Isobars

This is an image of Isobars. An isobar is a line of equal or constant pressure on a map. The lines are drawn to represent equal lines of pressure. Meteorologists use these types of maps when practicing the weather and climate conditions.
Image found at:http://www.newmediastudio.org/DataDiscovery/Hurr_ED_Center/Hurr_Structure_Energetics/Closed_Isobars/Closed_Isobars_fig02.jpg