ESS124
Prof. Jin-Yi Yu
Frictional Force
•Frictional force (drag) is strongest near the Earth’s surface and decreases rapidly with
height.
•The atmospheric layer in which frictional force is important is call thed boundary layer, whose depth can vary from a few hundred meters to a few thousand
meters.
•There are three sources to generate turbulence eddies to give rise to the frictional force: (1) mechanical
turbulence (airs
encounter surface roughness), (2) thermal turbulence (air near Earth’s surface get heated, and (3) wind-shear induced turbulence.
