Influence of gravitational settling on turbulent droplet clustering and radar reflectivity factor

Keigo Matsuda, Ryo Onishi, Keiko Takahashi

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

For radar cloud observations, the microwave refectivity of clouds is measured as the radar reflectivity factor Z, which is dependent on the cloud microphysical properties. Previous study has clarified that turbulent droplet clustering can be a cause of significant increase of the radar reflectivity factor. However, the influence of gravitational settling still remains to be clarified. This study, thus, investigates the influence of gravitational settling on the spatial distribution of turbulent clustering droplets and the radar reflectivity factor. A three-dimensional direct numerical simulation (DNS) of particle-laden isotropic turbulence is conducted for several values of the nondimensional terminal velocity Sv. The results show that the power spectrum of droplet number density fluctuation, which is calculated from the DNS data, depends on Sv as the droplet settling becomes stronger, the spectrum increases at small wavenumbers and decreases at large wavenumbers. The radar reflectivity factor Z is estimated from the power spectrum under ideal cloud conditions. The results indicate that the influence of turbulent clustering is suppressed under strong gravitational-settling conditions.

Original languageEnglish
Title of host publication9th International Symposium on Turbulence and Shear Flow Phenomena, TSFP 2015
PublisherTSFP-9
ISBN (Electronic)9780000000002
Publication statusPublished - 2015
Externally publishedYes
Event9th International Symposium on Turbulence and Shear Flow Phenomena, TSFP 2015 - Melbourne, Australia
Duration: 2015 Jun 302015 Jul 3

Publication series

Name9th International Symposium on Turbulence and Shear Flow Phenomena, TSFP 2015
Volume3

Conference

Conference9th International Symposium on Turbulence and Shear Flow Phenomena, TSFP 2015
CountryAustralia
CityMelbourne
Period15/6/3015/7/3

ASJC Scopus subject areas

  • Fluid Flow and Transfer Processes

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