Observations and modeling of low ozone pockets in stratospheric anticyclones

In the middle and upper stratosphere (above ~900 K), both dynamics and chemistry are involved in the formation of "low-ozone pockets" in stratospheric anticyclones. Results from a climatology of occultation ozone in anticyclones show that the repeated formation of these pockets acts to reduce the monthly mean ozone concentration by 10% in high latitude wintertime anticyclones. Here, ozone observations from a larger variety of sources (SAGE I/II/III, POAM II/III, HALOE, ILAS, CLAES, MLS, ECMWF analyses, and ozonesondes) are combined with the climatology of stratospheric anticyclones with an emphasis on establishing a climatology of low-ozone pockets and estimating their contribution to ozone variability and trends. Low-ozone pocket statistics based on 20 years of observations will then be compared to the frequency and structure of pockets and their parent anticyclones in the stratosphere of the Whole Atmosphere Community Climate Model (WACCM). Preliminary comparisons between WACCM and the occultation data indicate that pockets are more robust and anticyclones are more isolated in the model than in the real atmosphere.