Observation And Simulation Study Of Spatio-temporal Changes Of Near-surface CO₂ In Beijing-Tianjin-Hebei Region

Beijing Tianjin Hebei area is one of the most serious air pollution areas in China.There are many natural and artificial conditions in this area,thus,the atmospheric CO₂ monitoring and simulation results in this area are highly representative and easy to be applied to other areas.In this study,CO₂ concentration near the ground was observed through base stations,vehicular mobile equipment and sounding vertical profile.At the same time,the process of CO2 emission,transport and mixing near the ground in Beijing Tianjin Hebei region is simulated.The high spatial and temporal resolution characteristics of CO₂ in Beijing Tianjin Hebei region were obtained.It is of great significance to reveal the carbon emission of Beijing Tianjin Hebei region,to analyze the carbon source and sink change of terrestrial ecosystem,to implement the carbon emission reduction policy,to explore the sustainable development path,and to cope with the global warming trend and climate change in the future.The main conclusions are as follows:?1?Based on the observation data,the spatial distribution characteristics of high and low level CO₂concentration in Beijing Tianjin Hebei region are analyzed.The CO₂concentration in Beijing,Tianjin and Hebei is more than 400 ppm,and there are significant difference in different urban areas,which can reach 30-60 ppm in winter.CO₂ concentration decreases with the increase of atmospheric height,which is the most significant trend in winter.The seasonal and daily variation of CO₂ concentration in this area is significant.CO₂ concentration peak in winter and valley in summer.The daily variation of CO₂concentration can reach 7-43 ppm.The peak value in high and low layers mostly observed in the morning,while the valley value mostly observed in the afternoon.?3?Picarro and miniaturized instruments are used to monitor CO₂concentration at the same time.The results show that the miniaturized CO₂ observation instrument with low cost and medium precision is feasible in mobile observation,with mean square error at 5 ppm and the precision is about 1%.?4?The WRF-Chem model can well simulate the main distribution characteristics,daily variation and time trend of the four monitoring stations.However,the simulation effect for different stations in different seasons is quite different.The main factors influencing the simulation results include potential temperature,boundary layer height and fossil fuel combustion.There is a negative correlation between the height of the boundary layer and the CO₂concentration.The CO₂ concentration below the boundary layer height is obviously affected by the ground emission source,while the CO₂concentration above the boundary layer is very little affected by the ground source.