Abstract
Carbon dioxide (CO2) is the most important greenhouse gas and several satellites have been launched to monitor the atmospheric CO2 at regional and global scales. Evaluation of the measurements obtained from these satellites against accurate and precise instruments is crucial. In this work, aircraft measurements of CO2 were carried out over Qinhuangdao, China (39.9354°N, 119.6005°E), on 14, 16, and 19 March 2019 to validate the Greenhous gases Observing SATellite (GOSAT) and the Orbiting Carbon Observatory 2 (OCO-2) CO2 retrievals. The airborne in situ instruments were mounted on a research aircraft and the measurements were carried out between the altitudes of ~0.5 and 8.0 km to obtain the vertical profiles of CO2. The profiles captured a decrease in CO2 concentration from the surface to maximum altitude. Moreover, the vertical profiles from GEOS-Chem and the National Oceanic and Atmospheric Administration (NOAA) CarbonTracker were also compared with in situ and satellite datasets. The satellite and the model datasets captured the vertical structure of CO2 when compared with in situ measurements, which showed good agreement among the datasets. The dry-air column-averaged CO2 mole fractions (XCO2) retrieved from OCO-2 and GOSAT showed biases of 1.33 ppm (0.32%) and −1.70 ppm (−0.41%), respectively, relative to the XCO2 derived from in situ measurements.
Highlights
Atmospheric carbon dioxide (CO2 ) is the most important greenhouse gas and its concentration has increased globally from 280 ppm before industrialization to over 410 ppm at present [1,2,3]
GEOS-Chem and CarbonTracker data were used to extrapolate the missing vertical profiles based on a method described in a previous study [57]
GEOS-Chem and CarbonTracker were selected for many reasons: first, both models are widely used by the CO2 community and are, representative of the current understanding of atmospheric transport
Summary
Atmospheric carbon dioxide (CO2 ) is the most important greenhouse gas and its concentration has increased globally from 280 ppm before industrialization to over 410 ppm at present [1,2,3]. Ground stations and tall towers with flask sampling, such as stations within the Global Atmospheric Watch (GAW) network [8], can measure the atmospheric CO2 concentration with high precision and can provide the mole fractions of atmospheric CO2 at regional and global scales. A comprehensive network of ground-based, sun-viewing, near-infrared Fourier transform spectrometers known as the Total Carbon Column Observing Network (TCCON) accurately measures the concentrations of various greenhouse gases including CO2 , CO, CH4 , and N2 O [10,11]. Satellite-based measurements provide the most effective way to monitor the atmospheric CO2 at regional and global scales with high spatiotemporal resolutions.
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