Abstract
Abstract. 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 (CO2), methane (CH4), and other gaseous species. By comparing the g-b FTS measurements with the airborne measurements, the column-averaged dry air mole fractions of CO2 (XCO2) and CH4 (XCH4) retrieved from the g-b FTS measurements at Tsukuba were biased low by 0.33 ± 0.11% for XCO2 and 0.69 ± 0.29% for XCH4. The g-b FTS values at Moshiri were biased low by 1.24% for XCO2 and 2.11% for XCH4. The GOSAT data show biases that are 3.1% ± 1.7% lower for XCO2 and 2.5% ± 0.8% lower for XCH4 than the aircraft measurements obtained over Tsukuba.
Highlights
Global warming by greenhouse gases is one of the most important environmental issues of our time
The XCO2 and XCH4 values retrieved from the g-b FTS measurements at Tsukuba (February 2010) and Moshiri (August 2009) were compared with those calculated from the aircraft measurements
The g-b FTS data were corrected for an airmass-dependent artifact for XCO2 and were calibrated with the Total Carbon Column Observing Network (TCCON) common scaling factors empirically determined using aircraft profiles over many TCCON sites to place the TCCON data on the WMO standard reference scales (Wunch et al, 2010) for XCO2 and XCH4
Summary
Global warming by greenhouse gases is one of the most important environmental issues of our time. CO2, in particular, is an important greenhouse gas, second only to water vapor, and the global-averaged concentration of atmospheric CO2 increased from 280 ppm in the pre-industrial era to 389.0 ppm in 2010 (World Meteorological Organization Greenhouse Gas Bulletin, 2011). Space-based instruments have to be validated using other measurements, such as in situ or sampling measurements by aircraft and remote sensing measurements by ground-based high-resolution Fourier Transform Spectrometers ((g-b) FTS). The total column from space is directly validated by the total column measurement from the ground (i.e., the TCCON FTS instruments). For this reason the g-b FTS at Tsukuba must be calibrated against an instrument with high precision and accuracy obtained independently.
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