Spectroscopic evidence for NAT, STS, and ice in MIPAS infrared limb emission measurements of polar stratospheric clouds

M. Höpfner, B.P. Luo, P. Massoli, F. Cairo, R. Spang, M. Snels, G. Di Donfrancesco, G. Stiller, T. Von Clarmann, H. Fischer, U. Biermann

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Abstract

We have analyzed mid-infrared limb-emission measurements of polar stratospheric clouds (PSCs) by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) during the Antarctic winter 2003 with respect to PSC composition. Coincident Lidar observations from McMurdo were used for comparison with PSC types 1a, 1b and 2. Application of new refractive index data of β-NAT have allowed to accurately simulate the prominent spectral band at 820 cm-1observed by MIPAS at the location where the Lidar instrument observed type 1a PSCs. Broadband spectral fits covering the range from 780 to 960cm-1and from 1220 to 1490cm-1showed best agreement with the MIPAS measurements when spectroscopic data of NAT were used to simulate the MIPAS spectra. MIPAS measurements collocated with Lidar observations of Type 1b and Type 2 PSCs could only be reproduced by assuming a composition of super-cooled ternary H2SO4/HNO3/H2O solution (STS) and of ice, respectively. Particle radius and number density profiles derived from MIPAS were generally consistent with the Lidar observations. Only in the case of ice clouds, PSC volumes are partly underestimated by MIPAS due to large cloud optical thickness in the limb-direction. A comparison of MIPAS cloud composition and Lidar PSC-type determination based on all available MIPAS-Lidar coincident measurements revealed good agreement between PSC-types 1a, 1b and 2, and NAT, STS and ice, respectively. We could not find spectroscopic evidence for the presence of nitric acid dihydrate (NAD) from MIPAS observations of PSCs over Antarctica in 2003.
Original languageEnglish
Pages (from-to)1201 - 1219
Number of pages19
JournalAtmospheric Chemistry and Physics
Volume6
Issue number5
DOIs
Publication statusPublished - 2006
Externally publishedYes

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All Science Journal Classification (ASJC) codes

  • Atmospheric Science

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