Radar Observations and Simulation of the Melting Layer of Precipitation

Abstract

The melting layer in precipitation is physically modeled and compared with high resolution Doppler radar data. The model includes a new formulation of the dielectric properties and can handle all ice particles with densities ranging from pure snow to hail. The air temperature is calculated from the vertical air velocity. The model can simulate the aggregation and breakup of the melting particles. The melting layer is often observed as a bright band; the prominence of the bright band is related to the density of particles before melting. The width of the band increases with the rain intensity; according to the model this is mainly caused by an increase in the almost isothermal layer at the upper part of the melting layer. The results of the model are in good agreement with Doppler radar observations. According to the model, the reflectivity is very sensitive to the dielectric properties and density of the melting particles and the influence of aggregation is restricted. Because of the assumption of stationarity the best results are found in stratiform precipitation.