Multilevel measurements of fluxes and turbulence over an urban landscape in Beijing

To obtain a better understanding of the behaviour of the energy balance, CO₂ fluxes and the turbulence characteristics in cities, eddy covariance (EC) measurements of turbulent fluxes and variances were collected continuously during the entire year of 2009 at three levels, 47, 140 and 280 m, over an urban landscape in Beijing. The results showed that the summer daytime maximum of the sensible heat (105 W m⁻²) was similar to the winter value (102 W m⁻²), although the summer daytime maximum of the latent heat (167 W m⁻²) was greater than the winter value (23 W m⁻²). The heat storage as the residual of the energy balance ranged from −145 to 404 W m⁻² and from −95 to 90 W m⁻² in summer months and winter months, respectively. The annual CO₂ emissions were estimated at 32.6, 34.6 and 34.2 kg CO₂ m⁻² yr⁻¹ at 47, 140 and 280 m, respectively, which is considerably higher than the yearly emissions obtained for other urban and suburban landscapes. The variation of turbulence characteristics supported the well-known empirical formulation.