2:30 PM - 2:45 PM
[AAS11-10] Spatial and temporal variations of atmospheric methane concentration and its carbon and hydrogen isotopic ratios in the upper troposphere/lower stratosphere over the Eurasian continent observed by commercial airliner
Keywords:Methane, carbon and hydrogen isotopic ratios, upper troposphere/lower stratosphere, Eurasian continent
In the upper troposphere, CH4 concentrations, δ13C and δD showed no clear seasonal variations. In the lower stratosphere, on the other hand, CH4 and δ13C, δD showed clear aniti-phase seasonal variations; seasonal maximum (minimum) of the CH4 concentration (δ13C, δD) was found in November to January and seasonal minimum (maximum) was in spring. They can be explained by effective flushing of the lowermost stratospheric air with the tropospheric air in autumn and subsidence of the middle stratospheric air in spring (Sawa et al., 2015). Moreover, compact correlations of CH4 with respect to δ13C and δD were found in the lower stratosphere, suggesting the occurrence of reactions of CH4 not only with OH, but also with Cl and O(1D).