Abstract
Examining the data of field experiments of elevated-source diffusion at some coastal regions of Japan and paying special attention to the analysis of vertical concentration profile, we have obtained the following results:
1. Sometimes a remarkable rise of tracer cloud occurs over a hill or a ridge, which makes the surface concentration pattern much different from that typical of the elevated-source diffusion over a flat terrain.
2. The sea breeze, usually stably stratified over the sea in the daytime of warm season, is subject to the heating from below inl a nd and a convective layer develops with the downwind distance from the coastline. Accompanying the modification of sea breeze inl a nd, the diffusion rate changes from one over the sea to that in the neutral layer. This is well reflected in the change of Pasqu i ll stability in the vertical spread of concentration.
3. Two peaks are found in the vertical concentration profile, when the source height is below the base of the inversion or s t able layer. One corresponds to the source height and the other coincides with the base of the inversion or stable layer. The concentration of the latter is much larger than that of the former, which makes the surface concentration decrease.
