 |
| Titel |
Explosive Ice Multiplication Induced by multiplicative--Noise fluctuation of Mechanical Break--up in Ice-Ice Collisions |
| VerfasserIn |
Jun-Ichi Yano, Vaughan Phillips |
| Konferenz |
EGU General Assembly 2017
|
| Medientyp |
Artikel
|
| Sprache |
en
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250154452
|
| Publikation (Nr.) |
 EGU/EGU2017-19549.pdf |
|
|
|
|
|
| Zusammenfassung |
| The number of ice fragments generated by break–up of large graupel in collisions with small
graupel fluctuates randomly due to fluctuations in relative sizes and densities of colliding
graupel particles and the stochastic nature of fracture propagation. This paper investigates an
impact of the stochasticity of break–up on ice multiplication.
When both the rate of generation of primary ice and the initial number concentration of
ice–crystals are low, the system most likely loses all the initial ice and graupel due to a
lack of sustaining sources. Even randomness does not change this mean evolution
of the system in its phase-space. However, a fluctuation of ice break–up number
gives a small but finite chance that substantial ice crystal fragments are generated
by break–up of large graupel. That, in turn, generates more large graupel. This
multiplicative process due to fluctuations potentially leads to a small but finite chance of
explosive growth of ice number. A rigorous stochastic analysis demonstrates this point
quantitatively.
The randomness considered here belongs to a particular category called “multiplicative”
noise, because the noise amplitude is proportional to a given physical state. In order to
contrast the multiplicative-noise nature of ice break–up with a standard “additive”
noise process, fluctuation of the primary ice generation rate is also considered as an
example of the latter. These processes are examined by taking the Fokker–Planck
equation that explicitly describes evolution of the probability distribution with time. As
an important conclusion, stability in the phase-space of the cloud-microphysical
system of break-up in ice-ice collisions is substantially altered by the multiplicative
noise. |
|
|
|
|
|
|