In Israel’s Judean desert, a good weather forecast can mean the difference between life and death.
But meteorologists don’t have any effective methods to help them predict the flash floods that might occur in the southern region of the country.
Each year floods wash over the normally arid landscape, often causing death and destruction without warning. And this disturbing situation had Pinhas Alpert, a geophysicist at Tel Aviv University very concerned and seeking for an antidote.
“I can tell you that we’ve looked at two flash flood cases,” he says. “People were killed … no advance warning.”
Alpert worked as a weather forecaster for 35 years and has since has turned his attention to predicting phenomena such as floods. In a study published in April’s Atmospheric Chemistry and Physics journal, he details a way of predicting a flood’s occurence and its intensity.
“An advance warning, of even a few minutes, could save a life,” he says.
His proposed method makes use of a high-tech infrastructure already being deployed around the world – granting measurement access to rough terrain and remote locations.
By taking measurements of the changes to the signals emmitted by cell phone towers, a flood could be predicted up to an hour ahead of time.
Since the weather affects the electromagnetic field that cell phones and reception towers use to exchange microwaves, the wireless networks can serve as built-in environmental monitoring facilities. By applying the right measurements, forecasters could learn of atmospheric moisture levels to a high degree of accuracy, both regarding time and place.
What’s more, cell towers are usually close enough to the ground to detect near-ground moisture – the important factor in predicting floods, Alpert explains.
“Near-surface monitoring of atmospheric moisture needs to be improved,” he says. “This was proven as the major reason for failing to predict floods over the (Israeli) Alpine region.”
The cell towers can also be used to monitor rainfall and assist in short-range forecasting of flood threats, the geophysicist adds.
It’s a preliminary method and not about to become widespread practice among meteorologists. You won’t start getting a flood risk predictor with your daily chance of rain and temperature in your weather reports any time soon.
But Environment Canada is still interested.
“Environment Canada is continuously examining new techniques aimed at improving water vapour estimates and precipitation forecasts,” a spokesperson says, adding that such activities could have positive implications for flood forecasting.
“We are currently undertaking related research looking at mapping and utilization of column water vapour with GPS receiver stations.”
Of course, there are challenges associated with the flood prediction method that relies of cell phone tower signals. Any rain, fog paths between the cell tower and measuring device could interfere with the readings — as could winds that cause movement in the towers.
Environment Canada concedes that the study results are “quite preliminary and based on a relatively small data set,” and says the development of proper quality control techniques will be important.
For now, Canadian forecasters will stick to tracking water levels and flows to determine flood threats.
Alpert’s study may have been small, but it was very accurate. It used two cell towers in Israel over a period of 28 days and compared their microwave link measurements to a humidity gauge.
One site was able to predict the humidity levels with 90 per cent accuracy, while the other had 82 per cent accuracy.
Cellcom and Pelephone were the carriers in Israel that provided the microwave data.
Alpert says the method could be used anywhere there are cell towers, including Canada. To do it, it would require collecting cell phone tower data, applying the algorithms developed to determine atmospheric moisture, creating a weather model with the improved surface moisture predictions and then evaluating the skill of the models.
But it may be along way off from being put into use.
Telus Corp. was unable to provide a spokesperson that could discuss what would be required to apply the method to its network of cell towers.
In Israel, Alpert plans to continue to refine his technique and eventually see the day when his method will result in flood predictions – and saved lives.
