noun
isocheim; isochime; isochryme
Technical term in meteorology and climatology: a contour line on a map connecting points with the same mean winter temperature.
気候図で等寒線を引くと、冬の気温分布がよくわかる。
Drawing isocheims on a climate map clearly shows the distribution of winter temperatures.
等暑線 is an isothere (equal summer temperature), the warm-season counterpart of 等寒線.
Compound of 等 (equal) + 寒 (cold) + 線 (line), modeled on Western meteorological terminology for isocheim.