A cloud is a visible mass of droplets or frozen crystals floating in the atmosphere above the surface of the Earth or another planetary body. A cloud is also a visible mass attracted by gravity, such as masses of material in space called interstellar clouds and nebulae. Clouds are studied in the nephology or cloud physics branch of meteorology.
Welcome to CWAnswers
CWAnswers is your guide to the sprawling world wide web. The directory aims to provide a useful guide made by users. You can share your knowledge as well - simply sign up and edit your first entry. For questions just contact the team at support - at - cwanswers.com.
Weblinks for Cloud
Top 10 for Cloud
Things about Cloud you find nowhere else.
Select content modules
A cloud is a visible mass of droplets or frozen crystals floating in the atmosphere above the surface of the Earth or another planetary body. A cloud is also a visible mass attracted by gravity, such as masses of material in space called interstellar clouds and nebulae. Clouds are studied in the nephology or cloud physics branch of meteorology.
On Earth the condensing substance is typically water vapor, which forms small droplets or ice crystals, typically 0.01 mm in diameter. When surrounded by billions of other droplets or crystals they become visible as clouds. Dense deep clouds exhibit a high reflectance (70% to 95%) throughout the visible range of wavelengths. They thus appear white, at least from the top. Cloud droplets tend to scatter light efficiently, so that the intensity of the solar radiation decreases with depth into the gases, hence the gray or even sometimes dark appearance at the base. Thin clouds may appear to have acquired the colour of their environment or background and clouds illuminated by non-white light, such as during sunrise or sunset, may appear coloured accordingly. In the near-infrared range, clouds look darker because the water that constitutes the cloud droplets strongly absorbs solar radiation at those wavelengths.
Condensation
As air parcels cool due to expansion of the rising air mass, water vapor begins to condense on condensation nuclei such as dust, ice and salt. This process forms clouds. Sometimes an elevated portion of a frontal zone forces broad areas of lift, which form cloud decks such as altostratus or cirrostratus. Stratus is a large dark low cloud deck that tends to form when a stable cool air mass is trapped underneath a warm air mass. It can also form due to the lifting of advection fog during breezy conditions. Clouds can also be formed due to lifting over mountains and other topography.
Classification of clouds
Clouds are divided into two general categories: layered and convective. These names distinguish a cloud's altitude. Clouds are classified by the base height, not the cloud top. This system was proposed in 1802, when it was presented to the Askesian Society by Luke Howard.
High clouds (Family A)
- Cirrocumulus
- Cirrus cloud
- Cirrostratus
Middle clouds (Family B)
- Altostratus
- Altocumulus
