Pollutants emitted from an elevated offshore source often bring a higher level concentration pattern due to the strong mixing in the internal boundary layer over land. This phenomenon is well known as fumigation and has been analysed by the conventional fumigation model. In this paper, however, it is analysed by a puff model which is more widely applicable to unsteady conditions around the offshore airport, such as the interaction of sea and land breezes and moving sources.
A good many tracer experiments were carried out around the proposed site of New Kansai Offshore Airport. In those experiments, there was a case in which two kinds of tracers were emitted simultaneously from the elevated and lower sources and the concentration patterns were obtained. In a previous paper the diffusion process for the lower source was studied in detail and three dimensional diffusion parameters as well as a few meteorological ones were determined with optimization technique by matching the calculated isopleths to the observed ones.
These parameters are modified by the unknown coeffficients in the present analysis and applied to the diffusion process for the elevated source. These coefficients are determined by using the optimization technique again.
All obtained parameters are quite reasonable compared with the characteristics of the dispersion process in the internal boundary layer and observed meteorological conditions. Good agreement is also presented between calculated and observed concentration isopleths.