Clouds Tell All

By Derek Geise

OBJECTIVES

This activity will be used to allow students to observe clouds and the resulting weather they bring. The students will classify cloud types and use these classifications to forecast weather conditions. Students will be able to use investigations to enhance and integrate terms given to the various cloud types.

MATERIALS

  • Earth Science Book with Meteorology chapter for reference.
  • Weather forecasts
  • Cloud type pictures.

PROCEDURES

1) Knowledge, Observation, Data Collection.

Begin the activity by introducing how clouds are formed. Clouds are formed when water vapor in the air becomes visible. Water vapor becomes visible and thus clouds when the air is cooled as it rises. A good activity to demonstrate this is the cloud in a bottle activity which. accompanies this activity. The clouds tell all activity should be used as an enhancement to a lesson on clouds. The actual investigation will take a week and can be extended into two weeks or more. The more fronts moving through your area, the better. Explain to the students that they will be observing cloud types and coming up with a weather forecast based on their observations. Have the students observe the sky at least once a day for a week. The student should use a lab notebook to sketch cloud type, current weather, time, day, and any other useful information. There should be patterns emerging based on weather conditions and cloud types as to forecasting what clouds bring what weather. A cloud description and related weather phenomenon can be found attached to the back of this activity.

During class, have students break into groups and compare and confirm cloud types and weather conditions. Then have the class come back together and demonstrate the different cloud types, how they classified them and the weather associated with them.

2) Application

Next, have students find a partner to observe clouds with for the next week. This can be done in 5-10 minutes at the beginning of class. Have students use the current day's clouds to predict the next days weather. Use weather forecasts and have the students compare their forecasts with the ones provided by the national weather service, television news, or newspapers. A local meteorologist could be brought into the classroom as a guest to help with the forecasting and to demonstrate to students the use of Meteorology in our everyday lives.

3)Evaluation

Since there are no real right or wrong answers, the evaluation process would best be carried out by evaluating the students data collection procedures and forecasts. If all students do the required work and come away with a sense of what clouds are, what they can tell us, and how meteorology is an important, applicable and real science, then everyone gets an A!!!

CLOUD TYPES AND ASSOCIATED WEATHER

Cloud Reading 101

Below the major cloud types are described. Some of these clouds, when combined with wind from a certain direction, will tell you what weather to expect in the next 12 to 24 hours. For instance, if you see cirrus clouds and the wind is blowing from the north, expect fair weather. Forecasts generally hold for May through October, but can't take into account localized weather patterns.

High Level Clouds

High clouds typically form above 20,000 ft. (6,000 m) and are composed primarily of ice crystals, since the temperatures are so cold at such high elevations. These clouds are rather thin and usually white in appearance.

Types of High Level Clouds

The most common variation of high-level clouds are cirrus clouds. They are thin, whispy clouds composed of ice crystals. Cirrus generally ocur in fair weather and move from west to east across the sky, indicating the direction of the prevailing winds at their elevation. Wind from N: fair weather E: increasing cloudiness S: increasing clouds, showers W: fair weather.

Cirrostratus are sheetlike clouds composed of ice crystals. Even though cirrostratus can cover the entire sky and can be up to several thousand feet deep, they are relatively transparent, as the sun or the moon can be easily seen through them. Sometimes, the only indication of their presence is given by an observed halo (around the sun or moon).

Middle Level Clouds

Mid-level clouds have cloud bases typically between 6,500 to 23,000 ft (2,000 to 6,000 m). Because of their lower altitudes, they are Composed primarily of water droplets, however, when the temperatures are cold enough, they can be composed of ice crystals as well.

Types of Middle Level Clouds

Altocumulus clouds generally appear as puffy masses, or are sometimes aligned in parallel waves or bands. One part of the cloud is usually darker than the rest, which makes it distinguishable from the higher cirrocumulus. These clouds are a result of slow lifting that is common ahead of an advancing cold front, and are typically located about 3-4 km. above the ground. In the presence of rising air at cloud level, altocumulus take on the appearance Of "little castles", and these clouds are often seen on warm, humid summer mornings, sometimes followed by thunderstorms later in the afternoon. Winds from N: little change E: cloudy, possible showers S: showery W: possible rain clearing.

Alto stratus clouds have a more uniform and diffuse coverage where it is difficult to detect individual elements or features.. Winds from N: little change E: unsettled S: showery W: possible rain clearing.

Low Level Clouds

Low clouds are almost always comprised of water droplets, since their bases generally He below 6,500 ft (2000 m). The one exception occurs when the temperatures are cold enough and these clouds may contain ice particles and snow.

Types of Low Level Clouds

Nimbostratus clouds are typically dark grey and are associated with light to moderately falling rain or snow. Because of the failing precipitation, the sun or moon is not visible through nimbostratus, unlike with cirrostratus clouds, where the sun or moon can be seen. Cloud bases are often difficult to accurately determine, since a layer of fog commonly forms beneath and around the bases of these clouds.

Stratocumulus clouds are a low, lumpy layer of clouds that typically appears near sunset, and are the spreading remains of much larger cumulus clouds. They range in color from dark to light grey and can appear in rows, patches, or as rounded masses with breaks of clear sky in between. Rain or snow rarely fall from these clouds and they are different from altocumulus clouds since their individual elements are larger than those of their altocumulus counterparts. You can easily decipher the difference between the two cloud types by holding your hand at arm's length and pointing it towards the sky. Altocumulus elements are about the size of your thumb nail, while stratocumulus are about the size of your fist. Winds from N: clearing, cool E: stormy S: showery W: clearing.

Stratus clouds are usually the lowest of the low clouds. Stratus often appear as an overcast deck but can be scattered. The individual cloud elements have very ill-defined edges compared to most low cumuloform clouds.

Convective Clouds

Probably the most familiar of the classifications is the Cumulus Cloud, and the variety of shapes, sizes, and colors it is able to attain. Generated most commonly through either thermal convection or frontal lifting, that may begin the day as harmless-looking cumulus clouds, exists the potential for tremendous vertical development come afternoon. Sometimes to a height in excess of 39,000 ft (12,000 in), releasing incredible amounts of energy by the condensation of water vapor within the cloud itself.

Convective Cloud Types

Fair Weather Cumulus clouds have the appearance of floating cotton with a flat base and distinct outlines, while having a lifetime anywhere from 5-40 minutes. The color shading ranges from white to light gray, with bases that can be as low as 1,000 in above the ground, and have a diameter of about a kilometer or so. The cloud tops, likewise, are usually not very high and designate the limit of the rising air. Called cumulus humilis, these clouds show only slight vertical growth. However, given suitable conditions, what may initially begin as harmless Fair Weather Cumulus, can later develop into towering cumulus clouds that have an appearance resembling that of a cauliflower, with strong updrafts and possibly precipitation. Fair weather cumulus are distinguishable from stratocumulus by the fact that they are detached, while stratocumulus generally appear in patches or groups. The tops of fair weather cumulus have a domed-shape to them while in contrast, the tops of stratocumulus are flat. Winds from N: clearing and cool E: increasing cloudiness S: thunderstorms W: possible showers.

Cumulonimbus clouds are much larger and more vertically developed than the Fair Weather Cumulus. It can exist as a single towering cloud, or can even develop into a line of such towers, also known as a "squall line". Fueled by vigorous convection, which leads to strong vertical updrafts, sometimes in excess 50 (mi/hr), these clouds can climb vertically in the atmosphere to an altitude of 39,000 ft (12,000 in) or higher. The lower portion of the cloud is made up of water droplets, while at the cloud top, where temperatures are well below 0 degrees Celsius, there are primarily ice crystals. These, clouds are capable of developing into great thunderheads which contain all forms of precipitation-snowflakes, snow pellets, large raindrops, and sometimes hailstones. Lightning, thunder, and even violent tornadoes sometimes accompany intense cumulonimbus clouds. Winds from N: slow improvement E: stormy, then showers S: slow improvement W: showers, then clearing.

CLOUD IN A BOTTLE

Materials:

  • A jar
  • warm water
  • a plastic bag of ice that fits over the jar opening
  • a sheet of black paper
  • matches

Preparation: Tape the black paper on the back of the jar so you can't see through the jar. Fill the jar one third full of warm water. Fill the bag with ice and close the top of the bag with a tie or rubber band. Have matches ready.

Procedure: Light the match and hold it over the jar opening. After a few seconds, drop the match into the jar and cover the top of the jar with bag of ice. Observe what happens inside the jar.

Time needed: About 15 minutes

Questions:

  1. What formed in the jar?
  2. What processes led to the formation of the cloud?
  3. Why was the smoke from the match important to the formation of the cloud?
  4. Would cold water work?