Why is atmosphere heated more by terrestrial radiation than by insolation?
Answers
Question:
Why is atmosphere heated more by terrestrial radiation than by insolation?
Answer:
◆ The Greenhouse Effect
The Greenhouse EffectSolar and terrestrial radiation occupy different ranges of the electromagnetic spectrum that we have been referring to as shortwave and longwave.
◆ For reasons explained in the next section, water vapor, carbon dioxide, and other gases whose molecules have electric dipole moments absorb radiation more strongly in the longwave part of the spectrum occupied by outgoing terrestrial radiation than the shortwave part occupied by incoming solar radiation.
◆ This distinction is reflected in the transmissivity spectra of the atmosphere shown in the lower part.
◆ Hence, incoming solar radiation passes through the atmosphere quite freely, whereas terrestrial radiation emitted from the Earth's surface is absorbed and reemitted in its upward passage through the atmosphere.
◆ The following highly simplified exercise shows how the presence of such greenhouse gases in a planetary atmosphere tends to warm the surface of the planet.