Characterization of stratospheric liquid ternary solution aerosol from broadband infrared extinction measurements

Abstract

[1] Characterization of stratospheric liquid ternary solution (LTS) aerosol is studied as an inverse problem in retrieving particle volume size distribution and chemical composition of ternary droplets using the extinction coefficient over wavelengths of 3 to 12 mm. The retrieval method comprises a constrained, weighted least squares minimization procedure between measured and modeled spectra. The constraints restrict the first derivative of the particle size distribution with respect to particle size and restrict the relationship between weight percents of discrete partials (H 2 SO 4 /H 2 O/HNO 3 ) in the ternary droplets using the Carslaw equilibrium model. In the inverse modeling, emphasis is given to minimize the number of reference spectra up to consideration of two mostly binary components composed of H 2 SO 4 /H 2 O and HNO 3 /H 2 O solutions. This permits the retrieval of particle volume size distribution independently of particle chemical composition and therefore simply adopts the inversion method for the processing of spaceborne occultation measurements when other aerosol/cloud components along with trace gases are subject to identification. We initially carry out numerical tests by applying the inversion method to synthetic extinction measurements in order to study the limitations of the retrievals over wide ranges of microphysical parameters. A case study in processing actual space-borne data obtained by the Improved Limb Atmospheric Spectrometer (ILAS) demonstrates the efficiency of the retrievals.Citation: Sasano, Y., S. Oshchepkov, T. Yokota, and H. Nakajima (2005), Characterization of stratospheric liquid ternary solution aerosol from broadband infrared extinction measurements,

ILAS data processing for stratospheric gas and aerosol retrievals with aerosol physical modeling: Methodology and validation of gas retrievals

“…The LTS in this model were represented as two sets of reference spectra that each had mostly binary components: one was a mixture of H 2 SO 4 /H 2 O that was 75% sulfuric acid by weight (upper left‐hand panel in Figure 1), and the other was a mixture of HNO 3 /H 2 O that was 40% nitric acid by weight (upper middle panel in Figure 1). An earlier paper [ Sasano et al , 2005] showed that inverse modeling that calculated the total PSD using primary retrievals of nitric and sulfuric acid yielded acceptable data for the total PSD, total volume density, and the AEC spectra for ternary droplets in which the chemical compositions varied widely. Therefore the PSD of the LTS was presented as a sum of those PSDs retrieved from sulfuric and nitric acid reference spectra.…”

Properties of polar stratospheric clouds obtained by combined ACE-FTS and ACE-Imager extinction measurements

“…To a large extent, the depletion of polar stratospheric ozone is controlled by the presence of PSCs, which at very low temperatures, can be quite extensive (von Hobe et al, 2006). Many satellite-based PSC observations, including those by POAM (Polar Ozone and Aerosol Measurement), SAGE (Stratospheric Aerosol and Gas Experiment), CLAES (Cryogenic Limb Array Etalon Spectrometer), ISAMS (Improved Stratospheric and Mesospheric Sounder), MIPAS (Michelson Interferometer for Passive Atmospheric Sounding) and ILAS (Improved Limb Atmospheric Spectrometer, Fromm et al, 2003;Hopfner et al, 2002;Lambert et al, 1996;Massie et al, 1997;Sasano et al, 2005) have provided a multi-decade record that shows that there is a good correlation between ozone depletion and PSC volume, both of which increase dramatically with decreasing stratospheric temperatures (Rex et al, 2006).…”