A balloon-borne gondola for a comprehensive
study of polar stratospheric clouds (PSCs) was launched on 25 January 2000 from
Kiruna, Sweden. Besides a
mass spectrometer experiment for chemical particle analysis, the gondola carried
optical particle counters, two backscatter sondes, a hygrometer and several
temperature and pressure sensors.
A mountain wave induced PSC was sampled between
20 and 23 km altitude. Strongly correlated data of PSC particle properties from
the different instruments were obtained. A large variability of particle types
was measured in several PSC layers, and particle development was followed for
more than 2 hours. Liquid
ternary PSC layers were found at temperatures near the ice frost point. A large
fraction of the sampled cloud layers consisted of solid nitric acid trihydrate (NAT)
particles with a molar ratio H2O:HNO3 of 3 at temperatures near and slightly
above the equilibrium temperature TNAT.
These observations, which are the first direct measurements indicating the existence of these solid hydrate particles in the atmosphere, will be presented and discussed.