1. Bin resolved modeling of ice microphysics Wolfram Wobrock, Andrea Flossmann Workshop on Measurement Problems in Ice Clouds Zurich, Switzerland July 5-6, 2013

2. Ice microphysics in clouds Cotton et al, 2011

3. MODEL Configuration in 3D a 3D cloud model with detailed microphysics Example: a cumulonimbus cloud Necessity to follow at every grid point env. 40 classes per cat. => Limits regarding computer time and storage, in particular for meso-scale models

4. Bulk schemes 1 Moment schemes: Walko et al (1995): pristine ice, snow, aggregates, graupel and hail, 3D Straka, Mansell (2005): 10 ice categories : two ice crystal habits (column and plate), rimed cloud ice, snow (ice crystal aggregates), three categories of graupel with different densities and intercepts, frozen drops, small hail, and large hail, 3D 2 Moment schemes: Meyers et al (1997): mixing ratio and number concentration of rain, pristine ice crystals, snow, aggregates, graupel and hail, 3D Seifert et al (2006): cloud ice, snowkflakes, graupel, prescribed  distributions, 2D Morrison, Grabowski (2007): mixing ratio due to vapour deposition, mixing ratio due to riming, ice number concentration, 2D kinematic

5. MIN-BIN-Configuration: Drop number density distribution: dN/d(log D), assuming spherical form (D: equiv. diameter) Ice particle number density distribution: 200 µm 500 µm Needs at least 2 informations, instead of just diameter! Which parameters to select? 2 dimensions (largest, smallest?) Mass + density? Volume + surface? Currently: just one parameter used (e.g. dimension or mass); other parameters are prescribed

6. Bin ice microphysics models: Radius coordiante: Hall (1980): 18 categories ice crystals, 10 for transistion, 23 for graupel, 2D Farley and Orville (1986): hail Respondek et al (1995): ice crystals, graupel, 2D Khvorostyanov, Sassen (1998): ice crystals, mass equ. radius, 2D/3D Mass coordinates: Reisin et al (1996): ice crystals, graupel, snow, 2D Ovtchinnokov, Kogan (2000): smallest 15 categories are ice crystals while the largest 13 categories are graupel, 3D Flossmann, Wobrock (2010): spherical ice particles, 3D Khain et al (2011): ice crystals (plate-, columnar- and branch types), aggregates, graupel and hail, 2D

7. Processes: Nucleation: The onset temperatures and relative humidities for deposition/condensation freezing and immersion freezing for bioaerosols, solid ammonium sulphate and BC (soot) Adapted from Hoose and Möhler (2012). Which particles form ice (chemical composition, size) under which atmospherical conditions (temperature, humidity)?

8. Processes: Vapour deposition: Mass growth as a funtion of the capacitance C of a corresponding conductor (information on form: spherical, disk, spheroid,..)

9. Processes: Sedimentation: Terminal velocity as a funtion of the selected parameters ?

10. Processes: Riming and aggregation: Collection efficiencies as a funtion of the selected parameters ?

11. Processes: Melting:

12. Processes: Radiation: cristaux gouttes Optical parameters as a funtion of the selected size and form parameters ?

13. Conclusion: Modelling of the ice phase in clouds is trapped between:  Not enough informationand  Too much information What are the most adapted parameters and how do all processes relate to these (2?) parameters?