Articles | Volume 16, issue 14
Atmos. Chem. Phys., 16, 9435–9455, 2016
Atmos. Chem. Phys., 16, 9435–9455, 2016

Research article 29 Jul 2016

Research article | 29 Jul 2016

Evaluating model parameterizations of submicron aerosol scattering and absorption with in situ data from ARCTAS 2008

Matthew J. Alvarado1, Chantelle R. Lonsdale1, Helen L. Macintyre2,a, Huisheng Bian3,4, Mian Chin4, David A. Ridley5, Colette L. Heald5,6, Kenneth L. Thornhill7, Bruce E. Anderson7, Michael J. Cubison8,b, Jose L. Jimenez8, Yutaka Kondo9, Lokesh K. Sahu9, Jack E. Dibb10, and Chien Wang2 Matthew J. Alvarado et al.
  • 1Atmospheric and Environmental Research, Lexington, Massachusetts, USA
  • 2Center for Global Change Science, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
  • 3Goddard Earth Sciences and Technology Joint Center for Earth Systems Technology, University of Maryland Baltimore County, Baltimore, Maryland, USA
  • 4NASA Goddard Space Flight Center, Greenbelt, Maryland, USA
  • 5Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
  • 6Department of Earth, Atmospheric and Planetary Science, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
  • 7NASA Langley Research Center, Hampton, Virginia, USA
  • 8Department of Chemistry and Biochemistry, and Cooperative Institute for Research in the Environmental Sciences, University of Colorado, Boulder, Colorado, USA
  • 9Department of Earth and Planetary Science, University of Tokyo, Tokyo, Japan
  • 10Department of Earth Sciences and Institute for the Study of Earth, Oceans, and Space, University of New Hampshire, Durham, New Hampshire, USA
  • anow at: Public Health England, Chilton, Oxfordshire, UK
  • bnow at: Tofwerk AG, Thun, Switzerland

Abstract. Accurate modeling of the scattering and absorption of ultraviolet and visible radiation by aerosols is essential for accurate simulations of atmospheric chemistry and climate. Closure studies using in situ measurements of aerosol scattering and absorption can be used to evaluate and improve models of aerosol optical properties without interference from model errors in aerosol emissions, transport, chemistry, or deposition rates. Here we evaluate the ability of four externally mixed, fixed size distribution parameterizations used in global models to simulate submicron aerosol scattering and absorption at three wavelengths using in situ data gathered during the 2008 Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) campaign. The four models are the NASA Global Modeling Initiative (GMI) Combo model, GEOS-Chem v9-02, the baseline configuration of a version of GEOS-Chem with online radiative transfer calculations (called GC-RT), and the Optical Properties of Aerosol and Clouds (OPAC v3.1) package. We also use the ARCTAS data to perform the first evaluation of the ability of the Aerosol Simulation Program (ASP v2.1) to simulate submicron aerosol scattering and absorption when in situ data on the aerosol size distribution are used, and examine the impact of different mixing rules for black carbon (BC) on the results. We find that the GMI model tends to overestimate submicron scattering and absorption at shorter wavelengths by 10–23 %, and that GMI has smaller absolute mean biases for submicron absorption than OPAC v3.1, GEOS-Chem v9-02, or GC-RT. However, the changes to the density and refractive index of BC in GC-RT improve the simulation of submicron aerosol absorption at all wavelengths relative to GEOS-Chem v9-02. Adding a variable size distribution, as in ASP v2.1, improves model performance for scattering but not for absorption, likely due to the assumption in ASP v2.1 that BC is present at a constant mass fraction throughout the aerosol size distribution. Using a core-shell mixing rule in ASP overestimates aerosol absorption, especially for the fresh biomass burning aerosol measured in ARCTAS-B, suggesting the need for modeling the time-varying mixing states of aerosols in future versions of ASP.

Short summary
Understanding the scattering and absorption of light by aerosols is necessary for understanding air quality and climate change. We used data from the 2008 ARCTAS campaign to evaluate aerosol optical property models using a closure methodology that separates errors in these models from other errors in aerosol emissions, chemistry, or transport. We find that the models on average perform reasonably well, and make suggestions for how remaining biases could be reduced.
Final-revised paper