Measurement and Analysis of Puff Dispersion above the Atmospheric Boundary Layer Using Quantitative Imagery

Abstract

Collection and analysis of puff dispersion data in the atmosphere using a remote sensing technique are presented. Quantitative measurements of standard deviation of the concentration distribution in the along-wind and crosswind direction have been generated via observations of sulfur hexafluoride (SF6) puffs released from an elevated blimp (850 m above mean sea level) and simultaneous imaging from multiple infrared cameras. The imagery data were collected as part of the Model Validation Program experiments at Vandenberg Air Force Base, California, during 21?23 May 1997. Some detailed quantitative imagery of the evolution of the puffs is shown. The puff imagery data were used to derive time histories for the along-wind and crosswind material distribution standard deviations (σ). Although there is considerable variation, it is found that a linear growth rate of σ gives a reasonable fit to the data. The material σ values are then used to estimate the turbulence intensities. Apart from the enhanced crosswind dispersion on 21 May from persistent wind shear, the turbulence intensities (along- or crosswind standard deviation of wind speed divided by mean wind speed) are roughly on the order of 1° or 2° in both the along-wind and crosswind directions for averaging times of about 5?10 min.