Properties of polar stratospheric clouds obtained by combined ACE-FTS and ACE-Imager extinction measurements

Abstract. We report the compositions and size distributions of aerosol particles in typical polar stratospheric clouds (PSCs) observed between 24 January and 28 February 2005 in the Arctic stratosphere. The results are obtained by combining the extinction measurements made by the Atmospheric Chemistry Experiment (ACE) Fourier-Transform Spectrometer and the visible/near IR imagers on the SCISAT satellite. The extended wavenumber range provided by this combination (750 to 20 000 cm −1 ) enables the retrieval of aerosol particle sizes between 0.05 and 10 μm as well as providing extensive information about the compositions. Our results indicate that liquid ternary solutions with a high (>30 wt%) content of HNO 3 were the most probable component of the clouds at the (60–70° N) latitudes accessible by ACE. The mean size of these ternary aerosol particles is in the range of 0.3 to 0.8 μm. Less abundant, although still frequent, were clouds composed of NAT particles having radii in the range of 1 μm and clouds of ice particles having mean radii in the 4–5 μm range. In some cases, these last two types were found in the same observation.