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<br />3) "Blowover" index such that addit ional ice crystals produced <br />through cloud seeding would not blo\o1 beyond the barrier and <br />evaporate <br /> <br />4) The existence of an inversion means it is necessary to seed by <br />aircraft (not 1n 80-81) or by high elevation ground generators <br /> <br />5) Seeding IS norMally suspended if the freezing level is above <br />7000 ft <br /> <br />During Feb. and ~ar. 1981 the conditions]) and 4) were of primary <br />concern, i.e., seeding depended upon the cloud top temperature and <br />the presence or absence of an inversion. <br /> <br />In the actual application of the operational project In Utah <br />(according to the CSU design study) seeding is conducted at all times <br />during winter storms except when <br /> <br />1) The 700 mb wind is greater than 50 kts. <br /> <br />2) The "lifted cLono top" IS colder than -30oC; except when <br />700 mb winds are weak (less than 20 kts)o <br /> <br />3) Low-level stability is so strong that it prevents the use <br />of even high-level seeding generators. <br /> <br />Actual seedi ng during these two months 1n the local area of the <br />fushar's is summarized in Table 1. A more detailed tabulation of seeding <br />activities in the vicinity of the Tushar's is given in Appendix B. <br /> <br />~2 Therma~!!ability. As recognized In the seeding criteria the <br />existence of inversions may be an important factor in a cloud seeding <br />project utilizing ground based generators. Although cloud cover generally <br />inhibits loss of surface heat by radiation during nighttime, there may <br />yet be sufficient radiational cooling when clouds are present to cause <br />low level inversions. Therefore, it is of particular concern to examine <br />soundings at night or when the sun's elevation angle is low. <br /> <br />In Table 2 soundings taken at Beaver (ESe) and Adamsville (NAWC) <br />during February anrl March, 1981 are listed according to whether there is <br /> <br />14 <br />