Lukas Fischer, Mario Simon, Martin Heinritzi, Ken Carslaw, CLOUD Collaboration, University of Leeds
Abstract Number: 759 Working Group: Aerosol Modeling
Abstract New particle formation (NPF) in the atmosphere accounts for over half of global cloud condensation nuclei (CCN) in our simulations1 with the GLOMAP model2. When organic molecules participate in NPF and in growth of nanometer-size particles, global CCN concentrations at the level of low clouds increase by around 20%.
The production of the low volatility, highly oxidised organic molecules (HOMs) that affect new particle formation in atmospheric models is usually fairly crude. New particle formation in regions dominated by organics is known to be affected by NOx, isoprene, and temperature, among other factors. The auto-oxidation process by which most HOMs are thought to form3 is only starting to be understood (e.g. 4). Many models, including ours, do not account for the effects of different environmental and chemical conditions on this mechanism, and this leads to disagreement between the model and observations. For example, our model produces unrealistically high new particle formation rates in some regions, especially the Amazon5.
In this study, we discuss ways to refine the treatment of HOM production in large-scale models, and thereby improve the agreement of our model of new particle formation and growth with observations. Yields of HOMs from the CERN CLOUD experiment arecombined with simplified reaction schemes derived from the Master Chemical Mechanism6 to account for the influence of NOx and isoprene chemistry on HOM production. We implement a new HOM formation mechanism into the GLOMAP aerosol model and examine the effects on new particle formation and growth. The model is re-evaluated against measurement data and the implications for the indirect effects of aerosols on climate are discussed.
We thank CERN for supporting CLOUD with important technical and financial resources and the PS beam. This research has received additional funding from numerous sources.
1. Gordon, H. et al, (2017) J. Geophys. Res. 122 8739. 2. Mann, G. W. et al, (2010) Geosci. Model Dev., 3 519. 3. Ehn, M. et al, (2014) Nature, 506 476. 4. Rissanen M. et al, (2015) J. Phys. Chem. A. 119, 4633. 5. Gordon, H. et al, (2016) Proc. Natl. Acad. Sci. 113 12053. 6. Jenkin, M. E. et al, (1997) Atmos. Environ., 31, 81.