Measured plume width versus sampling time: A look beyond 10 kilometers: Fid-Bau Portal

Measured plume width versus sampling time: A look beyond 10 kilometers

Mueller, Stephen F. / Reisinger, Lawrence M.

Abstract Previous investigators of the relationship between measured plume width and sampling time τ (τ ranges from just a few minutes to several hours) have found that width is proportional to $τ$ ^m, where, in general, $0.2 ⩽ m ⩽ 0.3$ . These results are related to the dependency of average in-plume pollutant concentration, ξ, on τ, where ξ ∞ $τ$ ^p with, generally, $−0.7 ⩽ p ⩽ −0.2$ . Data previously used to determine exponents $m and p$ have almost exclusively been collected at distances of 10 km or less from a source. Lidar observations of plume width are used here to investigate sampling time effects at distances of 10–68 km downwind. Results of the analysis of the lidar observations indicate that sampling time effects on plume width exist out to at least 68 km. The value of sampling time exponent $m$ was found to be about 0.25. These results are very similar to those found by others at short ( $⩽ 10 km$ ) pollutant travel distances. No evidence was found to suggest that plume width sensitivity to τ is affected by vertical wind shear. A comparison is made between the results presented here and those previously presented by Hino (1968, Atmospheric Environment 2, 149–165). Values of $m$ inferred from Hino's values for $p$ are comparable to lidar-based estimates of $m$ . The effects of pollutant travel distance on the comparison of Hino's analysis with the lidar data analysis are briefly described.