Unusual Phenomenon of Freezing Rain in Perm Krai

摘要

Analyzed is a phenomenon of the freezing rain observed in Perm krai on December 14. 2010, when the surface temperature was -10.9℃. The process of cooling of falling drops is numerically simulated and their temperature is computed on the basis of the data of radio sounding of the atmosphere. It is demonstrated that the large-size drops do not have time to reach the supercooling state and, when falling to the ground, have a positive temperature. The finer drops are cooled to the negative temperature. An executed estimation of the process of transformation of falling drops into ice at the crystallization of the supercooled water demonstrated that the volume fraction of the ice crust of drops at the phase transition does not exceed 3% even under optimum cooling conditions.