Empirical Relationships for Estimating Liquid Water Fraction of Melting Snowflakes

Abstract

he liquid water fraction of individual snowflakes f is an important parameter when calculating the radar reflectivity of a melting layer. A ground-based observation of f at Nagaoka, Japan, was conducted by using dye-treated filter papers that were kept at a temperature of 0°C. From the results of these measurements, which consisted of 6179 particles taken with 44 sheets of filter paper, two empirical relationships are proposed. The first is a relationship between the ratio of liquid water flux to total precipitation intensity (FL; taking values from 0 to 1) and meteorological surface data. The second is a relationship to estimate f using the melted diameter of a snowflake, median mass diameter, and FL. It was determined that the root-mean-square errors for estimating FL and f by using these relationships were 0.160 and 0.144, respectively. It was also found that the ratio of raindrop flux to the total precipitation intensity FR was always below 0.1 when FL was less than 0.6 but increased rapidly when FL exceeded 0.8.