Mid stratospheric ozone minima in polar regions

Recent springtime measurements of ozone vertical profiles in polar regions have revealed local ozone depressions of about 25% at altitudes near 30 km. Similar features are also identified in three‐dimensional photochemical model results. The modeled ozone depressions are local and temporary, often associated with stratospheric warming events which transport air from low latitudes, altering its photochemical history. The feature may be a component of the climatology of the region, but occurs less frequently in the model, possibly because of the long‐standing problem of the underprediction of upper stratospheric ozone.