## Vertical Motion Methods

The trajectory vertical motion method is set by a single digit in the CONTROL
file. This method would apply to all meteorological data files. The default value
is to use the vertical velocity data fields supplied with the meteorologcal model
data.

- 0 = uses the data fields from the meteorological model
- 1 = isobaric follows constant pressure surfaces
- 2 = isentropic follows potential temperature surfaces
- 3 = the calculation follows constant density surfaces
- 4 = isosigma follows the internal terrain following coordinate system, the closest approximation to no vertical velocity
- 5 = computes the vertical velocity by integrating the divergence
- 6 = assumes the vertical velocities are relative to MSL which are remapped to AGL
- 7 = horizontally averages the vertical velocities to be consistent with the temporal frequency of the data
- 8 = damps the magnitude of the vertical velocity based upon the ratio of data frequency to grid size

Note that methods 1,2,3,4 are only approximations. Instead of remapping the data
fields to these surfaces, a vertical velocity is computed that would maintain the
trajectory on the selected surface.

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