WMOD00546

• Project Name: High Plains Cooperative Program
• Title: On the Sampling Variance of Raingage Networks
• Weather Modification - Doc Type: Report

of total precipitation from 112 convective storms that were observed during
the 1976 and 1977 Montana HIPLEX program by digitized 5.4 cm radar (Schroeder
and Klazura, 1978). The rainfall for each convective storm was estimated
from the radar reflectivity factor measured at the 10 elevation scan every 5
minutes and accumulated in each 0.5 km by 10 radar bin over the lifetime of
the storm to obtain the total precipitation footprint. The Marsha'll-Palmer
(1948) Z-R relationship, Z = 200 Rl.6, was used to determine the radar-
derived rainfall patterns with a 25 dBZ threshold being applied to account
for evaporation in the dry, subcloud layer of the Montana environml~nt
(Hildebrand et al., 1979). These isohyetal maps were then analyzed to
determine storm sizes, rain volumes, durations, raincell composition, and the
sizes and rain volumes of the raincells. The statistical characteristics of
these storm precipitation paraml~ters, which were extremely well-fitted to a
log-normal distribution, are shown in Table 4.

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