Bad weather sometimes plays havoc with cellular phone service, but Israeli engineers have found that these same wireless communication networks can be used to efficiently and accurately monitor the amount of rainfall around the country in real time. Prof. Hagit Messer-Yaron and colleagues at Tel Aviv University's School of Engineering published their discovery in the May 5 issue of the prestigious journal Science. They found that measuring electromagnetic signals transferred among base stations - which exist on almost every street to facilitate wireless communications around the country - to determine amount of precipitation was much more accurate than the use of expensive satellites or radar. Working with Prof. Pinhas Alpert, of TAU's geophysics and planetary sciences department, and Artem Zinevich, a doctoral student at the Porter School of Environmental Studies, Messer-Yaron succeeded in collecting accurate data about precipitation at any given point. The interdisciplinary research, carried out without any outside funding, is expected to arouse much interest around the world. The authors noted that the potential of cellular environmental monitoring was not limited to rainfall measurements - microwaves could be used to monitor solid particles, fog, snow, sleet, hail and even water vapor, which plays a key role in weather and the global climate system. For years, engineers tried to minimize the effects of weather changes on the quality of cellular phone reception. But the new TAU research turns this fact on its head, taking advantage of the influence of weather on reception to measure the amount of rainfall. To demonstrate this idea, the researchers used data collected every 15 minutes from a cellular network during a rainstorm to calculate the surface rainfall. "We did the reverse process; from interruptions caused by the weather, we [calculated] how much rain fell," said Messer-Yaron. Since wireless communications networks are spread throughout the country, they can serve as a ready-made monitoring network without the need for expensive equipment. The article is based on measurements carried out in January 2005 and supplied by the researchers to Cellcom. The data about the power of the signals enabled the team to create a rain map that proved more accurate than ones provided by radar and was very close to physical measurements of precipitation collected in rain gauges that have to be visited and viewed individually.