Developments of Single-Moment ALARO Microphysics Scheme with Three Prognostic Ice Categories

Microphysics schemes are important components of numerical weather prediction and climate models. They are responsible for correctly estimating precipitation accumulations, cloud cover, and composition, one of the most important meteorological and climatological quantities. Microphysics schemes are gradually improving. Both more sophisticated parameterizations of processes and introductions of additional hydrometeors make schemes more physically accurate.

In this article, the single-moment two-ice microphysics scheme in ALARO is extended for graupel, introducing a new three-ice scheme. A proposal for graupel parameterization is presented, including a discussion of some options. Further, improvements in parameterizations of autoconversion and evaporation in the three-ice scheme are tested. Tests are performed for various weather regimes, including strong summer convection, as the condensation fluxes from the cloud scheme and moist deep convection parameterization are summed before they enter one shared call of microphysics. The new scheme improves the forecasting skill. The bias of precipitation accumulation is reduced, mainly in autumn. In addition, the precipitation shadow behind mountain ranges is better simulated.