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<br />ABSTRACT <br /> <br />A comprehensive examination of the evolution and vertical distribution of <br />supercool E~d 1 i qu'id. water fn Sierra Nevada wi nterstorrns. has bee~n completed as' <br />part of the Sierra Cooperaiive Pilot Project. Measurements 6f' s~percooled water <br />were made with a dual-channel radiometer located near the Sierra Nevada crest- <br />line in 63 storms which affected the area from the 1983/84 through the 1986/87 <br />winter field seasons. <br /> <br />The analyses were carried out in two parts. In the first part, winter <br />storms were grouped into two general categories based on the prevailing flow and <br />resultant storm trajectory. The two storm types consisted of those propagating <br />in zonal flow and others in meridional flow. A complete description of the <br />storm typing is provided. Storms in zonal flow were either developing, <br />occluding, or dissipating during the time they affected the Sierra Nevada. The <br />stage of evolution of the storm dictated the characteristics of supercooled <br />water observed during the storm's passage over the Sierra Nevada. The presence <br />of supercooled water in meridional storms was influenced mainly by the trajec- <br />tory of the storm. <br /> <br />Results indicated that zonal storms had the most sustained periods of super- <br />cooled water in the post-frontal region. Sustained supercooled water measure- <br />ments in meridional storms were usually greatest within the pre-frontal portions <br />of the storm. These periods of supercooled water were associated primarily with <br />orographic clouds. Studies of the vertical supercooled water distribution <br />showed that saturation often existed within 1 km of the local terrain when <br />supercool(~d water was measured by the radiometer. Fifty percent of the rawin- <br />sondes launched through supercooled water-bearing clouds measured water- <br />