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A Fresh Approach to Weather Forecasting: Ringing in the Rain
Posted By Leora Eren Frucht On April 12, 2006 @ 12:49 pm In | No Comments
Cellphones can already take photos, surf the Net, and even measure heart rate.
But how about using cellphone signals to measure rainfall?
A Tel Aviv University (TAU) researcher recently showed that, yes, mobile phone signals can be used to measure rainfall more accurately than current meteorological methods and, that, in turn could improve weather forecasting.
In a study published in the prestigious journal Science, Prof. Hagit Messer-Yaron, a professor of electrical engineering and her TAU colleagues Prof. Pinhas Alpert and graduate student Artem Zinevich, demonstrated that the ups and downs of signal strength in wireless communications can be used to accurately monitor rainfall in real time over a wide area.
The principal behind this is something commonly experienced in the days before cable television: Stormy weather meant a bad picture on your TV. That?s because electromagnetic signals are weakened by certain types of weather, in particular, rain. It?s that same phenomenon that causes cellphone communication to falter during bad weather.
By measuring fluctuations in signal strength from the base stations of cellphone transmitters, Messer-Yaron was able to chart a precise, real-time record of rainfall over a broad area.
That?s important because the more accurate the measure of rainfall, the better weather forecasts will be. ?Garbage in, garbage out,? explains Messer-Yaron, an expert in statistical signal processing.
Accurate, real-time data on rainfall is also valuable for those who have to decide whether to open dams ? like the one in the Sea of Galilee. Open the dam too soon and you waste precious water; open it too late and you risk flooding.
Seated in front of her computer, Messer-Yaron produces a series of diagrams with blue patterns. They are measurements of precipitation in different parts of Israel at 15-minute intervals on the same day, with each shade of blue corresponding to a different quantity of rain. ?Here is the graph we compiled using cellphone signal data. And here,? says Messer-Yaron, switching the screen to show what looks like the typical aerial cloud map shown on TV weather forecasts, ?is the one compiled by conventional radar measurements.? They look very similar, but they?re not. ?Ours turned out to be more accurate.?
How does she know?
By comparing these graphs with the results produced by a third method: rain gauges ?containers used to collect and measure rain. This traditional method is the most accurate, but also expensive and highly localized one (You don?t get data if you don?t have a container in a particular location.)
?The great advantage of our method is that it provides accurate rainfall measure at no cost since we are using data that already exist. Cellular measurement can either replace existing techniques or complement them.?
Messer-Yaron is something of a rarity in the field of electrical engineering where even today women comprise only 10 percent of graduate students. Finding women at the top echelons of academia in general, and in science and technology, in particular, is even more unusual ? both in Israel and other Western countries. Messer-Yaron is a full professor, a former chief scientist of the Ministry of Science and currently the vice president of Research and Development at TAU.
The topic of women in science is close to her heart and she has held a number of high-level positions aimed at advancing women in science.
That women have to be considerably better than men to make it in the field is a given ? she says, citing an article in the prestigious journal Nature that proved this empirically.
The article showed that men scientists were widely considered to be more competent by their peers than women scientists even when objective evidence ? the number of times a scientist?s work is cited in journals and its impact in the field ? showed the opposite to be true.
What isn?t yet as evident, but is no less important in her view, is that women scientists have a different way of looking at the world.
Her own research with cell phone signals is a perfect example, she contends.
Faced with the fact that bad weather interferes with cellphone signals, most male scientists strive to amplify the signals in order to improve transmission. Messer-Yaron took a different tack: She chose to use the very problem to solve an entirely different challenge ? rainfall measure. ?It?s turning the issue around,? she explains.
She came up with the idea while making her rounds in the university shortly after being appointed head of its environmental school. In one such meeting, meteorologist Prof. Pinhas Alpert told her that one of the obstacles in his weather forecasting research is that the input data he uses is not of a high enough resolution.
Messer-Yaron offered a potential solution on the spot. ?He was surprised ? it was an approach that hadn?t occurred to him.?
Messer-Yaron is not the first to measure rainfall by monitoring electromagnetic signals. In the UK, two antennas were erected for this very purpose. But she is the first to use existing signals ? supplied by a cellphone company ? to do this. The advantage is that her method, while scientifically more challenging, is free, whereas erecting antennas all over a country is prohibitively expensive. Her method takes advantage of the fact that wireless communications networks are spread all over the country, and can serve as a ready-made monitoring network.
The initial study has raised many more research questions and potential applications which are now being pursued by five graduate students in what is becoming a burgeoning new field. Among the questions: Can cellphone signals provide better measurements of air pollution? Can they be used to distinguish between hail, snow and rain? Can the use of data from individual cellphones ? as opposed to data from base stations ? provide even more accurate measurements?
Messer-Yaron has even more far-ranging questions that touch on anthropology.
?I have begun to think of wireless communication as a brain ? in which you have the equivalent of signals connecting neurons and supporting them. ?The cellular network is like the brain of human society. If an alien were to look at earth only on the basis of electro-magnetic signals, it would know exactly where humans live and could even chart a map of the land and sea, all on the basis of signals.?
?I look at wireless networks as a scientist, rather than a technologist. The difference,? she explains, ?is that in technology you try to manipulate things for mankind; in science you just explore what is, rather than alter it.?
?Men,? she maintains, ?tend to look at technology. Women?s perspective tends to be wider, more multidisciplinary.
?I attend many forums devoted to fourth generation cellphones, and the majority of participants there are men. They will talk endlessly about 4g applications, but no one will raise the question of the radiation problem ? unless there is a woman there. Questions about the environment invariably come from women.?
Messer-Yaron is used to being an anomaly. And used to people assuming she?s a man. When her work was cited in the French newspaper Le Monde recently, the article referred to her as Monsieur Messer-Yaron. ?When I stand next to a male colleague at a conference, people automatically assume I?m his wife.?
As for the million-dollar question ? why do so few women rise to the top in science and technology ? Messer-Yaron can only speculate. ?I have no doubt that women can do it ? the question is whether they want to. Or do they internalize society?s expectation that they should curb their ambition in favor of devoting themselves to family??
She herself has managed to do it all. She?s a mother of three, her youngest child, aged 11. She has published over 60 refereed journal papers, worked in hi-tech, served as Israeli representative on international scientific committees, and held visiting positions at leading institutions in the U.S. and France. In the course of the interview, she receives a call from her elderly mother who is expecting her to visit soon. She is constantly glancing at her own cellphone, anxiously awaiting word from her just-mobilized son, now in Lebanon.
Having a husband who took over day to day care of the house was one of the reasons she has been able to combine a family life with a driven career, she says. ?I think that both men and women need to liberate themselves from social pressure. In a lot of cases, if men were honest with themselves they would admit that they actually like staying home. Not everyone fits the ?classic? male role. I always advise my young women students that when choosing a mate, they should both be honest with themselves about the roles that really suit them.?
Messer-Yaron hopes to see many of her women students pursue careers in science and technology ? and not just for the sake of equality. ?Women bring a different approach to science. Without them, the world simply loses out.?
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