Concentration variations of atmospheric CO2 over Syowa Station, Antarctica and their interpretation

Aircraft and ground-based measurements of the atmospheric CO₂ concentration have been made at Syowa Station, Antarctica since January 1983. The minimum concentration of the average seasonal CO₂ cycle occurs in March throughout the troposphere, while the maximum concentration appears in mid-August in the upper troposphere and in late September in the lower and middle troposphere. The peak-to-peak amplitude of the cycle decreases slightly with height. The CO₂ concentration increases with height during most of the year, but from late winter to spring this height dependency is minimal. To examine the contribution of the atmospheric transport processes to these variations of the CO₂ concentration, a 3-dimensional trajectory analysis was performed using data from the US National Meteorological Center. From the results obtained, it is postulated that northern hemispheric air with relatively high CO₂ concentration is transported to the antarctic region through the upper troposphere from late fall to winter, while air with low CO₂ concentration is transported from the southern hemisphere middle latitudes into the antarctic region through the lower troposphere in the remaining seasons. It is hypothesized that these air transport processes could influence CO₂ variations over the station.