A new site: ground-based FTIR XCO 2 , XCH 4 and XCO measurements at Xianghe, China

Abstract. The column-averaged dry-air mole fractions of CO2 (XCO2), CH4 (XCH4) and CO (XCO) have been measured with a Bruker IFS 125HR Fourier transform infrared spectrometer (FTIR) at Xianghe (39.75° N, 116.96° E, North China) since June 2018. The site and the FTIR system are described in this study. The instrumental setup follows the guidelines of the Total Carbon Column Observing Network (TCCON), and the near-infrared spectra are recorded by an InGaAs detector together with a CaF2 beam splitter. The HCl cell measurements that are recorded regularly to derive the instrument line shape (ILS) show that the instrument is correctly aligned. The Xianghe site lies in a polluted area in North China where there are currently no TCCON sites. It can fill the TCCON gap in this region and expand the global coverage of the TCCON measurements. The TCCON standard retrieval code (GGG2014) is applied to retrieve XCO2, XCH4 and XCO. The time series, seasonal cycles and day-to-day variations of XCO2, XCH4 and XCO measurements at Xianghe between June 2018 and July 2019 are shown and discussed. In addition, the FTIR measurements have been used to validate Orbiting Carbon Observatory-2 (OCO-2) and Tropospheric Monitoring Instrument (TROPOMI) satellite observations, as also shown in this paper. The Xianghe FTIR CO2, CH4 and CO data can be accessed at https://doi.org/10.18758/71021049 (Yang et al., 2019).