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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/acp-2017-941
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
16 Nov 2017
Review status
This discussion paper is a preprint. A revision of this manuscript was accepted for the journal Atmospheric Chemistry and Physics (ACP) and is expected to appear here in due course.
In situ measurements of angular dependent light scattering by aerosols over the contiguous United States
W. Reed Espinosa1,2, J. Vanderlei Martins1,2, Lorraine A. Remer1,2, Anin Puthukkudy1,2, Daniel Orozco1,2, and Gergely Dolgos1,2,3 1Department of Physics, University of Maryland Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250, USA
2Joint Center for Earth Systems Technology, University of Maryland Baltimore County, 5523 Research Park DR, Baltimore, MD 21228, USA
3Micos Engineering GmbH, Überlandstrasse 129, CH-8600, Dübendorf, Switzerland
Abstract. This work provides a synopsis of aerosol phase function (F11) and polarized phase function (−F12/F11) measurements made by the Polarized Imaging Nephelometer (PI-Neph) during the Studies of Emissions and Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys (SEAC4RS) and the Deep Convection Clouds and Chemistry (DC3) field campaigns. In order to more easily explore this extensive dataset, an aerosol classification scheme is developed that identifies the different aerosol types measured during the deployments. This scheme makes use of ancillary data that includes trace gases, chemical composition, aerodynamic particle size and geographic location, all independent of PI-Neph measurements. The PI-Neph measurements are then grouped according to their ancillary data classifications and the resulting scattering patterns are examined in detail. These results represent the first published airborne measurements of F11 and −F12/F11 for many common aerosol types. We then explore whether PI-Neph light-scattering measurements alone are sufficient to reconstruct the results of this ancillary data classification algorithm. Principal component analysis (PCA) is used to reduce the dimensionality of the multi-angle PI-Neph scattering data and the individual measurements are examined as a function of ancillary data classification. Clear clustering is observed in the PCA score space, corresponding to the ancillary classification results, suggesting that indeed a strong link exists between the angular scattering measurements and the aerosol type or composition. Two techniques are used to quantify the degree of clustering and it is found that in most case the results of the ancillary data classification can be predicted from PI-Neph measurements alone with better than 85 % recall. This result both emphasizes the validity of the ancillary data classification as well as the PI-Neph's ability to distinguish common aerosol types without additional information.

Citation: Espinosa, W. R., Martins, J. V., Remer, L. A., Puthukkudy, A., Orozco, D., and Dolgos, G.: In situ measurements of angular dependent light scattering by aerosols over the contiguous United States, Atmos. Chem. Phys. Discuss., https://doi.org/10.5194/acp-2017-941, in review, 2017.
W. Reed Espinosa et al.
W. Reed Espinosa et al.

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Short summary
This work presents airborne, angularly resolved measurements of light scattered by atmospheric aerosols. A classification scheme, making use of optically independent ancillary data, is developed and used to categorize each of the individual light scattering measurements. This classification is shown to correlate very strongly with the measured aerosol scattering properties demonstrating that in situ angular light scattering measurements alone are sufficient to identify many major aerosol types.
This work presents airborne, angularly resolved measurements of light scattered by atmospheric...
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