The 12/13 January 1988 narrow cold-frontal rainband observed during MFDP/FRONTS 87. Part II: microphysics

Abstract

The microphysics of a narrow cold-frontal rainband is investigated by using a microphysical retrieval model. The equations of evolution of the water substance and of the temperature are solved using a wind field prescribed from dual-Doppler radar observations. The main result was that the precipitation associated with the NCFR was mostly composed of graupel particles, essentially formed by riming. Rain was produced by accretion of cloud water in the condensation zone and by melting of graupel. The choice of the type of ice-precipitating particles introduced in the model appeared very important. Only rimed particles (graupel) could reproduce observed precipitation. The temperature drop observed at low levels just behind the frontal discontinuity could be explained at the time of the observations by two cooling effects of equal importance: the melting of graupel and the evaporation of precipitation. -from Authors