The Friction Layer
The lowest layer of the earth's atmosphere, usually up to 3,300 feet.
Surface friction is effective in slowing down wind up to approximately
1,500 to 3,000 feet above the ground. Above this level, air tends to flow
parallel to the isobars. Wind distribution within this layer is determined
by vertical temperature gradient and the physical contours of the underlying
surface features. This layer is sometimes called the boundary layer or
surface boundary layer.
The Mississippi river valley has gently rolling plains that constitute
only a minimal friction layer that permits frontal systems and air mass
ingress in the Gulf coast region.