Laserfiche WebLink
<br />3. A moist layer thicker than 1 km. A layer < 1 km is as- <br />sumed to be too shallow to produce adequate precipitation at <br />the ground from artificial release. Fletcher (1962) suggested <br />the figure 1300 m as the minimum thickness necessary for a <br />high probability of induced precipitation from silver iodide <br />(AgI) seeding of sub-freezing clouds. <br />4. A cloud top temperature between -5 and -15oC. Clouds having <br />top temperatures in this range are eminently sui table for <br />artificial release of precipitation) because (1) phase in- <br />stability of the water substance is often present due to the <br />small number of active natural ice nuclei) and (2) common <br />seeding reagents are available for this temperature range, <br />This author feels that this temperature range is a con- <br />servative one) and that experiments on these cloud systems <br />may indicate that the potential for artificial release of <br />precipitation does extend to colder cloud systems. In- <br />cluded in this report is an estimate of the effect a widened <br />range of cloud top temperatures has on the number of oc- <br />currences of seedable conditions per year at one of the <br />High Plains rawinsonde stations. <br />5. A distinct moist layer top. This criterion distinguishes <br />shallow cloud systems from the deep cyclonic storm systems in <br />which the relative humidity appears to decrease slowly with <br />height (fig, 2). A strict interpretation of criterion No.1 <br />would include some of the deep cyclonic storm systems in the <br /> <br />5 <br />