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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 24, issue 12
Ann. Geophys., 24, 3267–3277, 2006
https://doi.org/10.5194/angeo-24-3267-2006
© Author(s) 2006. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ann. Geophys., 24, 3267–3277, 2006
https://doi.org/10.5194/angeo-24-3267-2006
© Author(s) 2006. This work is distributed under
the Creative Commons Attribution 3.0 License.

  21 Dec 2006

21 Dec 2006

Simultaneous lidar observations of a polar stratospheric cloud on the east and west sides of the Scandinavian mountains and microphysical box model simulations

U. Blum1, F. Khosrawi2, G. Baumgarten3, K. Stebel4, R. Müller5, and K. H. Fricke6 U. Blum et al.
  • 1Forsvarets forskningsinstitutt, 2027 Kjeller, Norway
  • 2Institutionen för tillämpad miljövetenskap/Meteorologiska institutionen, Stockholms Universitet, 10691 Stockholm, Sweden
  • 3Leibniz-Institut für Atmosphärenphysik e.V., 18225 Kühlungsborn, Germany
  • 4Norsk institutt for luftforskning, 9296 Tromsø, Norway
  • 5Institut für Chemie und Dynamik der Geosphäre: Stratosphäre (ICG-I), Forschungszentrum Jülich, 52425 Jülich, Germany
  • 6Physikalisches Institut der Universität Bonn, 53115 Bonn, Germany

Abstract. The importance of polar stratospheric clouds (PSC) for polar ozone depletion is well established. Lidar experiments are well suited to observe and classify polar stratospheric clouds. On 5 January 2005 a PSC was observed simultaneously on the east and west sides of the Scandinavian mountains by ground-based lidars. This cloud was composed of liquid particles with a mixture of solid particles in the upper part of the cloud. Multi-colour measurements revealed that the liquid particles had a mode radius of r≈300 nm, a distribution width of σ≈1.04 and an altitude dependent number density of N≈2–20 cm−3. Simulations with a microphysical box model show that the cloud had formed about 20 h before observation. High HNO3 concentrations in the PSC of 40–50 weight percent were simulated in the altitude regions where the liquid particles were observed, while this concentration was reduced to about 10 weight percent in that part of the cloud where a mixture between solid and liquid particles was observed by the lidar. The model simulations also revealed a very narrow particle size distribution with values similar to the lidar observations. Below and above the cloud almost no HNO3 uptake was simulated. Although the PSC shows distinct wave signatures, no gravity wave activity was observed in the temperature profiles measured by the lidars and meteorological analyses support this observation. The observed cloud must have formed in a wave field above Iceland about 20 h prior to the measurements and the cloud wave pattern was advected by the background wind to Scandinavia. In this wave field above Iceland temperatures potentially dropped below the ice formation temperature, so that ice clouds may have formed which can act as condensation nuclei for the nitric acid trihydrate (NAT) particles observed at the cloud top above Esrange.

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