HR: 0800h
AN: A51D-0804    [Abstracts]
TI: The Latitude Dependence of the Effect Of Pinatubo on Stratospheric Ozone
AU: * Stolarski, R S
EM: stolar@polska.gsfc.nasa.gov
AF: NASA, Goddard Space Flight Center Code 916, Greenbelt, MD 20771 United States
AU: Douglass, A R
EM: douglass@persephone.gsfc.nasa.gov
AF: NASA, Goddard Space Flight Center Code 916, Greenbelt, MD 20771 United States
AB: Statistical analyses of TOMS and SBUV total ozone data indicate that the eruption of Pinatubo in 1991 led to a significant decrease in ozone at northern midlatitudes with little or no effect at southern midlatitudes despite the fact that aerosols were observed in both hemispheres. We argue that this puzzling absence of a southern hemisphere effect may be an artifact of the statistical analysis which does not fully account for interannual variability in dynamics. We have run a 3D CTM simulation of the past 30 years of stratospheric photochemistry with variable forcing due to chlorine/bromine compounds, solar ultraviolet radiation, and volcanic aerosols. This integration used winds from a general circulation model, which has similar interannual variability to the atmosphere. When this CTM output was examined with a standard time-series analysis, we found an effect of Pinatubo in the southern hemisphere, but not in the northern hemisphere. We then reran the CTM without volcanic aerosols. The subtraction of the two simulations indicated, as expected, that Pinatubo affected both emispheres in the model. This means that the northern hemisphere effect was in the model but did not show up in the statistical analysis. We also had an on-line parameterized chemical ozone tracer with seasonally repeating production and loss over the simulation. We used this as a dynamical surrogate to remove interannual variability from the original model output The residual time series was then analyzed for the Pinatubo effect and we were able to find it in both hemispheres. We suggest that the combination of the two volcanoes, El Chichon and Pinatubo, with the solar cycle and interannual variability led to this problem of analysis in the northern hemisphere of our model. We furthermore suggest that a similar effect may mask the response to Pinatubo in the southern hemisphere of the data. An analysis of the atmosphere's southern hemisphere with a good dynamical surrogate may solve the mystery of the missing southern hemisphere effect of Pintubo on ozone.
DE: 0340 Middle atmosphere--composition and chemistry
DE: 0341 Middle atmosphere--constituent transport and chemistry (3334)
DE: 0370 Volcanic effects (8409)
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting