Isobar

http://www.newmediastudio.org/DataDiscovery/Hurr_ED_Center/Hurr_Structure_Energetics/Closed_Isobars/Closed_Isobars.html

Isobars are used to create isoline maps, but are not limited to just being a part of them. They can also create different maps of there own, isboars simply distinguish between the variables being asked. In the map above the Isobar map is showing the pressure changes of North America. the closwer the bars get together the higher the pressure is, and as they become more spread out the pressure lowers. With the result of a low pressure system in the middle.