Investigations of the March 2006 African dust storm usingground-based column-integrated high spectral resolutioninfrared (8-13 μm) and visible aerosol optical thicknessmeasurements:2. Mineral aerosol mixture analyses

摘要

The mineral aerosol mixture composition for the March 2006 Saharan dust stormis assessed in this paper on the basis of the analysis of visible to near-infrared (VIS-NIR)and infrared (IR) aerosol optical thickness (AOT) spectra obtained during the PortableInfrared Aerosol Transmission Experiment (PIRATE). The AOT spectra from 8 to 13 pmwere determined using column-integrated solar transmission measurements using aFourier transform infrared spectrometer. To determine the mineralogy and mixturecomposition of the dust, we determined the expected mineralogy of dust from the Algeriansource region in a dust storm environment. Then we computed the modeled VIS-IR AOTspectra using Mie theory for external and internal mixtures. We compared the modeledVIS-NIR AOT spectra and derived index of refraction and single-scattering albedowith the measured values from AERONET and compared the modeled IR AOT spectrawith the values from our IR measurements. The fit between the measured and modeledvalues was best when we used an extinction resonance correction to the Mie theoryresults to better account for the exact wavelengths and shapes of some of the AOT peaksfor mineral particles. The mineralogy and mixture composition of the best dust modelincludes external mixtures, internal mixtures, and mineralogy dominated by quartz, illite,and calcite. The modeled mean radius was determined, and several modes were computedin agreement with AERONET results.