摘要
This study presents atmospheric N_(2)O mole fractions measured from discrete air samples from 2001 to 2018 at Mt.Waliguan(WLG)station(36°17′N,100°54′E,3816 m asl)in China,which is a global background station of the World Meteorological Organization/Global Atmosphere Watch Programme(WMO/GAW)in central Eurasia.Observed N_(2)O characteristics of annual means,interannual variability,and seasonal cycles were investigated.Our results show that N_(2)O at WLG possess a distinct increasing trend and a statistically significant seasonal cycle,with an average growth rate of 0.9±0.01 ppb yr^(−1)(1σ)(1ppb=10^(−9)),which is close to the global mean.The detrended seasonal cycle shows a trough of−0.25±0.04(1σ)ppb in June and a peak of 0.13±0.07(1σ)ppb in September,with an amplitude of 0.38 ppb.The pattern is due to combined effects of variation in surface sources,vertical convection within the boundary layer and stratosphere to troposphere transportation(STE).The interannual variability in growth rate was partly driven by quasi-biennial oscillation(QBO)of tropical zonal wind through stratospheric transport into the troposphere.According to a cluster analysis of back trajectories and the corresponding average N_(2)O load,most air masses cover arid and semi-arid areas in inner Asia with low N_(2)O emissions,indicating that the atmospheric N_(2)O at the WLG represents the background N_(2)O level in central Eurasia.
基金
This work was supported by the National Natural Science Foundation of China(Grant Nos.41730103&41805129).
