Characterization of Particle Size Distribution Uncertainties using SAGE II and SAGE III/ISS Extinction Spectra

Abstract

Abstract. A new algorithm was developed to infer particle size distribution parameters from the Stratospheric Aerosol and Gas Experiment II (SAGE II) and SAGE III on the International Space Station (SAGE III/ISS) extinction spectra using a lookup table (LUT) approach. Here, the SAGE-based extinction ratios were matched to LUT values and, using these matches, weighted statistics were calculated to infer the median particle size distribution values as well as quantify the uncertainty in these estimates. This was carried out by solving for both single and bimodal lognormal distributions. The work presented herein falls under 2 general headings: 1. a theoretical study was carried out to determine the accuracy of this methodology; 2. the solution algorithm was applied to the SAGE II and SAGE III/ISS records with a brief case study analysis of the 2022 Hunga Tonga eruption.

An Empirical Characterization of the Aerosol Ångström Exponent Interpolation Bias using SAGE III/ISS Data

“…Converting aerosol extinction measurements from one wavelength to another requires knowledge of the spectral behavior of aerosol, which is dependent upon its composition and the particle size distribution (PSD). Knowledge of the PSD is also important for both calculating aerosol extinctions using Mie theory (Malinina et al, 2018;Wrana et al, 2021;Pohl et al, 2023;Knepp et al, 2023) as well as for retrieval of aerosol from limb scatter measurements (von Savigny et al, 2015;Rieger et al, 2018Rieger et al, , 2019Taha et al, 2021;Zawada et al, 2018). The most commonly assumed spectral dependency of aerosol extinction is that of the Ångström exponent (AE) (Kar et al, 2019;Kovilakam et al, 2020), though the curvature of the AE shape and that of an actual aerosol spectrum do not exactly match (Thomason et al, 2010).…”