Sensitivity of a simulated squall line to horizontal resolution and parameterization of microphysics

Four different microphysical setups are used, with either single-moment (1M) or double-moment (2M) microphysics, and either hail or graupel as the dense (rimed) ice species. Three different horizontal grid spacings are used: ∆x = 4, 1, or 0.25 km (with identical vertical grids).

Overall, results show that simulated squall lines are sensitive to both microphysical setup and horizontal resolution, although some quantities (i.e., surface rainfall) are more sensitive to Δx in this study. Simulations with larger Δx are slower to develop, produce more precipitation, and have higher cloud tops, all of which are attributable to larger convective cells that do not entrain mid-level air. The highest-resolution simulations have substantially more cloudwater evaporation which is partly attributable to the development of resolved turbulence.