Altitude Distributions in the Arctic Vortex Derived From Multiple Tracer Relationships

Canonical trace gas relationships that are established in the middle latitude lower stratosphere are the result of altitude-dependent photochemical decomposition of trace gases and horizontal transport and mixing of the airmasses. It has been shown that these relationships change significantly in the Arctic vortex, and, based on the estimates of mixing across the edge of the vortex, these changes result mostly from the differential descent (analogous to the original altitude distribution) of air inside the vortex. The importance of studying the altitude distribution of air comes from the fact that air descending from very high altitudes is completely deprived of photolytic tracers and therefore should cause rapid and dramatic changes to tracer-tracer correlations in the lower stratosphere. The amount of descended air and its ozone content, in turn, influences the estimated flux of ozone-rich air across the edge of the vortex, which affects the calculations of ozone loss in the vortex. An earlier analysis using a simple integral model of the evolution of the midlatitude canonical tracer relationships to the vortex ones indicated that at 20 km in the vortex, about 70% of the air in an air parcel originated at higher altitudes, 10% at lower altitudes and only 20% at similar 20 km altitude. Previous analyses, however, bore an artifact caused by the contribution of photolysis to the different midlatitude tracer-tracer correlations. This study utilizes multiple tracer correlations and a reverse approach to quantify altitude distributions of air in the Arctic vortex air parcels.