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8. Wake Turbulence

Every aircraft produces a wake when in flight. This turbulence is in the form of two
counter-rotating vortices of air extending backward from the tips of the wings. The strength
of the vortex produced by the wing tip is determined primarily by the weight, speed, and
shape of the wing of the aircraft. The wake produced by a large aircraft can be particularly
dangerous to a small, light aircraft.

9. Wind Shear
Wind shear exists when there is contact between currents of air flowing in different
directions and/or at different speeds. There is a tearing or shearing effect where the currents
are in contact with each other. The eddies formed in this contact area are called wind shear
turbulence. Wind shear can exist at the horizontal boundary between layers of air moving in
different directions and/or at different speeds, or it can exist along a vertical boundary when
upward or downward currents are in contact with currents moving in a different direction
and/or at a different speed. Horizontal or vertical wind shear can exist at any altitude. The
intensity of the turbulence increases as the amount of wind shear increases.