Observation of Greenhouse gases by ground-based FTIR at Hefei site and comparison with satellite data

A ground-based high-resolution Fourier Transform Spectrometer (FTS) station has been established in Hefei, China to remotely measure CO 2 , CH4 and other greenhouse gases based on near-infrared solar absorption spectra. Total column measurements of atmospheric CO 2 and CH 4 have been successfully achieved from 2015 to 2020. Time series of individual measurements, daily averages of column-averaged DMF of CO 2 and CH 4 suggest that CO 2 and CH 4 variation showed a clear seasonal cycle. Also, CO 2 and CH 4 slowly increased from 2015 to 2020. Further, we made use of satellite measurements to compare with our data. The direct comparison of our observations with the Greenhouse gases Observing Satellite (GOSAT) data shows good agreement of daily median XCO 2 , with bias of −0.52 ppm and standard deviation of 1.63 ppm, respectively. The correlation coefficient (R) is 0.89 for XCO 2 between our FTS and GOSAT observations. Orbiting Carbon Observatory 2 (OCO-2) data produce a positive bias of 0.81 ppm and standard deviation of 1.73 ppm relative to our ground-based data, respectively. Our XCO 2 also show strong correlation with OCO-2 data, with correlation coefficient (R) of 0.91. For CH4, average differences between GOSAT and FTIR data were 1.60 ppb (0.09%) ± 13.0 ppb (0.70%), and the correlation coefficient (r) of the two dataset is 0.77. The results confirm the suitability of the observatory for ground-based long term measurements of greenhouse gases with high precision and accuracy.