DOI: 10.1002/2012MS000209
Scopus记录号: 2-s2.0-84904915315
论文题名: Effects of entrainment and mixing on droplet size distributions in warm cumulus clouds
作者: Tölle M ; H ; , Krueger S ; K
刊名: Journal of Advances in Modeling Earth Systems
ISSN: 19422466
出版年: 2014
卷: 6, 期: 2 起始页码: 281
结束页码: 299
语种: 英语
英文关键词: Clouds
; Drops
; Evaporation
; Mixing
; Precipitation (meteorology)
; Shock tubes
; Size distribution
; Supersonic aerodynamics
; Time measurement
; Turbulent flow
; Cumulus cloud
; Droplet concentration
; Droplet size distributions
; EMPM
; Individual droplets
; Spatial variability
; Turbulence dissipation rate
; Turbulent mixing
; Air entrainment
英文摘要: A long-standing problem in cloud physics is the broadening of the cloud droplet spectrum in warm cumulus clouds. To isolate the changes of the droplet size distribution (DSD) due to entrainment and turbulent mixing, we used the Explicit Mixing Parcel Model (EMPM). The EMPM explicitly represents spatial variability due to entrainment and turbulent mixing down to the smallest turbulence scales in a one-dimensional domain. Several thousand individual droplets evolve by condensation or evaporation according to their local environments. We used EMPM results to characterize the evolution of the DSD due to entrainment and isobaric mixing for a wide range of conditions in a 20 m domain, including variations in entrained environmental air fraction, the turbulence dissipation rate, the size of the entrained blobs, and the relative humidity of the entrained air. We found that the broadening of the DSD due to entrainment and isobaric mixing for a specific value of the entrained air relative humidity depends only on the eddy mixing time scale and the LWC after mixing. Broadening increases substantially as the evaporation time scale decreases due to decreasing relative humidity of the entrained air. Our results also show that it is possible to parameterize the effects of entrainment and mixing on the droplet number concentration. The comprehensive results obtained for one set of values of entrained air relative humidity, droplet size, and droplet concentration should be extended to other values. Key Points DSD broadening depends on the mixing time scale and the LWC after mixing DSD broadening increases substantially as the evaporation time scale decreases We related the fraction of droplets that totally evaporate to two DSD parameters © 2014. The Authors. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/76104
Appears in Collections: 影响、适应和脆弱性 气候变化与战略
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作者单位: Institute of Coastal Research, Helmholtz-Zentrum Geesthacht, Geesthacht, Germany; Department of Bioclimatology, University of Göttingen, Göttingen, Germany; Department of Atmospheric Sciences, University of Utah, Salt Lake City UT, United States
Recommended Citation:
Tölle M,H,, Krueger S,et al. Effects of entrainment and mixing on droplet size distributions in warm cumulus clouds[J]. Journal of Advances in Modeling Earth Systems,2014-01-01,6(2)