A history of classic atmospheric dispersion field experiments

This paper is part of an AMS conference session on historical atmospheric dispersion field experiments. A whirlwind overview is given of the classic field experiments and the scientific issues being investigated. The experiments are categorized by scientific topic area, by distance and time scales, and by sampling technology. It is shown how the classic experiments up through about 1960 were mostly focused on military applications related to better understanding of short range transport and dispersion of releases from chemical weapons. After ambient air quality standards were set and environmental agencies formed in the 1960s, the emphasis of field experiments shifted to environmental issues such as dispersion from tall stacks. This evolved into experiments investigating longer range (mesoscale and regional) transport and dispersion, which required development of special tracers that could be observed at very low concentrations. Focused issues such as dispersion in complex terrain and dry deposition and chemical removal began to be studied. Since the 1980s, due to concerns about accidental releases of hazardous gases, there have been numerous dense gas field experiments sponsored by various government agencies and industries. The 2000s have seen many large urban dispersion experiments. Those in the U.S. are investigating possible accidental or terrorist releases in urban areas. Those in Europe are investigating traffic pollution in large urban areas.

Computers have been invented during the course of this 100-year history and are now universally used. Naturally, the field experiments prior to about 1960 were used mainly to improve parameterizations in one-or two line analytical dispersion models. Recent experiments, in the era of computers, are often used to improve parameterizations in computational fluid dynamics models. It is interesting, however, that over the entire range of field experiment and model complexity, our analysis methodology has little changed - fitting a line through a series of observed points.