I recently learned about the use of GPS signals to measure the amount of water vapor in the atmosphere. The amount of humidity in the air makes the air denser, so it takes longer for the GPS signal to travel from the GPS Earth-orbiting satellites to receivers on the ground. Scientists are applying global climate models to the GPS signal strength in order to monitor the atmosphere.
Researchers have measured the time delay equivalent to roughly one-tenth millimeter extra path length, which translates to about a half-millimeter to one-millimeter precipitation. A benefit of this methodology is that GPS has the ability to detect moisture through clouds.
There is now a very large moisture-sensing sensor web system called SuomiNet with GPS receivers and other sensors that measure surface temperature, humidity and pressure. The near-real time feeds from the sensor network assist in predicting the weather, mitigating flash floods and informing firefighters of fire conditions.
The research network is funded by the National Science Foundation and the University Center for Atmospheric Research.
