Jan 12, 2004

Storm Warnings


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A new device onboard two NASA satellites could improve 3- to 12-hour forecasts of severe weather.





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January 12, 2004:  "A severe weather watch is in effect for Okaloosa, Walton and Escambia counties until 11:00 p.m." That's what a typical severe-weather warning looks like, flashing across your prime-time television screen. Helpful, but a little vague.


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How about this instead? "A severe storm with 60-70 mph winds and 3-4 inches of precipitation is expected in Walton county tonight between 8:00 and 8:30 p.m." Much better! In the near future, forecasters expect to achieve this new level of potentially life- and property-saving detail.


Right: Scientists hope to improve 3 to 12 hour forecasts of severe weather.

Some fundamental limits to the predictability of weather do exist, but today the greatest barrier to more detailed forecasts is the amount and quality of data available to forecasters. A new generation of weather satellites, which NOAA plans to begin launching around 2011, will carry advanced sensors capable of producing higher-resolution images containing more information about the atmosphere and ground than today's satellites can provide. This sharper, richer picture of the ever-changing atmosphere--available to forecasters in near real-time--will bring a new level of detail and accuracy to short-term forecasts.




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But scientists don't need to wait another 7 years to learn how to use this higher-quality data. Sensors of this caliber are already in orbit: they're aboard NASA's newest climate research satellites, Terra and Aqua. That's why NASA has joined forces with NOAA's National Weather Service (NWS) to start learning how to incorporate such high-quality data into 3- to 12-hour forecasts now.

"What we're trying to do is to give the National Weather Service a head start with incorporating this higher-quality data into their forecasts," explains Gary Jedlovec, a meteorologist at NASA's Marshall Space Flight Center. Jedlovec is one of the leaders of this collaborative project, known as SPoRT (Short-term Prediction Research and Transition).

"The aviation community is especially keen to improve 3- to 12-hour forecasts as soon as possible," adds Tom Bradshaw, science operations officer at the NWS forecast office in Huntsville, Alabama. "The better the quality of the data going [into our computer models], the better the chance you have of a good prediction coming out."

The SPoRT project uses data from a sensor called MODIS (MODerate-resolution Imaging Spectrometer), which rides aboard both Terra and Aqua. MODIS picks up between 16 and 100 times more spatial detail than current GOES weather satellites.


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Left:  A side-by-side comparison of MODIS and GOES images taken over the same area, a four county region in Alabama, on the same day. The MODIS image is much sharper. [ ]


Even more importantly, MODIS observes 36 separate frequencies of incoming light, ranging from the visible to the infrared. GOES detects only 5 frequencies. So the MODIS data lets scientists use the power of spectroscopy to distill a wide range of information about the landscape below -- important characteristics such as atmospheric moisture, cloud phase, nighttime fog, and surface temperature.

"Traits of the ground and atmosphere such as temperature or moisture leave their imprint in the spectrum of the light they emit," Jedlovec explains. "Looking at 36 different frequencies in this spectrum is enough to fish out some of these imprints and calculate those physical traits." Using MODIS data, scientists can produce region-wide maps of important weather variables that GOES data can't even discern.

The raw ability to detect these important traits is not enough. The data must be presented to forecasters in a form that actually helps them to make their predictions. If an image shows too little detail, or if it uses confusing coloration, it may not help the forecasters as much as it could. So NASA scientists are collaborating closely with the NWS forecasters to learn exactly what they need.

"The Huntsville office of the NWS shares a building with some of the NASA scientists, so we see each other face-to-face every day," Bradshaw says. "We give them on-going feedback about how well the satellite data aids our forecasts and how it could be better."


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Above:  Daily sea-surface temperature data provides valuable information for coastal weather forecasting. The increased spatial resolution and calibration accuracy of MODIS (left image) provides better input for forecasters than current GOES data (right image). Image courtesy NASA.

Along with the Huntsville office, the NWS offices in Birmingham (Alabama), Nashville (Tennessee), and Jackson (Mississippi) are participating in the SPoRT pilot program. As the program is coming into its third and final year, the leaders plan to expand the program to include the Great Falls (Montana), Mobile (Alabama), Jacksonville (Florida), and Miami offices.

"These new cities will let us show how the MODIS data also applies to regions where oceans and snowy terrains play a major role in local weather," Bradshaw says. Eventually the program leaders hope to apply the lessons learned to all 130 NWS forecast offices around the country. After the kinks have been worked out of the system and NWS forecasters are using the data in daily operations, the project leaders expect that the NWS will continue relying on Terra and Aqua for this higher-quality data until the new NOAA satellites are launched, Jedlovec says.

Which means that this next generation of accurate, detailed storm warnings may be coming soon to a television near you.


Web Links

SPoRT -- home page for the NASA/NWS project discussed in this article

MODIS -- home page of the MODerate-resolution Imaging Spectrometer

Terra -- home page for the Terra satellite, part of NASA's Earth Observing System

Aqua -- home page for the Aqua satellite, part of NASA's Earth Observing System

GOES -- Web page about the GOES series of geosynchronous weather satellites, from the National Oceanic and Atmospheric Administration

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