Chapter 3 of the book introduces the concept of upper air maps. For example Figure 3-8 is a graph the heights of the 500 mb pressure surface. This type of map is called a 500 mb constant pressure chart. We will be analyzing upper air maps from now until the end of the course. For now, it is important to be able to identify troughs and ridges on these maps. Below is an exercise to help you with this. (You may have to adjust the width of your web viewer.) The blue lines are of constant height of the 500 mb pressure. The dashed red lines are lines of constant temperature, or isotherms. We will interpret the wind barbs and in the next lesson.

There is a second applet that demonstrates the relationship between the ridge at 500 mb and the ridge at 300 mb (which is at a higher altitude). Note that the ridge at 300 mb is further west than the ridge at 500 mb.

Locating a Ridge on a 500 mb map

Notice the tilt of the ridge.