Determination of a Z-R Relationship for Snowfall Using a Radar and High Sensitivity Snow Gauges

Yasushi Fujiyoshi Institute of Low Temperature Science, Hokkaido University, Sapporo, Japan

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Tatsuo Endoh Institute of Low Temperature Science, Hokkaido University, Sapporo, Japan

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Tomomi Yamada Institute of Low Temperature Science, Hokkaido University, Sapporo, Japan

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Kazuhisa Tsuboki Institute of Low Temperature Science, Hokkaido University, Sapporo, Japan

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Yoshihiro Tachibana Institute of Low Temperature Science, Hokkaido University, Sapporo, Japan

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Gorow Wakahama Institute of Low Temperature Science, Hokkaido University, Sapporo, Japan

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Abstract

A best-fit power-law relationship (Z = 427 R1.09) between 1-minute integrated averages of snowfall rate (R) and radar reflectivity factor (Z) was determined on the basis of observations made by using high sensitivity snow gauges (accuracy 0.03 mm h−1) and a radar (wavelength 3.2 cm, beamwidth 1.1°) of three 1987 Sapporo snowstorms. The relationship Z = 554R0.88, using 30-minute integrated averages of Z and R, produced the best radar estimate of total snowfall. The ratio of the estimated to the observed amount of snowfall decreased with increasing density of new fallen snow ρ, the ratio roughly equaling 1, when ρ ≈ 0.05 g cm−3.

Abstract

A best-fit power-law relationship (Z = 427 R1.09) between 1-minute integrated averages of snowfall rate (R) and radar reflectivity factor (Z) was determined on the basis of observations made by using high sensitivity snow gauges (accuracy 0.03 mm h−1) and a radar (wavelength 3.2 cm, beamwidth 1.1°) of three 1987 Sapporo snowstorms. The relationship Z = 554R0.88, using 30-minute integrated averages of Z and R, produced the best radar estimate of total snowfall. The ratio of the estimated to the observed amount of snowfall decreased with increasing density of new fallen snow ρ, the ratio roughly equaling 1, when ρ ≈ 0.05 g cm−3.

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