Cloud Formation

Water vapor, which is a result of evaporation, is one of the key components in the formation of a cloud. Cloud formation is a result of rising air; this occurs when the ground warms air, or when air is forced up when wind blows into the side of a terrain, such as a mountain. These two ways of air rising create different types of clouds. The former creates types including cumulus, cumulonimbus, mammatus, and stratocumulus clouds; and the latter creates lenticular and stratus clouds. Air may also rise when two large masses of air collide, giving them no choice but to go up.

In any case, rising air causes pressure and temperature to drop, making the water vapor within it condense. This occurs because as air rises, it expands due to the lower pressure. The temperature decreases at 9.8 degrees celsius per kilometer until saturation, at which the water condenses to form clouds. 

Water molecules found in the air are too small to condense on their own. Therefore, particles found in abundance in the atmosphere become the surface on which these water molecules condense, called cloud condensation nuclei. Oftentimes particles of soil, dust, pollen, salt crystals and smoke become cloud condensation nuclei. These particles are at least one micrometer and 1/100 size of cloud droplet. They also must be hygroscopic, or able to attract and absorb water from the environment. Despite these particles forming the core of each cloud droplet, clouds are still considered to be pure water. 

When more water condenses than evaporates, clouds grow. When the opposite occurs, clouds dissipate. As the atmosphere is constantly changing, condensation and evaporation are constantly occurring on cloud condensation nuclei, leading to the formation and dissipation of clouds. 

References:

Clouds and How They Form. (n.d.). University Corporation for Atmospheric Research-Center for Science Education. Retrieved March 30, 2024, from https://scied.ucar.edu/learning-zone/clouds/how-clouds-form

How Clouds Form. (n.d.). National Oceanic and Atmospheric Administration. Retrieved March 30, 2024, from https://www.noaa.gov/jetstream/clouds/how-clouds-form