Atmos. Chem. Phys. Discuss., 11, 11939-11957, 2011
www.atmos-chem-phys-discuss.net/11/11939/2011/
doi:10.5194/acpd-11-11939-2011
© 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.
Seasonal differences in the vertical profiles of aerosol optical properties over rural Oklahoma
E. Andrews1, P. J. Sheridan2, and J. A. Ogren2
1Cooperative Institute for Research in Environmental Sciences, Mail Box 216, University of Colorado, Boulder, CO 80309, USA
2Earth Systems Research Laboratory, National Oceanic and Atmospheric Administration, 325 Broadway, Boulder, CO 80305, USA

Abstract. A small airplane made more than 450 aerosol optical property (light absorption and light scattering) vertical profile measurements (up to 4 km) over a rural Oklahoma site between March 2000 and July 2005. These profiles suggest significant seasonal differences in aerosol properties. The highest amounts of scattering and absorbing aerosol are observed during the summer, while the relative contribution of aerosol absorption is highest in the winter (i.e., single scattering albedo is lowest in winter). Aerosol absorption generally decreased with altitude below ∼1.5 km and then was relatively constant above that. Aerosol scattering decreased sharply with altitude below ∼1.5 km but, unlike absorption, also decreased at higher altitudes, albeit less sharply. The seasonal variability observed for aerosol loading is consistent with other aerosol measurements in the region including AERONET aerosol optical depth (AOD), CALIPSO vertical profiles, and IMPROVE aerosol mass. The column averaged single scattering albedo derived from in situ airplane measurements shows a similar seasonal cycle as the AERONET single scattering albedo inversion product, but a comparison of aerosol asymmetry parameter from airplane and AERONET platforms suggests differences in seasonal variability. The observed seasonal cycle of aerosol loading corresponds with changes in air mass back trajectories: the aerosol scattering was higher when transport was from polluted areas (e.g., the Gulf Coast) and lower when the air came from cleaner regions and/or the upper atmosphere.

Citation: Andrews, E., Sheridan, P. J., and Ogren, J. A.: Seasonal differences in the vertical profiles of aerosol optical properties over rural Oklahoma, Atmos. Chem. Phys. Discuss., 11, 11939-11957, doi:10.5194/acpd-11-11939-2011, 2011.
 
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