P87  Evaluation of WRF Stochastic Kinetic-Energy Backscatter Perturbation in a Storm-Scale Ensemble Forecasting System

Zhu, Jiangshan, Center for Analysis and Prediction of Storms, University of Oklahoma,  Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China, Fanyou Kong, Xuguang Wang, CAPS and University of Oklahoma, Jeff Duda, University of Oklahoma, Judith Berner, NCAR, Ming Xue, CAPS and University of Oklahoma

The newly available stochastic kinetic-energy backscatter (SKEB) perturbation in the Weather Research and Forecasting Model version 3.3.1 has been applied through a 5-member, storm-scale ensemble forecasting (SSEF) system that covers the full continental United States with 4-km grid spacing during the 2012 NOAA HWT Spring Experiment, to investigate the impact of the SKEB perturbation on SSEF system. The SKEB members are evaluated against a group of same 5-member non-SKEB members through the HWT Spring Experiment period. Different SKEB perturbation amplitudes and different vertical structures are examined through a severe storm case of April 27, 2011 to reveal the SKEB perturbation growth at the convection-permitting model resolution and to look for possible optimal SKEB configuration for the SSEF system. The case study shows that the SKEB-induced perturbation growths are more prominent in active convection area, suggesting moist convective instability intensifies the perturbations from SKEB. Doubling the SKEB perturbation amplitudes leads to much larger overall perturbation intensity and more broader spatial extent and has more intensive impact than halving the perturbation amplitudes. In general, adding SKEB perturbations does not change the overall precipitation distribution, but can cause displacement of the local maxima. The overall impact of SKEB on the storm-scale ensemble forecasting system through the HWT experiment period has been evaluated and will be presented at the workshop.