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The making of a cloud

Clouds affect us every day, no matter the weather. But what exactly are clouds and how do they form? And how can they help us predict severe storms, the availability of water, and our future climate?


Created by NOVA.

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Video transcript

Most of the time if we pay attention to clouds at all. It's because of their effect on our local weather or Maybe it's because they make a sunset prettier But what you might, not know is that clouds affect us every day even if we're staring at a clear blue sky? The clouds we [see] when we look out the window our important components of a complex global weather system They play a key role in Earth's water cycle carrying huge amounts of Fresh water and dropping it as precipitation and Depending on their properties and where and when they form clouds can have dramatic effects on our climate Influencing the locations and severity of floods and droughts and even the temperature of our planet as a whole So by understanding clouds we can better predict severe storms the global Distribution of fresh water and the course of climate change, but what exactly are clouds and how do they [form]? all clouds share the same basic ingredient water They're made up of water droplets or ice crystals that [are] formed from water Vapour in the atmosphere Although you can't see it or feel it the air around us contains water even on the clearest summer day The main sources of this vapor are evaporation. Which is the escape of water molecules from the surface of oceans lakes and soil and Transpiration the release of Water by Plants as The Sun Warms Earth's surface heat is transferred into the atmosphere along with water vapor The warmer the air the more moisture it can hold but warm air doesn't usually stay near the [surface] for long Like a hot air balloon. It rises as it does it cools the Colder the air becomes the less water vapor It's able to hold if the air becomes cold enough It reaches a state called super Saturation which causes some of the water vapor to transition back to a liquid or solid state Water molecules in the vapor form around tiny particles of dust ice sea salt and pollution suspended in the atmosphere These particles called condensation Nuclei serve as the starting point for the formation of water droplets and ice crystals With this final step repeated billions and billions of times the water that's been in the atmosphere all along is suddenly visible and a cloud is born While we can now see the cloud the individual droplets, or ice crystals are tiny Which is why they remain airborne? But they can combine to form larger drops or crystals and if they become large enough and too heavy to stay aloft They'll fall as rain snow sleet Or hail back to Earth's surface where the water in them came from originally?