Large XCH4 anomaly in summer 2013 over Northeast Asia observed by GOSAT

M. Ishizawa, O. Uchino, I. Morino, M. Inoue, Y. Yoshida, K. Mabuchi, T. Shirai, Y. Tohjima, S. Maksyutov, H. Ohyama, S. Kawakami, A. Takizawa
2015 Atmospheric Chemistry and Physics Discussions  
Extremely high levels of column-averaged dry-air mole fractions of atmospheric methane (XCH<sub>4</sub>) were detected in August and September 2013 over Northeast Asia (~ 20 ppb above the averaged summertime XCH<sub>4</sub> over 2009–2012, after removing a long-term trend), as being retrieved from the Short-Wavelength InfraRed (SWIR) spectral data observed with the Thermal And Near-infrared Sensor for carbon Observation-Fourier Transform Spectrometer (TANSO-FTS) onboard Greenhouse Gases
more » ... g Satellite (GOSAT). Similar enhancements of XCH<sub>4</sub> were also observed by the ground-based measurements at two Total Carbon Column Observing Network (TCCON) sites in Japan. <br><br> The analysis of surface CH<sub>4</sub> concentrations observed at three monitoring sites around the Japan islands suggest that the extreme increase of XCH<sub>4</sub> has occurred in a limited area. The model analysis was conducted to investigate this anomalously high XCH<sub>4</sub> event, using an atmospheric transport model. The results indicate that the extreme increase of XCH<sub>4</sub> is attributed to the anomalous atmospheric pressure pattern over East Asia during the summer of 2013, which effectively transported the CH<sub>4</sub>-rich air to Japan from the strong CH<sub>4</sub> source areas in East China. The two Japanese TCCON sites, ~ 1000 km east-west apart each other, coincidentally located along the substantially CH<sub>4</sub>-rich air flow from East China. The GOSAT orbiting with three-day recurrence successfully observed the synoptic-scale XCH<sub>4</sub> enhancement in the comparable accuracy to the TCCON data. This analysis demonstrates the capability of GOSAT to monitor an XCH<sub>4</sub> event on a synoptic scale.
doi:10.5194/acpd-15-24995-2015 fatcat:rn35ofvl4bac5op3hn426argyi