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How are the meteorological model's vertical motion fields used in the calculation?

In most circumstances the meteorological data will contain a vertical motion field, usually in pressure units, and regardless upon which vertical coordinate system these data are provided, the vertical velocity field is almost always relative to the meteorological model's native terrain-following coordinate system. The trajectory and dispersion model calculations can use these data fields directly because the model's internal coordinate system is terrain-following. This is one of the primary reasons why the meteorological data for the dispersion model are always re-mapped internally to a common terrain-following vertical coordinate system. Model produced vertical motion fields may at times contain considerable noise, however frequently the trajectory position will advect with the vertical motion pattern and maintain its relative position to major features.

In the example shown below, for the previous trajectory, the vertical motion field near the initial trajectory position indicates a value near 10 hPa/h (downward motion), however 24 h later, near the end of the trajectory, the position is in an area of weak upward motion (0 to -5 hPa/h).

Initial vertical motion field Vertical motion field 24 hours later
Initial vertical motion field Vertical motion field 24 hours later