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tundra

(Encyclopedia)tundra tŭnˈdrə [key], treeless plains of N North America and N Eurasia, lying principally along the Arctic Circle, on the coasts and islands of the Arctic Ocean, and to the north of the coniferous ...

growing season

(Encyclopedia)growing season, period during which plant growth takes place. In temperate climates the growing season is limited by seasonal changes in temperature and is defined as the period between the last killi...

hail, in meteorology

(Encyclopedia)hail, precipitation in the form of pellets composed of ice or of ice and snow, occurring at any time of the year, usually during the passage of a cold front or during a thunderstorm. Small hailstones ...

heat capacity

(Encyclopedia)heat capacity or thermal capacity, ratio of the change in heat energy of a unit mass of a substance to the change in temperature of the substance; like its melting point or boiling point, the heat cap...

Kelvin, William Thomson, 1st Baron

(Encyclopedia)Kelvin, William Thomson, 1st Baron, 1824–1907, British mathematician and physicist, b. Belfast. He was professor of natural philosophy at the Univ. of Glasgow (1846–99). He is known especially for...

Hertzsprung-Russell diagram

(Encyclopedia)CE5 The Hertzsprung-Russell diagram shows the relation between the luminosity and surface temperature (which is related to spectral class, or color) of the stars in the Milky Way. Most stars fall a...

climate

(Encyclopedia)climate, average condition of the atmosphere near the earth's surface over a long period of time, taking into account temperature, precipitation (see rain), humidity, wind, barometric pressure, and ot...

chinook, warm, dry air mass

(Encyclopedia)chinook, warm, dry air mass that descends the eastern slopes of the U.S. and Canadian Rocky Mts. after having lost moisture by condensation over the western slopes. Chinooks occur mainly in winter. Th...

cline

(Encyclopedia)cline, in biology, any gradual change in a particular characteristic of a population of organisms from one end of the geographical range of the population to the other. Gradients of characteristics us...

Geysir

(Encyclopedia)Geysir gāˈsĭr [key], hot spring, SW Iceland, c.75 mi (120 km) W of Reykjavík. Although in medieval times it erupted three times daily, weeks now elapse between eruptions. The height and temperatur...