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<br />.)' ... <br /> <br />','~ <br /> <br />These results from several independent sources formed a, clearer picture of <br />processes at work in Sierra Nevada storms. However, the data base from <br />which these conclusions were derived contains extremes and, thus, may not <br />be representative of normal conditions. <br /> <br />e. <br /> <br />The winter of 1976-77 was unusual because of drought conditions; only <br />1 imited data were collected. The abundance of precipitation during the <br />winter of 1977-78 was equally unusual. Storm types we're generally south- <br />westerly, with warm bases, deep clouds, and cold tops. <br /> <br />The general objectives of the 1978-79 calibration SE~ason were to gain <br />additional insight into the seedabi1ity of Sierra Nevada storms, select the <br />optimum seeding modes and rates for the three major cloud types identified <br />at that time, and identify and correct operational problems in preparation <br />for the exploratory experiment. The first calibration season yielded a <br />number of important results that will aid in designing the exploratory <br />experiment. They were: <br /> <br />e <br /> <br />1. Pre1 iminary results indicated that deep co1d-tolP orographic clouds <br />have little supercooled water, except possibly at very low levels in the <br />cloud system. <br /> <br />2. Two general types of cloud bands were apparent in the study area. <br />The first variety tends to form in a homogeneous lIareall type precipita- <br />tion regime. The origin for these stable bands is believed by some <br />scientists to be the destabilization of the atmosphere near the melting <br />layer which causes wave motion. These bands generany lack convective <br />elements and usually dissipate on the barrier. The more convective <br />variety of the cloud bands usually occur along or near frontal surfaces <br /> <br />e <br /> <br />1-6 <br />