Analysis of the carbon dioxide mole fraction variation and its transmission characteristics in Taiyuan

Abstract

Based on the concentrations of CO2, PM2.5 and PM1.0, and conventional meteorological observation data from 2016 to 2018 at Taiyuan station, which belongs to the Shanxi greenhouse gas observation network, the CO2 concentration monthly and daily distribution characteristics, the weekend effect, and the variation characteristics on haze days and non-haze days, are analyzed. By using the Hybrid Single-Particle Lagrangian Integrated Trajectory model (backward trajectory model) and surface wind data, the transmission characteristics of atmospheric CO2 in Taiyuan are studied in various seasons. The results show that, in Taiyuan, the CO2 mole fraction in autumn and winter is higher than that in spring and summer, and on haze days is higher than that on non-haze days. The diurnal variation characteristic of CO2 mole fraction in each season is ‘single peak and single valley’ with the peak value around 0700 (hereafter refers to Beijing Time) and the valley value around 1600. The CO2 mole fraction on workdays is slightly higher than that on non-workdays and obviously different around 0800 of the early peak. Horizontal diffusion can reduce the CO2 mole fraction, while breezy weather is not beneficial to CO2 diffusion. The wind direction and speed in the upper levels are different from those near the surface, and the close air masses in the southwest–west–northwest sector raise the CO2 concentration in Taiyuan obviously. This indicates that the CO2 in Taiyuan is mainly contributed by local sources.