| A | B |
|---|
| Autumnal equinox | the equinox that occurs on September 22 or 23 in the Northern Hemisphere and on March 21 or 22 in the Southern Hemisphere |
| Mesosphere | the layer of the atmosphere immediately above the stratosphere and characterized by decreasing temperatures with height |
| Ozone | a molecule of oxygen containing three oxygen atoms |
| Spring equinox | the equinox that occurs on March 19 or 20 in the Northern Hemisphere |
| Stratosphere | the layer of the atmosphere immediately above the troposphere, characterized by increasing temperatures with height, due to the concentration of ozone |
| Summer solstice | the solstice that occurs on June 20 or 21 in the Northern Hemisphere and on December 20 or 21 in the Southern Hemisphere |
| Thermosphere | the region of the atmosphere immediately above the mesosphere and characterized by increasing temperatures due to absorption of very short-wave solar energy by oxygen |
| Troposphere | the lowermost layer of the atmosphere, generally characterized by a decrease in temperature with height |
| Winter solstice | the solstice that occurs on December 21 or 22 in the Northern Hemisphere and on June 21 or 22 in the Southern Hemisphere |
