Explosive ice multiplication by mechanical breakup in iceice collisions : A dynamical systembased study
(2016) In Quarterly Journal of the Royal Meteorological Society 142(695). p.867879 Abstract
Mechanical breakup in iceice collisions observed in the laboratory can lead to explosive ice multiplication. The possibility is examined in detail by constructing an idealized analytical singlepoint (zerodimension) 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 mixedphase 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 breakup in iceice collisions observed in the laboratory can lead to explosive ice multiplication. The possibility is examined in detail by constructing an idealized analytical singlepoint (zerodimension) 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 mixedphase 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 supercritical 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 timescale from 30 to 200 min under the idealized singlepoint model studied. Importantly, in real clouds a typical number density of large graupel is above the threshold needed for explosive breakup.
(Less)
 author
 Yano, Jun Ichi; Phillips, Vaughan T J ^{LU} and Kanawade, Vijay ^{LU}
 organization
 publishing date
 20160101
 type
 Contribution to journal
 publication status
 published
 subject
 keywords
 Dynamical system, Explosive process, Ice mechanical breakup, 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
 wos:000372951300028
 ISSN
 00359009
 DOI
 10.1002/qj.2687
 language
 English
 LU publication?
 yes
 id
 45a802d941d24327a2ca8d3975512a04
 date added to LUP
 20160921 10:11:21
 date last changed
 20170924 05:00:58
@article{45a802d941d24327a2ca8d3975512a04, abstract = {<p>Mechanical breakup in iceice collisions observed in the laboratory can lead to explosive ice multiplication. The possibility is examined in detail by constructing an idealized analytical singlepoint (zerodimension) 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 mixedphase 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 supercritical 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 timescale from 30 to 200 min under the idealized singlepoint model studied. Importantly, in real clouds a typical number density of large graupel is above the threshold needed for explosive breakup.</p>}, author = {Yano, Jun Ichi and Phillips, Vaughan T J and Kanawade, Vijay}, issn = {00359009}, keyword = {Dynamical system,Explosive process,Ice mechanical breakup,Ice multiplication}, language = {eng}, month = {01}, number = {695}, pages = {867879}, publisher = {Royal Meteorological Society}, series = {Quarterly Journal of the Royal Meteorological Society}, title = {Explosive ice multiplication by mechanical breakup in iceice collisions : A dynamical systembased study}, url = {http://dx.doi.org/10.1002/qj.2687}, volume = {142}, year = {2016}, }