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<br />2.5.1 Remote SF6 Release <br /> <br />Both propane dispenser sites d7 and d9 were equipped to allow remote release oftracer SF". <br />Site d7 \2225 m) was located on the Sierra crest, and site d9 (2207 m) was positioned about <br />5 kIn west of the crest as shown on figure 2.3. Two different locations were used to identify <br />which site transported seeded crystals more reliably into supercooled clouds. Each site had <br />12 50-kg bottles of SF". Six bottles ,'-ere manifolded together. The supply line from the <br />bottles ""as plumbed through a mass flow controller then to a solenoid. A release tube was <br />run up the mast of the propane dispenser to within a fe'\,. inches of the propane vah'e box. <br />The solenoid was actuated in the same manner as propane release-by remote-controlled <br />relay activated from Sacramento. The mass flow controller was set to release at 22 kg/h <br />using an electric flow meter. Based on tank weights taken after the field 1992-93 season, <br />flow rates determined by the flow controller were determined to be within 5 pct of actual for <br />site d7 and 1 pct for site d9. <br /> <br />2.5.2 SF 6 Analyzer <br /> <br />A continuous SPa analyzer (Benner and Lamb, 1985) was proyided. installed, and operated <br />by Korth American Weather Consultants at the Jackson Creek high elevation (1951 m) <br />obsen;atory, located near the JCC precipitation gauge (fig 2.6~. The analyzer was mounted <br />in a small, 15-ft office trailer. An external pump was used to draw ambient air through a 5- <br />m-Iong teflon tube routed through a window and mounted to a support on the trailer roof. <br />This tube was connected to the analyzer inlet port. The analyzer was calibrated before and <br />after each experiment using six calibration gases of known SF" concentrations (10.2, 95, 485, <br />972, 2902, and 4870 pIt [parts per trillion]). Instrument response was nearly linear oyer the <br />range of calibration gases. Concentrations measured during this project fell well within the <br />first three ranges of test gases. Based on instrument calibrations and stability. it was felt <br />that SF" concentrations could be resolved down to 5 pit. <br /> <br />2.5.3 SF 6 Sequential Samplers <br /> <br />Four time-sequential syringe samplers were used to collect 15-min air samples at specified <br />locations within the valley. The eight project sampling sites are noted in table 2.4. Four of <br />these eight sites were selected based on wind direction for each experiment. They were set <br />in place about 30 min prior to data collection. Each sampler had nine 30-cm3 syringes. The <br />samplers were programmed to start sampling at the same time as the SF 6 gas was to be <br />released. The nine SjTmges provided 2.25 h of sampling time. <br /> <br />Table 2.4. - Syringe sampler locations. <br /> <br />'I <br /> <br />Site Xo. Site X ame Latitude '. ~X'l Longitude! OW) <br />1 Tv,-o Rivers 39.82 120.66 <br />2 Blairsden 39.78 120.62 <br />3 Gold Lake H'\,'y. 89 39.75 120.60 <br />4 Johnsyille Rd. 39.77 120.68 <br />5 Lee Summit 39.88 120.76 <br />6 :\Iohawk Yista 39.77 120.59 <br />7 Bonta Ridge 39.80 120.65 <br />8 Jackson Creek 39.85 120.66 <br /> <br />14 <br />