The Microphysics of Snow Crystal and Snowflake Melting
Final rept. 1 Sep 1980-31 Dec 1982
UTAH UNIV SALT LAKE CITY
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A new portable, vertically-diverging wind tunnel was developed for studying melting of natural snowflakes and snow crystals during their free fall under controlled condition of the air stream. Using the tunnel, their size and fall velocity were measured and the regression equations were obtained. Their observed melting time depended only weakly with the size suggesting the possibility of internal melting due to air flow through their structure. Rotating and orbiting motions were commonly detected with snow crystals. Disruption was found frequently towards the end of melting of both snowflakes and ice crystals and resulted in instability in their suspension. A theoretical development was carried out for melting snowflakes and ice crystals considering their non-spherical shape. A new simple model of snowflake melting had been developed and was applied to a representative atmospheric condition. Comparison of the model behaviors of radar bright bands suggested that the shape and its development as well as size during aggregation play important roles in the bright band mechanism. The model predicts that the higher the snowfall rate, the larger the reflectivity increase and the lower the altitude of the bright band center.
- Snow, Ice and Permafrost