Roland R. Draxler and G.D. Hess


NOAA Technical Memorandum ERL ARL-224, Air Resources Laboratory

Silver Spring, Maryland, December 1997  (Revised: August 1998, September 2002)


Abstract - The HYSPLIT_4 (HYbrid Single-Particle Lagrangian Integrated Trajectory) model (Version 4) is a complete system for computing simple trajectories to complex dispersion and deposition simulations using either puff or particle approaches. The model uses previously gridded meteorological data on one of three conformal map projections (Polar, Lambert, Mercator). Air concentration calculations associate the mass of the pollutant species with the release of either puffs, particles, or a combination of both.  The dispersion rate is calculated from the vertical diffusivity profile, wind shear, and horizontal deformation of the wind field.  Air concentrations are calculated at a specific grid point for puffs and as cell-average concentrations for particles.


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