Isobar

An isobar is a unvarying line of pressure. The pressure information is reflective of atmospheric pressure. These types of maps usually have multiple lines which represents the changes in pressure over large areas.

The example map shows a low pressure cell.

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