To investigate the gravitational separation of atmospheric components in the stratosphere, air samples collected using an aircraft during the Arctic Airborne Measurement Program 2002 (AAMP02) were analyzed for the O 2/N 2 ratios (δ(O 2/N 2)), δ 15N of N 2, δ 18O of O 2 and Ar/N 2 ratio (δ(Ar/N 2)). The relationship between observed stratospheric δ 15N of N 2, δ 18O of O 2 and δ(Ar/N 2) over the Svalbard Islands and Barrow showed mass-dependent fractionation of atmospheric components in the stratosphere, which suggested that gravitational separation could be observable in the lowermost stratosphere inside the polar vortex. By examining the rates of change in δ(O 2/N 2) and δ 13 C of CO 2 relative to the CO 2 concentration, such observed correlations were bound to be mainly attributable to upward propagation of their seasonal cycles produced in the troposphere and height-dependent air age as well as gravitational separation in the stratosphere. Air samples collected over Syowa Station, Antarctica, Kiruna, Sweden and Sanriku, Japan using balloon-borne cryogenic air samplers were analyzed for δ 15N of N2 and δ 18O of O 2. Strength of the gravitational separation was a function of latitude, showing the largest separation inside the polar vortex over Kiruna. It is suggested that information on increase of gravitational separation with height is useful in understanding the vertical transport of air masses in the stratosphere. By comparing the gravitational separations, mean age of air and N 2O concentration at two height intervals with N 2O concentrations > 125 ppb and > 45 ppb, the effect of descending air was found to be more significant over Kiruna than over Syowa Station and Sanriku. The variation in the gravitational separation with height is found to be weaker in the region with N 2O concentrations between 45 and 125 ppb than in other regions, which might suggest that vertical mixing of air occurred in this region.
|出版ステータス||Published - 2010 12月 1|
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