Preprints
https://doi.org/10.5194/amt-2020-277
https://doi.org/10.5194/amt-2020-277

  08 Sep 2020

08 Sep 2020

Review status: a revised version of this preprint was accepted for the journal AMT and is expected to appear here in due course.

Retrieval of stratospheric aerosol size distribution parameters using SAGE-III/ISS extinction measurements at three wavelengths

Felix Wrana1, Christian von Savigny1, Jacob Zalach1, and Larry W. Thomason2 Felix Wrana et al.
  • 1Institute of Physics, University of Greifswald, Felix-Hausdorff-Str. 6, 17489 Greifswald, Germany
  • 2NASA Langley Research Center, Hampton, Virginia, USA

Abstract. In this work a novel approach to determine the particle size distribution (PSD) parameters of stratospheric sulfate aerosols is presented. For this, ratios of extinction coefficients obtained from SAGE III/ISS solar occultation measurements at 449 nm, 756 nm and 1544 nm were used to retrieve the mode width and median radius of a size distribution assumed to be monomodal lognormal. The estimated errors at the peak of the stratospheric aerosol layer on average lie between 20 % and 25 % for the median radius and 5 % and 7 % for the mode width. The results are consistent in magnitude with other retrieval results from the literature, but a robust comparison is difficult, mainly because of differences in temporal and spatial coverage. Other quantities like number density and effective radius were also calculated. A major advantage of the described method over other retrieval techniques is that both the median radius and the mode width can be retrieved simultaneously, without having to assume one of them, due to the broad wavelength spectrum covered by the SAGE III/ISS measurements. Also the extinction coefficients from SAGE III/ISS solar occultation measurements, on which the retrieval is based, are calculated without a priori assumptions about the PSD. For those reasons, the data produced with the presented retrieval technique may be a valuable contribution to better understand the variability of stratospheric aerosol size distributions, e.g. after volcanic eruptions. While this study focuses on describing the retrieval method and a future study will discuss the PSD parameter data set produced in depth, some exemplary results for background conditions in June 2017 are shown.

Felix Wrana et al.

 
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Status: closed
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Felix Wrana et al.

Felix Wrana et al.

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Short summary
In this paper we describe a new method to calculate the size of naturally occurring droplets (aerosols) made mostly of sulfuric acid and water, that can be found roughly in 20 km altitude in the atmosphere. For this we use data from the instrument SAGE III/ISS that is mounted on the International Space Station. We show that our method works well and that the size parameters we calculate are reasonable and can be a valuable addition to better understand the aerosols and their effect on climate.