Atmospheric diffusion from an off-shore site

From symposium on the physical behavior of radioactive containment in the atmosphere; Vienna, Austria (12 Nov 1973). Analysis of the fate of airborne effluerts from a nuclear reactor at an off-shore site requires a better understanding of overwater atmospheric dispersion than currently exists. For this reason, a diffus1on study was undertaken off the south shore of Long Island, New York, about 100 km from New York City. This study is using tracer material (oil fog smoke) released from an anchored boat. Measurements of mean wind, turbulence, and temperature are made on portable towers on the beach, from an aircraft, and aboard the source boat. Plume geometry 1s documented by photography and from quantitative concentration measurements. Experiments under a variety of meteorolog1cal conditions indicate that over-water dispers1on is very sensitive to meteorological conditions. From measured is significantly less than over land, particularly when the onshore flow is due to the sea breeze. This is because of the low aerodynamic roughness of the water, and because low level stable conditions are established because the water is at lower temperature than the air. Crosswind standard deviations of the plume a factor two less than the prediction of Pasquill category F have been observed at the shore with the source 6 km off shore. (auth