scostep 2010 (stp12) - Leibniz-Institut für Atmosphärenphysik an der ...

STP12 Abstracts
Berlin, 12 - 16 July 2010
SCOSTEP Symposium 2010
Effects of solar particle events on the middle atmosphere's chlorine chemistry
Winkler Holger 1 , Kazeminejad Shahin 2 , Wieters Nadine 1 , Sinnhuber Miriam 1 , Wissing Jan Maik 3 ,
Kallenrode May-Britt 3 , Stiller Gabriele 4 , Von Clarmann Thomas 4 , Funke Bernd 5 , Santee Michelle 6 ,
James M. Russell III 7
1 Institut für Umweltphysik, Universität Bremen, Germany, 2 Deutsches Zentrum für Luft- und
Raumfahrt (DLR), Bonn-Oberkassel, Germany, 3 Fachbereich Physik, Universität Osnabrück,
Germany, 4 Institut für Meteorologie und Klimaforschung, Karlsruher Institut für Technologie,
Germany, 5 Instituto de Astrofisica de Andalucia, Granada, Spain, 6 Jet Propulsion Laboratory,
Pasadena, USA, 7 Langley Research Center, USA
It is well established that solar proton events (SPEs) are sources of distinct chemical
disturbances in the Earth’s polar atmosphere. While the SPE caused production of NOx and
HOx and the subsequent destruction of ozone can be reproduced quite well by atmospheric
models using basic parameterizations for NOx and HOx release as a function of the particle
impact ionization rate, there are significant differences between measurements and model
predictions concerning chlorine compounds. Satellite measurements (HALOE, MIPAS,
MLS/Aura) have shown that there is also chlorine activation in the stratosphere and
mesosphere, and an increase of chlorine nitrate in the lower and middle stratosphere during
SPEs. This cannot be explained by the NOx and HOx increase alone. Atmospheric models
with standard parameterizations of NOx and HOx production due to SPEs fail to reproduce
the magnitude of the observed chlorine disturbances.
Numerical simulations using the University of Bremen ion chemistry (UBIC) model show a
much better agreement with measurements if full negative ion chemistry is considered
additionally to the NOx and HOx production. The UBIC results in combination with
atmospheric models indicate that reactions of negative cluster ions can have a significant
impact on the middle atmosphere’s chlorine chemistry during SPEs. There is a transformation
of HCl into active chlorine via anion cluster chemistry. Additionally, the release of O(1D)
through N(2D) + O2 → NO + O(1D) has a considerable impact on chlorine species.
Results of UBIC simulations for different SPEs (July 2000, October 2003, January 2005) are
presented. They are compared with the observed changes of chlorine compounds – HCl,
HOCl, ClO and ClONO2 – from the satellite instruments HALOE, MIPAS and MLS/Aura.