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Four scientists at NOAA’s Earth System Research Lab in Boulder, Colo., will be awarded with a U.S. Department of Commerce Gold Medal for their role in developing a new technology that uses Global Positioning System signals to continuously measure the total amount of water vapor in the atmosphere. Real-time GPS-based data can be used to improve forecasts of relative humidity and other weather variables, track climate change, calibrate satellite instruments, and provide new opportunities for atmospheric research. NOAA’s National Weather Service has incorporated the data into two of its primary operational forecast models and similar systems have followed NOAA’s lead in Canada, Europe, and Japan.
“The NOAA team’s persistence and creativity in developing this new GPS-based technology can improve weather forecasts across the nation,” said retired Navy Vice Admiral Conrad C. Lautenbacher Jr., Ph.D., under secretary of commerce for oceans and atmosphere and NOAA administrator. “The additional benefits of this new tool for calibrating Earth-observing satellites and reliably monitoring global climate may extend far into the future.”
On November 8, Seth Gutman, Kirk Holub, Stan Benjamin, and Susan Sahm, all of NOAA’s Earth System Research Lab, will be in Washington, D.C., to accept the Commerce Department’s Gold Medal for Scientific or Engineering Achievement — the highest honorary award granted by the Secretary of Commerce.
Along with other government and university partners, including the University Corporation for Atmospheric Research, the NOAA/ESRL team spent 13 years developing, refining, and testing GPS meteorology. They took the lead in creating a NOAA-operated network of land-based GPS receivers throughout the United States and adapting the real-time data for operational weather forecasting.
Radio signals emitted by GPS satellites for positioning purposes are bent and slowed by water vapor as they travel through Earth’s atmosphere. The ESRL team measures that delay by comparing the signals’ ideal speed in a vacuum to their actual speed as they travel from the satellites to a network of more than 300 ground-based receivers. They then convert the difference into estimates of total water vapor along the signal paths. NOAA scientists have quantified the impact of these real-time moisture estimates when used in numerical weather prediction models, which are the basis for most weather forecasts. Early results show that the data improve forecasts of relative humidity, rainfall, and severe thunderstorms.
"Sometimes the most useful things come from unexpected places," says group leader Seth Gutman. "The people who designed the Global Positioning System for the military more than 30 years ago could not anticipate its applications to weather forecasting, climate monitoring, and atmospheric research. That’s what makes science exciting."
Traditional methods of measuring atmospheric water vapor have various shortfalls. Balloon-borne instruments, launched every 12 hours, miss more rapid atmospheric changes. Surface measurements are frequent but give little information about upper-air moisture. Infrared measurements from satellites do not penetrate cloud layers, and satellite-borne microwave sounders can be used only over open bodies of water. Hourly GPS-derived estimates of absolute water content from the top of the atmosphere to the ground solves fills these voids all at once.
2007 the National Oceanic and Atmospheric Administration, an agency
of the U.S. Commerce Department, celebrates 200 years of science and
service to the nation. From the establishment of the Survey of the
Coast in 1807 by Thomas Jefferson to the formation of the Weather
Bureau and the Bureau of Commercial Fisheries in the 1870s, much of
America's scientific heritage is rooted in NOAA.
On the Web:
NOAA’s Earth System Research Lab: http://www.esrl.noaa.gov
GPS-Met Network: http://gpsmet.noaa.gov