Elevated Plume Transport and Diffusion: 20-150 km Downwind of Beijing, P.R.C

摘要

Three mobile continuous analyzers and an array of fixed sequential syringesamplers were used to measure plume dispersion rates of SF6 released from a 300 m tower in Beijing during strong, steady winds with neutral conditions. The plume trajectories over the flat, open terrain downwind of Beijing were relatively straight. Predicted plume trajectories based on interpolated wind fields from surface and upper air data exhibited a mean separation error of 4 km at 70 km downwind. Maximum predicted concentrations from a Gaussian puff model agreed within a factor of two with observed surface profiles when the source was given an initial vertical distribution to account for the effects of wind shear upon horizontal dispersion. Short-term (i.e., 10 to 20 min averaging time) horizontal dispersion rates were essentially equal to the neutral Pasquill-Gifford curve. Dispersion coefficients from hourly-averaged concentration profiles were 30% larger than the PG neutral curve, but 50% smaller than a linear neutral curve based upon dispersion data collected downwind of a power plant.