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Vaughan Phillips

Research in the Area of Clouds, Aerosols and Climate

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Ice multiplication by breakup in ice-ice collisions. Part II : Numerical simulations

Author

  • Vaughan T.J. Phillips
  • Jun-Ichi Yano
  • Marco Formenton
  • Eyal Ilotoviz
  • Vijay Kanawade
  • Innocent Kudzotsa
  • Jiming Sun
  • Aaron Bansemer
  • Andrew G. Detwiler
  • Alexander Khain
  • Sarah A. Tessendorf

Summary, in English

In Part I of this two-part paper, a formulation was developed to treat fragmentation in ice-ice collisions. In the present Part II, the formulation is implemented in two microphysically advanced cloud models simulating a convective line observed over the U.S. high plains. One model is 2D with a spectral bin microphysics scheme. The other has a hybrid bin-two-moment bulk microphysics scheme in 3D. The case consists of cumulonimbus cells with cold cloud bases (near 0° C) in a dry troposphere. Only with breakup included in the simulation are aircraft observations of particles with maximum dimensions >0.2mmin the storm adequately predicted by both models. In fact, breakup in ice-ice collisions is by far the most prolific process of ice initiation in the simulated clouds (95%-98% of all nonhomogeneous ice), apart from homogeneous freezing of droplets. Inclusion of breakup in the cloud-resolving model (CRM) simulations increased, by between about one and two orders of magnitude, the average concentration of ice between about 0° and -30°C. Most of the breakup is due to collisions of snow with graupel/hail. It is broadly consistent with the theoretical result in Part I about an explosive tendency for ice multiplication. Breakup in collisions of snow (crystals > ~1mm and aggregates) with denser graupel/hail was the main pathway for collisional breakup and initiated about 60%-90% of all ice particles not from homogeneous freezing, in the simulations by both models. Breakup is predicted to reduce accumulated surface precipitation in the simulated storm by about 20%-40%.

Department/s

  • Dept of Physical Geography and Ecosystem Science
  • MERGE: ModElling the Regional and Global Earth system

Publishing year

2017-09-01

Language

English

Pages

2789-2811

Publication/Series

Journals of the Atmospheric Sciences

Volume

74

Issue

9

Document type

Journal article

Publisher

Amer Meteorological Soc

Topic

  • Meteorology and Atmospheric Sciences

Keywords

  • Cloud microphysics
  • Clouds
  • Hail
  • Ice particles

Status

Published

ISBN/ISSN/Other

  • ISSN: 0022-4928