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We plan our lives around rain. We always want to know when and

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where and how much. Not just for our weekend plans,

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but for how we make decisions about our safety and transportation, our economy,

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our livelihoods. So, how do we measure rain?

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Well, we can set out a rain gauge, like this one, and it measures the amount

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of rain that falls over time. The problem with this is that only measures rain in one

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very small spot. In fact, if you took all the rain gauges in the world

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packed them together, they would into two basketball courts. Now

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we can cover more ground if we use radar. Radar sends out a signal,

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and it measures how much of that signal is scattered by rain or snow. But radars

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are only available in certain parts of the world, and many countries just don't have access to

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that technology. And that's just on land. Think about

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how we're going to measure rain over all of the world's oceans.

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Look, the point is it's impossible to cover the entire Earth with enough instruments

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that are going to give us accurate precipitation rates for the whole globe.

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So, we have to think bigger and higher. Instead of having a

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patchy network of rain gauges and radars, we can have a whole constellation of satellites

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looking down at the Earth, measuring things like falling rain,

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snow and even ice. The Global Precipitation Measurement mission, or GPM,

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is going to do that. And it's going to give us precipitation rates for the whole

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globe every three hours. Now GPM is going to cover it all:

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from land and oceans, from the tropics to the edge of the poles,

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over mountains and valleys, from our

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farmland to our cities and towns. We're going to need

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more than a perspective on the ground if we're going to look at precipitation from a truly global

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standpoint, and GPM is just the mission that's going to give us that big picture.

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[music ends]

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