CO2 in Beijing and Xianghe Observed by Ground-Based FTIR Column Measurements and Validation to OCO-2/3 Satellite Observations

Abstract

Monitoring the atmospheric CO2 columns inside and around a city is of great importance to understand the temporal–spatial variation of XCO2 near strong anthropogenic emissions. In this study, we use two FTIR CO2 column measurements in Beijing (Bruker EM27/SUN) and Xianghe (Bruker IFS 125HR) between 2019 and 2021 to investigate the differences of XCO2 between Beijing (urban) and Xianghe (suburb) in North China and to validate the OCO-2 and OCO-3 satellite XCO2 retrievals. The mean and standard deviation (std) of the ΔXCO2 between Beijing and Xianghe (Beijing–Xianghe) observed by two FTIR instruments are 0.206 ± 1.736 ppm, which has a seasonal variation and varies with meteorological conditions (wind speed and wind direction). The mean and std of the XCO2 differences between co-located satellite and FTIR measurements are −0.216 ± 1.578 ppm in Beijing and −0.343 ± 1.438 ppm in Xianghe for OCO-2 and 0.637 ± 1.594 ppm in Beijing and 1.206 ± 1.420 ppm in Xianghe for OCO-3. It is found that the OCO-3 snapshot area mode (SAM) measurements can capture the spatial gradient of XCO2 between urban and suburbs well. However, the FTIR measurements indicate that the OCO-3 SAM measurements are about 0.9–1.4 ppm overestimated in Beijing and Xianghe.

Seasonal and Diurnal Variations in XCO2 Characteristics in China as Observed by OCO‐2/3 Satellites: Effects of Land Cover and Local Meteorology

“…Similar overestimation was also found by Zhou et al. (2022a), who attributed it to the uncertainty of the SAM mode of OCO‐3 observations. There is a slight variation in the results between the different OCO observation modes, with the bias of 1.39 ppm for the SAM mode data being larger than that of 0.91 ppm for the land nadir mode data (Figure S1 in Supporting Information ).…”

“…Specifically, in terms of the period with data available for validation, the TCCON value was 413.94 ± 2.79 ppm in comparison to the OCO-2 value of 414.75 ± 2.88 ppm, and the TCCON value was 414.05 ± 2.89 ppm in comparison with the OCO-3 value of 415.25 ± 3.11 ppm. Similar overestimation was also found by Zhou et al (2022a), who attributed it to the uncertainty of the SAM mode of OCO-3 observations. There is a slight variation in the results between the different OCO observation modes, with the bias of 1.39 ppm for the SAM mode data being larger than that of 0.91 ppm for the land nadir mode data (Figure S1 in Supporting Information S1).…”

“…Compared with the satellite remote sensing that receives solar radiation reflected back to space from the ground, direct light detection reduces the influence of factors such as clouds, aerosols, and surface albedo. Thus, TCCON plays an important role in providing an essential validation resource for the OCO-2/3 satellites (Taylor et al, 2023;Wunch et al, 2017;Zhou et al, 2022a) and other spaceborne instruments such as GOSAT, GOSAT-2, TanSat, and the Sentinel 5P instrument TROPOMI (Lorente et al, 2021;Noël et al, 2022;Yang et al, 2020a).…”

Urban XCO2 Gradients From a Dense Network of Solar Absorption Spectrometers and OCO‐3 Over Mexico City

“…Kiel et al (2021) discovered that OCO-3 measurements closely align with co-located TCCON observations in Los Angeles, yielding an RMSE of 0.23 ppm. M. Zhou et al (2022) observed that OCO-3 measurements consistently surpassed ground-based readings in various settings. Specifically, at the COCCON site in Beijing, OCO-3 XCO 2 were 0.64 ppm higher than FTIR measurements, and at the TCCON station in Xianghe, the difference increased to 1.2 ppm.…”

Evaluating the Ability of the Pre-Launch TanSat-2 Satellite to Quantify Urban CO2 Emissions

“…The precision of its X CO 2 measurements is expected to be less than 1 ppm. It is intended to verify satellite data using ground-based measurements from the Total Carbon Column Observing Network [53][54][55] and EM27/SUN measurements [56] for optimizing parameters in satellite sampling. In this paper, we evaluate the theoretical ability of TanSat-2 to detect urban CO 2 emission signatures based on a closed-loop inversion system (Figure 1).…”