Isobar, << EYE suh bahr, >> is a line drawn on a map to connect locations that have the same atmospheric pressure. Maps showing atmospheric pressure are useful in weather forecasting. There are many measures used for atmospheric pressure. Pressure may be marked in inches or millimeters of mercury. The metric system measure is the pascal. Another common measure is a bar. Meteorologists, scientists who study weather, commonly use the millibar (1/1,000 of a bar) to show pressure on weather maps.
Meteorologists often make pressure measurements in cities with different elevations. They then adjust these measurements to a common elevation, normally sea level. They plot isobars of sea level pressure on a map at constant intervals, such as 1000 millibars, 1004 millibars, 1008 millibars, and so on. Isobars on maps are often overlaid on other information, such as temperature or precipitation.
