Japan Geoscience Union Meeting 2016

Presentation information


Symbol A (Atmospheric and Hydrospheric Sciences) » A-AS Atmospheric Sciences, Meteorology & Atmospheric Environment

[A-AS11] Stratosphere-troposphere Processes And their Role in Climate

Mon. May 23, 2016 1:45 PM - 3:15 PM A01 (APA HOTEL&RESORT TOKYO BAY MAKUHARI)

Convener:*Yousuke Yamashita(National Institute for Environmental Studies), Hideharu Akiyoshi(National Institute for Environmental Studies), Kaoru Sato(Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo), Yoshihiro Tomikawa(National Institute of Polar Research), Chair:Yousuke Yamashita(National Institute for Environmental Studies)

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

*Ryo Fujita1, Shinji Morimoto1, Shuji Aoki1, Toshinobu Machida2, Yousuke Sawa3, Hidekazu Matsueda3, Yosuke Niwa3, Kazuhiro Tsuboi3, Keiich Katsumata2, Takakiyo Nakazawa1 (1.Center for Atmospheric and Oceanic Studies, Graduate School of Science, Tohoku University, 2.National Institute for Environmental Studies, 3.Meterological Research Institute)

Keywords:Methane, carbon and hydrogen isotopic ratios, upper troposphere/lower stratosphere, Eurasian continent

Aircraft observation campaigns over the northern high latitudes have been conducted to clarify the spatial and temporal variations of GHGs concentrations and their sources in the surfaces (Sugawara et al., 1996; Tohjima et al., 1997; Nakazawa et al., 1997; Paris et al., 2008); however, systematic time-series observations using aircrafts are still limited (Matsueda et al., 2002; Haszpra et al., 2012; Umezawa et al., 2012). In addition, there is no systematic and simultaneous observation for the atmospheric CH4 concentrations and their isotopic ratios (δ13C, δD) in the upper troposphere/lower stratosphere over the northern high latitudes; except for a few studies using balloon flights and aircraft observation campaigns (Sugawara et al., 1997; Rice et al., 2003; Röckmann et al., 2011). In this study, we have conducted monthly air sampling on-board a commercial airliner between Europe and Japan from April 2012, and clarified the spatiotemporal variations of CH4, δ13C and δD in the upper troposphere/lower stratosphere over the 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).