HYPOTHETICAL PARTICLE TRAJECTORY AND DISPERSION SIMULATIONS USING REAL-TIME FORECAST SYSTEM VIA ASSIMILATION OF RADIAL VELOCITIES FROM A SINGLE WSR-88D

This paper describes a real time trajectory and dispersion forecast system (WRFDA-HYSPLIT) and presents a case study in which trajectories and concentrations were computed using various meteorological models with and without the assimilation of Doppler radar radial wind observations. The forecast system comprises WRF 3D VAR data assimilation system using WSR-88D radial winds from a single Doppler radar, Weather Research and Forecasting model (WRF), and Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model. The overall goal is to provide first responders more accurate transport and dispersion of hazardous releases in real time. The forecast system runs twice a day providing 12 h forecasts for weather conditions as well as trajectories and dispersions originated from a single source location. The Local Data Manager (LDM) program acquires the latest raw radar data (level-II) from the WSR-88D KLIX (Slidell, Louisiana) station. A Four-Dimensional De-aliasing algorithm (4DD) and some statistical properties of radial winds and reflectivities are first applied to radial winds for quality controls. The end products such as WRF and HYSPLIT forecast outputs and graphics are made available to the public. Control and experiment simulations agreed well when a high pressure system was settled in within the study region. On the other hand, significant deviations and discrepancies in trajectory and dispersion simulations were noted as a cold frontal passage altered the wind field.