单选题
Forecasting the weather requires huge quantities of data,
mainly collected by high-tech means such as satellites and radar, but low-tech
tools are important too—especially old-fashioned rain gauges (雨量器).
Each technique has its strengths and weaknesses. Radar and satellites can
cover swathes of land, yet they lack detail. Gauges are much more accurate, but
the price of that accuracy is spotty coverage. Now, though, Aart Overeem of the
Royal Netherlands Meteorological Institute and his colleagues reckon they have
come up with another way to watch the rain carefully. It offers, they believe,
both broad coverage and fine detail. Best of all, it relies on something that is
already almost everywhere—the mobile-phone network. Their
scheme starts from the observation that rain can make it harder for certain
sorts of electromagnetic radiation to travel through the atmosphere. Measure
this resistance and you can measure how rainy it is. The researchers do not
measure the strength of mobile-phone signals themselves. Instead, they rely on
something that mobile networks already do, and measure the strength of the
microwave links that base stations use to talk to each other.
The idea itself is not new, and there have been trials in recent years. Like all
the best science, the idea is both technically elegant and practically useful,
since it allows better cross-checking of existing methods. There are other
advantages. Coverage is one. Even in rich countries with well-financed weather
forecasters, there are probably far more mobile-phone base stations than rain
gauges. That is truer still in poor countries, where rain gauges are scarce and
radar often nonexistent, but mobile phones common. Another boon is that network
operators tend to keep a close eye on their microwave links. Although the
researchers were able to obtain data only every 15 minutes, some firms sample
their networks once a minute. That means rainfall could, in principle, be
measured almost in real time, something that neither gauges nor radar nor
satellites can manage. The technology is not perfect: snow and
hail are harder than rain for microwaves to spot, for example. Besides, mobile
networks are densest in urban areas, which are also the places that probably
have weather-forecasting equipment already. Even in the rich, urbanized
Netherlands, coverage outside cities is noticeably irregular.
单选题
Paragraph 3 mainly talks about ______.
A. how to use the mobile-phone network to measure rainfall
B. the equipment for measuring rainfall with the mobile-phone network
C. the limits of using the mobile-phone network to measure rainfall
D. the efficiency of measuring rainfall with the mobile-phone
network