Crystal M. Japngie-Green1, Elisabeth Andrews3,4, Ian B. McCubbin2, John A. Ogren3,4, Anna G. Hallar 1,2

Department Atmospheric Sciences, University of Utah, Salt Lake City, UT 84112, USA
Storm Peak Laboratory, Desert Research Institute, Steamboat Springs, CO 80477, USA
NOAA Earth System Research Laboratory, Boulder, CO 80305, USA
Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO 80309, USA

Received: May 31, 2018
Revised: March 13, 2019
Accepted: April 18, 2019
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Cite this article:
Japngie-Green, C.M., Andrews, E., McCubbin, I.B., Ogren, J.A. and Hallar, A.G. (2019). Climatology of Aerosol Optical Properties at Storm Peak Laboratory. Aerosol Air Qual. Res. 19: 1205-1213.


  • Aerosols influence the energy budget via direct and indirect effects.
  • Aerosols are a large source of uncertainty for climate change prediction.
  • Climate prediction can be improved by elucidating seasonal aerosol patterns.
  • Scattering and absorption data from Storm Peak Laboratory are summarized.


Aerosols create large uncertainty in the planetary energy balance due to both direct and indirect radiative forcing. Understanding aerosol seasonal patterns is essential for accurate climate change prediction, but mountain regions are often difficult for climate models to resolve. Therefore, long-term observations collected at high elevations are particularly useful. In-situ surface aerosol optical measurements were analyzed for the years 2011–2016 at a mountain site located in western Colorado and tied to potential sources based on relationships among the aerosol properties.

The peak values for the scattering and absorption coefficients were observed during the summer, suggesting greater aerosol loading (likely due to wildfires), whereas the lowest values were observed during the winter, indicating cleaner conditions (due to less influence from the boundary layer). The scattering Ångström exponent, a property that provides information about size distributions, revealed the predominance of coarse-mode particles during the spring, which is consistent with the presence of dust. The aerosols observed during the summer, however, were mostly composed of fine-mode particles. This increase in the fine fraction points to combustion, likely wildfires during the dry season (Hallar, 2015), as a source, which is further supported by the absorption Ångström exponent dropping to its lowest value (close to 1) during the summer after exhibiting a slightly higher value (~1.3) during the spring. Schmeisser et al. (2017) suggests that, for in-situ aerosol, absorption Angstrom exponents larger than 1.5 may be indicative of dust if they are associated with low (< 1.3) scattering Ångström exponents. The increase in combustion aerosols during the summer accompanied by high values for the single scattering albedo suggests that these aerosols underwent processing in the atmosphere before reaching Storm Peak Laboratory. These results are important for improving visibility and predicting future aerosol concentrations in the western U.S.

Keywords: Absorption; Scattering; In-situ measurements; Mountain; Climate.


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