VARIATIONS OF ATMOSPHERIC CO_2 CONCENTRATION OVER SYOWA STATION, ANTARCTICA AND AIR TRANSPORT PROCESS

Aircraft and ground-based measurements of the atmospheric CO_2 concentration have been made respectively at and over Syowa Station, Antarctica since January 1983. The minimum concentration of the average seasonal CO_2 cycle occurs in March throughout the troposphere and the maximum concentration appears in mid-August and late in September in the upper troposphere and in the lower and middle troposphere, respectively. The peak-to-peak amplitude of the cycle decreases slightly with height. The CO_2 concentration increases with height during most of the year and the height-dependent concentration difference is smaller from late winter to spring than in the remaining seasons. To interpret these variations of the CO_2 concentration, 3-dimensional trajectory analysis was done using U.S. NMC data. From the results obtained, it is suggested that the northern hemispheric air with high CO_2 concentration is transported to the Antarctic region through the upper troposphere from late fall to winter, while the air with low CO_2 concentration is transported from southern middle latitudes into the Antarctic region through the lower troposphere in the remaining seasons. These air transport processes are especially important for variations of the CO_2 concentration over the station