MTEOR 411/511 WEEK 4 SUPPORTING MATERIAL

Week 4 - Geostrophic and Gradient Wind

To better understand the atmosphere, approximations are sometimes made in the equations that govern it. Two of these approximations result in the concept of geostrophic and gradient winds. The geostrophic approximation is based on the fact that the pressure gradient force is nearly balanced by the Coriolis force in many regions. By making the geostrophic approximation, we can determine wind speed and direction from height or pressure fields. This approximation will most closely resemble the real wind in regions without much curvature in the flow, regions away from the equator, and at levels far enough above the ground to not experience much friction. The gradient wind approximation allows curvature (centripetal accelerations) to influence the wind but still does not include effects of friction.