Clouds can float because clouds are made up of tiny micron size water droplets that can float similar to dust particles in the air. Due to tiny size, the water droplets and ice crystals have low terminal velocity and hence, they fall very slowly. The continuous warm updrafts in the atmosphere also force clouds upwards and keep them floating.
How can clouds float?
Clouds weigh hundreds of tons, but have you ever wondered how do clouds float in the air?
The science behind the floating of clouds is a lot more complex than we think. There can be several reasons for the cloud to float in the air. Here are a few reasons why and how cloud float in the atmosphere.
Micron size water droplets
One of the reasons why clouds float is the tiny size of the water droplets. We know that clouds are formed when the water vapors in the air condense to water droplets and ice crystals. These water droplets have a radius of microns and are denser than that of air and dust. These water droplets and ice crystals are so tiny that the gravitation force has an almost negligible effect on them and they float similar to dust particles in the air. However, note that these water droplets do fall but they fall very slowly due to their tiny size.
You will be surprised to know that a typical cloud at an altitude of 10,000 feet has only 0.5g to 1g of water per cubic meter in it. These clouds are generally spread over hundreds of kilometers such that their total mass can be more than 1 million kilograms. For example, a cloud having 1 cubic kilometer of volume can weigh more than 500 tons.
1 cubic kilometer = 1 billion cubic meter
1 cubic kilometer of cloud has 0.5*1000,000,000 g of water (= 500,000 Kg)
Therefore, 1 km3 of cloud has mass of 500 tons.
Now imagine the mass of the clouds that are spread over thousands of miles. Even after having such a large mass they still float because of their large surface area. It is similar to a feather slowly falling as compared to a stone of the same mass.
Updrafts in the atmosphere
Another reason that causes clouds to float is updrafts in the atmosphere. Updrafts or vertical drafts are small scale upward current of rising air. These updrafts are caused due to the heat from the sun. The sunlight gets absorbed by the ground surface. Then, the surrounding air near the ground surface gets warm and rises up.
Updrafts can also occur at a hill or mountain when a wind rises up to climb the mountain. These rising winds add buoyancy to the cloud and hence the clouds float in the air.
Absorption of radiations by clouds
A lot of radiations from the sun are directly and indirectly (reflected from the earth’s surface) absorbed by the clouds. This heat absorption keeps these clouds warmer compared to their surrounding air. Thus, this warm temperature helps clouds to float.
Clouds can float but they can’t stay forever in the atmosphere. Eventually, when millions of water droplets combine together to form large water drops, gravity starts to dominant the effect of buoyancy. When these water drops become heavy enough, they fall to the ground in the form of rain or snow.
Read: 🌦️ Why Are Clouds White?
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