4.02 Analyze the formation of clouds and their relation

to weather systems

Essential Question

Clouds are made up of millions of tiny droplets of water and ice.

Each of these droplets of water is smaller than a grain of flour, and they are so light that they can float on air.

When pilots in airplanes fly through clouds they can see nothing but clouds. It's like being inside a thick fog or a steamy room.

How do Clouds form?

Clouds form when the relative humidity 100%.

Humidity is the amount of water vapor in the air. So when the air is very saturated with water vapor (can’t hold anymore “invisible water”) the relative humidity is 100%.

How are clouds made?

These 3 conditions are necessary for clouds to form:

•evaporation• cooling

•condensation

The air around us contains water vapor (water vapor is a gas). Water is constantly evaporating into the air.

When this air rises it gets cooler and the water vapor condenses (it turns

into tiny drops of water) to form clouds. FYI: condensation is the

reverse of evaporation.

What do clouds tell us?

• Clouds just don’t happen - there’s always a reason

• A particular cloud’s shape and location depend on (and can therefore tell us about):- the movement of the air- amount of water vapor in air- stability (flat clouds = stable air while puffy clouds = unstable air)

Clouds are named according to their altitude (how high up something is in the sky) and their general shape

How are clouds named?

These are low level clouds, usually ground level to 5,000 feet. They appear as unbroken sheets of low gray clouds. They are bringing light rain, light snow, or drizzle. (Fog is a stratus cloud on the ground.)

These clouds are white, puffy heaps that look like cotton balls or cauliflower . They are also low clouds from ground level to 5, 000 feet. These clouds indicate that the weather will be good.

These clouds indicate an immediate threat of bad weather. It could be a sprinkle or heavy precipitation. If they are at the beginning of a cold front, gusty winds or a thundershower may follow.

Nimbus clouds are storm clouds. They are dark and gray.

Cirrus Clouds are the highest and whitest in the sky; 20,000 to 40,000 feet . They are thin and made up of ice droplets. They signal the weather will be changing.

What makes rain?

Remember, clouds are made up of millions of droplets of water and ice that are very small and very light. They are so small and light that they can float on air. When these small droplets collide with each other, they join together. They get larger and heavier until they get too heavy to float. Then they fall to the ground as raindrops.

Credits

• Fuller Photo Galleryhttp://www.fullerphotos.co.uk/storm2.htm

• Cloud and Weather Photo Galleryhttp://www.jburroughs.org/science/astromet/clouds/gallery.html

• Enchanted Learninghttp://www.enchantedlearning.com/subjects/astronomy/planets/earth/clouds/