solitary_mode_smallereddies
Solitary wave breaks into smaller instabilities and transverse overturning
transverseII
Transverse overturning on the right with an upward ejection of surface air on the left

The axes of transverse vortices are perpendicular to the wind.   In the stable boundary layer, such vortices transport warmer air downward and lift colder air upward.  Transverse modes are common in the fog videos once the wind speed has exceeded a few m/s and may dominate the total transport.

Transverse overturning in the boundary layer rarely comprises a complete cycle where a parcel circulates  through an entire rotation.  The above video shows typical transverse overturning where the rotation is incomplete.

Transverse overturning is best defined in cases of wind direction reversal with height, as  occurs with downslope drainage flow underneath ambient flow from the opposite direction.  An example of vigorous overturning with a wind direction reversal of unknown cause is shown in the following video

The following video shows vigorous transverse overturning when a wave like mode causes wind direction reversals and temporary change of wind direction with height.  This wave like mode survived for approximately five cycles.

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