Parameterization of convective precipitation in mesoscale numerical models: a critical review

Abstract

The traditional approach utilizes cumulus parameterization at convectively unstable points and explicit (nonparameterized) condensation at convectively stable points. The fully explicit approach uses explicit methods regardless of stability. The hybrid approach parameterizes convective scale updrafts and downdrafts, but "detrains' a fraction of parameterized cloud and precipitation particles to the grid scale. This allows the path and phase changes of such particles to be explicitly predicted over subsequent time steps. In the absence of large rotation, the fundamental assumptions of cumulus parameterization begin to break down once grid spacing falls below 20-25km. For models with such resolution, the time scale of the convection being parameterized approaches the characteristic time scale of the grid, and parameterized and unparameterized convective clouds often exist simultaneously in a grid column. -from Authors