In this study, we perform idealized numerical simulations of VORTEX2 supercells with a triple-moment microphysics scheme, with and without size sorting allowed, and compare the resulting surface and near-surface DSDs with that observed from disdrometers. We emphasize qualitative comparisons utilizing a simple time-to-space conversion of the time series of 1-min DSDs. We then compute polarimetric radar observables from the observed and simulated DSDs and compare them with polarimetric radar observations from available mobile radar platforms.
Results indicate that good qualitative agreement with observed disdrometer time series for metrics such as the mean volume diameter (Dmr) is obtained when size sorting is allowed in the numerical model. In particular, both the simulation and observed DSDs exhibit a marked decrease in Dmr from the leading (right) flank to the trailing (left flank), as well as from the leading to trailing edge of the hook echo, for the right-moving supercells examined in this study. Differential reflectivity ZDR exhibits similar trends. When size sorting is disallowed in the model, no such decrease is apparent in the simulated DSDs. This result is consistent with the aforementioned work implicating size sorting as an important or even dominant process controlling low-level DSD behavior in these storms.
Finally, we present preliminary results of simulations using a spectral bin scheme and compare and contrast with the results of the triple-moment bulk scheme.