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[music]

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VO: This is rain and snow. Not just a day.

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Or even a year. This is the culmination of

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almost twenty years of precipitation, all at once.

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Led by the Global

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Precipitation Measurement mission, the newest version of the NASA product

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called the Integrated Multi-satellitE Retrievals for GPM,

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or IMERG analysis, has remastered almost twenty

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years of rain and snow, creating a crisper, clearer

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and more complete picture than ever before. This marks

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a major milestone in the effort to generate a long-term record of

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global precipitation. With this two-decade long record

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you can see regional and global patterns in unprecedented

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detail. Seasons pulse.

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Over India and Southeast Asia,

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massive monsoon rains shift.

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Storm tracks march along in higher latitudes.

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The seas bubble in the Southern Ocean, which scientists consider

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one of our planet’s last great unknowns. If we look a little

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closer, we can see the wettest and driest places on Earth.

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Huffman: Extreme high events tend to be very concentrated and very

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localized. Whereas, the opposite, what we would call droughts, tend

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to be very widespread and sort of diffuse-looking.

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VO: The wettest places on the globe occur over oceans, particular in places where

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the surrounding land forces air into a converging pattern over

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warm waters that provide a lot of evaporation.

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For example, off the coast of Indonesia.

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As well as off the northwest coast of Colombia.

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And just two thousand miles to the south is one of the driest

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areas, the Atacama Desert in Chile.

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Across the Atlantic, Namibia experiences some of the least rain as well.

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Huffman: The interesting thing of the the last two is that they're

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next to the ocean, they’re next to cold ocean. And so in fact those dry zones

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actually extend over the ocean. We tend not to think of

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ocean deserts but, in fact, that’s what’s going on.
VO: Over the past two

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decades, precipitation has been changing.

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What we’re seeing isn’t a change in the overall amount of rainfall,

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but rather how that rainfall is distributed.

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Huffman: What seems to be happening—and this is still subject to some interpretation—is

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that the regions that get more precipitation are getting even more,

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and the areas that get less precipitation are getting even less.

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You perhaps heard the phrase “The wet get wetter and the dry get drier.”

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VO: This long record allows researchers to better test climate models,

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by comparing the model’s virtual scenario with decades of real

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precipitation. We’re able to go back in time and reanalyze

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large-scale events, like El Niño.
Huffman: By making these revised

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estimates in the past, it gives us better insight into

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the behavior of the atmosphere, and it allows people who are doing, say, model

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verification to do a more accurate job of verifying their models for that

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particular event, which happened in the past, than they could have done at the time.

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VO: Improving the models with the past will help predict the future.

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And that doesn’t stop with weather forecasts. A long

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precipitation record is a vital tool for researchers modeling floods

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and landslides, disease outbreaks,

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agricultural forecasts. Tracking our main

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source of freshwater. All of these applications need

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lots of data over many decades to fine tune the

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statistics and models that agencies rely upon for making decisions

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around the globe.

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[music]

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