Estimated Effective Chimney Heights Based on Rawinsonde Observations at Selected Sites in the United States

Abstract

The plume rise equations of Briggs (1975) for variable vertical profiles of temperature and wind speed are described and applied for hypothetical short and very tall chimneys at five National Weather Service rawinsonde stations across the United States. Annual average effective chimney heights are presented and from other available data additional information on plume behavior is deduced. For example, based on the 0515 CST soundings at Nashville, 61% of the effective plume heights for 50 m chimneys were in a temperature inversion, but only 21% of the plumes for 400 m chimneys were so constrained. Ordinarily, such plumes would be in a fanning configuration. Most of the plumes from tall chimneys (60%) were above an inversion, practically isolated from the ground. Overall, 98% of the short-chimney plumes were reached by the afternoon mixing height, but only 85% of the tall-chimney plumes were reached. Such information supports the obvious presumption that the effluent from tall chimneys remains airborne longer than that from short chimneys, is transported over greater distances, and has more opportunity to undergo chemical transformations before reaching the ground.