NOAA Air Resources Laboratory
The seminar will consist of two important but unequal parts. First, the HYSPLIT system will be reviewed starting with the model's history, a description of Lagrangian approaches, the trajectory computational method, and sources of trajectory error. The single-trajectory discussion will be expanded to show how multiple-trajectories can be used to describe the transport and dispersion of a cluster of pollutant particles to quantify air concentrations. Results from three-dimensional particle simulations will be compared with hybrid approaches that use "puff" approximations to model the growth of the horizontal particle distribution rather than the individual particle transport. The model's similarity, deformation, velocity variance, and TKE parameterization options available to compute pollutant dispersion will be reviewed. Examples of concentration probabilities based upon the underlying trajectory uncertainty will be shown. Finally, finally the model's performance will be compared to measurements for some short-range experimental data, forest fire plumes, dust storms, and several historical tracer experiments. The second, and much shorter part of the seminar, will consist of several examples (radiological, volcanic ash, and homeland security) contrasting the existing NCEP operational system with the new integrated system, now running in "para" mode.