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Explosive ice multiplication by mechanical break-up in ice-ice collisions : A dynamical system-based study

Yano, Jun Ichi; Phillips, Vaughan T J LU and Kanawade, Vijay LU (2016) In Quarterly Journal of the Royal Meteorological Society 142(695). p.867-879
Abstract

Mechanical break-up in ice-ice collisions observed in the laboratory can lead to explosive ice multiplication. The possibility is examined in detail by constructing an idealized analytical single-point (zero-dimension) model assuming spatial homogeneity within a cloud. The rate of generation of primary ice is fixed at a constant value over time, corresponding to a situation in which the relative humidity (at water saturation as for a mixed-phase cloud) and updraught speed are fixed. This would further imply an infinite supply of vapour, if the crystal concentration were somehow infinite. Fixed times are assumed for the transformation of the generated primary ice into small graupel, which then grow into large graupel. Secondary ice... (More)

Mechanical break-up in ice-ice collisions observed in the laboratory can lead to explosive ice multiplication. The possibility is examined in detail by constructing an idealized analytical single-point (zero-dimension) model assuming spatial homogeneity within a cloud. The rate of generation of primary ice is fixed at a constant value over time, corresponding to a situation in which the relative humidity (at water saturation as for a mixed-phase cloud) and updraught speed are fixed. This would further imply an infinite supply of vapour, if the crystal concentration were somehow infinite. Fixed times are assumed for the transformation of the generated primary ice into small graupel, which then grow into large graupel. Secondary ice particles produced by collisions between small and large graupel, in turn, potentially multiply explosively, because the secondary ice may eventually grow to become splintering graupel with a positive feedback. Two basic processes can lead to explosive ice multiplication. The first process is the generation of primary ice, which initiates ice multiplication only with a relatively low threshold (∼10-4 m-3 s-1) compared to typical observed values for deep convective clouds. Then the second process is induced by a sufficiently large initial number of ice crystals, which generate enough both small and large graupel particles, leading to explosive multiplication, even when the rate of generation of primary ice is below the threshold. These initial crystals at super-critical amounts may be from any source. Only a low number density of crystals of the order of 1 m-3 (or 10-3 l-1) is required initially. In both cases, the ice number literally explodes within a finite time, with a time-scale from 30 to 200 min under the idealized single-point model studied. Importantly, in real clouds a typical number density of large graupel is above the threshold needed for explosive break-up.

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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Dynamical system, Explosive process, Ice mechanical break-up, Ice multiplication
in
Quarterly Journal of the Royal Meteorological Society
volume
142
issue
695
pages
13 pages
publisher
Royal Meteorological Society
external identifiers
  • Scopus:84961875451
ISSN
0035-9009
DOI
10.1002/qj.2687
language
English
LU publication?
yes
id
45a802d9-41d2-4327-a2ca-8d3975512a04
date added to LUP
2016-09-21 10:11:21
date last changed
2016-09-21 10:11:21
@misc{45a802d9-41d2-4327-a2ca-8d3975512a04,
  abstract     = {<p>Mechanical break-up in ice-ice collisions observed in the laboratory can lead to explosive ice multiplication. The possibility is examined in detail by constructing an idealized analytical single-point (zero-dimension) model assuming spatial homogeneity within a cloud. The rate of generation of primary ice is fixed at a constant value over time, corresponding to a situation in which the relative humidity (at water saturation as for a mixed-phase cloud) and updraught speed are fixed. This would further imply an infinite supply of vapour, if the crystal concentration were somehow infinite. Fixed times are assumed for the transformation of the generated primary ice into small graupel, which then grow into large graupel. Secondary ice particles produced by collisions between small and large graupel, in turn, potentially multiply explosively, because the secondary ice may eventually grow to become splintering graupel with a positive feedback. Two basic processes can lead to explosive ice multiplication. The first process is the generation of primary ice, which initiates ice multiplication only with a relatively low threshold (∼10<sup>-4</sup> m<sup>-3</sup> s<sup>-1</sup>) compared to typical observed values for deep convective clouds. Then the second process is induced by a sufficiently large initial number of ice crystals, which generate enough both small and large graupel particles, leading to explosive multiplication, even when the rate of generation of primary ice is below the threshold. These initial crystals at super-critical amounts may be from any source. Only a low number density of crystals of the order of 1 m<sup>-3</sup> (or 10<sup>-3</sup> l<sup>-1</sup>) is required initially. In both cases, the ice number literally explodes within a finite time, with a time-scale from 30 to 200 min under the idealized single-point model studied. Importantly, in real clouds a typical number density of large graupel is above the threshold needed for explosive break-up.</p>},
  author       = {Yano, Jun Ichi and Phillips, Vaughan T J and Kanawade, Vijay},
  issn         = {0035-9009},
  keyword      = {Dynamical system,Explosive process,Ice mechanical break-up,Ice multiplication},
  language     = {eng},
  month        = {01},
  number       = {695},
  pages        = {867--879},
  publisher    = {ARRAY(0x7cdcee8)},
  series       = {Quarterly Journal of the Royal Meteorological Society},
  title        = {Explosive ice multiplication by mechanical break-up in ice-ice collisions : A dynamical system-based study},
  url          = {http://dx.doi.org/10.1002/qj.2687},
  volume       = {142},
  year         = {2016},
}