An evaluation of isentropic transport across the subtropical stratospheric dynamical barrier of the southern hemisphere

This thesis focuses on an evaluation of isentropic transport across the subtropical stratospheric dynamical barrier of the southern hemisphere. Our strategy consists in isentropic transport events reconstitution using MIMOSA high-resolution model to advect potential vorticity (PV) fields. This model was initialized by the European model ERA-40 winds and temperature fields computed over 26 years (1980-2005). DYBAL algorithm has calculated dynamical barrier and mixing intensity. Also the k-means algorithm was applied on PV field to reconstitute laminae which is the characteristic form of isentropic transport events. Finally, subtropical barrier permeability was evaluated by following exchanges across this barrier and the distribution of lateral routes determined. Impact of these events on ozone distribution was estimated as the influence of quasi-biennial oscillation and 11-years solar cycle. Results shows on isentrope 600 K an increase of the tropical reservoir and the mid-latitude size with the diminution of the polar vortex. The results indicate also the reduction of exchange intensity across subtropical barrier since the 1980's.