Abstract
Abstract. Atmospheric aerosols have major impacts on regional and global climate through scattering and absorption of solar radiation. A new instrument, the Cloud and Aerosol Spectrometer with Polarization (CASPOL) from Droplet Measurement Technologies measures light scattered by aerosols in the forward (4° to 12°) and backward (168° to 176°) directions, with an additional polarized detector in the backward direction. Scattering by a single particle can be measured by all three detectors for aerosols in a broad range of sizes, 0.6 μm < diameter < 50 μm. The CASPOL is a unique measurement tool, since unlike most in-situ probes, it can measure optical properties on a particle-by-particle basis. In this study, single particle CASPOL measurements for thirteen atmospherically relevant dusts were obtained and their optical scattering signatures were evaluated. In addition, Scanning Electron Microscopy (SEM) was used to characterize the shape and morphology of each type of dust. The total and polarized backscatter intensities varied with particle size for all dust types. Using a new optical signature technique all but one dust type could be categorized into one of three optical scattering groups. Additionally, a composite method was used to derive the optical signature of Arizona Test Dust (ATD) by combining the signatures of its major components. The derived signature was consistent with the measured signature of ATD. Finally, calculated backscattering cross sections for representative dust from each of the three main groups were found to vary by as much as a factor of 7, the difference between the backscattering cross sections of white quartz (5.3 × 10−10 cm−2) and hematite (4.1 × 10−9 cm−2).
Highlights
Aerosol Spectrometer with Polarization (CASPOL) from Droplet Measurement Technologies measures light scattered by aerosols in the forward (4◦ to 12◦) and backward
Diameters measured by the Cloud and Aerosol Spectrometer with Polarization (CASPOL) for olive oil particles are in good agreement with those chosen by the Vibrating Orifice Aerosol Generator (VOAG) operating conditions
The uncertainties in the CASPOL diameters are the standard deviations from the mean diameter of the log normal size distributions fitted to the CASPOL measured calibration particle size generated by the VOAG
Summary
Aerosol Spectrometer with Polarization (CASPOL) from Droplet Measurement Technologies measures light scattered by aerosols in the forward (4◦ to 12◦) and backward Scattering by a single particle can be measured by all three detectors for aerosols in a broad ing of the atmosphere (CaqMuineetahuoedt sal.a, n20d02). The CASPOL is In addition, atmospheric dust influences liquid droplet and a unique measurement tool, since unlike most in-situ probes, ice nucleation (Chen et al, 1998; Kanji and Abbatt, 2009), it can measure optical properties on a particle-by-particle basis. Single particle CASPOL measurements for thirteen atmospherically relevant dusts were obtained and the deposition of micronutGrieentos sinctoieocnetainfsic(Duce and Tind(Parleo,sp1e9r9o1, ;2U00e6Mm; aPotsrduoseeptelraDol.,eet2v0a0le.3,l)o20apn0md1).reeMgniiontnearlalaidruqstualilfitey-. The total and polarized backscatter intensities varied with particle size for all dust types.
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