Dramatic decline of observed atmospheric CO_(2) and CH_(4) during the COVID-19 lockdown over the Yangtze River Delta of China

摘要

The temporal variation of greenhouse gas concentrations in China during the COVID-19 lockdown in China is analyzed in this work using high resolution measurements of near surface ΔCO_(2),ΔCH_(4) andΔCO concentrations above the background conditions at Lin’an station(LAN),a regional background station in the Yangtze River Delta region.During the pre-lockdown observational period(IOP-1),bothΔCO_(2) andΔCH_(4) exhibited a significant increasing trend relative to the 2011-2019 climatological mean.The reduction ofΔCO_(2),ΔCH_(4) andΔCO during the lockdown observational period(IOP-2)(which also coincided with the Chinese New Year Holiday)reached up to 15.0 ppm,14.2 ppb and 146.8 ppb,respectively,and a reduction ofΔCO_(2)/ΔCO probably due to a dramatic reduction from industrial emissions.ΔCO_(2),ΔCH_(4) and ΔCO were observed to keep declining during the post-lockdown easing phase(IOP-3),which is the synthetic result of lower than normal CO_(2) emissions from rural regions around LAN coupled with strong uptake of the terrestrial ecosystem.Interestingly,the trend reversed to gradual increase for all species during the later easing phase(IOP-4),with ΔCO_(2)/ΔCO constantly increasing from IOP-2 to IOP-3 and finally IOP-4,consistent with recovery in industrial emissions associated with the staged resumption of economic activity.On average,ΔCO_(2) declined sharply throughout the days during IOP-2 but increased gradually throughout the days during IOP-4.The findings showcase the significant role of emission reduction in accounting for the dramatic changes in measured atmosphericΔCO_(2) and ΔCH_(4) associated with the COVID-19 lockdown and recovery.