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Show TABLE 8 COMPARISON OF PREDICTED AND OBSERVED PLUME WIDTHS I~ I~ --------=-------------::------------------------lij ! Downwind Observed Pasquill 11 Distance (km) Spread (m) Gifford (m) 11. 1 11. 1 25. 0 25.9 40. 7 40. 7 2410 2600 4080 3520 8340 5190 2400 2400 4800 5600 7000 7000 ------------------------------------- 11 ' 11; w~ Ml o( ie )! _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __._~ l!) iiMST are shown in Figure 62 . . The release at 10, 000 ft. MSL was characterirt1ized by a stratification slightly more stable than neutral. During th e second irnrelease series a sampling pass was made through two seeding lines within five :it,m inutes after the release of the first line and almost immediately after the second pass of the seeding- aircraft. The results of this sampling pass are in Figure 63. The peak nuclei count went above 700 liter- 1. This is the only pass of the entire series to record nuclei counts so high. The indication is ri1 that local overseeding is a very real possibility in the immediate vicinity of 1irr t tiliithe release (< 15 min. travel from release). - 11 1 ~,Figures 64 and 65 are two tracks for the first release series on the same day 11 _(a separate test from Figure 63). Figure 64 is an early pass for the first 11 :series. The peak nuclei counts are high, but not as high as in Figure 63. Fig1~ure 65 is a pass much later and > 30 km from the release lines. Except for two peaks of nuclei count, the material was spread over a broad area of counts rllbf the order of 5 lit er - l. 1 :Uf, mllT his series of diffusion tests with aircraft releases has indicated the following: 1) Initial spread of the material from the aircraft is quite rapid. 1!rtThe maximum nuclei count observed was near 700 liter-l immediately after trilrelease. More typical concentrations are 50 liter - l after 15 minutes of travel. 2) Local overseeding from pyrotechnic releases. from an aircraft is ritnot a serious problem if the release is made at least 15 minutes upwind of the initial target zone. 3) The Pasquill-Gifford plume spread (0 ) curves for a point source :ilpredict the horizontal plume spread of seeding tracks well within operational 101 |