cloud in a jar

Frances points to the water vapor trapped in a clear glass jar.

cloud in a jar

cloud in a jar

april 21

What are clouds? Can you make one in your home? Join our STEAMwork science exploration for a lesson in water vapor with Frances, and see what you can create!

behind the science:

Clouds are formed when warm air rises, expands and then cools. Cool air can’t hold as much water vapor as warm air. The vapor will then begin to condense and form itself around dust particles that are floating in the air. When billions of these particles come together, they form a cloud.

how cloudy is it?

Total cloud cover is the fraction of the sky covered by all the visible clouds. There are different ways to calculate cloud cover. Meteorologists measure in oktas, or eighths of the sky. Try imagining the sky as 8 equal parts and then mentally rearranging the clouds you see so they are bunched together. How many sections are filled with clouds? How many sections are empty? The okta scale ranges from 0 – sky completely clear to 8 – sky completely overcast.

how much does a cloud weigh?

Scientists estimate that the density of one cumulus cloud is approximately 0.5 gram per cubic meter. Although clouds vary in size, an average cumulus cloud is approximately one kilometer across and one kilometer tall. One cubic kilometer (km3) cloud contains 1 billion cubic meters.

When we do the math: 1,000,000,000 x 0.5 = 500,000,000 grams of water droplets in our cloud. That is about 500,000 kilograms or 1.1 million pounds (about 551 tons). But, that “heavy” cloud is floating over your head because the air below it is even heavier— the lesser density of the cloud allows it to float on the dryer and more-dense air.