Articles | Volume 16, issue 14
Atmos. Chem. Phys., 16, 9149–9161, 2016
Atmos. Chem. Phys., 16, 9149–9161, 2016

Research article 26 Jul 2016

Research article | 26 Jul 2016

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

Misa Ishizawa1, Osamu Uchino1, Isamu Morino1, Makoto Inoue1,a, Yukio Yoshida1, Kazuo Mabuchi1, Tomoko Shirai1, Yasunori Tohjima1, Shamil Maksyutov1, Hirofumi Ohyama2, Shuji Kawakami3, Atsushi Takizawa4, and Dmitry Belikov1,5,6 Misa Ishizawa et al.
  • 1National Institute for Environmental Studies, Tsukuba, Japan
  • 2Solar-Terrestrial Environmental Laboratory, Nagoya University, Nagoya, Japan
  • 3Japan Aerospace Exploration Agency, Tsukuba, Japan
  • 4Japan Meteorological Agency, Tokyo, Japan
  • 5Tomsk State University, Tomsk, Russia
  • 6National Institute of Polar Research, Tachikawa, Japan
  • anow at: Akita Prefectural University, Akita, Japan

Abstract. Extremely high levels of column-averaged dry-air mole fractions of atmospheric methane (XCH4) were detected in August and September 2013 over northeast Asia (∼  20 ppb above the averaged summertime XCH4 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 Observing Satellite (GOSAT). Similar enhancements of XCH4 were also observed by the ground-based measurements at two Total Carbon Column Observing Network (TCCON) sites in Japan.

The analysis of surface CH4 concentrations observed at three monitoring sites around the Japan archipelago suggest that the extreme increase of XCH4 has occurred in a limited area. The model analysis was conducted to investigate this anomalously high XCH4 event, using an atmospheric transport model. The results indicate that the extreme increase of XCH4 is attributed to the anomalous atmospheric pressure pattern over East Asia during the summer of 2013, which effectively transported the CH4-rich air to Japan from the strong CH4 source areas in east China. The two Japanese TCCON sites, ∼  1000 km east–west apart each other, coincidentally located along the substantially CH4-rich air flow from east China. This analysis demonstrates the capability of GOSAT to monitor an XCH4 event on a synoptic scale. We anticipate that the synoptic information of XCH4 from GOSAT data contributes to improve our understanding of regional carbon cycle and the regional flux estimation.

Short summary
Greenhouse gases Observing SATellite (GOSAT) was launched to monitor CO2 and CH4 concentrations from the space. This paper analyses an extremely high XCH4 event over Northeast Asia observed by GOSAT in the summer of 2013. Results indicate that the high XCH4 event was caused by fast transport of CH4-rich air from East China to Japan due to anomalies of north Pacific high-pressure system over East Asia. This study demonstrates the capability of GOSAT to detect an XCH4 event on a synoptic scale.
Final-revised paper