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[ Music, wind and rain ]

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Voice: This is what we

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call severe damage.

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This is the bridge out of town, and we're not going anywhere.

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[ rushing water ]

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[ rushing water ]

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Voice: A woman was stranded here all day long through the storm...

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[ bridge collapses ]
Voice: Oh my God!

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Tropical Storm Irene bears down on New England. In Vermont

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the storm pushes up agains the higher terrain, and the rain intensifies.

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This is the worst flooding Vermont has seen in nearly

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75 years. Tropical cyclones,

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a general term for hurricanes, typhoons, and tropical storms like Irene,

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don't just stick to the tropics. These storms can charge

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northward and wreak havoc in areas that normally wouldn't see

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this kind of extreme weather. Satellites provide us with

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near real-time information about the intensity of storms

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and where they're headed. Since its launch in 1997,

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TRMM, the Tropical Rainfall Measuring Mission, has remained a

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gold standard in collecting global rainfall data on storms.

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Scott Braun: TRMM's usage for hurricanes has also been a major application.

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Operational agencies use it to get 

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center fixes on storms to monitor how the internal structure

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of a storm is changing and how that might relate to the potential for

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a storm to either intensify or weaken.
And while TRMM provides essential information

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on cyclones for tropical areas, for regions like New England,

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TRMM simply falls short.
Braun: We knew going into TRMM that there

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were going to be some limitations. The primary one being its relatively low

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sensitivity so that it would not be able to get the very low rainfall

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rates that you might see up at higher latitudes.

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Carlisle: So part of what GPM is supposed to do was just continue those measurements,

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but also GPM is to improve those measurements by being able to

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for example, measure precipitation over a wider swath

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of the Earth. TRMM is just at about 35 degrees,

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GPM gets more of the Earth in its measurements, going

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all the way into southern Canada, for example.
The Global Precipitation

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Measurement mission, or GPM, is a constellation of satellites

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unified by the GPM Core Spacecraft that will provide a global picture

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of rain and snow every three hours. When GPM launches in

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2014, it will greatly improve upon some of the limitations

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of TRMM. In addition to measuring a wider swath of the globe,

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the GPM Core Spacecraft will carry more advanced instruments with

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greater sensitivity. There's the GPM Microwave Imager, or

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the GMI, a radiometer that will use 13 microwave

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channels to capture precipitation intensities and horizontal

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patterns. Then there's the Dual-frequency Precipitation Radar,

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or the DPR. That uses two frequencies to

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visualize in 3D the precipitation structure from the cloud down

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to the surface.
Braun: With GPM we have the opportunity now

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with more advanced technologies to improve upon TRMM

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by having that second frequency and being able to measure

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the lighter rainfall and produce a more accurate rainfall estimate

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by having the two combined.
With GPM's more sensitive instruments

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and wider coverage of the globe, we can more accurately profile a tropical

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cyclone, predicting where they're likely to form, how intense

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they're likely to become and tracking the path they'll take

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so that agencies can make better decisions to help get people out

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of harm's way.
[ music ]

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[ music ]

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[ beeping, thunder ]

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