Take heart, cellphone users. All those dropped calls you experience may someday be used for a greater good: to help forecast the weather. That’s the suggestion of an Israeli electrical engineer, Hagit Messer, who has demonstrated that the ups and downs of signal strength in wireless communications can be used to measure rainfall accurately and continuously over a wide area. Raindrops and other particles in the atmosphere can weaken electromagnetic signals. Satellite TV viewers who lose the signal when a thunderhead passes know this well. Wireless companies know it, too. ‘‘To ensure reliable communications, they need to cope with disturbances caused by weather and other effects,’’ said Dr Messer, a professor at Tel Aviv University. Wireless companies constantly analyse signal strength so they know, for example, when to increase the power at their base stations. Messer’s idea, reported in the journal Science, was to analyse those same data to determine the rainfall that is causing the disturbance. ‘‘All we need to do is exploit this information to get better monitoring of environmental conditions,’’ she said. It may also be possible to track pollution using the technique, she added. Eventually, she said, it should be possible to use phone transmissions, which would provide more readings over a given area, increasing accuracy. Most rainfall measurements are made using rain gauges, costly to set up and monitor, or radar, which is less accurate close to the ground. Messer reported that her technique produced results comparable to those two methods. But it has the advantage that it uses existing data. ‘‘Why do we need a special-purpose machine,’’ she asked, ‘‘when the information is there anyway?’’ The monsoon experimentMonsoons are often associated with the Indian Ocean, but they occur around the world, including North America. They are storms caused by seasonal shifts in winds, and the North American ones, which occur from July to September, are a critical element in the climate and the environment of the American Southwest and northwestern Mexico. The experiment, which began in 2004 and runs to 2008, is an international effort, with scientists from the United States, Mexico, Belize and Costa Rica. The goal of the research, which involves rain gauges, weather stations, research flights, atmospheric profiles, radar and other observations, is to improve monitoring and prediction. It also has an educational arm, to bring teachers into the field and produce materials for science classes. One thing is safe to predict: monsoon thunderstorms, like the one over Arizona shown above, will begin in a couple of months, and occur almost daily.
