New Implementation of Buoyant Transport and Dispersion in Weather Research and Forecasting's Large-Eddy Simulation Framework

Numerical modeling of turbulent buoyant plumes of scales ranging from wildfires to volcanic eruptions is critical in understanding and analyzing the effects of such extreme events. This study explores the mean and turbulent characteristics for a continuous buoyant plume released into neutral, slightly-stable, and slightly-unstable atmospheric conditions using Weather Research and Forecast models Large-Eddy Simulation (WRF-LES) framework. The default WRF-LES framework is modified to simulate the transport and dispersion of a newly added buoyant source inside the domain. This buoyant source is added analogous to the potential temperature equation present in WRF. The additional tendencies due to this buoyant source are calculated and added to the respective forcing tendencies of the WRF’s momentum equations. Turbulent mixing of the plume within the boundary layer as a function of initial source conditions and atmospheric stability is addressed. Plume metrics such as ascent rate, half-width, centroid and radial profiles of momentum and buoyancy fluxes are presented. Results from this new framework are compared against WRF-AERMOD and WRF-HYSPLIT dispersion models initiated with the meteorological fields from the LES runs. This novel implementation of buoyant source(s) in WRF-LES would benefit researchers modeling high-resolution case studies driven by realistic boundary conditions during before mentioned extreme events.