Investigation 8A 2024-25

The focus of Investigation 8A is on the forces that cause the wind to blow at the Earth’s surface. The 3 forces that are discussed are the pressure gradient force (PGF), Coriolis force (f) and Friction (Fr). The PGF is caused by changes in pressure over a horizontal distance and is directed from high to low pressure, perpendicular to the isobars. The Coriolis force is caused by latitudinal variations in the Earth’s radial velocity, is proportional to the wind speed and is always directed 90 degrees to the right of the wind. The “geostrophic wind” results from a balance between the PGF and f, and blows parallel to the isobars with low pressure to the left of the wind. Friction slows the wind, which reduces f and causes the PGF to become the dominant force. The resulting wind (much closer to the real wind) crosses the isobars at an angle from higher to lower pressure.