Vaughan Phillips
Universitetslektor
Explosive ice multiplication induced by multiplicative-noise fluctuation of mechanical breakup in ice-ice collisions
Författare
Summary, in English
The number of ice fragments generated by breakup of large graupel in collisions with small graupel fluctuates randomly owing to fluctuations in relative sizes and densities of colliding graupel particles and the stochastic nature of fracture propagation. This paper investigates the impact of the stochasticity of breakup 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 owing 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 breakup number gives a small but finite chance that substantial ice crystal fragments are generated by breakup 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. To contrast the multiplicative-noise nature of ice breakup 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 the evolution of the probability distribution with time. As an important conclusion, stability in the phase space of the cloud microphysical system of breakup in ice-ice collisions is substantially altered by the multiplicative noise.
Avdelning/ar
- Institutionen för naturgeografi och ekosystemvetenskap
- MERGE: ModElling the Regional and Global Earth system
Publiceringsår
2016
Språk
Engelska
Sidor
4685-4697
Publikation/Tidskrift/Serie
Journals of the Atmospheric Sciences
Volym
73
Issue
12
Dokumenttyp
Artikel i tidskrift
Förlag
Amer Meteorological Soc
Ämne
- Meteorology and Atmospheric Sciences
Nyckelord
- Cloud microphysics
Status
Published
ISBN/ISSN/Övrigt
- ISSN: 0022-4928