Reported May 2006

BACKGROUND: New technology is helping scientists with the National Center for Atmospheric Research better detect weather patterns and make predictions. This includes new mobile Doppler radar, radio-controlled aircraft carrying weather instruments in and around storms, phased array radar, and new real-time computer modeling programs for atmospheric conditions.

WHAT IS DOPPLER RADAR: During the 1980s and early 1990s, the National Weather Service installed Doppler radars around the United States. All weather radars send out radio waves from an antenna. Objects in the air, such as raindrops, snow crystals, hailstones or even insects and dust, scatter or reflect some of the radio waves back to the antenna. All weather radars, including Doppler, electronically convert the reflected radio waves into pictures showing the location and intensity of precipitation. Doppler radars also measure the frequency change in returning radio waves. Waves reflected by something moving away from the antenna change to a lower frequency, while waves from an object moving toward the antenna change to a higher frequency. The computer that's a part of a Doppler radar uses the frequency changes to show directions and speeds of the winds blowing around the raindrops, such as insects and other objects that reflect the radio waves.

PHASED ARRAY RADAR: Adapted from the SPY-1 radar technology used by the United States Navy to spot severe weather while ships are at sea, phased array radar uses multiple beams and frequencies to reduce scan time to less than one minute, enabling faster updates on weather conditions. This technology may help forecasters in the future provide earlier warnings for severe and hazardous weather; for example, it could increase the average lead-time for tornado warnings beyond the current average of 11 minutes.

The American Meteorological Society contributed to the information contained in the TV portion of this report.

If you would like more information, please contact:

National Severe Storms Laboratory 1313 Halley Circle
Norman, Oklahoma 73069
405-360-3620

The American Meteorological Society
45 Beacon Street
Boston, MA 02108-3693
(617) 227-2425
http://www.ametsoc.org

FACTOID...

Austrian scientist Christian Doppler discovered the Doppler effect in 1842 using sound waves, long before radio, much less radar, was invented. The same principle applies to radar's radio waves.

ON THE WEB...

www.nssl.noaa.gov