The Splitting of Plume Centerline Height in Elevated-Source Diffusion

Abstract

In the tracer experiment of elevated-source diffusion, sometimes there are found two peak values in the vertical concentration profile, which means two centerline-heights of concentration. One corresponds to the tracer release height and the other, the lower-level one, seems to correspond to the lower neutral or near-neutral layer. The vertical spread of concentration in the lower layer is larger than that in the upper layer. In this circumstance the surface concentration near the source is mostly determined by the diffusion from the lower-level centerline height of plume, namely the extraordinarily high surface concentration is expected to occur near the source, which cannot be explained in the light of customary knowledge of elevated-source diffusion.