Atmos. Chem. Phys. Discuss., 11, 26791-26813, 2011
www.atmos-chem-phys-discuss.net/11/26791/2011/
doi:10.5194/acpd-11-26791-2011
© Author(s) 2011. This work is distributed
under the Creative Commons Attribution 3.0 License.
Review Status
This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
Laboratory and modeling studies on the effects of water and soot emissions and ambient conditions on the formation of contrail ice particles in the jet regime
H.-W. Wong1, A. J. Beyersdorf2, C. M. Heath3, L. D. Ziemba2, E. L. Winstead2, K. L. Thornhill2, K. M. Tacina3, R. C. Ross3, S. E. Albo1, D. L. Bulzan3, B. E. Anderson2, and R. C. Miake-Lye1
1Center for Aero-Thermodynamics, Aerodyne Research, Inc., Billerica, Massachusetts, USA
2Chemistry and Dynamics Branch, Science Directorate, NASA Langley Research Center, Hampton, Virginia, USA
3Combustion Branch, NASA Glenn Research Center, Cleveland, Ohio, USA

Abstract. Contrails and contrail-induced cirrus clouds are identified as the most uncertain components in determining aviation impacts on global climate change. Parameters affecting contrail ice particle formation immediately after engine exit plane (<5 s in plume age) may be critical to ice particle properties used in large scale models predicting contrail radiative forcing. Despite this, detailed understanding of these parametric effects is still limited. In this paper, we present results from recent laboratory and modeling studies conducted to investigate the effects of water and soot emissions and ambient conditions on the near-field formation of contrail ice particles. The Particle Aerosol Laboratory (PAL) at the NASA Glenn Research Center and the Aerodyne microphysical parcel model for contrail ice particle formation were employed. Our studies show that exhaust water concentrations have a significant impact on contrail ice particle formation. When soot was introduced, ice particle formation was observed only when exhaust water concentration was above a critical level. When no soot or sulfuric acid was introduced, homogeneous ice particle formation was unfavorable. Soot particles were found to compete for water vapor condensation, and higher soot concentrations emitted into the chamber resulted in smaller ice particles being formed. Chamber conditions corresponding to higher altitude standard day conditions were found to favor ice particle formation as expected. The microphysical model captures experimental trends well, but discrepancies between the model and the experiments exist as the model predicts narrower ice particle size distributions and ice particle sizes nearly a factor of two larger than measured. These discrepancies are likely due to the lack of treatment of turbulent mixing in the model and particle loss and scatter during the experimental sampling process. Future measurement activities are planned to investigate other important parameters, such as soot surface properties and sulfuric acid concentrations, using the PAL and microphysical model.

Citation: Wong, H.-W., Beyersdorf, A. J., Heath, C. M., Ziemba, L. D., Winstead, E. L., Thornhill, K. L., Tacina, K. M., Ross, R. C., Albo, S. E., Bulzan, D. L., Anderson, B. E., and Miake-Lye, R. C.: Laboratory and modeling studies on the effects of water and soot emissions and ambient conditions on the formation of contrail ice particles in the jet regime, Atmos. Chem. Phys. Discuss., 11, 26791-26813, doi:10.5194/acpd-11-26791-2011, 2011.
 
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