noun
definition
A line on a graph or chart, such as a weather map, along which all the points have the same temperature.
Examples of isotherms in a Sentence
In January the northern water areas of the continent are frozen and snow-covered; Hudson Bay becomes unduly cold, and the greatest southward bending of the isotherms is somewhat east of the continental axis, with an extension of its effects out upon the Atlantic; but the southward bending isotherms are somewhat looped back about the unfrozen waters of the lower Great Lakes.
The thermodynamics of this can be explained by pressure composition isotherms.
In the same midsummer month all the eastern half of the United States is included between the isotherms of 66 and 82; the contrast between Lake Superior and the coast of the Gulf of Mexico, 1200 m.
The distribution of life-zones is primarily a matter of altitude and corresponds to that of the isotherms. The mountain goat and mountain sheep live in the Sierran upper-land, though long ago well-nigh exterminated.
Although the temperature of the entire lower peninsula is considerably influenced by the lakes, yet, the prevailing winds being westerly, it is in the west portion of that peninsula that the moderation is greatest, both the summer and winter isotherms being there deflected more than half the length of the peninsula.
The study of geography was advanced by improvements in cartography (see MAP), not only in the methods of survey and projection, but in the representation of the third dimension by means of contour lines introduced by Philippe Buache in 1737, and the more remarkable because less obvious invention of isotherms introduced by Humboldt in 1817.
The arrangement of the isotherms thus affords a basis for valuable deductions as to the direction of ocean currents.
As a result, the isotherms of July are strongly convex poleward as they cross the United States, the isotherm of 70 Sweeping up to the northern boundary in the north-west, and the heat equator leaping to the overheated deserts of the south-west, where the July mean is over 90.
Conversely, the isotherms of January are convex southward, with a monthly mean below 32 in the northern third of the interior, and of zero on the mid-northern boundary.
The seasonal bending of the isotherms is, however, unsymmetrical for several reasons.
The continent being interrupted on its eastern side by the Gulf of Mexico and Hudson Bay, with the Great Lakes between these two large water bodies, the northward bending of the July isotherms is most pronounced in the western part of the United States.
Indeed the contrast between the moderate temperatures of the Pacific coast and the overheated areas of the next interior deserts is so great that the isotherms trend almost parallel to the coast, and are even overturned somewhat in southern California, where the most rapid increase of temperatures in July is found not by moving southward over the ocean toward the equator, but north-eastward over the land to the deserts of Nevada and Arizona.
In July, on the other hand, the isotherms show an almost constant temperature all over the country, and the linguiform curves are wanting.
The isotherms are exceedingly interesting.