アイテム詳細

要旨

A three year long record of regular vertical aircraft profiling for continuous atmospheric CO₂ mixing ratio measurements as well as for flask sampling to derive the climatology of other greenhouse gases (CH₄, SF₆ and N₂O), is presented. Measurements were undertaken in the lower troposphere between 100 and 3000 m over the eastern European taiga about 100 km south east of the city of Syktyvkar (61°24′N, 52°18′E). From the continuous profiles mean CO₂ mixing ratios were calculated for the atmospheric boundary layer (ABL) and for the “free troposphere” up to 3000 m. The amplitudes of the respective seasonal cycles are 22.1 ± 3.5 and 14.0 ± 2.1 ppm. ABL mixing ratios are generally larger than free tropospheric values during the winter period, and smaller during the summer due to the change of the continental biosphere from a source to a sink. The phasing of the seasonal cycles is slightly different between the two height intervals (by about 30 days), with the ABL extremes occurring earlier. Very abrupt concentration changes up to 8 ppm are observed in the free troposphere associated with changes in air mass origin. Mean CO₂ mixing ratios derived from flask samples at 3000 m compare well with the respective integrated values measured in the continuous profiles above the ABL (ΔCO₂ = 0.3 ± 1.6 ppm). CH₄ mixing ratios also show a pronounced seasonality, and winter time vertical gradients correlate well with those of CO₂. Similarly, SF₆ vertical gradients are correlated with CO₂ gradients possibly pointing to some anthropogenic origin of the boundary layer CO₂ signal during winter. N₂O and SF₆ also show a slight seasonality with almost the same phasing. The main reasons for the seasonality of both gases are probably transport processes with a possible contribution from stratosphere/troposphere exchange.