…or vertical velocities we always want to use the cell of the particle location

Summary

The previous interpolation scheme tested on where the particle location was relative to the plane between the face velocities; for the vertical velocities we don't want to do this because we always want to use the velocities at the k location of the particle position (otherwise there is a discrepancy between the particle being identified as in cell k but being below the threshhold for using the vertical velocities associated with cell k)

Additional background

Note this only affects cases where the velocity components are on faces and where the mesh is "distorted", i.e. with terrain-following coordinates

Checklist

The proposed changes:

• fix a bug or incorrect behavior in AMReX
• add new capabilities to AMReX
• changes answers in the test suite to more than roundoff level
• are likely to significantly affect the results of downstream AMReX users
• include documentation in the code and/or rst files, if appropriate