Whenever you see the Cloud, you might be wonder how these clouds are formed and why they sometimes look like a wavy sand beach or puffy like cotton candy.
Clouds are made up of very light water droplets or ice crystals. These particles can float in the air. Many water droplets formed together scatter reflect sunlight and you see a white cloud, but with a dark or gray cloud, the sunlight is scattered in all directions instead of reflected.
When warmer air rises through colder regions, the air cools and the moisture in the air starts to condense around nucleation points into many droplets of water. There are around 350 billion droplets of water in a cubic foot of a cloud.
This high density of water vapor leads to the formation of clouds, and the resulting conditions and weather patterns lead to many different kinds of clouds.
The clouds are classified into 10 different types: cumulus, cumulonimbus, stratus, stratocumulus, altocumulus, altostratus, nimbostratus, cirrus, cirrocumulus, and cirrostratus.
To better understand what cloud you’re observing, it’s best to get to know these 10 different cloud types based on their different species, varieties, and features. Knowing how they form, their altitude levels (high, middle, or low base), and what makes each cloud type unique and different from one another will also be helpful.
High Level Cloud
High-level clouds occur above about 20,000 feet and are given the prefix “cirro.” Due to cold tropospheric temperatures at these levels, the clouds are primarily composed of ice crystals and often appear thin, streaky, and white (although a low sun angle, e.g., near sunset, can create an array of colors on the clouds). The three main types of high clouds are cirrus, cirrostratus, and cirrocumulus.
1. cirrus
Cirrus clouds are short, detached, hair-like clouds found at high altitudes. These delicate clouds are wispy, with a silky sheen, or look like tufts of hair. In the daytime, they are whiter than any other cloud in the sky. While the Sun is setting or rising, they may take on the colors of the sunset.
Cirrus clouds usually form from the ascent of dry air, making the small quantity of water vapor in the air undergo deposition into ice (to change from a gas directly into a solid). Cirrus is made up completely of ice crystals, which provide their white color and form in a wide range of shapes and sizes.
Cirrus clouds can also form through contrails, the vapor trails left by planes as they fly through a dry upper troposphere. These streaks can spread out and become cirrus, cirrostratus, and cirrocumulus.
Globally, they form anywhere between 4,000 and 20,000 meters (13,000 and 66,000 feet) above sea level, with the higher elevations usually in the tropics and the lower elevations in more polar regions.
When You’ll See Them
Cirrus clouds typically occur in fair weather. They can also form ahead of warm fronts and large-scale storms like nor’easters and tropical cyclones, so seeing them can also indicate storms may be coming.
NASA’s Earthdata site quotes a proverb that sailors learned to warn them of coming rainy weather: “Mares’ tails (cirrus) and mackerel scales (altocumulus) make lofty ships to carry low sails.”
2. Cirrocumulus
Cirrocumulus clouds are made up of lots of small white clouds called cloudlets, which are usually grouped together at high levels. Composed almost entirely of ice crystals, the little cloudlets are regularly spaced, often arranged as ripples in the sky.
Cirrocumulus can sometimes appear to look like the scaly skin of a fish and is referred to as a mackerel sky.
Cirrocumulus cloudlets are usually made up of both ice and ‘supercooled’ water. This means that the water remains a liquid, even at temperatures well below 0oC. They form when turbulent vertical currents meet a cirrus layer, creating the puffy cumulus shape.
Cirrocumulus clouds can also form through contrails, the vapor trails left by planes as they fly through a dry upper troposphere. These streaks can spread out and become cirrus, cirrostratus, and cirrocumulus.
They usually occur at an altitude of 5 to 12 km (16,000 to 39,000 ft). Like lower-altitude cumuliform and stratocumuliform clouds, cirrocumulus signifies convection.
When You’ll See Them
Cirrocumulus clouds are rare and relatively short-lived, but you’ll see them in winter or when it’s cold but fair.
3. Cirrostratus
Cirrostratus are transparent high clouds, which cover large areas of the sky. They sometimes produce white or colored rings, spots, or arcs of light around the Sun or Moon, which are known as halo phenomena. Sometimes they are so thin that the halo is the only indication that a cirrostratus cloud is in the sky.
Cirrostratus clouds can span thousands of miles, can be smooth or fibrous, and are often fringed with cirrus clouds. Shadows will normally still be cast by the Sun when shining through cirrostratus clouds, which can help distinguish them from similar altostratus clouds.
Cirrostratus are formed As a result of slowly rising air, cirrostratus clouds can form. Usually generated at the forefront of frontal weather systems, the movements of cirrostratus can be used to predict what the weather will do in the next 24 hours.
Cirrostratus clouds can also form through contrails, the vapor trails left by planes as they fly through a dry upper troposphere. These streaks can spread out and become cirrus, cirrostratus, and cirrocumulus.
Cirrostratus is usually located above 5.5 km (18,000 ft). Its presence indicates a large amount of moisture in the upper troposphere. Clouds resembling cirrostratus occasionally form in polar regions of the lower stratosphere.
When You’ll See Them
Cirrostratus indicate that a large amount of moisture is present in the upper atmosphere. They’re also generally associated with approaching warm fronts.
Middle-level Cloud
Middle-level Clouds are composed of ice crystals and water droplets in the middle region of the atmosphere, from 2,000 – 6,000 meters (6,500 to 23,000 feet); include altocumulus, altostratus, nimbostratus, and portions of cumulus and cumulonimbus clouds.
4. Altocumulus
Altocumulus clouds are small mid-level layers or patches of clouds, called cloudlets, which most commonly exist in the shape of rounded clumps. There are many varieties of altocumulus, however, meaning they can appear in a range of shapes. Altocumulus are made up of a mix of ice and water, giving them a slightly more ethereal appearance than the big and fluffy lower-level cumulus.
Altocumulus clouds can form in several ways, such as;
- Formation through the breakup of altostratus
- The lifting of moist air pockets which are cooled by gentle turbulence
- Mountainous terrain produces atmospheric waves from which clouds can form.
The presence of shading can help tell the difference between altocumulus and cirrocumulus. Cirrocumulus clouds are white and tiny, but altocumulus clouds can be white or grey with shaded sides.
Altocumulus generally forms at about 2,000 to 6,100 m (6,600 to 20,000 ft) above ground level, a similar level to altostratus formations, and satellite photography has revealed that the two types of cloud can create formations that can stretch for thousands of square miles
When You’ll See Them
Altocumulus are often spotted on warm and humid mornings, especially during summer. They can signal thunderstorms to come later in the day. You may also see them ahead of cold fronts, in which case they signal the onset of cooler temperatures.
5. Altostratus
Altostratus are large mid-level sheets of thin cloud. Usually composed of a mixture of water droplets and ice crystals, they are thin enough in parts to allow you to see the Sun weakly through the cloud. They are often spread over a very large area and are typically featureless.
Altostratus layers are often composed of both water and ice and usually form when a layer of cirrostratus descends from a higher level. The Sun often cannot cast shadows when shining through altostratus clouds. These layers can sometimes contribute to the formation of optical effects such as coronas and iridescence.
Altostratus clouds are mid-level clouds that form from 2,000 to 4,000 meters (6,600 to 13,000 ft) above sea level in polar regions. In temperate or Tropical regions, the ceiling increases drastically, allowing altostratus clouds to form up to 8000 meters (26,000 ft ) and can cover hundreds of kilometers of the Earth’s surface.
When You’ll See Them
Altostratus clouds tend to form ahead of a warm or occluded front. They can also occur together with cumulus at a cold front.
6. Nimbostratus
Nimbostratus clouds are dark, grey, featureless layers of cloud, thick enough to block out the Sun. Producing persistent rain, these clouds are often associated with frontal systems provided by mid-latitude cyclones. These are probably the least picturesque of all the main cloud types.
Nimbostratus clouds form through the deepening and thickening of an altostratus cloud, often along warm or occluded fronts. These clouds extend through the lower and mid-layers of the troposphere bringing rain to the surface below.
These mid-level clouds are often accompanied by continuous moderate rain or snow and appear to cover most of the sky. Nimbostratus will often bring precipitation which may last for several hours until the associated front passes over.
If there is hail, thunder, or lightning present it is a cumulonimbus cloud rather than nimbostratus.
When You’ll See Them
Nimbostratus is the quintessential rain cloud. You’ll see them whenever steady rain or snow is falling (or is forecast to fall) over a widespread area.
Low-level cloud
Low clouds occur below 6500 feet, and normally consist of liquid water droplets or even supercooled droplets, except during cold winter storms when ice crystals (and snow) comprise much of the clouds.
The two main types of low clouds include stratus, which develop horizontally, and cumulus, which develop vertically.
7. Cumulus
Cumulus clouds are detached, individual, cauliflower-shaped clouds usually spotted in fair weather conditions. The tops of these clouds are mostly brilliant white tufts when lit by the Sun, although their base is usually relatively dark.
All cumulus clouds develop because of convection. As air heated at the surface is lifted, it cools and water vapor condenses to produce the cloud. Throughout the day, if conditions allow, these can grow in height and size and can eventually form into cumulonimbus clouds.
Along coastlines, cumulus may form over land during daylight hours as a sea breeze brings in moist air, which is then warmed by the surface. This effect reverses overnight as the sea becomes warmer than the land and cumulus forms over the sea.
Cumulus clouds are low-level clouds, generally less than 2,000 m (6,600 ft) in altitude unless they are the more vertical cumulus congestus form. Cumulus clouds may appear by themselves, in lines, or in clusters.
When You’ll See Them
Cumulus clouds develop on clear, sunny days when the sun heats the ground directly below (a phenomenon known as diurnal convection). This is where they get their nickname of “fair weather” clouds. They appear in the late morning, grow, and then disappear toward evening.
8. Cumulonimbus
Cumulonimbus clouds are menacing-looking multi-level clouds, extending high into the sky in towers or plumes. More commonly known as thunderclouds, cumulonimbus is the only cloud type that can produce hail, thunder, and lightning. The base of the cloud is often flat, with a very dark wall-like feature hanging underneath, and may only lie a few hundred feet above the Earth’s surface.
Cumulonimbus clouds are born through convection, often growing from small cumulus clouds over a hot surface. They get taller and taller until they represent huge powerhouses, storing the same amount of energy as 10 Hiroshima-sized atom bombs. They can also form along cold fronts as a result of forced convection, where milder air is forced to rise over the incoming cold air.
When You’ll See Them
Cumulonimbus clouds are thunderstorm clouds, so if you see one you can be sure there’s a nearby threat of severe weather (such as short but heavy periods of rainfall, hail, and possibly even tornadoes).
9. Stratocumulus
Stratocumulus clouds are low-level clumps or patches of cloud varying in color from bright white to dark grey. They are the most common clouds on earth recognized by their well-defined bases, with some parts often darker than others. They usually have gaps between them, but they can also be joined together.
Stratocumulus clouds usually form from a layer of stratus cloud breaking up. They are indicators of a change in the weather and are usually present near a warm, cold, or occluded front.
When You’ll See Them
You’re likely to see stratocumulus on mostly cloudy days. They form when there’s weak convection in the atmosphere.
10. Stratus
Stratus clouds are low-level layers with a fairly uniform grey or white color. Often the scene of dull, overcast days in its ‘nebulosus’ form, can persist for long periods of time. They are the lowest-lying cloud type and sometimes appear at the surface in the form of mist or fog.
Stratus clouds form in calm, stable conditions when gentle breezes raise cool, moist air over colder land or ocean surfaces. These clouds can exist in a variety of thicknesses and are sometimes opaque enough to darken days, allowing for little light to pass through.
When You’ll See Them
Stratus clouds are seen on dreary, overcast days and are associated with light mist or drizzle.