Good question. The atmosphere is an extremely important part of life on Earth. You can think of it as a nice cozy blanket since it helps keep the planet warm. Plus, it acts as a filter for harmful pollutants, and it contains the Oxygen we need to live.

It's also like a water bottle lid. That sounds less comforting, but, without it the water would evaporate and go to space!

Some quick facts about the atmosphere before getting into why it helps keep water on the Earth's surface. It is a thin film of gas made up of ~78% Nitrogen, 21% oxygen, ~0.9% argon, 0.4% carbon dioxide, plus a few other elements. It clings to the Earth by gravity. Its mass accounts for 1 millionth of the whole planet. And about 80% of the atmosphere is contained within the first 7.5 miles (the troposphere), meaning it gets thinner as you go out to space.

Ok, now that we have the bases covered, let's talk about why it helps keep Earth's water...on Earth. As water evaporates from the Earth's surface, it goes from being a liquid to a gas (vapor). As this water vapor rises, it also cools (ever go up into the mountains and have it be much colder than down in the valley?). When the water vapor cools, clouds form, and clouds are what holds all this evaporated water! They move around various parts of the atmosphere until they drop all the water back to Earth as rain (sometimes much, much further away from where it evaporated)! Crazy how the answer was right above you the whole time eh :)

Fun fact: A drop of water may spend 3,000 years in the ocean before evaporating into the atmosphere. Once in the atmosphere, it stays only for an average of 9 days before falling back to Earth.

Another fun fact, clouds form because of dust particles in the air as well.

Concluding remark: The atmosphere can do too good of a job keeping us warm, especially as we continue to add CO₂ to the atmosphere. This is what causes the greenhouse effect, which results in global warming and climate change. There is a lot of reading online for that topic, which I highly recommend exploring.

Here is an extra link where you can read about water stored in the atmosphere.

Hope you enjoyed learning about the atmosphere. Stay Curious!

Yes the atmosphere is a big part of what we call The Water Cycle.

The Water Cycle is a way for water to circulate on land and in the atmosphere all over the earth. In hot areas water evaporates from oceans and lakes and the water goes into the atmosphere. The earth is always spinning which causes air masses to move -- that air mass with all the water moves across the globe and will eventually rain out that water somewhere else. The atmosphere is a big storage container for the earth's water. Next time you see a big dark, grey, rainy storm front arriving you can wonder to yourself, "I wonder where on earth all this water was evaporated before it was transported here and turned to rain at my house?".

This is a very interesting question! The short answer is yes, and there are a couple of reasons why the atmosphere helps keep liquid water at Earth’s surface.

First, the atmosphere is composed of a variety of different gases, some of which are very good at absorbing energy from incoming sunlight. We call these gases Greenhouse gases and they cause the atmosphere to warm up, similar to how greenhouses trap the sun’s heat for plants to grow. The main greenhouse gases in Earth’s atmosphere are water vapor, carbon dioxide, methane, nitrous oxide, and ozone.

If the atmosphere did not exist, there would be no greenhouse gases to keep Earth’s atmosphere warm and the temperature at Earth’s surface would be about 0 degrees Fahrenheit. All of the water would be frozen if this were the case!

Second, the gases in the atmosphere exert a pressure on Earth’s surface. We call this the atmospheric pressure and it helps prevent water on Earth from evaporating into space. Therefore, we need the atmosphere to not only keep water warm enough to stay liquid at the surface, but to also exert enough pressure on the water to prevent it all from evaporating away!

The boiling point of water depends on the pressure of the atmosphere that the water is in. At zero pressure (i.e. the vacuum of space), the boiling point is below the freezing point, so that any water that is not frozen will immediately boil. By having an atmosphere, Earth's oceans do not boil.

Earth's gravity is the main thing that keeps water on earth. Earth's gravity keeps the atmosphere on Earth from flying off into space. Water molecules are small, so gravity doesn't pull hard on individual water molecules; but water molecules interact with a lot of other molecules in the atmosphere, forming water droplets and other collections of molecules. Earth's gravity pulls harder on these larger collections of molecules in the atmosphere.

Here's a link about the atmosphere and water.