Observations of atmospheric CO and CO based on in-situ and ground-based remote sensing measurements at Hefei site, China.

The characteristics of long time series of CO and CO surface concentrations, tropospheric and total column dry-air mole fractions (DMF) from May 2015 to December 2019 were investigated. Both CO and CO show different seasonality for the three datasets. The annual increasing trend of CO is similar for all three datasets. However, the annual decreasing trend of CO for surface concentration is high compared to the other two measurements, mainly due to the improved combustion efficiency from power generation in recent years. The correlation between the tropospheric and total atmospheric CO and CO is higher than that between the surface concentration and tropospheric CO and CO. This is because the tropospheric and total atmospheric results both have common vertical profiles for CO and CO respective mole fractions that were observed in troposphere. Furthermore, the enhancement ratios of CO to CO derived from the three datasets during the period from 2016 to 2019 were compared. The ratio of ∆CO to ∆CO has an obvious increase with altitude each year, which means that the combustion efficiencies obtained from the three datasets are different. All ratios for the three datasets showed a slight increasing trend in recent years, which is attributed to increased combustion efficiency due to governmental measures for energy savings and emission reductions.