Reference Terms
from Wikipedia, the free encyclopedia
Cloud
A cloud is a visible mass of condensed droplets or frozen crystals suspended in the atmosphere above the surface of the Earth or another planetary body. Clouds form when the invisible water vapor in the air condenses into visible water droplets or ice crystals.
On Earth, the condensing substance is water vapor, which forms small droplets of water or ice crystals, typically 0.01 mm in diameter. When surrounded with billions of other droplets or crystals, they are 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 very efficiently, so that the intensity of the solar radiation decreases with depth into the cloud, hence the grey or even sometimes dark appearance of the clouds at their 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 be colored accordingly. In the near-infrared range, however, clouds would appear very dark because the water that constitutes the cloud droplets strongly absorbs solar radiation at these wavelengths.
Related Stories
1
2
Earth & Climate News
January 21, 2026
Jan. 21, 2026 A new building material developed by engineers at Worcester Polytechnic Institute could change how the world builds. Made using an enzyme that turns carbon dioxide into solid minerals, the material cures in hours and locks away carbon instead of ...
Jan. 21, 2026 Mountain regions around the world are heating up faster than the lands below them, triggering dramatic shifts in snow, rain, and water supply that could affect over a billion people. A major global review finds that rising temperatures are turning ...
Jan. 19, 2026 Plastic-coated fertilizers used on farms are emerging as a major but hidden source of ocean microplastics. A new study found that only a tiny fraction reaches beaches through rivers, while direct drainage from fields to the sea sends far more ...
Jan. 17, 2026 Tiny plastic particles drifting through the oceans may be quietly weakening one of Earth’s most powerful climate defenses. New research suggests microplastics are disrupting marine life that helps oceans absorb carbon dioxide, while also releasing ...
Jan. 15, 2026 New research shows tropical forests can recover twice as fast after deforestation when their soils contain enough nitrogen. Scientists followed forest regrowth across Central America for decades and found that nitrogen plays a decisive role in how ...
Jan. 15, 2026 In the rapidly disappearing Atlantic Forest, mosquitoes are adapting to a human-dominated landscape. Scientists found that many species now prefer feeding on people rather than the forest’s diverse wildlife. This behavior dramatically raises the ...
Jan. 14, 2026 For thousands of years, wildfires on Alaska’s North Slope were rare. That changed sharply in the 20th century, when warming temperatures dried soils and fueled the spread of shrubs, setting the stage for intense fires. Peat cores and satellite ...
Jan. 14, 2026 Scientists have identified a newly recognized threat lurking beneath the ocean’s surface: sudden episodes of underwater darkness that can last days or even months. Caused by storms, sediment runoff, algae blooms, and murky water, these “marine ...
Jan. 14, 2026 Earth’s oceans reached their highest heat levels on record in 2025, absorbing vast amounts of excess energy from the atmosphere. This steady buildup has accelerated since the 1990s and is now driving stronger storms, heavier rainfall, and rising ...
Jan. 13, 2026 Honey bees can normally keep their hives perfectly climate-controlled, but extreme heat can overwhelm their defenses. During a scorching Arizona summer, researchers found that high temperatures caused damaging temperature fluctuations inside hives, ...
Jan. 13, 2026 Scientists tracking Earth’s water from space discovered that El Niño and La Niña are synchronizing floods and droughts across continents. When these climate cycles intensify, far-apart regions can become unusually wet or dangerously dry at the ...
Jan. 12, 2026 Plastic pollution is not just in oceans and soil. Scientists have now found enormous amounts of microscopic plastic floating through urban air, far exceeding earlier estimates. Road dust and rainfall play a major role in moving these particles ...
Latest Headlines
updated 12:56 pm ET
Jan. 17, 2026 Scientists are uncovering a hidden and surprisingly complex earthquake zone beneath Northern California by tracking swarms of tiny earthquakes that are far too weak to feel. These faint tremors are ...
Jan. 16, 2026 Hydrogen cyanide, a toxic chemical, may have helped spark the chemistry that led to life. When frozen, it forms crystals with highly reactive surfaces that can drive unusual chemical reactions, even ...
Jan. 12, 2026 Microscopic ocean algae produce a huge share of Earth’s oxygen—but they need iron to do it. New field research shows that when iron is scarce, phytoplankton waste energy and photosynthesis ...
Jan. 10, 2026 Crystals hidden in Australia’s oldest rocks have revealed new clues about how Earth and the Moon formed. The study suggests Earth’s continents didn’t begin growing until hundreds of millions of ...
Jan. 7, 2026 Scientists have discovered that wildfires release far more air-polluting gases than previously estimated. Many of these hidden emissions can transform into fine particles that are dangerous to ...
Jan. 6, 2026 Earthquakes happen daily, sometimes with devastating consequences, yet predicting them remains out of reach. What scientists can do is map the hidden layers beneath the surface that control how ...
Jan. 6, 2026 When a huge earthquake struck near Kamchatka, the SWOT satellite captured an unprecedented, high-resolution view of the resulting tsunami as it ...
Jan. 5, 2026 A meltwater lake that formed in the mid-1990s on Greenland’s 79°N Glacier has been draining in sudden, dramatic bursts through cracks and vertical ice shafts. These events have accelerated in ...
Jan. 5, 2026 CO2 can stimulate plant growth, but only when enough nitrogen is available—and that key ingredient has been seriously miscalculated. A new study finds that natural nitrogen fixation has been ...
Jan. 4, 2026 Overfished coral reefs are producing far less food than they could. Researchers found that letting reef fish populations recover could boost sustainable fish yields by nearly 50%, creating millions ...