A Study of Radar Echo Clusters over Southeastern Montana

L Ronald Johnson, Mark R Hjelmfelt


Data recorded by the Skywater radar during the Cooperative Convective Precipitation Experiment were used to produce echo cluster statistics. The average echo cluster is initiated in the mid-afternoon (15:18 MDT) and continues for 1.8 hours. It has a maximum reflectivity of 45.4 dBz, and produces 296 km^2*mm of rainfall. The storm moves from the west to east at a speed of 12.5 m/s. Analysis revealed a bimodal distribution of maximum echo heights with the low mode at 6.9 km and the upper mode at 9.4 km. Comparison of predictors for radar estimated rainfall confirmed the value of the Area-Time-lntegral (ATI). Echo statistics were in good agreementĀ  with those obtained from a different project in North Dakota for the same year, with greater differences obtained for statistics from projects in more humid climates. The importance of year-to-year variability is affirmed.

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