Isobar

Definition and stakes

Henry Ambrose Hunt,  The Climate and Weather of Australia (1913)

“ It is for the latter type that the word "trough" is here used. In the case of a col, the isobars of the two "highs" are decidedly convex to one another along their common axis; in the case of a trough the rear isobars of the preceding "high" or the front isobars of the following "high", or both, tend to straighten and the convexity is more apparent in the isobars of the adjacent low pressure systems, producing often an hour glass appearance. The chart of 31st May, 1909, shows the straightening of the rear isobars of the preceding high very well. ”
Source: Wikisource

Alexander Buchan,  Encyclopædia Britannica, Ninth Edition (1878)

“ Here the highest pressure is in the centre of the system, and, as usually happens, the isobarics are less symmetrical than those near the centre of a cyclone. The winds, as usual in anticyclones, are light ; this, however, is the essential point of difference the winds do not flow inwards upon the centre, but outwards from the region of high pressure ; and it will be observed that in many cases they cut the isobarics at nearly right angles. ”
Source: Wikisource

Alexander Buchan,  Encyclopædia Britannica, Ninth Edition (1878)

“ Stand with your back to the wind, and the lowest barometer, or centre of depression, will be to your left in the northern hemisphere (in the southern hemisphere to the right) ; this rule holds universally. (2.) The force of the wind is proportional to the barometric gradient, or the quotient of the dis tance between two places stated in miles by the difference of pressure stated in inches of mercury as observed at the two places. Hence, in the Channel, where the isobarics are close together, winds are high, but in the north of Scotland, where the isobarics are far apart, winds are light. ”
Source: Wikisource

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