Vertical Profiles and Temporal Variations of Greenhouse Gases in the Stratosphere over Syowa Station, Antarctica

Stratospheric air sampling using balloon-borne cryogenic air samplers was conducted over Syowa Station, Antarctica in four austral summers between 1998 and 2013. The CH4 and N2O mole fractions decreased with increasing altitude due to chemical reactions and photodissociation in the stratosphere, and a compact positive correlation between CH4 and N2O was found in their vertical profiles. The vertical profiles of CO2 and SF6 mole fractions showed high values in the lower stratosphere, decreasing gradually with altitude, and then becoming almost constant at altitudes above 18 km. Stratospheric CO2 and SF6 above 18km over Antarctica increased secularly at the respective average rates of 1.82 +/- 0.31 ppm yr(-1) and 0.26 +/- 0.01 ppt yr(-1) during the study period. The CO2 and SF6 mole fractions increased in the Antarctic stratosphere, but were delayed 4.5 +/- 0.5 and 5.6 +/- 0.2 years, respectively, compared to the tropical troposphere. The secular increase in stratospheric CH4 was also detected by classifying the measured mole fractions in terms of the N2O depletion in the stratosphere.