HYBRID SINGLE‑PARTICLE LAGRANGIAN INTEGRATED TRAJECTORIES HY‑SPLIT): VERSION 3.0 -- USER'S GUIDE AND MODEL DESCRIPTION
Roland R. Draxler
NOAA Technical Memorandum ERL ARL ‑ 195, Last Revision: June 1992
Abstract - The algorithms and equations used in the calculation of long‑range pollutant transport and dispersion are presented from the meteorological data sources through the calculation of air concentrations. The model calculation methods are a hybrid between Eulerian and Lagrangian approaches. A single pollutant particle represents the initial source. Advection and diffusion calculations are made in a Lagrangian framework. However, meteorological input data can either be gridded from rawinsonde observations or archived from other sources, such as the analyses fields or forecast outputs from Eulerian primitive equation models. As the dispersion of the initial particle spreads it into regions of different wind direction or speed, the single particle is divided into multiple particles to provide a more accurate representation of the complex flow field. Air concentrations are calculated on a fixed three dimensional grid by integrating all particle masses over the sampling time. The model code can be run on a personal computer. Calculations consist of simple trajectories from a single source to complex multiple source emissions. A flow chart of the calculations as well as several examples are given. The code is structured so that concentration calculations or simple trajectory (forward or backward) calculations can be performed on sigma (terrain following) or pressure coordinates.
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