HR: 0800h
AN: A21E-0791    [Abstracts]
TI: Sensitivity of the climatic impact of Mt. Pinatubo eruption to the phase of the Quasi Biennial Oscillation
AU: * Thomas, M A
EM: manu.thomas@zmaw.de
AF: Max Planck Institute for Meteorology, Bundesstrasse 53, Hamburg, 20146, Germany
AU: Giorgetta, M
EM: marco.giorgetta@zmaw.de
AF: Max Planck Institute for Meteorology, Bundesstrasse 53, Hamburg, 20146, Germany
AU: Timmreck, C
EM: claudia.timmreck@zmaw.de
AF: Max Planck Institute for Meteorology, Bundesstrasse 53, Hamburg, 20146, Germany
AU: Graf, H
EM: hans.graf@geog.cam.ac.uk
AF: Department of Geography, University of Cambridge, Downing Place, Cambridge, CB2 3EN, United Kingdom
AU: Stenchikov, G
EM: gera@envsci.rutgers.edu
AF: Department of Environmental Sciences, Rutgers-The State University of New Jersey, 14 College Farm Rd., New Brunswick, 08901-8551, United States
AB: The quasi-biennial oscillation (QBO) is the dominant mode of variability in the equatorial stratosphere. Planetary wave activity is much less in the easterly phase of the QBO compared to the westerly phase. These different phases of the QBO have different effects on the stratospheric extratropical circulation. Here, we try to evaluate the sensitivity of the effect of large volcanic eruptions on the high latitude circulation to the QBO phase. Mt. Pinatubo erupted on June 15, 1991 during the easterly phase of the QBO at 30 hPa and the change to the westerly phase took place in Aug 1992 at 30 hPa and remained in the same phase till May 1993. It would be interesting to understand the climate impact of Mt Pinatubo eruption if it had erupted during the opposite shear. Here, in this study, a sensitivity analysis is carried out to understand the effect of the QBO phase on the response of the extratropical circulation to the Mt. Pinatubo eruption. For this, the middle atmosphere version of the general circulation model (MA)ECHAM5.4 is employed to carry out ensemble simulations for two years (June 1991 - May 1993) following the eruption. Two sets of experiments were performed - one with the QBO in the phase as observed and the other with an opposite QBO phase. The model is forced by zonally averaged values of aerosol extinction, single scattering albedo and asymmetry parameter and volcanically induced ozone anomalies. The differences in the responses will be discussed. The model is able to simulate the tropical and extratropical responses to Mt. Pinatubo eruption most realistically when all the known processes are included.
DE: 0360 Radiation: transmission and scattering
DE: 0370 Volcanic effects (8409)
DE: 3362 Stratosphere/troposphere interactions
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting