A High-resolution WRF Ensemble for Predicting Sea-breeze Convection during ESCAPE

To characterize and understand sea-breeze convection, the Experiment of Sea breeze Convection, Aerosols, Precipitation, and Environment (ESCAPE) field campaign took place around the Houston area in June 2022. During the campaign, 24-h real-time 1-km ensemble forecasting simulations were run daily at 06Z and 12Z with the Weather Research and Forecasting (WRF) model. The WRF simulations were driven by real-time operational forecasts with varying microphysics, planetary boundary layer (PBL) schemes, and aerosol loadings, creating an ensemble of 16 simulations per initialization during the campaign. After ESCAPE, additional WRF simulations targeted at the convections observed during ESCAPE were conducted with 2 more different initial/boundary conditions, resulting in 1600 simulations total spanning the campaign period. In this study, model simulations were verified against several available data products including the NCEP/EMC Stage IV surface precipitation, ASOS near-surface observations, and interpolated sondes collected around Houston.

The WRF ensemble struggles with predicting precipitation intensity and timing on short timescales. While near-surface temperatures and vertical profiles are generally well represented, deviations in low-level moisture are quite large. Moreover, the WRF ensemble shows substantial sensitivity to the different initial/boundary conditions and PBL scheme, with the sensitivity to the microphysics scheme and aerosol loading playing a secondary role. Results also suggest that the 1-km ensemble demonstrates superior performance than the coarser-resolution operational forecasts in terms of precipitation, near-surface thermodynamics, and atmospheric vertical profiles.