Unit 2 Water and Weather - Spokane Public Schools

The stratosphere, mesophere, and thermosphereStratosphereMesosphereThermosphereHeat transfer inthe thermosphereAbove the troposphere lies the stratosphere, extending from about11 to 50 kilometers above Earth’s surface. The temperatureincreases as you go up in the stratosphere because of a thin layerof ozone. The ozone layer absorbs the Sun’s high-energy ultraviolet(UV) radiation. As a result, the stratosphere is warm and we areprotected from the skin and eye damage caused by UV radiation.Above the stratosphere, the temperature begins to drop again.This marks the beginning of the mesosphere, which extends from50 to 80 kilometers above Earth. The mesosphere is the coldestlayer of the atmosphere. At its outer reaches the temperature canbe as low as –90 °C. Most meteors or “shooting stars” burn up inthe mesosphere.The layer that begins at about 80 kilometers above Earth’s surfaceis called the thermosphere. This layer has a low density of airmolecules—there are 100,000 times more air molecules in a cubicmeter of air at Earth’s surface than in the thermosphere. Thesemolecules have a lot of kinetic energy, because the energy from theSun hits them first. Temperatures in this layer can reach 1,800 °C.If you could hop out of a space shuttle into the thermosphere, youwouldn’t feel hot. Temperature, as you remember, measures theaverage kinetic energy of the particles (atoms and molecules) of asubstance. Heat, on the other hand, involves the transfer of energyfrom one object to another. Because the air molecules in thethermosphere are so far apart, very few of them would collide withyou, so there would be very little heat transferred.stratosphere - a layer ofatmosphere that occurs fromabout 11 kilometers to50 kilometers above Earth’ssurface; the location of the ozonelayer.mesosphere - a layer ofatmosphere that occurs fromabout 50 kilometers to80 kilometers above Earth’ssurface; the coldest layer.thermosphere - a layer ofatmosphere that occurs fromabout 80 kilometers to about500 kilometers; this layer has alow density of air molecules and avery high temperature.exosphere - the region of theatmosphere that begins at about500 kilometers above Earth andextends into space; the location ofthe orbits of satellites (see nextpage).ionosphere - portions of theatmosphere in the region of thethermosphere where electricitycan be transmitted (see nextpage).106UNIT 2 WATER AND WEATHER