Sudden jumps and deep laminations, observed on vertical stratospheric ozone profiles during the European Arctic Stratospheric Ozone Experiment (EASOE) (winter 1991--1992) are explained as resulting from transport on isentropic layers. This is obtained by comparing the ozone profiles with high-resolution reconstruction of the potential vorticity. Multilayer isentropic contour advection with surgery (CAS) is performed using European Center for Medium Range Weather Forecasts (ECMWF) analyzed winds. The results presented in this work are based on analyzing the location of the edge of the polar vortex, the horizontal and vertical extents of filamentary structures and intrusions within the polar vortex. The results are consistent with the assumption of high ozone content within the polar vortex which is valid during normal winter conditions of the northern hemisphere. The resolution required to carry out this study is much higher than that of current operational analysis by weather centers, while it is achievable by CAS reconstructions, which provide a dynamical understanding of the ozone variations.¿ 1997 American Geophysical Union