Growth of spread in convection-allowing and convection-parameterizing ensembles

During the 2007 NOAA/Hazardous Weather Testbed Spring Experiment (SE07), a 10-member 4-km grid-spacing Storm-Scale Ensemble Forecast (SSEF) system was run in real-time to provide severe weather forecasting guidance to the SE07 participants. The SSEF system consisted of five members using perturbed initial conditions (ICs) and lateral boundary conditions (LBCs) along with mixed physical parameterizations (mixed-physics), and five members using only mixed-physics so that the impacts of the different physical parameterization schemes could be isolated. This choice of ensemble configuration also facilitates a comparison of ensemble spread contributions in a convection-allowing ensemble generated by a combination of perturbed ICs/LBCs and mixed-physics to that generated by only mixed-physics, which will be examined in this short note. In addition, the ensemble spread in the two convection-allowing ensemble configurations will be compared to two similarly configured 20-km grid-spacing convection-parameterizing ensembles to examine the impact of horizontal resolution on spread growth for various forecast fields in the two different ensemble configurations.