Keywords:methane, troposphere, stratosphere, GOSAT, aircraft
Profiles of CH4 have been retrieved from satellite-borne nadir sensors since 1996 by measuring thermal infrared (TIR) emissions from the Earth's atmosphere. GOSAT/TANSO-FTS has been operated since 2009. Profiles of CO2 and CH4 are retrieved from the TIR band of the TANSO-FTS. In this study, we assess data quality for CH4, H2O, N2O, and temperature between the mid-troposphere and the stratosphere, contributing the improvement of our knowledge on CH4 distributions, for instance, in the western Siberia. For comparisons with the TIR data, we used the solar occultation sensor, ACE-FTS, and the routine aircraft observations in the western Siberia. We found that (1) TIR CH4 mixing ratios are systematically larger than ACE-FTS CH4 in the 400-200 hPa levels between January and April in 2010/2011, especially in January, several profiles exceeded 2.0 ppmv of CH4 at the 300 hPa level. (2) TIR H2O mixing ratios are larger than ACE-FTS H2O in the 300-250 hPa levels and the above throughout the period studied. (3) TIR CH4 at the 7 km (430 hPa) and the 5.5 km (500 hPa) altitudes are in good agreement with those from the aircraft observations from the temporal variation view within the range of variations in TIR CH4.
Acknowledgements: We thank Kaley A. Walker, University of Toronto, Canada for providing us the Version 3.5 ACE-FTS data through http://ace.uwaterloo.ca. This research was supported by the Environment Research and Technology Development Fund (ERTDF) of the Ministry of the Environment, Japan (A1202). Aircraft observations in the western Siberia are conducted by NIES with the cooperation of Russian Academy of Science (RAS).