Precipitation Parameterization in a Simulated Mei-Yu Front

Abstract

Observational and numerical studies have consistently shown the im portance of latent heat release associated with frontal precipitation in the development of a Mei-Yu front.However, a systematic evaluation of pre cipitation parameterization in the simulation of a Mei-Yu front has been rare in the literature.In order to enhance our understanding on precipita tion parameterization of Mei-Yu fronts, this study conducts numerical ex periments to evaluate the performance of subgrid-scale cumulus schemes and resolvable-scale microphysics schemes to simulate the Mei-Yu frontal system on 4-5 June 1998 at grid resolutions of 45 km and 15 km, using the Penn State/NCAR mesoscale model MM5.Principal findings are summa rized here.• The horizontal extent and intensity of precipitation, the partitioning of precipitation into grid-resolvable and subgrid-scale portions, the verti cal thermodynamic profile in the precipitation region and the embedded mesoscale structure are extremely sensitive to the choice of cumulus pa rameterization schemes.This is true for both the 45-and 15-km grids.• The partitioning of precipitation into subgrid scale and resolvable scale is sensitive to the particular cumulus parameterization that is used in the model, but it is nearly the same on both the 45-and 15-km grids for a given cumulus parameterization.•The detailed ice-phase microphysical processes do not have a signifi cant impact on the rainfall pattern on either the 45-and 15-km grids.How ever, the inclusion of cloud ice-snow-graupel microphysical processes in creases the total surface precipitation amount by 30 % compared to the amount with only warm rain processes.•Variations in the subgrid-scale cumulus parameterization have a much larger impact on the distribution and amount of Mei-Yu frontal precipita-