Observations and modeling of transport during the December 1998 stratospheric major warming

A stratospheric major warming in mid-December 1998 was the first major warming in nearly eight years, only the second major warming on record before the end of December, and had a profound impact on the stratospheric circulation during the remainder of the 1998-99 winter. Successful mechanistic model simulations of the December 1998 major warming, with online tracer transport, have been done. Unfortunately, with the aging of the Upper Atmosphere Research Satellite (UARS), three-dimensionally distributed tracer data are scarce during this period. There are, however, data available during portions of the warming period, and before and after the warming from the UARS Halogen Occultation Experiment (HALOE) and from the Polar Ozone and Aerosol Measurement (POAM III) instrument, both occultation instruments. Distributed tracer fields from these instruments can be obtained by mapping the data in Equivalent Latitude (PV)/theta space. Using such maps of HALOE CH4, H2O, HF and O3, and POAM III O3 and H2O, we compare observed and modeled trace gas distributions before and after the warming, to diagnose the patterns of large-scale transport during this event.