Isobar Maps



http://www.csulb.edu/~rodrigue/geog140/lectures/pressure.html

This is a topographic map with isobars added which show measurements of the air pressure in eastern Austrailia and New Zealand in terms of millibars.  Millibars are units of atmospheric pressure equal to one-thousandth of a bar.  A bar is a unit of pressure equal to one million dynes per square centimeter.  A dyne is equal to the force required to impart an acceleration of one centimeter per second to a mass of one gram.

Isobars are lines shown on weather maps that connect points which have equal atmospheric pressure.  Notice in the map above; each line with a numeric indicator, although not straight, has a single numeric value inserted into the line.  The curve in the line could be as a result of the curvature and/or elevation of the surface being shown on the map.