Water is essential to all life on Earth, but it cannot be created. Instead, it has been cycling in the same way since long before people ever inhabited Earth. We depend on and drink the same water that dinosaurs drank!
Without rain, lakes, ponds and rivers could dry up. We would not have water to drink and cook and clean with. Rain nourishes Earth with life-sustaining water that is necessary for all the plants and animals that inhabit this planet.
The water cycle consists of four phases: evaporation, condensation, precipitation and collection. Let’s take a closer look at each phase in the cycle.
Turning into vapor
Water vapor is what we call water in its gas form. Water is always present in our atmosphere. Sometimes we can feel the water in the air, and we say it feels humid outside. There are three main processes that put water vapor into our atmosphere.
Evaporation: Evaporation is when liquid water from rivers, lakes and puddles turns into water vapor.
Sublimation: Sublimation is when solid water like ice or snow turns directly into water vapor without melting into a liquid first.
Transpiration: Transpiration is the process of water vapor leaving trees and plants.
Let’s get together
Condensation is of the opposite of evaporation. Instead of water particles separating and drifting up through the atmosphere, condensation is the process of water vapor joining together to form a liquid or a solid. We can observe this happening when liquid droplets form on the outside of a glass of ice water. Your glass isn’t leaking. Water from the atmosphere has condensed on the outside of your glass.
Water has two important properties that help it condense.
Cohesion: Cohesion means water likes water, and if water droplets get close to one another they will join together.
Adhesion: Adhesion means water also likes to cling to other particles.
Clouds form when water vapor attaches to more water vapor and other particles in the sky, like dust, ash and salt. Depending on the temperature and height of the atmosphere, clouds may be liquid water or ice.
Precipitation: Come on down!
When the clouds get so heavy that gravity takes over, water falls back to the ground. This is called precipitation. When it falls, it gathers everywhere. This is called collection. It falls in our lakes, rivers and streams. It forms puddles. The water that falls on the ground soaks into the ground and collects underground.
Depending on the temperature, we can see different forms of precipitation. If it is very cold, precipitation can be solid, like snow, sleet or hail. When it is warmer, it rains.
If there is unstable air, like warm, humid air rising into cooler zones, we may see a thunderstorm. Thunderstorms can range from simple to very severe. Severe thunderstorms can include hail in addition to rain. An extremely severe storm could have hail larger than 2 inches in diameter.
We can also have rain without thunder and lightning. A drizzle is a slow light rain that can last a long time. A shower or downpour is a fast, heavy rain that lasts a short amount of time.
No matter what type of precipitation, it is always important to be safe. Stay tuned to your local forecast for updates and precautions about the weather. The National Weather Service offers best practices to follow during severe weather.
Although rain can upend our plans and send us running for cover, the cycle of water is essential to life on Earth. Each phase is dependent upon the others to keep the cycle going.
Check out this month’s Try It! to make your own rainstick and listen to the sound of rain whenever you choose.
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