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

STP12 Abstracts
Berlin, 12 - 16 July 2010
SCOSTEP Symposium 2010
Comparison of Observed 11-Year Signals in Stratospheric Ozone and Temperature with
CCM Simulations Including a Coupled Ocean and Troposphere
Hood Lon L. 1 , Matthes Katja 2 , Soukharev Boris E. 1 , Arblaster Julie M. 3 , Sassi Fabrizio 4 , Meehl
Gerald A. 5
1 Lunar and Planetary Laboratory, University of Arizona, Tucson, Arizona 85721, USA, 2 Helmholtz
Centre Potsdam - GFZ German Research Centre for Geosciences, Potsdam, Germany, 3 Center for
Australian Weather and Climate, Bureau of Meteorology, Melbourne, Australia, 4 Naval Research
Laboratory, Washington, DC 20375, USA, 5 National Center for Atmospheric Research, P.O. Box
3000, Boulder, Colorado 80307, USA
Observational studies of stratospheric ozone and temperature records since the onset of
continuous global satellite measurements (1979) indicate the existence of responses to 11-year
solar UV forcing at tropical and subtropical latitudes. In addition to an upper stratospheric
response that is attributable to direct photochemical and radiative forcing, a significant
variation is also observed in the lower stratosphere that appears to be dynamical in origin and
is much less well understood. The latter variation has not yet been fully simulated by
chemistry climate models that consider only stratospheric processes with fixed sea surface
temperatures. Observational studies have also identified 11-year surface climate signals in the
tropical Pacific that resemble those observed during cold ENSO events (van Loon et al., JGR,
2007). The latter signals have recently been approximately simulated using the WACCM
model coupled to the ocean, land, and sea ice components of an ocean-troposphere model
(CCSM3) (Meehl et al., Science, 2009). Here, we report an initial comparison of the latter
coupled WACCM/CCSM3 model output for stratospheric ozone and temperature (with and
without a modeled QBO) to observed 11-year responses derived using a multiple regression
statistical model. The purpose of the comparison is to better determine the origin of the
tropical lower stratospheric response, especially whether the response may be amplified by
feedbacks from the ocean-troposphere response. The statistical model includes a lagged
ENSO term and two lagged QBO terms to minimize any aliasing of the solar regression
coefficients by internal sources of stratospheric interannual variability. A number of
qualitative agreements are found. For example, the observed geographical dependence of the
total column ozone response in NH winter (characterized by low values in the equatorial
eastern Pacific and higher values in the subtropical eastern Pacific) is similar to that obtained
from the model ozone data. A more detailed comparison of the observed and modeled
tropical ozone and temperature responses and their dependences on season, altitude, latitude,
and longitude (with and without including a QBO in the WACCM model) will be presented.