| These polar stratospheric clouds form only in regions of very low temperature and as a result the clouds only exist in winter stratospheric polar regions. |
| A wetter and colder stratosphere means more polar stratospheric clouds, which is likely to lead to more severe ozone loss in both polar regions. |
| The extremely cold temperatures of the stratosphere during the polar winter enable the development of polar stratospheric clouds. |
| The presence of trace amounts of nitric and sulfuric acids enables the formation of polar stratospheric clouds a few degrees above the frost point. |
| Some of the extraterrestrial material could be incorporated into polar stratospheric clouds over Antarctica and sediment out of the lower stratosphere. |
| That triggered vast polar stratospheric clouds, some of them as big as the continental United States. |
