Sylvia's solution
How did you get on?
In this video, Sylvia demonstrates the solution to the air mass exercise in the previous Step.
You may have noticed the ‘geostrophic wind scale’ in the top left of these and other weather maps. You may remember that the closer the pressure contours are to each other, the faster the wind blows. This scale allows you to calculate the wind speed from the pressure contour separation.
Figure 1: Geostrophic wind scale for measuring wind speed. © Crown Copyright, Met Office
Figure 2: Example of how to measure wind speed with the geostrophic wind scale. © Crown Copyright, Met Office
The actual wind speed at the ground will always be less than the geostrophic wind speed because of friction. Friction will slow the wind more over land than over water. Rules of thumb suggest that the wind will be 2/3 of the geostrophic speed over water and 1/3 over land, but it will vary considerably.
Come Rain or Shine: Understanding the Weather
Come Rain or Shine: Understanding the Weather
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