Mesoscale Circulations Forced by Melting Snow. Part II: Application to Meteorological Features

Abstract

Various authors have proposed that the cooling associated with melting precipitation contributes significantly to the dynamics of mesoscale precipitation systems. In this study, we use the numerical model described in Part I of this paper to investigate the effects of the cooling-by-melting mechanism in three specific situations: rain/snow boundaries, the production of deep 0°C isothermal layers, and the trailing stratiform region associated with mesoscale convective systems. It is found that melting in the vicinity of a rain/snow boundary produces a thermally indirect mesoscale vertical circulation that may be responsible for enhanced precipitation near a rain/snow boundary. Melting in the presence of warm air advection above the melting layer and cold advection at and below it are necessary for producing deep 0°C layers within realistic times. The dynamic effects of cooling associated with melting and evaporation in the stratiform region of a mature squall line system produce a mesoscale circulation qualitatively similar to that recently reported in the literature.