HR: 0800h
AN: A51D-0805    [Abstracts]
TI: The Contribution of Dynamic Interannual Variability to Ozone Trends
AU: * Douglass, A R
EM: Anne.R.Douglass@nasa.gov
AF: NASA Goddard Space Flight Center, Code 916 Atmospheric Chemistry and Dynamics Branch, Greenbelt, MD 20771 United States
AU: Stolarski, R S
EM: Richard.S.Stolarski@nasa.gov
AF: NASA Goddard Space Flight Center, Code 916 Atmospheric Chemistry and Dynamics Branch, Greenbelt, MD 20771 United States
AB: At middle latitudes the total column ozone and the lower stratospheric ozone mixing ratio exhibit natural variability. Models and statistical analyses of observations such as SAGE ozone profiles and TOMS column measurements show that seasonal cycle, solar cycle, and interannual dynamical variability and dynamical phenomena such as the quasi-biennial oscillation all contribute to ozone variability. These must be accounted for when deriving ozone trends. Systematic or random changes in the atmospheric circulation may also contribute to ozone trends. It is presently unclear how much of the lower stratospheric ozone trend derived from observations is due to changes in the chemical composition of the stratosphere and how much is due to changes in the atmospheric circulation. We are attempting to resolve this issue by comparing a twenty-five year three-dimensional simulation of ozone with fixed source gas boundary conditions with an identical simulation with time dependent source gas boundary conditions. Both simulations are driven with output from a general circulation model that produces realistic interannual variability in dynamical forcing. The model trend in ozone due to changes in composition is determined from the difference in these simulations. We compare these trends with trends determined from observations and model output using the same statistical analysis techniques. Initial results emphasize the complications to attribution of observed ozone trends to dynamical and photochemical effects that are due to interrelationships between trends in transport, temperature, and photochemical effects. It may not be possible to describe the ozone trend as a superposition of dynamical and photochemical contributions.
DE: 3334 Middle atmosphere dynamics (0341, 0342)
DE: 0340 Middle atmosphere--composition and chemistry
DE: 0341 Middle atmosphere--constituent transport and chemistry (3334)
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting