Researchers at University of Hanover in Germany have come up with “Rain cars, an initiative that aims to use GPS-equipped moving cars as devices to measure rainfall. With a lab equipped with rain simulator, the researchers have been able to put their idea to the test. They placed cars with different wiper systems under the rain machine, which uses a sprinkler irrigation system with adjustable nozzle to simulate light to heavy rain, to find out exactly how wiper speed relates to rainfall intensity. In another set of experiments, the team used the rain machine to test optical sensors that are installed in many modern cars to automate wipers. The sensors use a system of infrared laser beams that detect when drops of rain accumulate on the surface of the device. Each sensor reading corresponds to a specific amount of water, with more frequent readings corresponding to more intense rainfall.
Researchers have mentioned that the experiments so far were carried out in an ideal and controlled environment. In nature there are external effects like wind, spray from other cars or shielding trees that can affect the readings and rainfall characteristics are different from rain simulator. However, they clarified that the value of using moving cars to measure rainfall is not about a higher accuracy of rainfall measurements but about a much higher number of measurement points. In a Hydrology and Earth System Sciences study published in 2010, two of the team members showed that a high number of less accurate rain gauges give more reliable rainfall readings than a low number of very accurate devices. The researchers are already working on filed experiments using cars to measure real rainfall in and around the City of Hanover.
For more information: http://www.egu.eu/news/85/
Journal Reference: E. Rabiei, U. Haberlandt, M. Sester, D. Fitzner. Rainfall estimation using moving cars as rain gauges – laboratory experiments. Hydrology and Earth System Sciences, 2013; 17 (11): 4701 DOI: 10.5194/hess-17-4701-2013