TRANSPORT OUT OF THE LOWER STRATOSPHERIC ARCTIC VORTEX BY ROSSBY-WAVEBREAKING

The fine-scale structure in lower stratospheric tracer transport durin g the period of the two Arctic Airborne Stratospheric Expeditions (Jan uary and February 1989; December 1991 to March 1992) is investigated u sing contour advection with surgery calculations. These calculations s how that Rossby wave breaking is an ongoing occurrence during these pe riods and that air is ejected from the polar vortex in the form of lon g filamentary structures. There is good qualitative agreement between these filaments and measurements of chemical tracers taken aboard the NASA ER-2 aircraft. The ejected air generally remains filamentary and is stretched and mixed with midlatitude air as it is wrapped around th e vortex. This process transfers vortex air into midlatitudes and also produces a narrow region of fine-scale filaments surrounding the pola r vortex. Among other things, this makes it difficult to define a vort ex edge. The calculations also show that strong stirring can occur ins ide as well as outside the vortex.