A Lidar study of the limits to buoyant plume rise in a well-mixed boundary layer

A series of 69 × 15 min trajectories of the plume from a direct-cooled, 360 MW(e) power station have been measured with a rapid-scanning Lidar to downwind distances of 3 km; the measurements were made in August and September 1993 in eastern England. The results indicate that, in sunny conditions, buoyant rise is halted when plume elements start to impinge on the top of the boundary layer. By contrast, the Briggs “break-up” model, according to which plume rise ceases when the plume is broken up by ambient turbulence, failed to predict the distribution of observed final plume heights. It is concluded that in U.K. conditions buoyant rise is likely to be limited by the depth of the boundary layer. Several methods of estimating the depth of the boundary layer from Lidar measurements are discussed. The initial plume rise at Staythorpe was similar to the plume rise at other inland power stations.