Effects of turbulence on the geometric collision rate of sedimenting droplets. Part 2. Theory and parameterization

Ayala, Orlando; Rosa, Bogdan; Wang, Lian‐Ping

doi:10.1088/1367-2630/10/7/075016

Cited by 131 publications

(200 citation statements)

References 37 publications

Supporting

Mentioning

185

Contrasting

Order By: Relevance

“…Numerical, theoretical and experimental studies (e.g. Ayala et al, 2008aAyala et al, , 2008bLu et al, 2010) have revealed that both parameters and their physical implications need to be carefully considered together in quantifying the pair interaction and collision of cloud droplets.…”

Section: Small-scale Turbulence and Cloud Microphysicsmentioning

confidence: 99%

“…More generally, 12 can be defined as the volume influx containing droplets of radius a 2 to a droplet of radius a 1 over the collision surface S c about the centre of droplets of radius a 1 and radius r c . For spherical droplets N 12 is given by (Sundaram and Collins, 1997;Wang et al, 1998aWang et al, , 2000Ayala et al, 2008b) N 12 = 4π r 2 c n 1 (a 1 )n 2 (a 1 + r c ) (−w 12 )| w 12 <0 ≈ 4π r 2 c 1 2 n 1 (a 1 )n 2 (a 1 + r c ) |w 12 | ≈ 2π r 2 c n 1 (a 1 )n 2 (a 1 + r c ) |w 12 | ≈ 2π r 2 c n 1 n 2 g 12 (r c )|w 12 |,…”

Section: The Collision Kernelmentioning

confidence: 99%

“…There have been many further attempts to derive improved analytical expressions for the droplet relative velocity (see, for example, Ayala et al (2008b) or Xue et al (2008) for a detailed review). Not surprisingly, the limiting cases of small and large droplet inertia, usually without gravity, have received more attention than cases with moderate inertia.…”

Section: Droplet Relative Velocitymentioning

confidence: 99%

“…Not surprisingly, the limiting cases of small and large droplet inertia, usually without gravity, have received more attention than cases with moderate inertia. When τ p τ η , Ayala et al (2008b) derived an analytical expression for sedimenting droplets which is partly based on the work by Dodin and Elperin (2002), who considered droplets with τ p τ η . The basic assumption of Ayala et al (2008b) is that the droplet relative velocity is mostly determined by gravitational sedimentation and that droplet inertia introduces a secondary correction.…”

Section: Droplet Relative Velocitymentioning

confidence: 99%

“…When τ p τ η , Ayala et al (2008b) derived an analytical expression for sedimenting droplets which is partly based on the work by Dodin and Elperin (2002), who considered droplets with τ p τ η . The basic assumption of Ayala et al (2008b) is that the droplet relative velocity is mostly determined by gravitational sedimentation and that droplet inertia introduces a secondary correction. This assumption is appropriate when the terminal velocity of droplets is large relative to the Kolmogorov velocity and works best when the two droplets are not close in size.…”

Section: Droplet Relative Velocitymentioning

confidence: 99%

See 4 more Smart Citations

Droplet growth in warm turbulent clouds

Devenish

Bartello

Brenguier

et al. 2012

Quart J Royal Meteoro Soc

245

281

View full text Add to dashboard Cite

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

show abstract

Section: Small-scale Turbulence and Cloud Microphysicsmentioning

confidence: 99%

Section: The Collision Kernelmentioning

confidence: 99%

Section: Droplet Relative Velocitymentioning

confidence: 99%

Section: Droplet Relative Velocitymentioning

confidence: 99%

Section: Droplet Relative Velocitymentioning

confidence: 99%

See 3 more Smart Citations

Droplet growth in warm turbulent clouds

Devenish

Bartello

Brenguier

et al. 2012

Quart J Royal Meteoro Soc

245

281

View full text Add to dashboard Cite

show abstract

Effects of turbulence on mixed‐phase deep convective clouds under different basic‐state winds and aerosol concentrations

2014

View full text Add to dashboard Cite

The effects of turbulence-induced collision enhancement (TICE) on mixed-phase deep convective clouds are numerically investigated using a 2-D cloud model with bin microphysics for uniform and sheared basic-state wind profiles and different aerosol concentrations. Graupel particles account for the most of the cloud mass in all simulation cases. In the uniform basic-state wind cases, graupel particles with moderate sizes account for some of the total graupel mass in the cases with TICE, whereas graupel particles with large sizes account for almost all the total graupel mass in the cases without TICE. This is because the growth of ice crystals into small graupel particles is enhanced due to TICE. The changes in the size distributions of graupel particles due to TICE result in a decrease in the mass-averaged mean terminal velocity of graupel particles. Therefore, the downward flux of graupel mass, and thus the melting of graupel particles, is reduced due to TICE, leading to a decrease in the amount of surface precipitation. Moreover, under the low aerosol concentration, TICE increases the sublimation of ice particles, consequently playing a partial role in reducing the amount of surface precipitation. The effects of TICE are less pronounced in the sheared basic-state wind cases than in the uniform basic-state wind cases because the number of ice crystals is much smaller in the sheared basic-state wind cases than in the uniform basic-state wind cases. Thus, the size distributions of graupel particles in the cases with and without TICE show little difference.

show abstract

Representation of microphysical processes in cloud‐resolving models: Spectral (bin) microphysics versus bulk parameterization

Хаин

Beheng

Heymsfield

et al. 2015

Reviews of Geophysics

339

322

View full text Add to dashboard Cite

Most atmospheric motions of different spatial scales and precipitation are closely related to phase transitions in clouds. The continuously increasing resolution of large-scale and mesoscale atmospheric models makes it feasible to treat the evolution of individual clouds. The explicit treatment of clouds requires the simulation of cloud microphysics. Two main approaches describing cloud microphysical properties and processes have been developed in the past four and a half decades: bulk microphysics parameterization and spectral (bin) microphysics (SBM). The development and utilization of both represent an important step forward in cloud modeling. This study presents a detailed survey of the physical basis and the applications of both bulk microphysics parameterization and SBM. The results obtained from simulations of a wide range of atmospheric phenomena, from tropical cyclones through Arctic clouds using these two approaches are compared. Advantages and disadvantages, as well as lines of future development for these methods are discussed.

show abstract

Effects of turbulence on the geometric collision rate of sedimenting droplets. Part 2. Theory and parameterization

Cited by 131 publications

References 37 publications

Droplet growth in warm turbulent clouds

Droplet growth in warm turbulent clouds

Effects of turbulence on mixed‐phase deep convective clouds under different basic‐state winds and aerosol concentrations

Representation of microphysical processes in cloud‐resolving models: Spectral (bin) microphysics versus bulk parameterization

Contact Info

Product

Resources

About