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isobar i·so·bar (ī'sə-bär')
Any of two or more kinds of atoms having the same atomic mass but different atomic numbers.
A line on a weather map connecting points of equal atmospheric pressure.
A line drawn on a weather map connecting places having the same atmospheric pressure. The distance between isobars indicates the barometric gradient (the degree of change in atmospheric pressure) across the region shown on the map. When the lines are close together, a strong pressure gradient is indicated, creating conditions for strong winds. When the lines are far apart, a weak pressure gradient is indicated and calm weather is forecast.
line on a weather map of constant barometric pressure drawn on a given reference surface. The isobaric pattern on a constant-height surface is extremely useful in weather forecasting because of the close association between pressure and weather. Regions of low pressure at sea level tend to be areas of bad weather, especially in winter. At higher elevations the wind blows approximately parallel to the isobars, with low pressure to the left in the Northern Hemisphere and to the right in the Southern Hemisphere with respect to the direction of air movement; the closer together the isobars are, the stronger is the wind speed. Only sea-level pressure patterns are routinely used in meteorology. At higher elevations pressure itself is used to define the reference surface upon which contours of the height above sea level are drawn; dynamically, the height contours of a constant pressure surface are completely analogous to the isobars of a constant-height surface