Clouds are made of extremely small liquid water droplets or ice crystals suspended in the air. A “small cloud of water droplets” typically refers to the numerous tiny droplets within a cumulus or stratiform cloud, each about 5–50 micrometers in radius, far smaller than raindrops, which are on the order of 0.1–2 millimeters in diameter. The collective of these microdroplets gives visible cloudiness, while their individual weight and the air’s updrafts keep them aloft. Key points about small cloud droplets:
- Size and distribution: Most cloud droplets are on the order of tens of micrometers in diameter; a cloud contains many millions of such droplets, often ranging from a few to several hundred per cubic centimeter depending on the cloud type and conditions.
- Formation mechanism: Droplets form when water vapor in saturated air condenses onto microscopic particles (aerosols) in the atmosphere, creating countless tiny droplets that bright clouds visually compose. Updrafts within the cloud continuously lift air, counteracting settling due to gravity.
- Dynamics: Droplet growth occurs via collision and coalescence and by condensation as air parcels rise and cool; as droplets grow large enough, air resistance can no longer balance gravity, leading to precipitation in the form of rain or snow.
- Visual appearance: Clouds’ characteristic “fogginess” arises from the sheer number of droplets distributed through the air; droplets are much smaller than visible raindrops, which is why clouds look hazy rather than solid.
If you’re after a concise definition for everyday use: a small cloud of water droplets is a visible assembly of countless microscopic liquid water droplets (and sometimes ice crystals) suspended in air, typically formed by water vapor condensing onto aerosols and kept aloft by upward air currents.
