ABSTRACT
The measurement of flow velocity is fundamental for understanding the physics of air movement in the atmosphere. The scope of this chapter considers primarily measurements to obtain the velocity vector of the movement of air in the atmosphere. Therefore, the goal of this chapter is to describe the various commonly used methods to measure winds. Since a parcel of air deforms continuously when subjected to a shear stress, it may be treated as a fluid and its conservation of mass and momentum may be expressed in the form of partial differential equations. Under commonly accepted conditions for air, namely, that the fluid is Newtonian (i.e., applied shear is proportional to the velocity gradient), the governing mathematics are known as the Navier-Stokes equations.
