Clouds and Weather Flashcards
https://scied.ucar.edu/webweather/clouds/cloud-types
Altocumulus Clouds
(“Layers of bread rolls”)
mid-level, grayish-white with one part darker than the other. Altocumulus clouds usually form in groups and are about one kilometer thick. Altocumulus clouds are about as wide as your thumb when you hold up your hand at arm’s length. If you see altocumulus clouds on a warm, humid morning, there might be a thunderstorm by late afternoon.
Altostratus clouds
(“The boring clouds”)
mid-level, gray or blue-gray clouds that usually covers the whole sky. The Sun or moon may shine through an altostratus cloud, but will appear watery or fuzzy. If you see altostratus clouds, a storm with continuous rain or snow might be on its way. Occasionally, rain falls from an altostratus cloud. If the rain hits the ground, then the cloud has become a nimbostratus.
Cirrocumulus clouds
(“Regularly spaced cloudlets, often rippled”)
Small rounded puffs that usually appear in long rows high in the sky. Cirrocumulus are usually white, but sometimes appear gray. They are the same size or smaller than the width of your littlest finger when you hold up your hand at arm’s length. When these clouds cover a lot of the sky, they can look like the scales of a fish, which is it is called a “mackerel sky.” Cirrocumulus are common in winter and indicate fair, but cold, weather.
Cirrostratus clouds
(“Delicate cloud streaks”)
high, thin sheet-like thin clouds that usually cover the entire sky. The clouds are so thin that the Sun or moon can sometimes shine through and appear to have a halo as light hits the ice crystals and bends. The halo is the width of your hand held at arm’s length. Cirrostratus clouds usually come 12 to 24 hours before a rain or snowstorm.
Cirrostratus clouds are difficult to spot and appear as a pale, milky lightening of the sky. Cirrostratus clouds never block out the sun completely, but rather produce a variety of optical effects.
Cirrus clouds
(“Delicate cloud streaks”)
made of ice crystals and look like long, thin, wispy white streamers high in the sky. They are commonly known as “mare’s tails” because they are shaped like the tail of a horse. Cirrus clouds are often seen during fair weather. But if they build up larger over time and are followed by cirrostratus clouds, there may be a warm front on the way.
Cirrus clouds are the highest of all clouds and are composed entirely of ice crystals. Cirrus clouds are precipitating clouds, although the ice crystals evaporate high above the earth’s surface. The crystals, caught in 100-150 mph winds create wisps of cloud.
Cumulonimbus clouds
(“The towering thunderclouds that scare us senseless”)
have vertical growth and can grow up to 10 km high. At this height, high winds will flatten the top of the cloud out into an anvil-like shape. Cumulonimbus clouds are thunderstorm clouds and are associated with heavy rain, snow, hail, lightning, and sometimes tornadoes.
Three critical conditions for cumulonimbus formation: • Ready supply of warm, moist air, which rises at speeds of up to 25-70 mph
- Tropospheric winds need to increase considerably with height to encourage it to slant forward
- The atmosphere around the cloud needs to be “unstable” – no temp. inversions here
Nimbostratus
(“Rainy day clouds”)
Nimbostratus clouds are dark gray, have ragged bases and sit low in the sky. Nimbostratus clouds are associated with continuous rain or snow. Sometimes they cover the whole sky and you can’t see the edges of the cloud.
It is a thick, wet blanket with a ragged base caused by the continual precipitation
Cumulus
Cumulus clouds have vertical growth. They are puffy white or light gray clouds that look like floating cotton balls. Cumulus clouds have sharp outlines and a flat base at a height of 1000m. They are generally about one kilometer wide which is about the size of your fist or larger when you hold up your hand at arm’s length to look at the cloud. Cumulus clouds can be associated with fair or stormy weather. Watch for rain showers when the cloud’s tops look like cauliflower heads.
There are three species of cumulus clouds: • humilis are wider than they are tall • mediocris are as wide as they are tall • congestus are taller than they are wide
Often called “fair-weather” clouds, cumulus clouds are common over land on sunny days, when the sun heats the land creating thermal convection currents Each thermal is distinct, and, consequently, each cumulus cloud is a distinct puff
Stratocumulus
(“The low, puffy layers”)
Stratocumulus clouds are low, lumpy, and gray. Sometimes they line up in rows and other times they spread out. Only light rain (usually drizzle) falls from stratocumulus clouds. To distinguish between a stratocumulus and an altocumulus cloud, point your hand toward the cloud. If the cloud is about the size of your fist, then it is stratocumulus.
Fast Facts: Typical Altitude: 2,000-6,500 ft. Location: Worldwide – very common Precipitation: Occasional light rain, snow Composition: Liquid water Formation: Spreading and joining of cumulus clouds below a temperature inversion, wind turbulence in a stratus layer Similar to cumulus clouds in form and composition, stratocumulus clouds are textured and puffy, but also joined into a semi-continuous layer Stratocumulus clouds usually form from cumulus or stratus clouds
Stratus
(“The clouds that weigh heavily on your mood”)
Stratus clouds are low and have a uniform gray in color and can cover most or all of the sky. Stratus clouds can look like a fog that doesn’t reach the ground. Light mist or drizzle is sometimes falling when stratus clouds are in the sky.
Stratus clouds are the lowest forming and are often called fog or mists when they are earth-bound Stratus clouds are formed when a large air mass cools at the same time (e.g. – a warm air parcel drifts into or above a cooler region)
Highest Clouds?
The highest clouds in the atmosphere are cirrocumulus, cirrus, and cirrostratus.
Cumulonimbus clouds can also grow to be very high.
Mid-level clouds?
Mid-level clouds include altocumulus and altostratus.
Lowest clouds?
The lowest clouds in the atmosphere are stratus, cumulus, and stratocumulus.
What are the layers of the atmosphere?
Thermosphere (top) - extends to space; ISS orbits here Mesosphere Stratosphere - ozone here Troposphere (bottom) - life
What is relative humidity?
A measure of the extent to which air is saturated, expressed as a percentage.
