THE FIRST SIMULATION OF AN OZONE QBO IN A GENERAL-CIRCULATION MODEL

The quasi-biennial oscillation (QBO) of ozone has been simulated for t he first time in a general circulation model (GCM). The model employed is the first version GCM developed at the Center for Climate System R esearch/National Institute for Environmental Studies (CCSR/NIES). The model has a horizontal resolution of T21 and 60 layers in the vertical . Modified Chapman reactions of ozone photochemistry are included in t he model, allowing the ozone to be fully interactive with the radiativ e and dynamical fields. The simulation is, for the most part, successf ul except that a deficiency of about 40 DU exists in the total ozone i n comparison with observations. The simulated zonal wind QBO has a rat her short period (about 1.5 years) and somewhat weak easterlies. The l ower stratospheric ozone QBO over the equator is qualitatively similar to that observed, although the simulated amplitude of about 0.3 ppmv is somewhat less than that observed. The phase relationship between th e equatorial upper and lower stratospheric ozone QBOs is successfully reproduced, although the phase of the modeled ozone QBO slightly prece des the observed phase in the upper stratosphere. The mid-latitude ozo ne QBO is out of phase with the equatorial ozone QBO. The phase propag ation of planetary-scale structure in ozone from the mid-latitudes to equatorial regions is more pronounced during the westerly than in the easterly phase of the stratospheric QBO, especially in the Northern He misphere winter.