Comparisons between XCH₄ from GOSAT Shortwave and Thermal Infrared Spectra and Aircraft CH₄ Measurements over Guam

Abstract

The Thermal and Near-infrared Sensor for Carbon Observation Fourier Transform Spectrometer (TANSO-FTS) on board the Greenhouse Gases Observing Satellite (GOSAT) simultaneously observes column abundances and profiles of CH 4 in the same field of view, from the shortwave infrared (SWIR) and thermal infrared (TIR) bands, respectively. We compared CH 4 column-averaged dry-air mole fractions (XCH 4 ) derived from the SWIR band, XCH 4 calculated from the TIR CH 4 profiles, and XCH 4 calculated from the CH 4 data obtained over Guam airport by commercial aircraft. The difference between the SWIR-XCH 4 and aircraft XCH 4 values (SWIR − aircraft) was −8 ppbv on average, and the 1σ standard deviation was 10 ppbv. The average difference between the TIR-XCH 4 and aircraft XCH 4 values (TIR − aircraft) was −5 ppbv, and the 1σ standard deviation was 15 ppbv. The ranges of uncertainties in the calculated aircraft XCH 4 values were estimated to be 9, 3, and 2 ppbv, which came from stratospheric CH 4 assumption, tropopause height determination, and meteorological dataset used, respectively. Both the SWIR-and TIR-XCH 4 values agreed within 0.5% of the aircraft XCH 4 values, demonstrating that the GOSAT CH 4 data are both valid and consistent with each other over the tropical ocean.

Comparison of GOSAT SWIR and Aircraft Measurements of XCH₄ over West Siberia

“…In this study, we followed a method similar to Saitoh et al (2012). For the altitudes between 0.5 and 7.0 km (about 400 hPa), aircraft measurements are available.…”

Algorithm update of the GOSAT/TANSO-FTS thermal infrared CO<sub>2</sub> product (version 1) and validation of the UTLS CO<sub>2</sub> data using CONTRAIL measurements

“…TANSO-FTS consists of three bands in the SWIR region and one band in the TIR region. Column amounts of greenhouse gases are observed in the SWIR bands, and vertical information of gas concentrations are obtained in the TIR band (Yoshida et al, 2011Saitoh et al, 2009Saitoh et al, , 2012Ohyama et al, 2012Ohyama et al, , 2013. Kuze et al (2012) provided a detailed description of the methods used for the processing and calibration of level 1B (L1B) spectral data from TANSO-FTS.…”

Bias corrections of GOSAT SWIR XCO<sub>2</sub> and XCH<sub>4</sub> with TCCON data and their evaluation using aircraft measurement data

“…Column-averaged dry air mole fractions of CO 2 (XCO 2 ) and CH 4 (XCH 4 ) are retrieved from the Short-Wavelength InfraRed (SWIR) spectra of the Thermal And Near-infrared Sensor for carbon Observation -Fourier Transform Spectrometer (TANSO-FTS) onboard GOSAT. Validation of XCO 2 and XCH 4 derived from the GOSAT TANSO-FTS has been conducted by using ground-based high-resolution Fourier Transform Spectrometer (ground-based FTS) data and aircraft measurements Saitoh et al, 2012;Yoshida et al, 2013;Inoue et al, 2013Inoue et al, , 2014Gavrilov et al, 2014). The results showed that the GOSAT SWIR XCO 2 measurements (Ver.…”

“…Measurements in the SWIR and thermal infrared (TIR) bands of TANSO-FTS allow the retrievals over cloud-free regions of XCO 2 and XCH 4 , and CO 2 and CH 4 profiles, respectively. Saitoh et al, 2012). More recently, Kuze et al (2016) reported update on the performance of GOSAT TANSO-FTS sensor and important changes to the data product which has been made available to users.…”