Aircraft measurements of carbon dioxide and methane for the calibration of ground-based high-resolution Fourier Transform Spectrometers and a comparison to GOSAT data measured over Tsukuba and Moshiri

Aircraft measurements of carbon dioxide and methane over Tsukuba (36.05 ° N, 140.12 ° E) (February 2010) and Moshiri (44.36 ° N, 142.26 ° E) (August 2009) were made to calibrate ground-based high-resolution Fourier Transform Spectrometers (g-b FTSs) and to compare with the Greenhouse gases Observing SATellite (GOSAT). The aircraft measurements over Tsukuba in February 2010 were successful in synchronizing with both the g-b FTS and GOSAT for the first time. Airborne in situ and flask-sampling instruments were mounted on the aircraft, and measurements were carried out between altitudes of 0.5 and 7 km to obtain vertical profiles of carbon dioxide (CO ₂), methane (CH ₄), and other gaseous species. By comparing the g-b FTS measurements with the airborne measurements, the column-averaged dry air mole fractions of CO ₂ (XCO ₂) and CH ₄ (XCH ₄) retrieved from the g-b FTS measurements at Tsukuba were biased low by 0.33 ± 0.11% for XCO ₂ and 0.69 ± 0.29% for XCH ₄. The g-b FTS values at Moshiri were biased low by 1.24% for XCO ₂ and 2.11% for XCH ₄. The GOSAT data show biases that are 3.1% ± 1.7% lower for XCO ₂ and 2.5% ± 0.8% lower for XCH ₄ than the aircraft measurements obtained over Tsukuba.