Courtesy of Spatial Source
Researchers at RMIT University will investigate using noise in GPS signals to determine how much water is in the atmosphere, leading to more accurate climate models and predictions.
Dr Suelynn Choy from RMIT ’s School of Mathematical and Geospatial Sciences will use the Malcolm Moore scholarship to see if data from Geoscience Australia (GA) and the Bureau of Meteorology (BoM) can be combined to give a record of atmospheric water content.
If successful, Australian scientists will have access to more than 10 years of GPS-derived water vapour data and current observations from across Australia and Antarctica, filling a void in data used to produce climate models.
Water vapour is the most abundant greenhouse gas in the Earth’s atmosphere and is responsible for more warming than any other gas, including carbon dioxide.
The concentration of water vapour is constantly changing, making it difficult to observe and measure.
By including water vapour in climate models, scientists will be able to better predict the impacts of future warming on Australia.
To determine how much water vapour is in the atmosphere, Dr Choy will tap in to an unused part of the GPS signal that is often discarded as “noise”.
“When the GPS satellite sends out its signal, the time it takes to travel to a receiver on Earth depends on the conditions of the atmosphere,” Dr Choy said.
“This interference creates ‘noise’ in the signal which needs to be removed to give an accurate position.
“However, this ‘noise’ tells us a lot about the atmosphere. By knowing the surface temperature and air pressure at the site of the receiver, we can work out how much water vapour there is around us.”
Geoscience Australia maintains a network of GPS receivers across the region, providing data extending back to 1998.
For the data to be useful, temperature and air pressure must be known accurately and often, but as GPS sites and weather stations are not located together, this data isn’t available.
Dr Choy plans to use numerical weather prediction models and atmospheric re-analysis products to provide the data needed to calculate water vapour content from GPS observations.
Her work will focus on assessing the quality of the GPS-derived water vapour data and developing a method for processing the observations.
A recent study by RMIT researchers, which included Dr Choy, has highlighted the application of GPS for atmospheric monitoring.
Dr Choy says that her new study could provide a supplementary atmospheric sensing tool for climate studies with applications in Australia and around the world.
“If this proof-of-concept study is successful it could be fully used to help monitor our changing climate.”