Mechanism of Shallow Winter-Type Stratiform Cloud Systems

摘要

In twelve shallow, upslope cloud systems, along the eastern slopes of the Rocky Mountains in Colorado, two parameters were measured. The rate of precipitation, by use of a Dew Scale, and the number flux of snow crystals, by use of photographs. Life histories of upslope snowstorms were plotted to show rate of precipitation, crystal flux, and mean mass of the crystals. In five storms the rate of precipitation and particle flux were proportional; in two more there was a less pronounced similarity of the curves. It is suggested that the observed proportionality is due to the rate of condensation, which is governed by the velocity of the updraft, in a strong feedback mechanism between the microscale and the mesoscale; water vapor is released to form liquid water and ice crystals at nucleation threshold temperatures.