WEBVTT FILE

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Now this is a familiar scene.

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The Sun's heat causes water

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from plants, lakes and oceans to turn from a liquid to a vapor.

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High in the atmosphere

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the water vapor then cools down and condenses from a gas

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back into a liquid. The liquid

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water then falls back to the surface in the form of rain, snow, ice,

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or hail. Water

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runs off into streams, lakes and oceans or is stored in the ground or

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in snowpack.

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This is the water cycle, and it describes

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how our most vital resource moves through the whole Earth system.

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But like most things in our world, when we

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look at the tiny parts that make up the whole, we can learn a lot more about the

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phenomena. Take

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the shape of a single raindrop. Small droplets of

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water in the atmosphere are spherical in shape due to the surface tension, or

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"skin," of the water molecules. As these droplets grow

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they become heavier and start to fall through the air.

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As they fall, the raindrop collides with other drops and continues to get

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bigger. These larger raindrops fall through the air faster.

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The wind resistance on the underside of the drop causes the bottom

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of the drop to flatten, resulting in a drop looking like a hamburger bun.

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As the drop continues to fall and grow, at some point, it becomes too

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large for the surface tension to hold it together, so the raindrop breaks

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apart into smaller spherical drops. Investigating the proceses

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we can't see with the naked eye is nothing new. Science and technology

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drive each other forward and often lead to insights and discoveries along the way.

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With the invention of high-speed photography, we finally saw

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the most basic elements of our watery planet in action.

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Understanding how a tiny

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raindrop falls through the atmosphere does more than debunk the myth that a

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raindrop falls like a teardrop. It actually makes a difference when it comes to

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measuring precipitation, in particular, for ground radars.

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Ground radars look at the sides of the raindrops and then estimate

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the vertical and horizontal size. A heavier flatter drop allows

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radars to identify heavier precipitation. In fact the two

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radars on board the GPM satellite can also measure drop sizes

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from space and so a more accurate look at raindrops gives us a more

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accurate look at how global rainfall is shaping up.

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