A Parameterization of Sticking Efficiency for Collisions of Snow and Graupel with Ice Crystals: Theory and Comparison with Observations*

Phillips, Vaughan T. J.; Formenton, Marco; Bansemer, Aaron; Kudzotsa, Innocent; Lienert, Barry R.

doi:10.1175/jas-d-14-0096.1

Cited by 31 publications

(18 citation statements)

References 50 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Finally, three points are defined in the parameter space with conditions similar to particular cloud states. A continental convective (CC) case has a stronger updraft and steeper CCN spectrum [Pruppacher and Klett, 1997]. Continental aerosol loading can be quite high, so the initial droplet radius is smaller than the default value, and the characteristic times for all hydrometeors are shorter because a stronger updraft yields faster ( i , g , G ) = (7.5, 12.5, 12.5) ( i , g , G ) = (7.5, 12.5, 12.5) ( i , g , G ) = (9, 22.5, 12.5) a All values are given in minutes.…”

Section: Simulationsmentioning

confidence: 99%

Investigating the contribution of secondary ice production to in‐cloud ice crystal numbers

2017

View full text Add to dashboard Cite

In‐cloud measurements of ice crystal number concentration can be orders of magnitude higher than the precloud ice nucleating particle number concentration. This disparity may be explained with secondary ice production processes. Several such processes have been proposed, but their relative importance and even the exact physics are not well known. In this work, a six‐hydrometeor‐class parcel model is developed to investigate the ice crystal number enhancement, both its bounds and its value for different cloud states, from rime splintering and breakup upon graupel‐graupel collision. The model also includes ice aggregation and droplet coalescence, ice hydrometeor nonsphericity, and a time delay formulation for hydrometeor growth. Conditions to maximize the breakup contribution, as well as the effects of nonsphericity and turbulence, are discussed. We find that the largest enhancement of ice crystal number occurs for “intermediate” conditions, characterized by moderate updrafts and activation and nucleation rates. In this case, vertical motion is strong enough, and new hydrometeor formation limited enough, to sustain supersaturation as hydrometeors grow to larger sizes. After these larger hydrometeors form at sufficient number concentrations, the ice crystal number can be enhanced by a factor of 104 in some cases relative to the number generated by primary ice nucleation alone. Excluding ice hydrometeor nonsphericity limits secondary production significantly, and the parcel updraft can modulate it by about an order of magnitude.

show abstract

Section: Simulationsmentioning

confidence: 99%

Investigating the contribution of secondary ice production to in‐cloud ice crystal numbers

2017

View full text Add to dashboard Cite

show abstract

“…for the collisions between the solid particles are computed using a new empirical parametrization developed by Phillips et al () using a long history of laboratory observations available in the literature. In Phillips et al (), E s, x , y is given by

E_{normals, x, y} = \exp ({}, \frac{β (T) K_{normalc}}{α}),

where β ( T ) is a temperature‐dependent thermal smoothness coefficient that caters for the surface texture of the particles. K c is the collision kinetic energy of the colliding particles and is proportional to the energy required to separate the particles after impact, while α is the surface area of the smaller particle involved in the collisions.…”

Section: Model Descriptionmentioning

confidence: 99%

“…The sticking efficiencies, E s,x,y (Eq. (12)) for the collisions between the solid particles are computed using a new empirical parametrization developed by Phillips et al (2015) using a long history of laboratory observations available in the literature. In Phillips et al (2015), E s,x,y is given by…”

Section: Sticking Efficienciesmentioning

confidence: 99%

Aerosol indirect effects on glaciated clouds. Part I: Model description

Kudzotsa

Phillips

Dobbie

et al. 2016

Quart J Royal Meteoro Soc

Self Cite

View full text Add to dashboard Cite

Various improvements were made to a state‐of‐the‐art aerosol–cloud model and comparison of the model results with observations from field campaigns was performed. The strength of this aerosol–cloud model is in its ability to explicitly resolve all the known modes of heterogeneous cloud droplet activation and ice crystal nucleation. The model links cloud particle activation with the aerosol loading and chemistry of seven different aerosol species. These improvements to the model resulted in more accurate prediction especially of droplet and ice crystal number concentrations in the upper troposphere and enabled the model to directly sift the aerosol indirect effects based on the chemistry and concentration of the aerosols. In addition, continental and maritime cases were simulated for the purpose of validating the aerosol–cloud model and for investigating the critical microphysical and dynamical mechanisms of aerosol indirect effects from anthropogenic solute and solid aerosols, focusing mainly on glaciated clouds. The simulations showed that increased solute aerosols reduced cloud particle sizes by about 5 μm and inhibited warm rain processes. Cloud fractions and their optical thicknesses were increased quite substantially in both cases. Although liquid mixing ratios were boosted, there was however a substantial reduction of ice mixing ratios in the upper troposphere owing to the increase in snow production aloft. These results are detailed in the subsequent parts of this study.

show abstract

“…A subsequent reduction in the tuning parameter for stratiform snow formation by aggregation further increases IWP in E63H23. Only few laboratory studies for sticking efficiency have been conducted and even fewer theories for sticking efficiency were developed (Phillips et al, 2015). We find that the simple formulation of Seifert and Beheng (2006) for sticking efficiency for accretion of ice crystals by snow improves the simulation of cloud ice in E63H23.…”

Section: Impact Of Changes and Improvements In E63h23mentioning

confidence: 94%

The global aerosol-climate model ECHAM6.3-HAM2.3 – Part 2: Cloud evaluation, aerosol radiative forcing and climate sensitivity

Neubauer¹,

Ferrachat²,

Drian³

et al. 2019

Preprint

View full text Add to dashboard Cite

The global aerosol-climate model ECHAM6.3-HAM2.3 (E63H23) and the previous model versions ECHAM5.5-HAM2.0 (E55H20) and ECHAM6.1-HAM2.2 (E61H22) are evaluated using global observational datasets for clouds and precipitation. In E63H23 low cloud amount, liquid and ice water path and cloud radiative effects are more realistic than in previous model versions. E63H23 has a more physically based aerosol activation scheme, improvements in the cloud cover 15 scheme, changes in detrainment of convective clouds, changes in the sticking efficiency for accretion of ice crystals by snow, consistent ice crystal shapes throughout the model, changes in mixed phase freezing and an inconsistency in ice crystal number concentration (ICNC) in cirrus clouds was removed. Biases that were identified in E63H23 (and in previous model versions) are a too low cloud amount in stratocumulus regions, deep convective clouds in the Atlantic and Pacific oceans form too close to the continents and there are indications that ICNCs are overestimated. 20Since clouds are important for effective radiative forcing due to aerosol-radiation and aerosol-cloud interactions (ERF ari+aci ) and equilibrium climate sensitivity (ECS), also differences in ERF ari+aci and ECS between the model versions were analyzed. ERF ari+aci is weaker in E63H23 (-1.0 W m -2 ) than in E61H22 (-1.2 W m -2 ) (or E55H20; -1.1 W m -2 ). This is caused by the weaker shortwave ERF ari+aci (new aerosol activation scheme and sea salt emission parameterization in E63H23, more realistic simulation of cloud water) overcompensating the weaker longwave ERF ari+aci (removal of an inconsistency in ICNC 25 in cirrus clouds in E61H22).The decrease in ECS in E63H23 (2.5 K) compared to E61H22 (2.8 K) is due to changes in the entrainment rate for shallow convection (affecting the cloud amount feedback) and a stronger cloud phase feedback.

show abstract

A Parameterization of Sticking Efficiency for Collisions of Snow and Graupel with Ice Crystals: Theory and Comparison with Observations*

Cited by 31 publications

References 50 publications

Investigating the contribution of secondary ice production to in‐cloud ice crystal numbers

Investigating the contribution of secondary ice production to in‐cloud ice crystal numbers

Aerosol indirect effects on glaciated clouds. Part I: Model description

The global aerosol-climate model ECHAM6.3-HAM2.3 – Part 2: Cloud evaluation, aerosol radiative forcing and climate sensitivity

Contact Info

Product

Resources

About