Researchers at RMIT University's SPACE Research Centre and the Bureau of Meteorology are using GPS and low earth orbit satellites to provide an additional type of temperature profile observation for use in weather forecasting computer models.

The computer models draw on about a hundred thousand million current weather observations, including data from 30 to 40 complementary satellite instruments, to generate the information used by meteorologists to prepare weather forecasts

RMIT Adjunct Professor John Le Marshall, Research Program leader at the Bureau of Meteorology and former Inaugural Director of the Joint Center for Satellite Data Assimilation, a joint NOAA, NASA and DOD research initiative in Washington, said: "What we've found through our work with RMIT's SPACE research team is that the GPS data improves the real-time temperature field and the cross-calibration of the data from a number of satellite instruments. This in turn significantly increases the usable quality of the satellite observations.

"We are actually able to measure the amount of bending in the GPS beam as it passes through the atmosphere. We can then use that knowledge to more accurately measure atmospheric temperatures and use this to improve temperature fields and calibrate other satellite readings. This extra information, in the data-sparse southern hemisphere, is now making our forecasts more accurate."

Professor Le Marshall said that "since the research was completed and began being used in forecasts this year, we estimate the Bureau is now delivering forecasts of the same accuracy 10 hours earlier."

He predicts that, as techniques improve, GPS data will also play a bigger role in climate monitoring and severe weather warnings.

Professor Kefei Zhang, Director of the RMIT SPACE Research Centre, said that GPS as a revolutionary technology for Positioning, Navigation and Timing (PNT), provided a low-cost, powerful means of precise measurement of the earth environment.

"Weather forecasting is dependent on accurate observations of the atmosphere surrounding the whole planet, but there is a significant lack of ground-based meteorological observation stations. That and the shortage of accurate surface level data from over the world's oceans and polar regions limits the reliability of climate and weather predictions.

"This is particularly true for Australia, where people live along long coastlines but forecasters can only draw on very limited measurements from the middle of the continent and surrounding oceans.

"GPS can fill that gap. It's revolutionary technology. It's the missing link," Professor Zhang said.

The RMIT SPACE Research Centre is a multi-disciplinary and international collaboration supported through the Federal Government's Australian Space Research Program.

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