Based on five years of eddy covariance measurements at multiple levels(47,140,and 280 m)of Beijing's 325-m meteorological tower,the exchange process of CO_(2) fluxes between the atmosphere and urban surface were i...Based on five years of eddy covariance measurements at multiple levels(47,140,and 280 m)of Beijing's 325-m meteorological tower,the exchange process of CO_(2) fluxes between the atmosphere and urban surface were investigated.As a result of the total vehicle control policy from 2011 in Beijing,the growth rate of annual total CO_(2) flux at 140 m is 7.8% from 2008-2010 but 2.3%from 2010-2012.With the minimum vegetation cover and largest population density,the 5-yr average annual total CO_(2) flux at 140 m is largest(6.41 kg C m^(−2) yr^(−1)),compared with that at 47 m(5.78 kg C m^(−2) yr^(−1))and 280 m(3.99 kg C m^(−2) yr^(−1)).With regards to annual total CO_(2) fluxes in Beijing,vehicle numbers and population are the main controlling factors.The measured CO_(2) fluxes were highly dependent on land cover/use in the prevailing wind direction.The CO_(2) fluxes at three layers all correlated positively with road fraction,with the R2 values being 0.69,0.57,and 0.54(P<0.05),respectively.The decreasing fraction of vegetation caused an increasing of the annual total CO_(2) flux,and there was an exponential relationship between them.The annual total CO_(2) fluxes were larger with higher population density.展开更多
基金funded by the National Key Research and Develop-ment Program of China[grant number 2017YFC1502101]the National Natural Science Foundation of China[grant numbers 41905010 and 41675013].
文摘Based on five years of eddy covariance measurements at multiple levels(47,140,and 280 m)of Beijing's 325-m meteorological tower,the exchange process of CO_(2) fluxes between the atmosphere and urban surface were investigated.As a result of the total vehicle control policy from 2011 in Beijing,the growth rate of annual total CO_(2) flux at 140 m is 7.8% from 2008-2010 but 2.3%from 2010-2012.With the minimum vegetation cover and largest population density,the 5-yr average annual total CO_(2) flux at 140 m is largest(6.41 kg C m^(−2) yr^(−1)),compared with that at 47 m(5.78 kg C m^(−2) yr^(−1))and 280 m(3.99 kg C m^(−2) yr^(−1)).With regards to annual total CO_(2) fluxes in Beijing,vehicle numbers and population are the main controlling factors.The measured CO_(2) fluxes were highly dependent on land cover/use in the prevailing wind direction.The CO_(2) fluxes at three layers all correlated positively with road fraction,with the R2 values being 0.69,0.57,and 0.54(P<0.05),respectively.The decreasing fraction of vegetation caused an increasing of the annual total CO_(2) flux,and there was an exponential relationship between them.The annual total CO_(2) fluxes were larger with higher population density.
