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New Empirical Formulation for the Sublimational Breakup of Graupel and Dendritic Snow

Deshmukh, Akash LU ; Phillips, Vaughan LU orcid ; Bansemer, Aaron ; Patade, Sachin LU and Waman, Deepak LU orcid (2022) In Journal of the Atmospheric Sciences 79(1). p.317-336
Abstract
Ice fragments are generated by sublimation of ice particles in subsaturated conditions in natural clouds. Conceivably, such sublimational breakup would be expected to cause ice multiplication in natural clouds. Any fragment that survives will grow to become ice precipitation that may sublimate and fragment further. As a first step toward assessing this overlooked process, a formulation is proposed for the number of ice fragments from sublimation of ice particles for an atmospheric model. This is done by amalgamating laboratory observations from previously published studies. The concept of a “sublimated mass activity spectrum” for the breakup is applied to the dataset. The number of ice fragments is determined by the relative humidity over... (More)
Ice fragments are generated by sublimation of ice particles in subsaturated conditions in natural clouds. Conceivably, such sublimational breakup would be expected to cause ice multiplication in natural clouds. Any fragment that survives will grow to become ice precipitation that may sublimate and fragment further. As a first step toward assessing this overlooked process, a formulation is proposed for the number of ice fragments from sublimation of ice particles for an atmospheric model. This is done by amalgamating laboratory observations from previously published studies. The concept of a “sublimated mass activity spectrum” for the breakup is applied to the dataset. The number of ice fragments is determined by the relative humidity over ice and the initial size of the parent ice particles. The new formulation applies to dendritic crystals and heavily rimed particles only. Finally, a thought experiment is performed for an idealized scenario of subsaturation with in-cloud descent. Scaling analysis yields an estimate of an ice enhancement ratio of about 5 (10) within a weak deep convective downdraft of about 2 m s−1, for an initial monodisperse population of dendritic snow (graupel) particles of 3 L−1 and 2 mm. During descent, there is a dynamic equilibrium between continual emission of fragments and their depletion by sublimation. A simplified bin microphysics parcel model exhibits this dynamical quasi equilibrium, consistent with the thought experiment. The fragments have average lifetimes of around 90 and 70 s for dendrites and graupel, respectively. Sublimational breakup is predicted to cause significant secondary ice production. (Less)
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author
; ; ; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Diffusion; Ice crystals; Ice particles; Sublimation; Clouds
in
Journal of the Atmospheric Sciences
volume
79
issue
1
pages
317 - 336
publisher
Amer Meteorological Soc
external identifiers
  • scopus:85124288447
ISSN
1520-0469
DOI
10.1175/JAS-D-20-0275.1
project
Secondary ice production: An empirical formulation and organization of mechanisms among simulated cloud-types
Secondary ice production: An empirical formulation and organization of mechanisms among simulated cloud-types
Mechanisms for the Influence from Ice Nucleus Aerosols on Clouds and their Indirect Effects: Cloud Modelling
language
English
LU publication?
yes
id
f1b266e3-1ccd-47f1-a577-1101511e2443
date added to LUP
2022-12-16 11:46:12
date last changed
2023-11-05 05:07:47
@article{f1b266e3-1ccd-47f1-a577-1101511e2443,
  abstract     = {{Ice fragments are generated by sublimation of ice particles in subsaturated conditions in natural clouds. Conceivably, such sublimational breakup would be expected to cause ice multiplication in natural clouds. Any fragment that survives will grow to become ice precipitation that may sublimate and fragment further. As a first step toward assessing this overlooked process, a formulation is proposed for the number of ice fragments from sublimation of ice particles for an atmospheric model. This is done by amalgamating laboratory observations from previously published studies. The concept of a “sublimated mass activity spectrum” for the breakup is applied to the dataset. The number of ice fragments is determined by the relative humidity over ice and the initial size of the parent ice particles. The new formulation applies to dendritic crystals and heavily rimed particles only. Finally, a thought experiment is performed for an idealized scenario of subsaturation with in-cloud descent. Scaling analysis yields an estimate of an ice enhancement ratio of about 5 (10) within a weak deep convective downdraft of about 2 m s−1, for an initial monodisperse population of dendritic snow (graupel) particles of 3 L−1 and 2 mm. During descent, there is a dynamic equilibrium between continual emission of fragments and their depletion by sublimation. A simplified bin microphysics parcel model exhibits this dynamical quasi equilibrium, consistent with the thought experiment. The fragments have average lifetimes of around 90 and 70 s for dendrites and graupel, respectively. Sublimational breakup is predicted to cause significant secondary ice production.}},
  author       = {{Deshmukh, Akash and Phillips, Vaughan and Bansemer, Aaron and Patade, Sachin and Waman, Deepak}},
  issn         = {{1520-0469}},
  keywords     = {{Diffusion; Ice crystals; Ice particles; Sublimation; Clouds}},
  language     = {{eng}},
  month        = {{01}},
  number       = {{1}},
  pages        = {{317--336}},
  publisher    = {{Amer Meteorological Soc}},
  series       = {{Journal of the Atmospheric Sciences}},
  title        = {{New Empirical Formulation for the Sublimational Breakup of Graupel and Dendritic Snow}},
  url          = {{http://dx.doi.org/10.1175/JAS-D-20-0275.1}},
  doi          = {{10.1175/JAS-D-20-0275.1}},
  volume       = {{79}},
  year         = {{2022}},
}