Hi,
So the way rain clouds work in my mind would be a cloud gets so heavy that it can not support the weight of the rain that it has absorbed and begins to release. If clouds are all just water and air then its not like there is a different formula from cloud to cloud, right? How can it rain for days from one cloud, then other clouds release a 30 minute spritz? ELI5
In: Earth Science
You’re really close with your belief in clouds.
Let’s change the word “heavy” to “dense,” and change “water and air” to “vapor.” Let’s also take a second to talk about polarity and how the chemical water works.
Clouds are a gas. They are water “vapor,” like steam. Steam is not very dense or heavy. It floats through the air, and usually dissipates or ‘spreads out’, as it does.
Water in any form, whether liquid, solid, or gas, has the same chemical composition – H2O. H2O is made with a single Oxygen atom that has two Hydrogen atoms attached to it and the shape it makes is kind of like a **V**, with the Oxygen at the bottom point of the **V**, and the two Hydrogen atoms at the top points of the **V**. Those atoms have a charge, which causes the shape to be the way it is, with the oxygen having a negative charge, which pushes away the hydrogen’s positive charge. This is called “polarity.” Water is polarized, causing movement, and magnetic attraction.
Opposites attract, and the positive charges look for negative charges to attach to like a magnet would. It attaches very well to other water molecules. As they attach to each other, they begin to pull each other closer together. The more molecules, the more tight the bond, or, the “heavier/denser” that they get.
Steam and vapor are created because heat speeds up how molecules move. With water heat can break off the molecules on the outside, turning them into steam/vapor. As steam and vapor climbs through the atmosphere, they are cooled down, and reconnect to each other. The more that connect, the denser the cloud gets, and eventually, the center of the cloud (the densest part) turns from gas to water, which is too heavy to float and falls in the form of rain.
Now that we’ve explained that process, why is it different one day to the next?
* **Temperature** – If it’s really hot, water keeps moving fast and struggles to connect to other water molecules. This can cause water to keep climbing into the atmosphere. Although temperature goes down as we climb, so does pressure.
* **Pressure -** Water can be broken apart, especially Single oxygen atoms can connect to the Oxygen in H2O leading to H2 and O2. O2 is the oxygen we breath. When pressure drops, it takes more effort to keep things together, and water molecules become less likely to stay together.
* **Humidity -** The amount of water in the air impacts the amount of water in the clouds. This is why rain often comes when it feels sticky or humid outside. Some days there is more overall water in the air in the area where you are because of weather patterns.
* **Weather -** Weather is localized and changes for a lot of reasons. Cold air moves together in large quantities. When the “front” of a large amount of heavier cold air comes into an area, it can push the lighter hot air (remember that heat makes molecules less dense?) upwards. This heat can speed up molecules, dissipating clouds. If clouds are already formed, or at lower altitudes, this can push water together, creating more and longer lasting rain. Cold fronts, warm fronts, and stationary fronts (What happens when a cold and warm air front hit each other and both don’t move) all influence how vapor connects, and what happens to the denser cloud masses.
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