Atmosphere 2012, 3(4), 495-521; doi:10.3390/atmos3040495
Article

Initial Assessment of the Spectrometer for Sky-Scanning, Sun-Tracking Atmospheric Research (4STAR)-Based Aerosol Retrieval: Sensitivity Study

1 Pacific Northwest National Laboratory, Richland, WA 99352, USA 2 BAERI, Sonoma, CA 95476, USA 3 NASA ARC, Moffett Field, CA 94035, USA 4 NASA GSFC, Greenbelt, MD 20771, USA
* Author to whom correspondence should be addressed.
Received: 25 July 2012; in revised form: 17 September 2012 / Accepted: 9 October 2012 / Published: 24 October 2012
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Abstract: The Spectrometer for Sky-Scanning, Sun-Tracking Atmospheric Research (4STAR) being developed for airborne measurements will offer retrievals of aerosol microphysical and optical properties from multi-angular and multi-spectral measurements of sky radiance and direct-beam sun transmittance. In this study, we assess the expected accuracy of the 4STAR-based aerosol retrieval and its sensitivity to major sources of anticipated perturbations in the 4STAR measurements. The major anticipated perturbations are (1) an apparent enhancement of sky radiance at small scattering angles associated with the necessarily compact design of the 4STAR and (2) an offset (i.e., uncertainty) of sky radiance calibration independent of scattering angle. The assessment is performed through application of the operational AERONET aerosol retrieval and constructed synthetic 4STAR-like data. Particular attention is given to the impact of these perturbations on the broadband fluxes and the direct aerosol radiative forcing. The results from this study suggest that limitations in the accuracy of 4STAR-retrieved particle size distributions and scattering phase functions have diminished impact on the accuracy of retrieved bulk microphysical parameters, permitting quite accurate retrievals of properties including the effective radius (up to 10%, or 0.03), and the radiatively important optical properties, such as the asymmetry factor (up to 4%, or ±0.02) and single-scattering albedo (up to 6%, or ±0.04). Also, the obtained results indicate that the uncertainties in the retrieved aerosol optical properties are quite small in the context of the calculated fluxes and direct aerosol radiative forcing (up to 15%, or 3 W∙m−2).
Keywords: Spectrometer for Sky-Scanning; Sun-Tracking Atmospheric Research (4STAR); retrievals of aerosol microphysical and optical properties; airborne multi-angular and multi-spectral measurements; sky radiance and direct-beam sun transmittance; operational AERONET aerosol retrieval; direct aerosol radiative forcing; sensitivity study

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MDPI and ACS Style

Kassianov, E.; Flynn, C.; Redemann, J.; Schmid, B.; Russell, P.B.; Sinyuk, A. Initial Assessment of the Spectrometer for Sky-Scanning, Sun-Tracking Atmospheric Research (4STAR)-Based Aerosol Retrieval: Sensitivity Study. Atmosphere 2012, 3, 495-521.

AMA Style

Kassianov E, Flynn C, Redemann J, Schmid B, Russell PB, Sinyuk A. Initial Assessment of the Spectrometer for Sky-Scanning, Sun-Tracking Atmospheric Research (4STAR)-Based Aerosol Retrieval: Sensitivity Study. Atmosphere. 2012; 3(4):495-521.

Chicago/Turabian Style

Kassianov, Evgueni; Flynn, Connor; Redemann, Jens; Schmid, Beat; Russell, Philip B.; Sinyuk, Alexander. 2012. "Initial Assessment of the Spectrometer for Sky-Scanning, Sun-Tracking Atmospheric Research (4STAR)-Based Aerosol Retrieval: Sensitivity Study." Atmosphere 3, no. 4: 495-521.

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