Atmospheric Chemistry and Physics www.atmos-chem-phys.net 1680-7316 1680-7324 4 9/10 2004 10.5194/acp-4-2401-2004 http://www.atmos-chem-phys.net/4/2401/2004/ http://www.atmos-chem-phys.net/4/2401/2004/acp-4-2401-2004.html http://www.atmos-chem-phys.net/4/2401/2004/acp-4-2401-2004.pdf 2401 2423 2004-12-02 NOGAPS-ALPHA model simulations of stratospheric ozone during the SOLVE2 campaign J. P. McCormack S. D. Eckermann L. Coy D. R. Allen Y.-J. Kim T. Hogan B. Lawrence A. Stephens E. V. Browell J. Burris T. McGee C. R. Trepte E.O. Hulburt Center for Space Research, Naval Research Laboratory, Washington DC, USA Remote Sensing Division, Naval Research Laboratory, Washington DC, USA Marine Meteorology Division, Naval Research Laboratory, Monterey, California, USA British Atmospheric Data Center, Rutherford Appleton Laboratory, Oxfordshire, UK NASA Langley Research Center, Hampton, Virginia, USA NASA Goddard Space Flight Center, Greenbelt, Maryland, USA This paper presents three-dimensional prognostic O₃ simulations with parameterized gas-phase photochemistry from the new NOGAPS-ALPHA middle atmosphere forecast model. We compare 5-day NOGAPS-ALPHA hindcasts of stratospheric O₃ with satellite and DC-8 aircraft measurements for two cases during the SOLVE II campaign: (1) the cold, isolated vortex during 11-16 January 2003; and (2) the rapidly developing stratospheric warming of 17-22 January 2003. In the first case we test three different photochemistry parameterizations. NOGAPS-ALPHA O₃ simulations using the NRL-CHEM2D parameterization give the best agreement with SAGE III and POAM III profile measurements. 5-day NOGAPS-ALPHA hindcasts of polar O₃ initialized with the NASA GEOS4 analyses produce better agreement with observations than do the operational ECMWF O₃ forecasts of case 1. For case 2, both NOGAPS-ALPHA and ECMWF 114-h forecasts of the split vortex structure in lower stratospheric O₃ on 21 January 2003 show comparable skill. Updated ECMWF O₃ forecasts of this event at hour 42 display marked improvement from the 114-h forecast; corresponding updated 42-hour NOGAPS-ALPHA prognostic O₃ fields initialized with the GEOS4 analyses do not improve significantly. When NOGAPS-ALPHA prognostic O₃ is initialized with the higher resolution ECMWF O₃ analyses, the NOGAPS-ALPHA 42-hour lower stratospheric O₃ fields closely match the operational 42-hour ECMWF O₃ forecast of the 21 January event. We find that stratospheric O₃ forecasts at high latitudes in winter can depend on both model initial conditions and the treatment of photochemistry over periods of 1-5 days. Overall, these results show that the new O₃ initialization, photochemistry parameterization, and spectral transport in the NOGAPS-ALPHA NWP model can provide reliable short-range stratospheric O₃ forecasts during Arctic winter.