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<br />available electric power operates other measuring systems;
<br />these sites were believed to be most representative of typical
<br />Mesa snowfalL The, gauge at the radar-radiometer site was
<br />to provide data for correlation with radar reflectivity; how-
<br />ever, the radar was blind (for unknown reasons) through the
<br />lowest kilometer above the radar. The other sites were cho-
<br />sen for accessibilityJo examine the spatial variability around
<br />the Mesa. All gauge locations except the, Vncompahgre Pla-
<br />teau site are shown on figure 1-1 in section 1. Data from the
<br />gauges operating during early and late 1983, when the cloud
<br />physics aircraft, radiometer, radar, and ground 2D-C were
<br />in use, were used in the case study analysis.
<br />
<br />3.2 Precipitation
<br />,Characteristics Atop
<br />Grand Mesa
<br />
<br />A two-winter "climatology" is available from the GM0-West
<br />site. For the 1983-84 season, the 1l.3-inch diameter, 6-inch
<br />capacity gauge was used as a standard, with the 3D-inch
<br />capacity gauge used to "fill in" when the standard had miss-
<br />
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<br />ing data. The resolutions were 0.005 and 0.02 inch, re-
<br />spectively, for the two gauges. For the 1984-85 season, the
<br />17.9-inch-diameter, 2.4-inch capacity gauge was preferred,
<br />and the 11..3-inch-diameter gauge was used as a backup. The
<br />resolutions were 0.002 and 0.005 inch, respectively, for
<br />these gauges. The memo of McPartland, et aL [14] gives
<br />further details on this data set and on the results to follow.
<br />
<br />t
<br />
<br />The total precipitation measured for the entire lO-month
<br />period was 51.4 inches, using daily totals. When hourly read-
<br />ings less than 0.01 inch were excluded, the lO-month total
<br />was 48.1 inches. Hourly readings of 0.005 inch from the
<br />11..3-inch gauge and 0.002 inch from the 17.9-inch gauge
<br />may not necessarily indicate actual precipitation during that
<br />hour. The data set shows many hours, perhaps half of the
<br />total hours, at hourly rates less than 0.01 inch, which con-
<br />tributed only a minor fraction to the season totaL
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<br />Precipitation cumulative distributions were made from this
<br />data set. Figure 3-1 shows the distributions for hourly
<br />amounts, and figure 3-2 shows daily amounts, both figures
<br />excluding readings less than 0.01 inch. On both figures, the
<br />upper curves show large percentages of precipitating hours
<br />
<br />1204 Hours of Precipitation
<br />48.1 Inches of Precipitation
<br />
<br />.02 .03 .04 .05 .07
<br />HOURLY PRECIPITATION
<br />
<br />.1
<br />[INCHES)
<br />
<br />.2
<br />
<br />.3 .4
<br />
<br />Figure 3-1. - Cumulative distributions for hourly precipitation.
<br />
<br />16
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