ACP Atmospheric Chemistry and Physics ACP 1680-7324 Copernicus GmbH Göttingen, Germany 10.5194/acp-6-1221-2006 MIPAS detects Antarctic stratospheric belt of NAT PSCs caused by mountain waves Höpfner M. 1 Larsen N. 2 Spang R. 3 Luo B. P. 4 Ma J. 5 Svendsen S. H. 2 Eckermann S. D. 6 Knudsen B. 2 Massoli P. 7 8 Cairo F. 7 Stiller G. 1 v. Clarmann T. 1 Fischer H. 1 Forschungszentrum Karlsruhe, Institut für Meteorologie und Klimaforschung, Karlsruhe, Germany Danish Meteorological Institute, Middle Atmosphere Research Division, Copenhagen, Denmark Forschungszentrum Jülich, Institut für Chemie und Dynamik der Geosphäre, Jülich, Germany Institut für Atmosphäre und Klima, ETH-Hönggerberg, Zürich, Switzerland Computational Physics, Inc., Springfield, VA, USA E. O. Hulburt Center for Space Research, Naval Research Laboratory, Washington, USA Consiglio Nazionale delle Ricerche, Istituto di Scienze dell’Atmosfera e del Clima, Rome, Italy now at: University of Colorado, Cooperative Institute for Research in the Environmental Sciences, Boulder, CO, USA 20 04 2006 6 5 1221 1230 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.atmos-chem-phys.net/6/1221/2006/acp-6-1221-2006.html The full text article is available as a PDF file from http://www.atmos-chem-phys.net/6/1221/2006/acp-6-1221-2006.pdf

Space borne infrared limb emission measurements by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) reveal the formation of a belt of polar stratospheric clouds (PSCs) of nitric acid trihydrate (NAT) particles over Antarctica in mid-June 2003. By mesoscale microphysical simulations we show that this sudden onset of NAT PSCs was caused by heterogeneous nucleation on ice in the cooling phases of large-amplitude stratospheric mountain waves over the Antarctic Peninsula and the Ellsworth Mountains. MIPAS observations of PSCs before this event show no indication for the presence of NAT clouds with volume densities larger than about 0.3 &micro;m<sup>3</sup>/cm<sup>3</sup> and radii smaller than 3 &micro;m, but are consistent with supercooled droplets of ternary H<sub>2</sub>SO<sub>4</sub>/HNO<sub>3</sub>/H<sub>2</sub>O solution (STS). Simulations indicate that homogeneous surface nucleation rates have to be reduced by three orders of magnitude to comply with the observations.