HR: 0800h
AN: A21E-0776    [Abstracts]
TI: Zonally asymmetric forcing of the stratosphere: Ozone and volcanic aerosols
AU: * Graf, H
EM: hfg21@cam.ac.uk
AF: University of Cambridge, Centre for Atmospheric Sciences, Downing Place, Cambridge, CB2 3EN, United Kingdom
AU: Gabriel, A
EM: gabriel@iap-kborn.de
AF: Leibniz Institut fuer Atmosphaerenphysik der Universitaet Rostock e.V., Schlosstrasse 6, Kuehlungsborn, D-18225, Germany
AU: Kirchner, I
EM: Ingo.Kirchner@met.fu-berlin.de
AF: Meteorologisches Institut, Freie Universitaet Berlin, Carl-Heinrich-Becker-Weg 6-10, Berlin, D-12165, Germany
AU: Peters, D
EM: peters@iap-kborn.de
AF: Leibniz Institut fuer Atmosphaerenphysik der Universitaet Rostock e.V., Schlosstrasse 6, Kuehlungsborn, D-18225, Germany
AB: Often studies concerning troposphere-stratosphere interaction are based on zonally symmetric features (e.g. zonal mean wind, Northern Annular Mode etc.). Also model simulations, used to study the effects of stratospheric ozone depletion or volcanic eruptions generally are forced by zonal symmetric anomalies. In many cases these simulations partly fail to reproduce the observed anomaly patterns. Reasons can be manifold, reaching from missing processes, model biases and inadequate surface conditions (to name but a few), to inadequate forcing. Here we will use two examples showing that the zonally asymmetric part of forcing in the UTLS, even if it only represents a fraction of the zonal mean forcing, may contribute significantly to the resulting anomaly pattern and amplitude. The examples are trends in stratospheric ozone representing decadal variability and volcanic aerosol representing interannual variability. Basically it could be any radiatively active substances, including water vapour. Our results show that: (i) zonally asymmetric forcing at the tropopause contributes an important part of observed climate change in the stratosphere, (ii) at least the recent volcanically induced climate anomalies cannot be understood based alone on zonally symmetric analysis, and (iii) if coupled climate-chemistry models shall reproduce observed features, planetary wave forcing, e.g. due to interannual (El Nino) or decadal (PDO, ADO) must be considered.
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 0322 Constituent sources and sinks
DE: 0360 Radiation: transmission and scattering
DE: 0370 Volcanic effects (8409)
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting