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Ann. Geophys., 24, 3267-3277, 2006
www.ann-geophys.net/24/3267/2006/
© European Geosciences Union 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
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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