master thesis abstract

Long-term observation on the triple oxygen isotopic composition of stratospheric CO2: Implications for photochemistry and air mass transport in the stratosphere （成層圏二酸化炭素の三酸素同位体組成分布モニタリングに基づく成層圏の光化学系と物質循環の解明）

The triple oxygen isotopic composition (δ18O, Δ17O) of stratospheric CO2 is useful as a tracer to study both photochemical reactions and air transport in the stratosphere. In this study, I quantified triple oxygen isotopic compositions of stratospheric CO2 sampled over Japan by using a balloon-borne cryogenic sampler, as well as their temporal variations for past 14 years. I found significant 17O anomalies (Δ 17O ≠ 0) in stratospheric CO2, while the temporal and seasonal variation was little in both δ18O and Δ17O. The triple oxygen isotopic compositions over Japan coincide well with those over France and Sweeden on the δ18O vs. Δ17O plot. Besides, the datasets from previous and my study exhibit similar trend on N2O vs. Δ17O plot. I conclude that the distribution of Δ 17OCO2 must be determined mostly through air mass mixing between troposphere and upper stratosphere. I further confirm that a two dimensional model which assume poleward advection accompanied with a slight vertical disturbance for stratospheric air transport can fully represent all the observed two dimensional distributions of Δ17OCO2, [CO2], and [N2O], as well as their mutual relation.