THE SCIENCE OF WEATHER PREDICTION
Scientific advances may not stop a tornado, hurricane or flood, but they can help us prepare for one.
       In the United States alone, severe weather events cause an average of $11 billion in damages every year, not to mention hundreds of deaths. Fortunately, weather research and technology are helping increase the amount of warning time before severe weather and other natural disasters strike. That’s where science and math come into play.

Previous Methods
Protecting us from our own environment is something scientists and others have tried to do for centuries. Astrologers throughout history attempted to predict the weather by observing the motion of planets and stars. Farmers and mariners sometimes relied on folklore, animal behavior and other unscientific weather rules to forecast nature’s next move. But they were often in for a big surprise.
       In the 1600s, the invention of such tools as the thermometer and barometer made it possible to record numerical weather data for the first time. Weather prediction and warnings took another big step forward in the 1800s with the invention of the telegraph. By 1900, forecasts were issued regularly by weather services in several countries and newspapers were publishing weather maps and predictions.
       Today, scientists look at weather from a higher vantage point — the sky. The inventions of radar and satellites have provided a new level of accuracy to weather forecasting, but experts still do not fully understand the Earth’s complex weather system.

Radar
Radar was first used during World War II to try to reflect radio beams off enemy aircraft, but raindrop reflections kept hindering the view. So it’s no wonder that radar is now an invaluable tool for weather forecasters.
      Radar uses radio waves to collect information about precipitation. It works by sending out electromagnetic signals, such as microwaves, that bounce off raindrops, snowflakes and hailstones. By measuring how long it takes for those signals to return, experts can determine the type of precipitation, its location and its intensity.
      The invention of Doppler radar in the 1950s allowed meteorologists also to measure wind direction and speed. By measuring the frequency of the returning signals from precipitation, experts can determine its direction and speed, as well as that of the wind carrying it. This type of radar makes use of the physical phenomena known as the Doppler Effect, which is marked by the difference in frequency depending on whether an object is moving toward or away from a point. For example, you might have noticed that the sound of an approaching train has a higher pitch than a receding train.
      Thus, Doppler radar can give a picture of the winds within a storm and, in some cases, can even detect rotation. Thanks to this technology, tornado warning lead times have increased over the last 10 years from an average of less than five minutes to nearly 12 minutes, according to the National Weather Service.

Satellites
By the mid-1960s, satellites were taking pictures of Earth from thousands of miles above. Instruments on board the satellites can capture visible as well as infrared images of Earth, which provide measurements of cloud cover, temperatures at various levels and water vapor.
      There are basically two types of satellites that keep an eye on our planet’s weather. Geostationary satellites, known as GOES (Geostationary Operational Environmental Satellites), are located about 22,000 miles above the equator. They circle the Earth at exactly the same rate as the Earth’s rotation. That means they stay over the same place above the Earth’s surface at all times. The images seen on television weathercasts usually come from geostationary satellites. Polar-orbiting satellites, or POES (Polar Operational Environmental Satellites), observe the rest of the Earth, including polar regions. They pass near the poles about once every couple of hours.
       Satellite technology also can help detect other natural disasters such as volcano eruptions. By helping map changes in landscape, gas emissions and changes in surface temperatures, satellites hold promising possibilities in the study of volcanoes.

Mathematical Models
Using a combination of radar and satellites, weather forecasters have a clearer picture of evolving storms and can predict which ones may become severe.
      Another way in which meteorologists can predict the weather is through the use of numerical weather prediction (NWP) models. Complex computer programs mathematically describe the physics and dynamics of the atmosphere’s current behavior and predict future temperature, pressure, moisture, rainfall and wind.
      There are many NWP models that simulate the atmosphere on three-dimensional grids for specific regions, continents, hemispheres or the entire globe. However, models are not always precise and the data often contains gaps. Therefore, human weather forecasters must interpret the models and come up with their own weather predictions. They do this by comparing various models to determine whether they agree or disagree.
       In addition to radar, satellites and mathematical models, information from a variety of other sources helps meteorologists make predictions. Some of the other data-gathering tools include atmospheric balloons, weather aircraft, radiosondes, weather rockets, weather ships, ground-based weather stations and, of course, citizen weather watchers.
      Scientific research has taken us a long way from the days when weather was predicted by observing the motion of the planets. But even with all our current tools and technology, experts agree there will always be room for improvement.

GLOSSARY
GOES — Geostationary Operational Environmental Satellites. They are located about 22,000 miles above the equator and circle the Earth at exactly the same rate as the Earth’s rotation.
POES — Polar Operational Environmental Satellites. They pass near the poles about once every couple of hours.
Doppler Effect — a physical phenomena marked by a change in frequency depending on the motion of an object toward or away from a point. The name comes from the Austrian scientist Christian Doppler who explained the effect in 1842.
Numerical weather prediction (NWP) models —  complex computer programs mathematically describe the physics and dynamics of the atmosphere’s current behavior and predict future weather.

SOURCES & SITES
“Hurricanes...Unleashing Nature’s Fury: A Preparedness Guide.” National Oceanic and Atmospheric Administration.

National Severe Storms Laboratory Web site: www.nssl.noaa.gov

“Thunderstorms...Tornadoes...Lightning...Nature’s Most Violent Storms: A Preparedness Guide.” National Oceanic and Atmospheric Administration.

“Understanding Science & Nature: Weather & Climate.” Time Life Inc. 1993.

USA Today Weather Web site: www.usatoday.com/weather/wearadar.htm

“Weather: An Explore Your World Handbook.” Discovery Communications, Inc. 1999.

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Last Updated: 03/04/04
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