Melting Models in Charactering Winter Precipitation Microphysics

Ice and mixed phases of hydrometeors play important rules in precipitation microphysics and corresponding processes such as accretion/breakup, deposition/sublimation and precipitation in all seasons. Understanding and effectively representing snow microphysics are required in developing an accurate and efficient parameterization scheme for numerical weather prediction (NWP). Two melting models are developed to investigate how a snow particle size distribution (PSD) is related to a raindrop size distribution (DSD) when snowflakes are completely melted to raindrops. Both models assume that the mass of a single particle is conserved. One model then assumes that the total number of drops is also conserved, and thus, the total liquid water content will be conserved. As a result, this model will be referred to as the ‘mass conservation' (MC) model. The other model assumes that the number flux of the distribution will be conserved, and is thus known as the ‘flux conservation' (FC) model. Using the melting models, snow PSDs are converted to rain DSDs to explore possible relations with the measured DSDs during the rain period. Results show that the melted DSDs during the snow period are similar to the DSDs in earlier rain period. The melting models are used to interpret radar data for stratiform precipitation.