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<br />I <br />I <br />I <br />I <br />I <br />, <br />I <br />I <br /> <br />The prlmary purpose of the SF6 measurements was to simulate <br />the transport and diffusion of seeding materials from either <br />a ground based, or airborne source. During the 1987 field <br />season all releases did occur from ground level. Once a plume <br />was intersected then the objective was to obtain data on the <br />conditions of the parcel of air in which it resided. In partic- <br />ular, the frequency of occurrence, amount, -and spatial distribu- <br />tions of supercooled liquid water, the ambient alr temperature, <br />stability, and other meteorological conditions which affect <br />the production and/or depletion of supercooled liquid water <br />were examined, The assessment of various cloud seeding techniques <br />over and around orographic barriers was also examined by observing <br />the transport and dispersion patterns of the SF6 gas. <br /> <br />I <br />1 <br />I <br />t <br />l <br /> <br />4.2 Description of Equipment <br /> <br />l <br /> <br />The continuous SF6' analyzer designed by Washington state <br />University (Benner, and Lamb, 1985) and manufactured by Scientech, <br />pullman, Washington was utilized on board the University of <br />wyoming's high performance King Air aircraft. The analyzer <br />was mounted in a rack along with one cylinder of ultra-pure <br />nitrogen and one cylinder of hydrogen, both necessary to operate <br />the analyzer. In addition, an external pump was used to draw <br />ln ambient air through a port located in the top right section <br />of the fuselage, through approximately ten feet of 1/8 inch <br />teflon tubing, and then injected into the inlet port of the <br />analyzer. The lag time through this ten foot section of tubing <br />was measured on the ground by releasing an excess flow of <br />95 ppt calibration gas into the port on the outside of the <br />plane, and then measuring the lag time between injection and <br />response. This lag time was found to be approximately three <br />seconds. <br /> <br />t <br />i <br /> <br />1 <br /> <br />4-5 <br /> <br />j <br /> <br />1_ <br />