This is the force that generates the wind by creating horizontal pressure differences. Isobars -- lines that connect places with equal air pressure - measure pressure data. The spacing between the isobars determine the pressure gradient (the pressure change that occurs over a given distance). Widely spaced isobars indicate light winds due to a weak pressure gradient, while closely spaced isobars indicate strong winds, as a result of a steep pressure gradient.
Friction directly acts to slow air movement, which in turn reduces the Coriolis effect, resulting in reduction of wind speed. The effect of friction on wind speed is apparent only close to the Earth's surface. Surface irregularities like mountains and hills affect the wind speed as it passes over these surfaces, and this decreases its speed. Since wind moves to low air pressure areas, cyclones or wind gusts will result. Whether in the Northern or the Southern Hemisphere, friction results in an inflow of air around a cyclone. Alternatively, an outflow occurs around the surface of an anticyclone.
The Coriolis effect is the apparent deflection of the wind caused by the Earth's rotation. In the Northern Hemisphere this effect causes winds to deflect to the right of their motion path, while in the Southern Hemisphere the deflection occurs to the left of their path of motion. The Coriolis effect also has a similar effect on ocean currents.
Solar energy results from sunlight striking the Earth's surface, heating it and, in turn, causing pressure differences. Solar energy is thus the ultimate cause of Earth's winds, and the pressure differences resulting from uneven heating causes the creation of winds of varying speeds. Uneven heating may also result in wind shear, where two air currents traveling at different speeds meet. This, in turn, produces air turbulence that results in a new wind phenomenon such as a tornado.
