Journal cover Journal topic
Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
Atmos. Chem. Phys., 17, 7175-7191, 2017
https://doi.org/10.5194/acp-17-7175-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
16 Jun 2017
Spectral- and size-resolved mass absorption efficiency of mineral dust aerosols in the shortwave spectrum: a simulation chamber study
Lorenzo Caponi1,2, Paola Formenti1, Dario Massabó2, Claudia Di Biagio1, Mathieu Cazaunau1, Edouard Pangui1, Servanne Chevaillier1, Gautier Landrot3, Meinrat O. Andreae4,11, Konrad Kandler5, Stuart Piketh6, Thuraya Saeed7, Dave Seibert8, Earle Williams9, Yves Balkanski10, Paolo Prati2, and Jean-François Doussin1 1Laboratoire Interuniversitaire des Systèmes Atmosphériques (LISA), UMR CNRS 7583, Université Paris-Est Créteil and Université Paris Diderot, Institut Pierre Simon Laplace, Créteil, France
2Department of Physics & INFN, University of Genoa, Genoa, Italy
3Synchrotron SOLEIL, L'Orme des Merisiers Saint-Aubin, France
4Biogeochemistry Department, Max Planck Institute for Chemistry, P.O. Box 3060, 55020 Mainz, Germany
5Institut für Angewandte Geowissenschaften, Technische Universität Darmstadt, Schnittspahnstr. 9, 64287 Darmstadt, Germany
6Climatology Research Group, University of the Witwatersrand, Johannesburg, South Africa
7Science Department, College of Basic Education, Public Authority for Applied Education and Training, Al-Ardiya, Kuwait
8Sallyport Global, Phoenix, Arizona, USA
9Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
10LSCE, CNRS UMR8212, CEA, Université de Versailles Saint-Quentin, Gif-sur-Yvette, France
11Geology and Geophysics Department, King Saud University, Riyadh, Saudi Arabia
Abstract. This paper presents new laboratory measurements of the mass absorption efficiency (MAE) between 375 and 850 nm for 12 individual samples of mineral dust from different source areas worldwide and in two size classes: PM10. 6 (mass fraction of particles of aerodynamic diameter lower than 10.6 µm) and PM2. 5 (mass fraction of particles of aerodynamic diameter lower than 2.5 µm). The experiments were performed in the CESAM simulation chamber using mineral dust generated from natural parent soils and included optical and gravimetric analyses.

The results show that the MAE values are lower for the PM10. 6 mass fraction (range 37–135  ×  10−3 m2 g−1 at 375 nm) than for the PM2. 5 (range 95–711  ×  10−3 m2 g−1 at 375 nm) and decrease with increasing wavelength as λ−AAE, where the Ångström absorption exponent (AAE) averages between 3.3 and 3.5, regardless of size. The size independence of AAE suggests that, for a given size distribution, the dust composition did not vary with size for this set of samples. Because of its high atmospheric concentration, light absorption by mineral dust can be competitive with black and brown carbon even during atmospheric transport over heavy polluted regions, when dust concentrations are significantly lower than at emission. The AAE values of mineral dust are higher than for black carbon (∼ 1) but in the same range as light-absorbing organic (brown) carbon. As a result, depending on the environment, there can be some ambiguity in apportioning the aerosol absorption optical depth (AAOD) based on spectral dependence, which is relevant to the development of remote sensing of light-absorbing aerosols and their assimilation in climate models. We suggest that the sample-to-sample variability in our dataset of MAE values is related to regional differences in the mineralogical composition of the parent soils. Particularly in the PM2. 5 fraction, we found a strong linear correlation between the dust light-absorption properties and elemental iron rather than the iron oxide fraction, which could ease the application and the validation of climate models that now start to include the representation of the dust composition, as well as for remote sensing of dust absorption in the UV–vis spectral region.


Citation: Caponi, L., Formenti, P., Massabó, D., Di Biagio, C., Cazaunau, M., Pangui, E., Chevaillier, S., Landrot, G., Andreae, M. O., Kandler, K., Piketh, S., Saeed, T., Seibert, D., Williams, E., Balkanski, Y., Prati, P., and Doussin, J.-F.: Spectral- and size-resolved mass absorption efficiency of mineral dust aerosols in the shortwave spectrum: a simulation chamber study, Atmos. Chem. Phys., 17, 7175-7191, https://doi.org/10.5194/acp-17-7175-2017, 2017.
Publications Copernicus
Download
Short summary
This paper presents new laboratory measurements of the shortwave mass absorption efficiency (MAE) used by climate models for mineral dust of different origin and at different sizes. We found that small particles are more efficient, by given mass, in absorbing radiation, particularly at shorter wavelength. Because dust has high concentrations in the atmosphere, light absorption by mineral dust can be competitive to other absorbing atmospheric aerosols such as black and brown carbon.
This paper presents new laboratory measurements of the shortwave mass absorption efficiency...
Share