Multi-level CO2 fluxes over Beijing megacity with the eddy covariance method |
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| Authors: | Yang Liu Huizhi Liu Qun Du Lujun Xu |
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| Affiliation: | 1. State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Chinese Academy of Sciences, Beijing, China;2. University of Chinese Academy of Sciences, Beijing, China |
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| Abstract: | 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 CO2 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 CO2 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 CO2 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 CO2 fluxes in Beijing,vehicle numbers and population are the main controlling factors.The measured CO2 fluxes were highly dependent on land cover/use in the prevailing wind direction.The CO2 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 CO2 flux,and there was an exponential relationship between them.The annual total CO2 fluxes were larger with higher population density. |
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| Keywords: | Eddy covariance CO2 flux Urban boundary layer Urban climate |
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