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<br />58 <br /> <br />JOURNAL OF APPLIED METEOROLOGY <br /> <br />VOLmm 17 <br /> <br /> <br />10 <br /> <br />L.IQUID WATER <br />CONTENT <br />o m-3 LO <br /> <br />e <br /> <br />o <br />WEST REL.ATIVE HORIZONTAL. DISTANCE, km <br /> <br />FIG. 5. The variability of the liquid and solid measurements with distance for <br />two consecutive passes. These values are contoured with time in Fig. 4. The ice <br />concentration values linearly averaged over the entire pass in the seeded cloud are <br />shown by the horizontal bar; these averaged values are contoured with time in Fig. 6. <br /> <br />two cloud physics aircraft were near cloud base. One <br />of the cloud-base aircraft found a firm but rapidly <br />decaying base on one of the tall altocumulus elements. <br />The two top aircraft. then penetrated it above; the <br />seeder aircraft encountered three bubbles on itseast-to- <br />west pass while the cloud physics aircraft, flying a bit <br />higher, went into only th~ middle bubble. It was <br />decided to seed those elements on the next run. East- <br />west penetrations by the upper cloud physics aircraft <br />were made for most of the next hour following seeding. <br />The cloud-base aircraft encountered snow at its level <br />16 min after seeding but later had to leave because of <br />equipment failures. The other lower cloud physics <br />aircraft then climbed toward cloud base and encountered <br />light precipitation until 40 min after seeding. The <br />experiment ended when it was too difficult for the <br />upper aircraft to locate the ice remnants. A local <br />resident who watched the operation from the ground <br />and the crews of the lower aircraft all reported that no <br />precipitation appeared to reach the surface. <br />The entire experiment is illustrated in the length- <br />time diagram in Fig. 4 and the altitude-time diagram <br />in Fig. 6; a brief portion is illustrated in Fig. 5. The <br />western and northern edge of the system had distinct <br /> <br />e <br /> <br />clear air boundaries while the eastern and southern <br />edges had other cloud elements nearby. The first three <br />passes of the upper aircraft were at higher altitudes <br />than the rest of the passes. The tracks of the aircraft <br />through the diagramed clouds are indicated. After its <br />fourth penetration, the second of which was the seeding <br />pass, the seeding aircraft left the experiment. Fig. 4 <br />presents the observations, at 5 s resolution, of the liquid <br />and solid components of the upper portion of the cloud, <br />based on those passes which were well within the cloud. <br />Edge and diagonal pass data are not shown; they were <br />used for confirming the lateral spreading of the ice cloud. <br />Fig. 5 shows the same measurements of ice particle <br />concentration and liquid water content for passes 4 <br />and 5 in detail. In this figure the variability of the values <br />is illustrated; they are plotted versus penetration <br />distance using a 1 s resolution of aSs running mean. <br />The horizontal bar indicates the linear average of ice <br />particle concentration for the entire pass later used in <br />the construction of Fig. 6. Several such averages were <br />combined in the effectiveness calculations quoted <br />earlier. The tiny ice patch at about the 7 km position <br />on pass 5 was a late development in the apparently <br /> <br />e <br />