Elevated-source dispersion is compared with simultaneous surfacesource dispersion. The analysis starts from the finding that the tracer cloud height generally varies with the downwind distance. Over a complicated terrain such as Kainan City the Pasquill stability of elevated-source dispersion is high and that of the corresponding surface-source dispersion is somewhat lower. Over a relatively flat terrain as Oita City the Pasquill stability for an elevated source is in general low or very low

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... er weather conditions not much different from those at the Kainan City experiment. While the Pasquill stability for a surface source is definitely higher, which is reverse to the dispersion over Kainan City. The height of tracer cloud generally increases with the downwind distance, irrespectively of the elevated or the surface source. The rise of the tracer is more remarkable over a sloped terrain. In the previous paper (SAKURABA, 1969) it was shown that the tracer cloud released from an elevated source in a sea-breeze layer rises more or less with the downwind distance. The rise is larger over an urban area than over a rural area, and over a sloped terrain than over a flat terrain. In our field experiment of dispersion, the tracers were released from an elevated and a surface source simultaneously. Two kinds of FP tracer were used, one from the elevated source and the other from the surface one. It was found that the tracer cloud from the surface source also rises with the downwind distance as in the case of the elevated source. At the same time it is possible to compare the surface-source dispersion with the elevated-source one.