Long-term variation of CO₂ concentration at Longfengshan regional background station in Heilongjiang province from 2009 to 2019

The long-term monitoring data of CO₂ concentration in the Longfengshan regional atmospheric background station from 2009 to 2019 were used to analyze the daily, monthly, and interannual variation trends of CO₂ concentration in Northeast China.The meteorological driving factors affecting the CO₂ concentration of atmospheric background stations in the Longfengshan region were discussed.The results show that the diurnal variation of CO₂ concentration in Longfengshan atmospheric background station is the largest in summer, followed by autumn, spring, and the smallest in winter.The daily peak value occurs before 08:00 and the lowest value occurs around 16:00.The monthly variation of CO₂ concentration shows that the maximum value appears in January, with an average value of about 416.1×10^-6, and the minimum value appeared in July, with an average value of 391.1×10^-6.The seasonal variation of CO₂ concentration shows that the CO₂ concentration in winter is significantly higher than that in other seasons, with an average value of 415.4×10^-6, and the lowest value appeared in summer, with an average value of 395.8×10^-6.During the study period, the average CO₂ concentration of Longfengshan station shows an increasing trend, with an annual growth rate of 2.45×10^-6/a.At the Longfengshan background station, the maximum frequency wind direction appears in SSW direction in spring (21.0%), the maximum frequency wind direction appears in SSW and S direction in summer (23.1% and 22.7%), the maximum frequency wind direction appears in SSW direction in autumn (23.4%), and the maximum frequency wind direction appears in SW direction in winter (31.6%).The high CO₂ concentration in different seasons occurs under the north wind dominant condition.There is a negative correlation between CO₂ concentration and temperature (- 0.54), and a significant negative correlation between relative humidity and CO₂ concentration in spring and autumn (- 0.44 and - 0.55).There is a small correlation between CO₂ concentration and wind speed, which may be related to the transport of higher-concentration CO₂ sources.