Laserfiche WebLink
<br /> 0 <br /> I'f') <br /> y -31.7 + 0.00524 X * <br /> R = 0.68 * * <br />r---, <br />II) * <br />Q) <br />.s:: <br />0 <br />c <br />'-0 <br />.........N <br />- <br />C <br />Q) <br />0 <br />.~ <br />~ <br />0- <br />W <br />L. <br />Q) <br />- <br />00 <br />~..- <br />..... <br />'i: <br />c. <br /><( * <br /> * <br /> * <br /> <br /> <br />o <br />7000 <br /> <br />8000 9000 <br />Elevation (teet msl) <br /> <br />Figure 3-9. - Average April 1 snowpack water equivalent VS. elevation in the Sevier River drainage. <br /> <br />10000 <br /> <br />gases have shown that high altitude ground-released seeding material can be expected to disperse over <br />about 600 m above the barrier crest in the absence of convection (e.g., Holroyd et al.1988). At that <br />elevation the cloud can be expected to be about -4 oC colder than indicated by surface observations. <br />Thus, a Blowhard Mountain temperature of -4 oC is probably cold enough for significant ice nucleation <br />near the top of an AgI plume passing over that location. <br /> <br />Much of the mountainous terrain in the Sevier Basin is below the 10,700 ft elevation of Blowhard <br />Mountain. It is reasonable to consider the Blowhard Mountain temperatures as representative of seeding <br />plume tops over more typical terrain. This is a conservative estimate because convection should carry the <br />seeding agent to higher, colder levels during some stonns, especially in early winter and spring. <br />Figure 3-12 shows that a mean surface temperature below -8 oC existed from December through March <br />suggesting most stonn events were cold enough for ground-based seeding with AgI. Somewhat fewer <br />stonns would be seedable by this means in November and April and AgI ground-seeding opportunities <br />are likely limited in October and May. <br /> <br />Figure 3-13 is a frequency distribution of mean temperatures during snowfall days for the 6 coldest <br />months of the winter. Again assuming Blowhard Mountain measurements are representative of the tops <br />of ground-released AgI seeding plumes over "typical" mountainous terrain, figure 3-13 suggests that <br />roughly half of all days with precipitation were cold enough for effective ground-based seeding, ignoring <br />any enhancement in vertical mixing due to convection. Similar conditions were found in Montana (Super <br />and Heimbach, 1983) where only about half the stable stonn days.appea~d seed able from the ground. <br /> <br />26 <br />