Discovery of a Nitric Acid Trihydrate (NAT) PSC Belt Around Antarctica by MIPAS on Envisat

HR: 08:30h
AN: A31D-02 [Abstracts]
TI: Discovery of a Nitric Acid Trihydrate (NAT) PSC Belt Around Antarctica by MIPAS on Envisat
AU: * Hopfner, M
EM: michael.hoepfner@imk.fzk.de
AF: Forschungszentrum Karlsruhe, Institut für Meteorologie und Klimaforschung, Postfach 3640, Karlsruhe, 76021 Germany
AU: Larsen, N
EM: nl@dmi.dk
AF: Danish Meteorological Institute, Middle Atmosphere Research Division, Lyngbyvej 100, Copenhagen, 2100 Denmark
AU: Spang, R
EM: R.Spang@fz-juelich.de
AF: Forschungszentrum Jülich, Institut für Chemie und Dynamik der Geosphäre, Institute I: Stratosphere (ICG-I), Jülich, 52425 Germany
AU: Luo, B
EM: beiping.luo@env.ethz.ch
AF: Institut fr Atmosphäre und Klima, ETH-H”nggerberg, Schafmattstr. 30, Zrich, 8093 Switzerland
AU: Ma, J
EM: unma@uap2.nrl.navy.mil
AF: Computational Physics, Inc., 8001 Braddock Road, Suite 210, Springfield, VA 22151 United States
AU: Svendsen, S H
EM: shs@dmi.dk
AF: Danish Meteorological Institute, Middle Atmosphere Research Division, Lyngbyvej 100, Copenhagen, 2100 Denmark
AU: Eckermann, S D
EM: eckerman@uap2.nrl.navy.mil
AF: E. O. Hulburt Center for Space Research, Naval Research Laboratory, 4555 Overlook Avenue SW, Washington, DC 20375 United States
AU: Massoli, P
EM: paola1476@libero.it
AF: Consiglio Nazionale delle Ricerche, Istituto di Scienze dell'Atmosfera e del Clima, Via Fosso del Cavaliere 100, Rome, 00133 Italy
AU: Cairo, F
EM: f.cairo@isac.cnr.it
AF: Consiglio Nazionale delle Ricerche, Istituto di Scienze dell'Atmosfera e del Clima, Via Fosso del Cavaliere 100, Rome, 00133 Italy
AU: Snels, M
EM: m.snelsnr.it
AF: Consiglio Nazionale delle Ricerche, Istituto di Scienze dell'Atmosfera e del Clima, Via Fosso del Cavaliere 100, Rome, 00133 Italy
AU: Di Donfrancesco, G
EM: didonfrancesco@casaccia.enea.it
AF: Ente per le Nuove tecnologie, l'Energie e l'Ambiente, Via Anguillarese 301, Rome, 00060 Italy
AU: Knudsen, B
EM: bk@dmi.dk
AF: Danish Meteorological Institute, Middle Atmosphere Research Division, Lyngbyvej 100, Copenhagen, 2100 Denmark
AU: Biermann, U
EM: Uta-Maritta.Biermann@spd.de
AF: Max-Planck-Institut für Chemie, Abteilung Atmosphärenchemie, Joh.-Joachim-Becher-Weg 27, Mainz, 55128 Germany
AU: Stiller, G
EM: gabriele.stiller@imk.fzk.de
AF: Forschungszentrum Karlsruhe, Institut für Meteorologie und Klimaforschung, Postfach 3640, Karlsruhe, 76021 Germany
AU: von Clarmann, T
EM: thomas.clarmann@imk.fzk.de
AF: Forschungszentrum Karlsruhe, Institut für Meteorologie und Klimaforschung, Postfach 3640, Karlsruhe, 76021 Germany
AU: Fischer, H
EM: herbert.fischer@imk.fzk.de
AF: Forschungszentrum Karlsruhe, Institut für Meteorologie und Klimaforschung, Postfach 3640, Karlsruhe, 76021 Germany
AB: Due to a globally changing climate with decreasing stratospheric temperatures, polar stratospheric cloud (PSC) occurrence might intensify in future. This could counteract the recovery of the ozone layer due to a decreasing stratospheric chlorine loading as consequence of the Montreal protocol and its amendments. To improve models of future ozone loss it is necessary to answer still open questions regarding nucleation processes of nitric acid containing solid cloud particles. The mid-infrared limb-emission sounder Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on Envisat is the first instrument able to monitor continuously the development of PSC appearance and composition with full coverage of the polar regions even during polar night. We have analyzed MIPAS observations during the Antarctic winter 2003 with respect to PSC composition. Coincident lidar observations from McMurdo were used for comparison. By application of new refractive index data we could prove that a distinct spectral signature at around 820~cm^-1 as observed by MIPAS is due to a composition of β-NAT. This has been the first evidence for the existence of NAT PSCs on a large scale. We could not find any spectroscopic evidence for the presence of nitric acid dihydrate (NAD) from any MIPAS PSC observation. During the initial phase of PSC development over Antarctica the MIPAS measurements reveal the formation of a belt of NAT PSCs in mid-June 2003. By mesoscale microphysical simulations we have shown that this sudden onset of NAT 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. This suggests a more significant role for mountain waves in Antarctic PSC formation than has heretofore been appreciated. MIPAS observations of PSCs in a period of three weeks before this event show no indication for the presence of NAT clouds, but are consistent with supercooled droplets of ternary H₂SO₄/HNO₃/H₂O solution (STS). Simulations indicate that homogeneous surface nucleation rates have to be reduced by three orders of magnitude to comply with these observations.
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 0305 Aerosols and particles (0345, 4801, 4906)
DE: 0320 Cloud physics and chemistry
DE: 0340 Middle atmosphere: composition and chemistry
SC: Atmospheric Sciences [A]
MN: Fall Meeting 2005