Fog often leads to serious, costly accidents---particularly around airports, docks and highways. Monitoring visibility conditions in real time could improve public safety and save tens of millions of dollars in the transportation area alone. But conventional fog -detection systems---including satellites, visibility sensors and human observations---can suffer from poor resolution (分辨率), high cost or low sensitivity near the ground ,where monitoring is quite critical.
Recently, engineers Noam David and H. Oliver Gao, both from Cornell University, developed a way to use signal data from cell-phone towers to detect atmospheric conditions that can easily develop fog. Wireless communications data are passed within networks of antenna towers (天线塔) as microwave radiation. And the change in weather conditions can affect the strength of signals received at the towers. Thus, communications data offer a low-cost, continuous means of fog monitoring.
David and Gao successfully employed this approach to predict fog around the land in Tel Aviv, Israel, for over an hour before it appeared. They identified patterns in how the strength of microwave signals is altered in response to different humidity (湿度) and temperature. Unlike satellites, the method distinguishes between ground-level fog and low-level clouds.
Communication networks are used effectively worldwide, which would make it easy to adopt this method in most regions. “In principle, we could use existing systems for day-to-day early detection of fog formation,” David says. “Because system data can be received in real time, we can imagine short-term early warning against fog." He advocates careful testing in diverse parts of the word to explore the method's limitations.
The new work shows it is possible to detect the conditions that happen before fog forms. Kelly Caylor, an environmental scientist, who was not involved in the work, says, “It's a significant step forward. There's something remarkable and quite satisfying about finding so many signals in what would otherwise be considered noise.”
【小题1】What can we know about the conventional fog-detection systems?| A．They do not work very well. |
| B．They're only elective in some areas. |
| C．They've been improved in transportation. |
| D．They do not monitor the situation near the ground. |
| A．Emphasized. . | B．Generated. | C．Detected. | D．Changed. |
| A．Indifferent. | B．Favorable. | C．Critical. | D．Doubtful. |
| A．Different opinions on a new way to detect fog. |
| B．The wide availability of communication networks. |
| C．The urgency of detecting fog to ensure public safety. |
| D．The detection of fog through signals from cell-phone towers. |
