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<br />5 <br /> <br />4 <br /> <br />,......, <br />.s 3 <br /> <br />ci. <br />"u <br />... <br />... <br />0... <br />""2 <br />~ <br /> <br /> <br />1 <br /> <br />o <br /> <br />Oct <br /> <br />Nov Dee <br /> <br />~ Cedar City <br /> <br /> <br />~ <br /> <br />Jan Feb Mar <br />Month <br /> <br />~ Blowhard Mtn. ~ Hatch <br /> <br />May <br /> <br />Apr <br /> <br />Figure 3-8. - Comparison of average monthly precipitation at Cedar City, Blowhard Mountain <br />radar site, and Hatch, UT, located at elevations of 5700, 10,700, and 6900 ft, respectively. <br /> <br />exists, a linear correlation coefficient of 0.68 was calculated between the two variables. This suggests that <br />elevation alone explains almost half the variance in snowpack water content. Other factors likc~ly include <br />slope and aspect of the terrain, measurement location relative to local topography and major barriers, and <br />latitude. <br /> <br />Figure 3-10 illustrates the relationship between April 1 snow water equivalent and latitude for the same <br />data set used in figure 3-9. The linear correlation coefficient was calculated to be 0.52 while the <br />coefficient was only 0.08 between elevations of the snowcourse sites and latitude (no relationship). This <br />indicates over one-fourth of the variance in snowpack water content is due to north-south position. <br />Figure 3-10 shows that water equivalent increases from south to north as might be expected. '!be winter <br />stonn tracks are such that northern Utah has more frequent passages than southern Utah. <br /> <br />Figures 3-9 and 3-10 do not indicate whether the precipitation increases are chiefly due to a greater <br />number of stonn events impacting higher elevations or are because precipitation intensity is greater on <br />higher terrain. However, based on obselVations from other barriers including the Tush~lfS, higher <br />elevations generally will have both higher precipitation rates and longer durations of precipitation per <br />stonn event. <br /> <br />Figure 3-11 shows the frequency distribution of daily snowfall depths at Blowhard Mountain. Over 50 <br />percent of the snowfalls were less than 3 in and almost 75 percent were less than 5 in. Only about 1 in <br />10 snowfall days produced depths greater than a foot. As discussed in section 3.2.1, these infrequent <br />heavier snowfall days would be expected to produce much of the SL W flux. <br /> <br />Figure 3-12 displays average precipitation, snow depth and temperature per stonn event. These were <br />defined by examining consecutive days with precipitation. The chart shows that average surface <br />temperatures during snowfall events were below -8 oC (approximate wannest temperature fOf' AgI to be <br />effective as a seeding agent) four out of the 8 months, Aircraft tracking of seeding plumes and tracer <br /> <br />25 <br />