An investigation was conducted on the effects of various physics parameterizations on wintertime precipitation predictions using a high-resolution regional climate model. The objective was to evaluate the sensitivity of cold-season mountainous snowfall to cloud microphysics schemes, planetary boundary layer (PBL) schemes, land surface schemes, and radiative transfer schemes at a 4-km grid spacing applicable to the next generation of regional climate models. The results indicated that orographically enhanced precipitation was highly sensitive to cloud microphysics parameterizations. Of the tested 7 parameterizations, 2 schemes clearly outperformed the others that overpredicted the snowfall amount by as much as ~30%–60% on the basis of snow telemetry observations. Significant differences among these schemes were apparent in domain averages, spatial distributions of hydrometeors, latent heating profiles, and cloud fields. In comparison, model results showed relatively weak dependency on the land surface, PBL, and radiation schemes, roughly in the order of decreasing level of sensitivity.

This paper investigates the effects of cloud microphysics parameterizations on simulations of warm-season precipitation at convection-permitting grid spacing. The objective is to assess the sensitivity of summertime convection predictions to the bulk microphysics parameterizations (BMPs) at fine-grid spacings applicable to the next generation of operational numerical weather prediction models. Four microphysical parameterization schemes are compared: simple ice (Dudhia), four-class mixed phase (Reisner et al.), Goddard five-class mixed phase (Tao and Simpson), and five-class mixed phase with graupel (Reisner et al.). The experimentation involves a 7-day episode (3–9 July 2003) of U.S. midsummer convection under moderate large-scale forcing. Overall, the precipitation coherency manifested as eastward-moving organized convection in the lee of the Rockies is insensitive to the choice of the microphysics schemes, and the latent heating profiles are also largely comparable among the BMPs. The upper-level condensate and cloudiness, upper-level radiative cooling/heating, and rainfall spectrum are the most sensitive, whereas the domain-mean rainfall rate and areal coverage display moderate sensitivity. Overall, the three mixed-phase schemes outperform the simple ice scheme, but a general conclusion about the degree of sophistication in the microphysics treatment and the performance is not achievable.

The effects of latent heating, gravity waves, and planetary rotation on numerically simulated convective cloud systems are investigated. First, the nonlinear response of an initially motionless, uniformly stratified, dry atmosphere to steady heating that interacts with the environment through inertial–gravity waves is examined. Planetary rotation confines the subsidence-induced adiabatic warming to the neighborhood of the heated region on a time scale comparable to the lifetime of mesoscale convective systems. In a moist atmosphere, rotation-induced localized descent stabilizes and dries the near environment and decreases the convective available potential energy. The Tropics is therefore a preferred region for convective clustering. This hypothesis is tested in two sets of multiday convection-resolving simulations on f planes representative of the Tropics, subtropics, and midlatitudes. Convection is maintained by radiative cooling and surface fluxes of heat and moisture. In a motionless mean sta... Abstract The effects of latent heating, gravity waves, and planetary rotation on numerically simulated convective cloud systems are investigated. First, the nonlinear response of an initially motionless, uniformly stratified, dry atmosphere to steady heating that interacts with the environment through inertial–gravity waves is examined. Planetary rotation confines the subsidence-induced adiabatic warming to the neighborhood of the heated region on a time scale comparable to the lifetime of mesoscale convective systems. In a moist atmosphere, rotation-induced localized descent stabilizes and dries the near environment and decreases the convective available potential energy. The Tropics is therefore a preferred region for convective clustering. This hypothesis is tested in two sets of multiday convection-resolving simulations on f planes representative of the Tropics, subtropics, and midlatitudes. Convection is maintained by radiative cooling and surface fluxes of heat and moisture. In a motionless mean sta...