BACKGROUND: Meteorologists are using many new techniques and technologies to help predict the weather. From flying sensor-equipped planes into storms, to using "night vision" infrared light on satellites, your local weathercaster is relying on improved ways of seeing ahead of the storms.
FLYING INTO THE STORM: Weather forecasters in the middle of the U.S. are making better local predictions for pilots and others thanks to an airborne sensor being tested by NASA's Aviation Safety Program. Known as TAMDAR, the instrument allows aircraft to automatically sense and report atmospheric conditions. The data is collected and sent via satellite to a ground data center that processes and distributes up-to-date information to weather forecasters and pilots. Initial research shows that the airborne sensor accounts for a 10 percent to 20 percent improvement in forecast errors in numerical models in measurements of temperature. The sensor also measures humidity, pressure, winds, icing and turbulence with the help of the GPS satellites, which gives location, time and altitude information.
NIGHT VISION AND WEATHER: Atmospheric scientists at the University of Alabama in Huntsville have developed a new weather forecasting system that uses both visible and infrared images taken by satellites. By merging the two sets of image data, the forecast model gets new readings for cloud top temperatures every 15 minutes. The system is 65 percent accurate in providing one-hour warning before heavy rain starts to fall within a thunderstorm. The new system can also help warn of possible turbulence above storms and downwind from mountain ranges. Doppler radar might miss this kind of turbulence in clear air, but the waves can be detected by satellite infrared sensors. Rising air cools while sinking air warms, and these alternating bands of temperature differences show up in the infrared. Satellite information is also available over most of the globe, and thus can provide hazard warnings over areas not covered by Doppler or aviation radar systems.
WHAT IS DOPPLER RADAR: Doppler radar uses a well-known effect of light called the Doppler shift. Just as a train whistle will sound higher as it approaches a platform and then become lower in pitch as it moves away, light emitted by a moving object is perceived to increase in frequency (a blue shift) if it is moving toward the observer; if the object is moving away from us, it will be shifted toward the red end of the spectrum. Doppler radar sends out radio waves that bounce off objects in the air, such as raindrops or snow crystals, and then measures how much the frequency changes in returning radio waves to better determine wind direction and speed.
The American Meteorological Society contributed to the information contained in the TV portion of this report.