Atmospheric propane (C₃H₈) column retrievals from ground-based FTIR observations at Xianghe, China

Abstract. Propane (C₃H₈) is an important trace gas in the atmosphere, as it is a proxy for oil and gas production and has a significant impact on atmospheric chemical reactions related to the hydroxyl radical and tropospheric ozone formation. In this study, solar direct absorption spectra near 2967 cm⁻¹ recorded by a ground-based Fourier Transform InfraRed spectrometer (FTIR) are applied to retrieve C₃H₈ total columns between June 2018 and July 2022 at Xianghe in North China. The systematic and random uncertainties of the C₃H₈ column retrieval are estimated to be 18.2 % and 18.1 %, respectively. The mean and standard deviation of the C₃H₈ columns derived from the FTIR spectra at Xianghe are 1.80±0.81(1σ) × 10¹⁵ molecules / cm². Good correlations are found between C₃H₈ and other non-methane hydrocarbons, such as C₂H₆ (R=0.84) and C₂H₂ (R=0.79), as well as between C₃H₈ and CO (R=0.72). However, the correlation between C₃H₈ and CH₄ is relatively weak (R=0.45). The FTIR C₃H₈ measurements are also compared against two atmospheric chemical transport model simulations (the Whole Atmosphere Community Climate Model (WACCM) and the Copernicus Atmosphere Monitoring Service (CAMS)). We find that the C₃H₈ columns from both models have different seasonal variations as compared to the FTIR measurements. Moreover, the mean C₃H₈ columns derived from the WACCM and CAMS models are about 68 % larger than the FTIR retrievals. The new FTIR measurements at Xianghe provide us an insight into the C₃H₈ column variations and underlying processes in North China.