Abstract
Abstract. Atmospheric CO2 mole fractions are observed at Beijing (BJ), Xianghe (XH), and Xinglong (XL) in North China using Picarro G2301 cavity ring-down spectroscopy instruments. The measurement system is described comprehensively for the first time. The geographical distances among these three sites are within 200 km, but they have very different surrounding environments: BJ is inside the megacity; XH is in the suburban area; XL is in the countryside on a mountain. The mean and standard deviation of CO2 mole fractions at BJ, XH, and XL between October 2018 and September 2019 are 448.4±12.8, 436.0±9.2, and 420.6±8.2 ppm, respectively. The seasonal variations of CO2 at these three sites are similar, with a maximum in winter and a minimum in summer, which is dominated by the terrestrial ecosystem. However, the seasonal variations of CO2 at BJ and XH are more affected by human activities as compared to XL. Using CO2 at XL as the background, CO2 enhancements are observed simultaneously at BJ and XH. The diurnal variations of CO2 are driven by the boundary layer height, photosynthesis, and human activities at BJ, XH, and XL. We also compare the CO2 measurements at BJ, XH, and XL with five urban sites in the USA, and it is found that the CO2 mean concentration at BJ is the largest. Moreover, we address the impact of the wind on the CO2 mole fractions at BJ and XL. This study provides an insight into the spatial and temporal variations of CO2 mole fractions in North China.
Highlights
Carbon dioxide (CO2) is the largest contributor to the total positive radiative forcing of the earth among anthropogenic gases
The three sites have very different surrounding environments: BJ is inside the megacity, XH is in the suburban area, Atmos
We show the CO2 measurements from the in situ Picarro instruments at BJ, XH, and XL between June 2018 and March 2020
Summary
Carbon dioxide (CO2) is the largest contributor to the total positive radiative forcing of the earth among anthropogenic gases. Dhakal (2009) showed that China’s urbanization rate had already reached 40 % in 2005 and it is predicted to reach up to the level of 60 % in 2030 This kind of increase certainly demands large quantities of energy consumption, leading to a large amount of CO2 emissions. It is important to understand atmospheric CO2 variations in urban, suburban, and rural areas. George et al (2007) pointed out that the horizontal gradients of CO2 mole fractions among urban, suburban, and rural areas are caused by different population densities and traffic volumes. The measurements between June 2018 and April 2020 at the three sites allow us to better understand the differences among the urban, suburban, and rural sites in relation to the seasonal, synoptic, and diurnal variations of CO2 mole fractions.
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