The influence of entrainment on the evolution of cloud droplet spectra: I. A model of inhomogeneous mixing

BAKER, MB; CORBIN, RG; LATHAM, J

doi:10.1256/smsqj.44913

Cited by 79 publications

(106 citation statements)

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“…Burnet and Brenguier, 2007). Latham and Reed (1977), Baker and Latham (1979) and Baker et al (1980) characterized mixing in terms of the relative time-scales of droplet evaporation and turbulent homogenization of a given control volume. If the length scale of the control volume lies within the inertial subrange of turbulence, then the ratio of these two time scales is the Damköhler number introduced in section 4.1.…”

Section: Homogeneous and Inhomogeneous Mixingmentioning

confidence: 99%

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Droplet growth in warm turbulent clouds

Devenish

Bartello

Brenguier

et al. 2012

Quart J Royal Meteoro Soc

239

281

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In this survey we consider the impact of turbulence on cloud formation from the cloud scale to the droplet scale. We assess progress in understanding the effect of turbulence on the condensational and collisional growth of droplets and the effect of entrainment and mixing on the droplet spectrum. The increasing power of computers and better experimental and observational techniques allow for a much more detailed study of these processes than was hitherto possible. However, much of the research necessarily remains idealized and we argue that it is those studies which include such fundamental characteristics of clouds as droplet sedimentation and latent heating that are most relevant to clouds. Nevertheless, the large body of research over the last decade is beginning to allow tentative conclusions to be made. For example, it is unlikely that small-scale turbulent eddies (i.e. not the energy-containing eddies) alone are responsible for broadening the droplet size spectrum during the initial stage of droplet growth due to condensation. It is likely, though, that small-scale turbulence plays a significant role in the growth of droplets through collisions and coalescence. Moreover, it has been possible through detailed numerical simulations to assess the relative importance of different processes to the turbulent collision kernel and how this varies in the parameter space that is important to clouds. The focus of research on the role of turbulence in condensational and collisional growth has tended to ignore the effect of entrainment and mixing and it is arguable that they play at least as important a role in the evolution of the droplet spectrum. We consider the role of turbulence in the mixing of dry and cloudy air, methods of quantifying this mixing and the effect that it has on the droplet spectrum. Copyright

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Section: Homogeneous and Inhomogeneous Mixingmentioning

confidence: 99%

“…Since τ s 10 s, mixing at scales greater than several metres will be inhomogeneous but not necessarily at centimetre scales. A length scale, l c = ε 1/2 τ 3/2 s , can be defined (Baker et al, 1980;Lehmann et al, 2009) at which there is a transition from inhomogeneous to homogeneous mixing (i.e. Da = 1).…”

Section: Homogeneous and Inhomogeneous Mixingmentioning

confidence: 99%

Droplet growth in warm turbulent clouds

Devenish

Bartello

Brenguier

et al. 2012

Quart J Royal Meteoro Soc

239

281

View full text Add to dashboard Cite

show abstract

“…Various numerical simulations have thus been performed to quantify the potential contributions of various physical processes that might explain enhanced condensational droplet growth, such as giant cloud condensation nuclei (Johnson, 1982;Blyth et al, 2003) and entrainment and mixing (Baker et al, 1980;Telford et al, 1984) or enhanced coalescence by turbulence (Khain and Pinsky, 1997;Xue et al, 2008).…”

Section: Introductionmentioning

confidence: 99%

The onset of precipitation in warm cumulus clouds: An observational case‐study

Burnet

Brenguier

2010

Quart J Royal Meteoro Soc

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Although the three clouds showed similar values of the droplet number concentrations and were able to generate precipitation embryos, the first two collapsed after reaching an altitude of 3 km above sea level, without producing any precipitation, while the third one reached a higher level of 4 km and produced significant precipitation. This case-study illustrates how sensitive the onset of precipitation is to cloud dynamics, revealing that in a conditionally unstable atmosphere hardly noticeable changes in cloud thermodynamics and microphysics may lead to major changes in cloud vertical development and precipitation.

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“…This size gap problem represents a longstanding challenge in the ongoing quest to understand the warm-rain initiation process. In the literature, various mechanisms have been proposed to accelerate rain development, such as small-scale turbulence (Vaillancourt and Yau, 2000), the 20 presence of giant aerosols (Johnson, 1982;Blyth et al, 2003;Jensen and Nugent, 2017), entrainment of unsaturated air (Baker et al, 1980;Lasher-trapp et al, 2005;Cooper et al, 2013) and large-eddy hopping (Cooper, 1989;Grabowski and Abade, 2017). This study focuses on the effect of small-scale turbulence containing eddies in the inertial-dissipative range with length-effect) and increase in the relative velocities between droplets (transport effect).…”

Section: Introductionmentioning

confidence: 99%

Bridging the condensation-collision size gap: a direct numerical simulation of continuous droplet growth in turbulent cloud

Chen¹,

Yau²,

Bartello³

et al. 2018

Preprint

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Abstract. In most previous DNS studies on droplet growth in turbulence, condensational growth and collisional growth were treated separately. Studies in recent decades have postulated that small-scale turbulence may accelerate droplet collisions when droplets are still small when condensational growth is effective. This implies that both processes should be considered simultaneously to unveil the full history of droplet growth and rain formation. This paper introduces the first DNS approach to explicitly study the continuous droplet growth by condensation and collisions inside an adiabatic ascending cloud parcel. 5Results from the condensation-only, collision-only, and condensation-collision experiments are compared to examine the contribution to the broadening of droplet size distribution by the individual process and by the combined processes. Simulations of different turbulent intensities are conducted to investigate the impact of turbulence on each process and on the condensationinduced collisions. The results show that the condensational process promotes the collisions in a turbulent environment and reduces the collisions when in still air, indicating a positive impact of condensation on turbulent collisions. This work suggests 10 the necessity to include both processes simultaneously when studying droplet-turbulence interaction to quantify the turbulence effect on the evolution of cloud droplet spectrum and rain formation.

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The influence of entrainment on the evolution of cloud droplet spectra: I. A model of inhomogeneous mixing

Cited by 79 publications

References 0 publications

Droplet growth in warm turbulent clouds

Droplet growth in warm turbulent clouds

The onset of precipitation in warm cumulus clouds: An observational case‐study

Bridging the condensation-collision size gap: a direct numerical simulation of continuous droplet growth in turbulent cloud

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