Know Your Clouds (With Photos)
Do you know very much about clouds?
I've often wondered what the different types of clouds were, but for some reason never looked them up.
Earlier today I noticed some awesome clouds in the sky, yet I had no way to describe them, except by trying to explain what they looked like. If I'd known what type of cloud they were, or at least had something to go on, it would have made my Google search that much easier.
Before getting into the different cloud types though, I think it's important to have a general grasp of what clouds are and how they form.
- What Are Clouds?
Clouds are simply a large collection of tiny water droplets or ice crystals that are so light they can float in air.
- How Do Clouds Form?
All air contains water, and near the ground it's usually in the form of an invisible gas called water vapor. The air is warmed by the sun, and as the warm air rises, it expands and cools. Since cool air can't hold as much water vapor as warm air, the air becomes saturated (reaches its dew point) and can't hold any more water. The excess water vapor condenses onto tiny pieces of dust, ice, or salt that are floating in the air, which forms small droplets of water. When billions of these droplets come together, a cloud is formed.
- Why Do Clouds Form At Different Heights?
The amount of water vapor available, the temperature at that altitude, the wind, and other factors determine whether clouds form, and also which types will form. The most basic factor, though, is at what height the air reaches its dew point and becomes saturated. As we'll see below, certain criteria must exist for each specific cloud type to develop.
Clouds are divided into four families, with each family representing a different height in the troposphere.
The troposphere is the lowest portion of the Earth's atmosphere. This area contains 99% of the atmosphere's water vapor, which is what clouds are made of.
The four main cloud types are:
- Stratus: Low level clouds (altitudes of 0-1 mi / 0-2 km)
- Alto: Medium level clouds (altitudes of 1-4 mi / 2-7 km)
- Cirrus: High level clouds (altitudes of 3-8 mi / 5-13 km)
- Clouds with vertical development (altitudes of 0-8 mi / 0-13 km)
Low Level Clouds (Stratus)
Altitudes of 0-1 mi / 0-2 km (Up to 6,500 feet)
- Stratus Clouds (St)
Flat, hazy, featureless, evenly gray, low layer clouds that may produce fog, light drizzle, or snow
Variations and sub-species: fractus (frazzled); nebulosus (fog, veil-like); opacus (dark); translucidus (translucent); undulatus (wavelike); and praecipitatio (with precipitation)
- Stratocumulus Clouds (Sc)
Large, dark, rounded clouds that form groups, lines, or waves
Variations and sub-species: castellanus (turret-like); duplicatus (multi-layered); lenticularis (lens-shaped); stratiformis (layered); lacunosus (perforated, round holes); opacus (dark); perlucidus (transparent); radiatus (parallel bands); translucidus (translucent); undulatus (wavelike); mamma (rounded growths on bottom side of cloud); praecipitatio (with precipitation); and virga (shaft of precipitation)
Medium Level Clouds (Alto)
Altitudes of 1-4 mi / 2-7 km (From 6,500 feet to 18,000 feet)
- Altostratus Clouds (As)
Dense, uniform, gray sheetlike clouds that let the sun shine through either a little bit or not at all
Variations and sub-species: duplicatus (multi-level); opacus (dark); radiatus (parallel bands); translucidus (translucent); undulatus (wavelike); mamma (rounded growths on bottom side of cloud); pannus (with frazzles); praecipitatio (with precipitation); and virga (shaft of precipitation)
- Altocumulus Clouds (Ac)
Gray, compound bundles, globular masses, or rolls of clouds in layers or patches
Variations and sub-species: castellanus (turret-like); duplicatus (multi-level); floccus (flaked puffy); lenticularis (lens-shaped); stratiformis (layered); lacunosus (perforated, round holes); opacus (opaque); perlucidus (transparent); radiatus (parallel bands); translucidus (translucent); undulatus (wavelike); mamma (rounded growths on bottom side of cloud); and virga (shaft of precipitation)
High Level Clouds (Cirrus)
Altitudes of 3-8 mi / 5-13 km (Above 18,000 feet)
- Cirrus (Ci)
Thin, wispy, threadlike, white feathery clouds of ice crystals that resemble ringlets or hair curls
Variations and sub-species: castellanus (turret-like); duplicatus (multi-level); fibratus (fibrous); floccus (flaked puffy); intortus (interlaced); spissatus (dense); uncinus (hooked); radiatus (parallel bands); vertebratus (fishbone-like); and mamma (rounded growths on bottom side of cloud)
- Cirrostratus (Cs)
Thin, uniform, translucent veil of ice crystal clouds that are difficult to detect, except when they form a halo around the sun or moon
Variations and sub-species: duplicatus (multi-level); fibratus (fibrous); nebulosus (fog, veil-like);and undulatus (wavelike)
- Cirrocumulus (Cc)
Small, fleecy clouds made of ice crystals, often forming large patches
Variations and sub-species: castellanus (turret-like); floccus (flaked puffy); lenticularis (lens-shaped); stratiformis (layered); lacunosus (perforated, round holes); undulatus (wavelike); mamma (rounded growths on bottom side of cloud); and virga (shaft of precipitation)
Clouds With Vertical Development
Altitudes of 0-8 mi / 0-13 km (Troposphere)
- Cumulus (Cu)
Puffy, cotton-like, heaped white clouds with a flat base that may appear alone, in lines, or in clusters
Variations and sub-species: arcus (horizontal arc); congestus (huge, towered); fractus (frazzled); humilis (low); mediocris (moderate); radiatus (parallel bands); pannus (with frazzles); pileus (with cap); praecipitatio (with precipitation); tuba (funnel cloud or tornado); velum (with veil); and virga (shaft of precipitation)
- Cumulonimbus (Cb)
Towering, tall, dense, vertical clouds often associated with thunderstorms, sometimes called a thunderhead
Variations and sub-species: arcus (horizontal arc); calvus (smooth); capillatus (haired, fibrous); incus (anvil shaped); pileus (with cap); tuba (funnel cloud or tornado); velum (with veil); and virga (shaft of precipitation)
- Nimbostratus (Ns)
Gray, indistinct, dark, and formless clouds that produce precipitation
Variations and sub-species: pannus (with frazzles); praecipitatio (with precipitation); and virga (shaft of precipitation)
Special Cloud Types
These are cloud formations that are often rare, occurring only in very specific and narrow circumstances. They are often the most fantastic displays, as you will see below.
Low, horizontal, arced clouds, including roll clouds and shelf clouds.
Shelf clouds are low, horizontal, wedge shaped, arced clouds that are generally associated with the front of a thunderstorm.
Roll clouds are long, tube-like clouds often associated with cold sea breezes or cold fronts.
This type of cloud formation is one of the most amazing and awe-inspiring cloud types, often resembling rippled cloth or intricately textured, highly unusual flowing patterns.
Undulatus Asperatus, as it's often called, is the newest cloud type to be classified. After 30 years of study, it was officially considered a new type of cloud formation in 2009.
They are common in the Great Plains of the United States, often following thunderstorms.
- Circumhorizontal Arc
This is a type of cloud phenomenon that often makes people do a double-take to make sure they just saw what they think they saw.
Sometimes called Fire Rainbows, these are neither rainbows, nor do they have anything to do with fire. They are an optical phenomenon involving the reflection of the sun off of ice crystals.
The sun must be high in the sky, high level (cirrus) clouds must be present, and in addition, the cirrus clouds must contain plate-shaped ice crystals. When all of these factors combine, a rainbow-colored halo forms in the clouds.
Cumulonimbus Incus is a cloud in the shape of an anvil or mushroom cloud.
This is a cumulonimbus cloud that has reached stratospheric stability, meaning that it's reached a point where the air ceases to continue cooling as the cloud increases in height.
These are considered mature thunderstorm cloud formations, often producing dangerous weather like lightning, hail, heavy rain, flash floods, and gale force winds.
These clouds are stationary and take the shape of a rounded lens or almond; some would even say they sort of resemble a UFO.
They're often formed perpendicular to the wind direction and are associated with mountains.
Large standing waves sometimes form when moist air passes over mountain ranges. If the crests of the waves correspond with a drop in temperature to the dew point (the temperature at which water condenses to form clouds), the outcome is often a lenticular cloud formation.
Sometimes also called Mammatocumulus, the literal translation is "mammary cloud" or "breast cloud." The formations are rounded growths, or pouches, hanging on the underside of the clouds. The shape is similar to a human breast (or as close as clouds come, anyway.)
These cloud formations are associated with heavy thunderstorms, and most often are found under altocumulus, altostratus, stratocumulus, and cirrus clouds, in addition to volcanic ash clouds.
- Polar Mesospheric
These are known as noctilucent (night) clouds and are most easily observed from space, where they can be seen "edge-on" against a darker background.
The peak season for this type of formation is 20 days after the summer solstice in both hemispheres.
These formations increase in both brightness and frequency with increasing latitude (from 60 to 85 degrees.)