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| air pollution containing ozone and reactive chemical compounds formed by sunlight on nitrogen oxides and hydrocarbons, often from auto exhaust |
| the upper portion of a cumulus cloud characterized by dense, sharply defined, cauliflower-like upper parts and sometimes by great verticality |
| parhelic circle | |
| —n | |
| meteorol a luminous band at the same altitude as the sun, parallel to the horizon, caused by reflection of the sun's rays by ice crystals in the atmosphere | |
| parhelic circle (pär-hē'lĭk) Pronunciation Key
A luminous halo visible at the height of the Sun and parallel to the horizon, caused by the Sun's rays reflecting off atmospheric ice crystals. |