The evolution of raindrop spectra. Part III: downdraft generation in an axisymmetrical rainshaft model

G. Feingold, Z. Levin, S. Tzivion

Research output: Contribution to journalArticlepeer-review

Abstract

As input to the model, a stationary cloud provides rainfall with a predetermined drop spectrum. Mass loading and evaporative cooling generate downdrafts below cloud base. For near-adiabatic lapse rates and moderate mass loading, microbursts develop. For a given liquid water content, the magnitude of these downdrafts depends primarily on the lapse rate of temperature, but also on the drop spectrum injected at cloud base. It is shown that drop collection and breakup may affect the magnitude of the generated downdrafts significantly. When spectra comprising mainly small drops evolve to create larger drops, or when spectra comprising mainly large drops evolve to create smaller drops, neglect of collection and breakup can modify the downdrafts by up to about 50%. It is shown that in a steady state situation the drop spectra evolve toward bi- or trimodal spectra. -from Authors

Original languageEnglish
Pages (from-to)315-330
Number of pages16
JournalJournals of the Atmospheric Sciences
Volume48
Issue number2
DOIs
StatePublished - 1991

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