Abstract
Abstract. Measurements of atmospheric column-averaged dry-air mole fractions of carbon dioxide (XCO2), methane (XCH4), and carbon monoxide (XCO) have been collected across the Pacific Ocean during the Measuring Ocean REferences 2 (MORE-2) campaign in June 2019. We deployed a shipborne variant of the EM27/SUN Fourier transform spectrometer (FTS) on board the German R/V Sonne which, during MORE-2, crossed the Pacific Ocean from Vancouver, Canada, to Singapore. Equipped with a specially manufactured fast solar tracker, the FTS operated in direct-sun viewing geometry during the ship cruise reliably delivering solar absorption spectra in the shortwave infrared spectral range (4000 to 11000 cm−1). After filtering and bias correcting the dataset, we report on XCO2, XCH4, and XCO measurements for 22 d along a trajectory that largely aligns with 30∘ N of latitude between 140∘ W and 120∘ E of longitude. The dataset has been scaled to the Total Carbon Column Observing Network (TCCON) station in Karlsruhe, Germany, before and after the MORE-2 campaign through side-by-side measurements. The 1σ repeatability of hourly means of XCO2, XCH4, and XCO is found to be 0.24 ppm, 1.1 ppb, and 0.75 ppb, respectively. The Copernicus Atmosphere Monitoring Service (CAMS) models gridded concentration fields of the atmospheric composition using assimilated satellite observations, which show excellent agreement of 0.52±0.31 ppm for XCO2, 0.9±4.1 ppb for XCH4, and 3.2±3.4 ppb for XCO (mean difference ± SD, standard deviation, of differences for entire record) with our observations. Likewise, we find excellent agreement to within 2.2±6.6 ppb with the XCO observations of the TROPOspheric MOnitoring Instrument (TROPOMI) on the Sentinel-5 Precursor satellite (S5P). The shipborne measurements are accessible at https://doi.org/10.1594/PANGAEA.917240 (Knapp et al., 2020).
Highlights
The greenhouse gases carbon dioxide (CO2) and methane (CH4) and the air pollutant carbon monoxide (CO) are the target constituents of a range of currently orbiting and planned Earth observing satellite missions (e.g., Kuze et al, 2009; Eldering et al, 2017)
After filtering and bias correcting the dataset, we report on XCO2, XCH4, and XCO measurements for 22 d along a trajectory that largely aligns with 30◦ N of latitude between 140◦ W and 120◦ E of longitude
The shipborne observations by Klappenbach et al (2015) were conducted on board the R/V Polarstern during a cruise from Cape Town, South Africa, to Bremerhaven, Germany, in March and April 2014. These measurements were used for evaluating XCO2 and XCH4 observations of the Greenhouse Gases Observing Satellite (GOSAT) and for improving the interhemispheric gradient modeled by the Integrated Forecasting System (IFS) for the Copernicus Atmosphere Monitoring Service (CAMS) CO2 and CH4 analysis and forecasting system (Agusti-Panareda et al, 2017)
Summary
The greenhouse gases carbon dioxide (CO2) and methane (CH4) and the air pollutant carbon monoxide (CO) are the target constituents of a range of currently orbiting and planned Earth observing satellite missions (e.g., Kuze et al, 2009; Eldering et al, 2017). To enable the evaluation of satellites and models over the oceans, Klappenbach et al (2015) developed a shipborne prototype of the EM27/SUN Fourier transform spectrometer (FTS) (Gisi et al, 2011, 2012) which is the instrument used within the COCCON (Frey et al, 2019). The shipborne observations by Klappenbach et al (2015) were conducted on board the R/V Polarstern during a cruise from Cape Town, South Africa, to Bremerhaven, Germany, in March and April 2014 These measurements were used for evaluating XCO2 and XCH4 observations of the Greenhouse Gases Observing Satellite (GOSAT) and for improving the interhemispheric gradient modeled by the IFS for the CAMS CO2 and CH4 analysis and forecasting system (Agusti-Panareda et al, 2017).
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