Sensitivity of Physical Parameterization Schemes to Stochastic Initial Conditions in WRF Tornado Outbreak Simulations

A better understanding of the performance in precision of physical
parameterizations in NWP models is necessary for improving forecasts of tornadic
outbreaks. For this study, WRF simulations of tornadic outbreaks were run using
configurations of three microphysics, three convective physics, and two PBL physics
schemes. Each configuration was subjected to ten iterations of SKEBS. The means of the
ten perturbation members of each parameterization configuration were bootstrapped for
severe weather diagnostic variables to find 95% confidence interval widths at each grid
point. Maps of these spreads provided a spatial analysis of the uncertainty. Analyses on
correlations and clusters were performed to determine how the configurations related
spatially and in magnitude. These uncertainties were further bootstrapped to compare the
mean of each configuration in boxplots. The effect on the uncertainty produced by each
configuration varied according to the diagnostic variable being analyzed.