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<br />- 120 - <br /> <br />However, the thick crystals were not always totally encapsulated by the Formvar <br /> <br />so that this observation must remain tentative in nature. The growth on many <br />of the isolated branches was unusual and often included multiple layers of <br />ice of varying shapes on a single branch. <br />The isolated branches were observed both in aggregates and as individual <br />isolated branches. <br /> <br />4.3 Aggregation of Ice Crystals <br /> <br />Aggregates play an important role in the total mass of ice observed in <br /> <br />the Pacific Northwest storms. On the ground at least 60% of the total <br /> <br />concentration of ice crystals are in the form of a~gregates. The aggregates <br /> <br />are often compased of needles and star-like crystals but side planes, columns, <br /> <br />and bullets are common in aggregates composed of crystals formed below -200C. <br /> <br />Aggregates composed solely of plates were never found on the groumd, although <br /> <br />they were in the air. On the ground plates were combined with cold region <br /> <br />crystals or often with dendrites. There were many aggregates composed of <br /> <br />almost exclusively star-like crystals. The ground observations indicate that <br /> <br />the shape of the aggregates resembled a large, flat but fairly thin disc, <br /> <br />Aggregates were also conspicuous in the particles collected from the <br /> <br />aircraft, although they rarely exceeded about 1% of the total concentration of <br /> <br />ice particles. As on the ground, aggregates in the air were composed of many <br /> <br />different crystal types. Commonly observed were aggregates of plates and <br /> <br />naturally fragmented star-like crystal branches, aggregates of primarily plates, <br />aggregates of star-like crystals, aggregates of plates and columns, and <br />aggregates of bullet-like crystals. Another common aggregate was a central <br />branch composed of many individual crystals. Due to the large size of many of <br /> <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />l <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />1 <br />I <br />