Abstract: Based on ground-based Fourier transform infrared remote sensing and in-situ surface measurement, the variation of atmospheric CH4 and CO2 concentrations in Hefei City, China, from January 2016 to December 2017 were investigated. The observation results show that there were obvious seasonal variations in CO2 and CH4 over Hefei. CO2 showed a minimum value in August 2016, and then gradually increased over time, reaching the maximum in April 2017. After that, it declined gradually, reaching another minimum value in early September 2017. In contrast , CH4 showed high level in summer and early autumn, and low concentrations in winter and early spring. In 2016, the seasonal amplitudes of the monthly mean concentrations of XCO2 and XCH4 measured by ground-based remote sensing were 5.96 ´ 10-6 and 0.047 ´ 10-6 respectively, while those of CO2 and CH4 measured in-situ were 31.46 ´ 10-6 and 0.26 ´ 10-6 respectively, about 5 times of the corresponding values measured by ground-based remote sensing. The correlation between atmospheric CO2 and CO, as well as CH4 and CO2, at Hefei Station was analyzed. It is shown that the correlation coefficient R between XCO2 and XCO measured by ground-based remote sensing in autumn is 0.75, and the ratio of XCO2 and XCO is 79.5. The strong correlation between XCO2 and XCO indicates that most of CO2 and CO in Hefei area in autumn originate from the same sources. On the other hand, the correlation coefficient R of CO2 and CO, CH4 and CO2 measured by in-situ surface measurement in winter is 0.80, the ratio of CO2 and CO is 52.2, and the ratio of CH4 and CO2 is 0.0036. The strong correlations between gases indicate that anthropogenic sources are main sources of CO2 at Hefei Station in winter, and CH4 and CO2 partially originate from biomass burning.

Key words: greenhouse gases, ground-based remote sensing, in-situ measurement, seasonal variation; concentration ratio