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Sure, what we need to understand

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you know, not just what's happening in our backyard, but also what's happening at the global

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scale, and because we're able to observe both light rain and heavy

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rain and snow. We're able to see how storm systems that originate in our part

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of the world, for example Hurricane Bertha, you know we can see how that affects

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other places. So Hurricane Bertha was not such an interesting storm for

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the U.S. but as it moved across the Atlantic it caused

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extensive flooding and actually some fatalities in the United Kingdom.

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So getting that global picture and being able to track patterns of weather from

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one place to another is a very powerful way to see how our water cycle

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and our weather is interconnected.

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It took about ten years to build the satellite and we have some great

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video showing how the instruments were added to the space spacecraft bus

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how they were tested, how we shipped the spacecraft

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From the United States, NASA Goddard Space Flight Center

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To Tanegashima Island in Japan, our partners with this satellite.

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But really the concept for this mission was about 10 years prior

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to that. So really from concept to launch was almost

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20 years. so it takes a long time to conceive. build. and launch

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such a satellite.

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Well knowing where when and how

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much it's raining and snowing is really vital for understanding extreme events like

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landslides or floods. You know one of the things that we observed is that there's

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different seasons for some of these intense hazards that can cause fatalities.

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For example the monsoon season in Asia, for example

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can cause extensive landsliding. Every August and September and October

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we have lots of landslides and flooding as a result

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of heavy rains from the monsoons. In other areas we have

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flooding from the spring rains or from heavy summer rains

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So it really depends on what season is and what the

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the topography of the areas that can cause both strange weather and

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impacts like natural disasters.

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Understanding how our water cycle is connected

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so where air moves and evaporates

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from the surface, it condenses to cause precipitation and where that goes

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whether it's over land or over ocean really tells us about what

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our reservoir in the sky is doing and how that feeds our reservoir

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on the surface and underground. And so with satellites we get

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this remote perspective allowing us to see the whole globe at once.

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You know if you look at water gauges for example, we don't have any over the oceans.

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But what you can see in this rainfall accumulation

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showing this Super Tyhoon Haglong is that

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we have a ton of rainfall over the ocean and then also it impacts land.

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and caused extensive flooding in Japan. And so if you take all of the

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rain gauges in the world and put them together they only fit into two basketball courts. So we really

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need that vantage point of space to tell us what's happening with our

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precipitation and where it might impact society.

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Well Earth is a very interesting system. We have

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this very, very tropical warm region which

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evaporates water from the surface and it condenses and it creates

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a lot of rain in the tropics. Now when you move farther up that air

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moves up and sinks at the kind of middle latitudes in the deserts and

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This is where we see most of the Earth's deserts in the Sahara, but

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also over the ocean. There's actually a desert over the ocean.

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If you look at areas that get a lot of rainfall, you know there's sometimes where,

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the fissures get really wet. You know we have these huge areas where

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you have a lot of freshwater coming into our oceans. And then higher up,

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we have, for example, light rainfall which is a huge contributer

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to freshwater resources in high latitudes. So that circling

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of and cycling of precipitation both from

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land to ocean as well as from the equator to the poles

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is important and vital for driving our global water cycle

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and our global energy cycle. And so that's why understanding precipitation

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where it is, how much we have and where it's moving is so important.

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Well the United States is a really interesting place because it's kind of sandwiched between the

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tropics and the higher latitudes. And what that allows us to have is a lot of

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different weather patterns in different regions. Now what matters in this

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region is that you see these storm systems moving from west to east

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across the country and that can dump a lot of rainfall in the midwest, but we've

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observed out west in California is a prolonged absense

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of rain actually causing lots of draught. And so what's important is that

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we can get this global picture, even this U.S. picture, to understand

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where we're getting more and less rainfall and how that's impacting our society.

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That really gets at the

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notion of climate zones. If you have precipitation

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which is very steady and dependable, then the vegetation

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will grow that depends on having lots of steady vegetation.

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Steady precipitation. On the other hand

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if precipitation very intermitent, for example in the west coast.

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Particularly in the southern California.

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they have a so-called Mediterrean climate. It's very dry in the summertime

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and it's supposed to rain in the wintertime, but of course the last few years that hasn't happened.

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but, having that very intermittent precipitation

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introduces really fundamental changes in the kind of vegetation

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that's easy to grow there.

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Well as you might imagine

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you can see from your local ground radars

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localized rain maps provided by the TV channels

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You can also see from satellite imagery white cloud tops taken

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at the tops of the clouds. So this new imagery allows us to provide

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uniform precipitation estimates using a constellation

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of satellites put all together. So you can

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see all the way down to the Earth's surface, the rain falling there impacting

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science and society.

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GPM is able to see the type of precipiation under the clouds

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because we are able to use the radar onboard. It's a new

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technology that allows you to see layer by layer within the clouds

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and within the precipitation. And so it provides something like a

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CT-scan that a doctor might use. And every 250 meters

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we see the structure of precipitation within the clouds with this radar

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instrument provided by the Japanese.

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Absolutely. The annual pattern is referred to as a seasonal cycle so

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you certainly know in the United States it's cold in the winter

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warm in the summer. But in addition there are precipitation patterns that go along with

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that. That's true around the entire world. And of course in the southern hemisphere

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the seasons are reversed. Our summer is their winter and vice versa.

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In the tropics it's not really warm and cold is just wet and dry.

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There's lots of places where it's wet part of the year and then dry part of the year.

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And so these patterns repeat every year

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and then there are other interesting variations that actually go from.. between years

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So there is more than just the annual cycle

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So the patterns change most notably

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in the tropical regions because this is where the year to year

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fluxuations are the largest. So you have perhaps heard of El Nino

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and La Nina which originate in the Pacific Ocean.

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but extend well beyond that. In El Nino you

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have a massive amount of precipitation which is in the eastern Pacific Ocean

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and in La Nina you get a sort of reinforcement of the usual pattern where

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the equator doesn't have precipitation

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in the eastern Pacific Ocean. There are other patterns which

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we're less familiar with. There's something called the north Atlantic

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oscillation, the Antarctic oscillation. These are sort of technical

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sounding. But all it means is there's the repeating patterns that are

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maybe seasonal in length. In addition there are longer

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Patterns, the most notable of which is the Pacific decade of oscillation

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that's a really big sounding word, but all it means is it takes about a

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decade or 10 years for this pattern to work itself through.

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The implication of that of course is you need say 20 years of data in order to

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reliably detect the Pacific decade of oscillation.

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So there's a lot of really interesting patterns to study.

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Well I think debunked is maybe not

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quite the term, but what we've got is a search to

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understand better what's going on. And so for example we

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always have known that there is snow at the top of hurricanes,

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but when we get these data which are for the first time are really working

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systematically to visualize snow, when you look at a hurricane, for example Hurricane

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Arthur, you see snow at the top. So the warm

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colors toward the surface are rain and the cool blue colors

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at the top are snow. Who knew all over the tropics it's

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snowing just four miles up. Another important factor

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that we haven't really understood is the precipitation

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in the Southern Ocean. There's very little land there. It's a very rough

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weather and people don't go there unless they have to. And so this

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satellite system allows us to systematically view

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the Southern Ocean in a way that we haven't before and I'm really hopeful that

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we will now see much more quantitative, accurate results there.