Presentation of Christine Lac during the 2nd AROME training course, Lisbon, 4-7 March 2008 : "Microphysics in AROME" by C.Lac , S.Malardel and J.-P.Pinty.

• General characteristics of the categories
  • A classical BULK mixed microphysical scheme
  • Particle size distributions
  • Microphysical characteristics
• Generalities on the processes
• Some details on a few processes
• Examples

Minutes of the Discussion about physics

• A question was asked about the usefulness of including aerosol effects in the microphysics, as planed by the MetOffice for fog forecast. It was answered that 2-moment microphysical schemes, required to take explicitly into account aerosol effects, are currently under development. Various warm 2-moment microphysical schemes exist in Meso-NH but are adapted to different types of clouds; a unified 2-moment scheme still doesn’t exist. Concerning mixed 2-moment microphysical schemes, the existing schemes are still under research and improvement. More generally, knowing the current weaknesses of the mesoscale simulations, 2-moment microphysical schemes do not appear as a priority. Aerosol concentration are important for the fog or Sc, but, at the moment, a diagnostic approach can be considered for the moment to take into account a polluted environment, instead of a prognostic approach as in the 2-moment microphysical schemes.
• Then discussion came on the added value of Arome compared to larger scale models for forecasters. At Météo-France structures like cloudiness, fog, and other details like fronts and convecting events were better predicted by Arome and are found very usefull by forecasters. Arome can predict events not resolved by large-scale models (like squall lines) which can only provide in such case favorable conditions for such events. Therefore it is important for forecasters to know how to use the outputs form Arome.
• Regarding the possibility of implementing a 3D turbulence scheme in Arome, it is not possible at the moment since vertical columns in the model are treated separately and a 3D scheme would then break parallelisation in the code.
  – S. Malardel wondered if there is a need for subgrid microphysics in Arome.