Related topics: climate change · earth · climate models · climate · sunlight

How do you know where volcanic ash will end up?

When the Eyjafjallajökull volcano in Iceland erupted in April 2010, air traffic was interrupted for six days and then disrupted until May. Until then, models from the nine Volcanic Ash Advisory Centres (VAACs) around the ...

Ice Age testing reveals challenges in climate model sensitivity

Key to the usefulness of climate models as tools for both scientists and policymakers is the models' ability to connect changes in atmospheric greenhouse gas levels to corresponding shifts in temperature. Equilibrium climate ...

Seeding ice clouds with wildfire emissions

For anyone who has ever witnessed a raging wildfire, ice is probably the last thing that comes to mind when recalling the experience. Yet nature works in mysterious ways, and researchers are beginning to reveal a link between ...

Cold dust cores in the central zone of the Milky Way

The Milky Way's central molecular zone (CMZ) spans the innermost 1600 light-years of the galaxy (for comparison, the Sun is 26,600 light-years away from the galactic center) and includes a vast complex of molecular clouds ...

page 1 from 40


A cloud is a visible mass of droplets or frozen crystals suspended 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 color of their environment or background and clouds illuminated by non-white light, such as during sunrise or sunset, may appear colored accordingly. In the near-infrared range, clouds look darker because the water that constitutes the cloud droplets strongly absorbs solar radiation at those wavelengths.

This text uses material from Wikipedia, licensed under CC BY-SA