Northern hemisphere summer ozone variability observed by POAM II

Zonal asymmetry in ozone mixing ratio was observed by POAM II during the 19 94-1996 summers between 55 degrees N and 65 degrees N and between 21 km aid 28 km in altitude. The zonal variance can be described as persistent large -scale ozone patterns that move approximately with the zonal mean wind. The histories of air parcels observed by FOAM are deduced from 20-day back tra jectories using UKMO winds which have been corrected for stationary anomali es. The ozone mixing ratio is found to correlate with the average latitude of the back trajectory throughout the summer, indicating that the zonal var iance is a result of meridional transport. The meridional transport appears to be caused by breaking of westward-propagating waves that are evanescent in the summer easterly flow.