Verification of diurnal cycle characteristics in the CAPS 2010 Storm Scale Ensemble Forecast System

Diurnal cycle characteristics for various fields (e.g., precipitation, CAPE, wind shear, low-level temperature and moisture, and winds) in the Storm Scale Ensemble Forecast (SSEF) system run by the Center for Analysis and Prediction of Storms (CAPS) for the 2010 NOAA/Hazardous Weather Testbed Spring Experiment are examined. Analyses using time-dimension diagrams of SSEF fields averaged over all available cases are computed to create “model climatologies”, and comparisons are made to observations to identify systematic biases. For precipitation, characteristics (e.g., coherent span and duration) of individual, rather than composite, time-space “rain streaks” are also examined to diagnose properties of simulated propagating rainfall systems. Accurate model climatologies in the members comprising an ensemble are important so that the ensemble forecasts depict a representative probability distribution function of possible observed atmospheric states. Because a subset of the 2010 SSEF system members were run with only varied physics parameterizations (i.e., the same initial and lateral boundary conditions), the sensitivity to various model configurations is emphasized.