16 December 2013

Sensitivity of Stratospheric Dynamics to O3 Production

Summary

The first research to examine how uncertainty in primary ozone (O3) production translates into changes in stratospheric temperature and circulation. The O3 production is varied through the ±30% uncertainty range (90% confidence interval) of the O2 cross sections in Hertzberg Continuum (200-240 nm).  These changes dramatically alter O3 in the lower stratosphere and also the temperature, but the key question asked here is whether this changes the overall Brewer-Dobson (BD) circulation and the net flux of stratospheric O3 into the troposphere. We find that reducing the O2 cross sections counterintuitively results in increased O3 in the lowermost stratosphere (less shielding of sunlight from above), increased temperatures by up to 2°C, and thus greater static stability or stratification near the tropopause. As a consequence, the dynamical coupling between stratosphere and troposphere changes, affecting the tropical annual cycle of temperature and ozone in the lower stratosphere as well as  the time-mean and interannual variability of temperature in polar vortices, particularly in the winter, but the overall Brewer-Dobson circulation of the middle stratosphere is hardly altered. We also found that this warming in the lower-middle stratosphere through increased O3 production resulted in weakened subtropical jets and the Hadley cell (as noted by others for similar temperature perturbations associated with the solar cycle), thus indicating that photochemical uncertainties have impact on tropospheric climate as well. In addition to basic chemical uncertainties, other factors affecting the O3 abundance near the tropopause include the cross-tropopause flux of very short lived bromine or iodine compounds from anthropogenic or oceanic sources.

Contact
Jeremy G Fyke
Los Alamos National Laboratory (LANL)
Acknowledgments

Implementation of the UCI fast-JX code into CESM CAM5 as part of the SciDAC research enabled this study. This research was supported by the Office of Science (BER) and Lawrence Livermore National Laboratory (LLNL), U.S. Department of Energy under contracts DE-AC52-07NA27344, DE-AC02-05CH11231 (LLNL authors), and DE-SC0007021 (all authors). The numerical simulations were carried out using resources of the National Energy Research Scientific Computing Center (NERSC) at LLNL.