Preprints
https://doi.org/10.5194/amt-2022-28
https://doi.org/10.5194/amt-2022-28
15 Feb 2022
 | 15 Feb 2022
Status: this preprint was under review for the journal AMT. A final paper is not foreseen.

A study of Mie scattering modelling for mixed phase Polar Stratospheric Clouds

Francesco Cairo, Terry Deshler, Luca Di Liberto, Andrea Scoccione, and Marcel Snels

Abstract. Mie scattering codes are used to study the optical properties of Polar Stratospheric Clouds (PSC). Backscattering and extinction can be computed once the particle size distribution (PSD) is known and a suitable refractive index is assumed. However, PSCs often appear as external mixtures of Supercooled Ternary Solution (STS) droplets, solid Nitric Acid Trihydrate (NAT) and possibly ice particles, making questionable the use of Mie theory with a single refractive index and with the underlying assumption of spherical scatterers. Here we consider a set of fifteen coincident measurements of PSC above McMurdo Station, Antarctica, by ground-based lidar and balloon-borne Optical Particle Counters (OPC), and in situ observations taken by a laser backscattersonde and an OPC during four balloon stratospheric flights from Kiruna, Sweden. This unique dataset of microphysical and optical observations allows to test the performances of Mie theory under fairly reasonable corrections when aspherical scatterers are present.

Here we consider particles as STS if their radius is below a certain threshold value Rth and NAT or possibly ice if above it. The refractive indexes are assumed known from literature. Moreover, the Mie result for solid particles are reduced by a factor C < 1, which takes into account the backscattering depression expected from the asphericity. Finally, we consider the fraction X of the backscattering from the aspherical part of the PSD as polarized, and the remaining (1-X) as depolarized. The three parameters Rth, C and X of our model are chosen to provide the best match with the observed optical backscattering and depolarization. The comparison of the calculations with the measures is satisfactory for the backscattering but not for the depolarization, and possible causes are discussed. The results of this work help to understand the limits of the application of Mie theory in modeling the optical response of particles of different composition and morphology.

This preprint has been withdrawn.

Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this preprint. The responsibility to include appropriate place names lies with the authors.
Francesco Cairo, Terry Deshler, Luca Di Liberto, Andrea Scoccione, and Marcel Snels

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on amt-2022-28', Anonymous Referee #1, 26 Feb 2022
    • AC1: 'Reply on RC1', Francesco Cairo, 07 Mar 2022
  • RC2: 'Comment on amt-2022-28', Anonymous Referee #2, 31 Mar 2022
    • AC2: 'Reply on RC2', Francesco Cairo, 13 Apr 2022
  • EC1: 'Comment on amt-2022-28', Omar Torres, 13 Apr 2022
  • EC2: 'Comment on amt-2022-28', Omar Torres, 20 Apr 2022

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on amt-2022-28', Anonymous Referee #1, 26 Feb 2022
    • AC1: 'Reply on RC1', Francesco Cairo, 07 Mar 2022
  • RC2: 'Comment on amt-2022-28', Anonymous Referee #2, 31 Mar 2022
    • AC2: 'Reply on RC2', Francesco Cairo, 13 Apr 2022
  • EC1: 'Comment on amt-2022-28', Omar Torres, 13 Apr 2022
  • EC2: 'Comment on amt-2022-28', Omar Torres, 20 Apr 2022
Francesco Cairo, Terry Deshler, Luca Di Liberto, Andrea Scoccione, and Marcel Snels
Francesco Cairo, Terry Deshler, Luca Di Liberto, Andrea Scoccione, and Marcel Snels

Viewed

Total article views: 1,040 (including HTML, PDF, and XML)
HTML PDF XML Total BibTeX EndNote
714 262 64 1,040 62 52
  • HTML: 714
  • PDF: 262
  • XML: 64
  • Total: 1,040
  • BibTeX: 62
  • EndNote: 52
Views and downloads (calculated since 15 Feb 2022)
Cumulative views and downloads (calculated since 15 Feb 2022)

Viewed (geographical distribution)

Total article views: 997 (including HTML, PDF, and XML) Thereof 997 with geography defined and 0 with unknown origin.
Country # Views %
  • 1
1
 
 
 
 

Cited

Latest update: 05 Dec 2024
Download

This preprint has been withdrawn.

Short summary
We study Mie theory on aspherical scatterers, computing on coincident measurements of PSC by lidar and Particle Counters, the backscatter and depolarization of mixed phase PSC. WParticles are assumed solid if larger than R; for these, Mie results are reduced by C < 1 and only a common fraction X < 1 of the backscattering is polarized. We retrieve R, C and X. The match of model and measurement is good for backscattering, poor for depolarization. The hypothesis on X may be not fulfilled.