The deflection also increases with increasing wind speed. The coriolis effect is important only in large-scale circulation systems. The friction of fluid flow, known as viscosity , is of two types, molecular and eddy. The molecular viscosity arises from the random motion of molecules composing a liquid or gas. The eddy viscosity arises from the random motion of eddies within a fluid such as air or water.
Turbulence is the flow field that is characterized by eddy motion.
Turbulent motion of eddies is either mechanical or thermal in origin. The atmospheric zone subjected to the friction is named as atmospheric boundary layer . The gravity force always acts downward and perpendicular to the Earth's surface. Therefore, it does not modify horizontal winds. When forces are in balance, no acceleration occurs, that is, there is no change in velocity such that an upward-moving air parcels continue upward at constant speed and vice versa.