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Ann. Geophys., 20, 711-715, 2002
www.ann-geophys.net/20/711/2002/
© European Geosciences Union 2002
An explanation for some fallstreak clouds
R. M. Worthington
RASC, Kyoto University, Uji, Kyoto 611–0011, Japan
Correspondence to: R. M. Worthington
(worth@kurasc.kyoto-u.ac.jp)
Abstract. Fallstreak cirrus clouds
are associated with super-saturated air, together with waves, instabilities
and/or turbulence; however, their precise cause is usually uncertain. This
paper uses already-published satellite, radiosonde and radar data, reanalysed
to study some large fallstreaks which had been previously overlooked. The
fallstreaks – up to 60 km long with a parent cloud 20 km wide – are caused
by lifting and/or turbulence from a mountain wave, rather than, for example,
Kelvin-Helmholtz instabilities. If turbulent breaking of mountain waves affects
ice particle formation, this may be relevant for the seeder-feeder effect on
orographic rain, and the efficiency of mountain-wave polar stratospheric clouds
for ozone depletion.
Key words. Meteorology and
atmospheric dynamics (turbulence; waves and tides) – Atmospheric composition
and structure (cloud physics and chemistry)
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