Beyond merely noticing how cloudy it is, how often do we really pay attention to clouds?

The variety and patterns of different types of clouds differ from time to time and throughout the day depending on wind, weather and light.

For centuries sailors observed clouds practically as aids to weather prediction. Today meteorologists study clouds for a multitude of practical reasons, but they can be enjoyed merely as nature’s paintings on the sky canvas.

Clouds are such simple things, nothing more than colloidal suspensions of water droplets or ice crystals in air, but they are the key to life outside the oceans. Without clouds there is no rain, and without rain there is only arid land where nothing lives.

Clouds play many roles in the global weather and climate systems. They are things of wonder not just because of the variety of their shapes and textures, but also because we cannot touch them to verify their nature with that most primal sense.

Combinations of three basic structures of clouds (cumulus, stratus and cirrus) at three ranges of altitudes (low, medium and high) give us the infinite possibilities of different skies that we might see on a given day.

Cumulus clouds are the cottony clumps of individual cloud masses with flat bottoms and vertical structure like rising domes or towers. They seem to pile up or accumulate and often have cauliflowerlike tops.

Stratus clouds are sheets or layers of clouds that might cover large areas of the sky with minor breaks but no individual cloud units.

Cirrus clouds are high- altitude, wispy or feathery veil-like patches.

All clouds have one of these three basic forms, or combinations and modifications of them. Common modifications are clouds of vertical development that span more than one altitude range, and dark nimbus clouds that are associated with precipitation.

With these various combinations there are 10 common types of clouds. To see examples and learn more about clouds, visit The Plymouth State University Cloud Boutique at vortex.plymouth.edu/cloudboutique.

High-altitude clouds are cirrus, cirrostratus and cirrocumulus.

At midlevel are altocumulus and altostratus, which look like miniature versions of their basic forms.

Low-level clouds are stratus, stratocumulus and nimbostratus. The latter are the slate skies that often associate with rainy days.

Clouds of vertical development are cumulus and cumulonimbus. The latter can reach tens of thousands of feet and spread out on top to form an “anvil head.” Cumulonimbus clouds are storm clouds associated with rain, thunder, lightning, hail and tornadoes.

Most clouds have relatively flat bottoms that represent the level at which water vapor condenses. Rising air cools, and when it reaches the dew point (where relative humidity is 100%), water vapor condenses into microdroplets.

Condensation actually begins at around 75% relative humidity depending on the type, size and number of microparticles of condensation nuclei such as salt, dust and smoke.

The bottoms and edges of the clouds are not as sharply defined as they look from a distance, as you may have noticed when driving up a mountain road into the clouds.

Clouds of different types can occur in different layers simultaneously. A sunrise or sunset sky full of various types of clouds at different layers, each layer changing from glowing orange and red to indigo, is one of nature’s most awesome displays.

Richard Brill is a retired professor of science at Honolulu Community College. His column runs on the first and third Fridays of the month. Email questions and comments to brill@hawaii.edu.