4.4. Geostrophic Wind

The velocity and direction of the wind are the net result of the wind generating forces. The winds in the upper atmosphere, 2 - 3 km above the surface, are free from frictional effect of the surface and are controlled by the pressure gradient and the Coriolis force. At such height in the free atmosphere, winds generally blow at right angles to the pressure gradient: this indicate that the pressure gradient force is exactly balanced by the Coriolis force acting in a diametrically opposite direction. This sort of air motion is known as the geostrophic wind (figure 16(a)).