STRATOSPHERIC MEAN AGES AND TRANSPORT RATES FROM OBSERVATIONS OF CARBON-DIOXIDE AND NITROUS-OXIDE

Measurements of stratospheric carbon dioxide (CO2) and nitrous oxide ( N2O) concentrations were analyzed to investigate stratospheric transpo rt rates. Temporal variations in tropospheric CO2 were observed to pro pagate into the stratosphere, showing that tropospheric air enters the lower tropical stratosphere continuously, ascends, and is transported rapidly (in less than 1 month) to both hemispheres. The mean age A of stratospheric air determined from CO2 data is approximately 5 years i n the mid-stratosphere. The mean age is mathematically equivalent to a conserved tracer analogous to exhaust from stratospheric aircraft. Co mparison of values for A from models and observations indicates that c urrent model simulations likely underestimate pollutant concentrations from proposed stratospheric aircraft by 25 to 100 percent.