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<br />1446 JOURNAL OF APPLIED METEOROLOGY V GLUME 35 <br /> TABLE 8. Sulfur hexaflouride plume characteristics from site 9 as observed by aircraft for the downwind track. <br /> Plume <br /> width <br /> Dist. site 9 Max SF6 Avg SF6 Alt Temp Avg LWC Wind speed Wind direction <br />Date Pass CO) (kIn) (kIn) (ppt) (ppt) (m) COC) (g m-3) (m s-') ("1') <br />9 March 16 21 14.2 39.0 62 27 2475 3.3 0.00 10 213 <br />9 March 17 20 13.8 38.5 43 23 2470 3.1 0.00 8 227 <br />9 March 18 20 13.7 39.9 64 30 2480 3.1 0.00 9 228 <br />16 March 18 II 6.7 33.9 14 8 2604 0.5 0.03 17 242 <br />19 March 10 4 2.4 38.0 13 7 2619 2.6 0.00 15 228 <br />Average 15 10.2 37.9 39 19 2530 2.5 0.01 12 228 <br /> <br />5 kIn farther southwest of the valley flight track. Thus, <br />the plumes will have about 7 min of additional disper- <br />sion time on average before being sampled along the <br />valley track. <br />There were 5 days on which SF6 releases were made <br />from both sites 7 and 9, allowing plume characteristics <br />to be compared. There were no simultaneous releases <br />on 17 February, but releases were separated by I h. <br /> <br />4 T <br /> <br />E <br />Q. <br />:E <br />w <br />I- .4 <br /> <br />o <br /> <br /> <br />-8 <br /> <br />M 0.4 <br />E <br />:2! <br />u 0,2 <br />;: <br />..J <br /> <br /> 0.0 <br /> 2700 <br />I 1858 <br />I- 2400 <br />..J <br /><( <br /> <br />1900 1902 1904 1906 1908 <br /> <br /> 2100 <br /> 80 <br />i=' <br />Q. <br />e:. <br /><D 40 <br />u. <br />Ul <br /> <br /> <br />o~ <br />18.95 <br /> <br />19.10 <br /> <br />19.15 <br /> <br />19.00 19.05 <br />Time (UTe) <br /> <br />FIG. 14. Same as Fig. II but for 9 March along the downwind <br />flight track. Plumes from sites 7 and 9 have merged at this downwind <br />location. <br /> <br />Site 9 plume dimensions averaged 5 kIn in width, while <br />site 7 dimensions averaged 3.3 kIn in width. Sulfur <br />hexaflouride average plume concentrations were 35 ppt <br />for site 9 and 43 ppt for site 7. Liquid water concen- <br />trations averaged 0.12 g m-3 in site 9 plumes and only <br />0.05 g m-3 in site 7 plumes. This will be discussed <br />further in section 4, which covers seeding effects. Since <br />the average sampling distance downwind from the dis- <br />pensers was 13 kIn for site 7 and almost 18 kIn for site <br />9, it would appear that site 9, being farther back from <br />the crest, is more effective for treating a larger cloud <br />volume. <br />Two VFR flight days, 9 and 19 March, provided <br />comparisons sampling for plumes from sites 7 and 9 at <br /> <br /> <br />114 <br /> <br />118 <br /> <br />122 <br /> <br />FIG. 15. Aircraft-observed SF6 concentrations above 10 ppt plotted <br />over target area terrain contours for 9 March 1993. GUIDE model- <br />predicted plumes from sites 7 and 9 are annotated. Symbols used for <br />SF6 concentrations are box, 10-15 ppt; plus sign, 15-50 ppt; cross, <br />50-100 ppt; asterisk, 100-150 ppt; shaded star, 150-200 ppt; sun, <br />200-250 ppt; and open star, greater than 250 ppt. The scale along <br />the outer boundary is in nautical miles. <br />