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Noctilucent clouds form mostly near the polar regions, [7] because the mesosphere is coldest there. [15] Clouds in the southern hemisphere are about 1 km (3,300 ft) higher than those in the northern hemisphere. [7] Ultraviolet radiation from the Sun breaks water molecules apart, reducing the amount of water available to form noctilucent clouds.
When these high clouds progressively invade the sky and the barometric pressure begins to fall, precipitation associated with the disturbance is likely about 6 to 12 hours away. A thickening and lowering of cirrocumulus into middle-étage altostratus or altocumulus is a good sign that the warm front or low front has moved closer and it may ...
The clouds do not become that color; they are reflecting long and unscattered rays of sunlight, which are predominant at those hours. The effect is much like if a person were to shine a red spotlight on a white sheet. In combination with large, mature thunderheads this can produce blood-red clouds.
A process whereby scientists seed a cloud with artificial ice nuclei to encourage precipitation is known as cloud seeding. This can help cause precipitation in clouds that otherwise may not rain. Cloud seeding adds excess artificial ice nuclei which shifts the balance so that there are many nuclei compared to the amount of super cooled liquid ...
A marine layer is an air mass that develops over the surface of a large body of water, such as an ocean or large lake, in the presence of a temperature inversion. The inversion itself is usually initiated by the cooling effect caused when cold water on the surface of the ocean interacts with a comparatively warm air mass. [1]
An ice cloud is a colloid of ice particles dispersed in air. The term has been used to refer to clouds of both water ice and carbon dioxide ice on Mars. [1] Such clouds can be sufficiently large and dense to cast shadows on the Martian surface. [1] Cirrus and noctilucent clouds on Earth contain ice particles. [2]
Ice crystals in the clouds cause them to usually appear white, but the rising or setting sun can color them various shades of yellow or red. [2] [5] At dusk, they can appear gray. [5] Cirrus comes in five visually-distinct species: castellanus, fibratus, floccus, spissatus, and uncinus: [2]
At night, the absence of clouds means that outgoing longwave radiation (i.e. heat energy from the surface) is not absorbed, giving cooler diurnal low temperatures in all seasons. When surface winds become light, the subsidence produced directly under a high-pressure system can lead to a buildup of particulates in urban areas under the ridge ...