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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