Tel Aviv University Researchers use Smartphone to Anticipate Flash Floods

By the north wind the golden rays emerge; The splendor about Hashem is awesome. Job 37:22 (The Israel Bible™)

Smartphones are so omnipresent throughout the world – as much in developing countries as in the West – that they have the potential to protect us from natural disasters. Tel Aviv University researchers, based on the prediction that by 2020 there will be six billion smartphones around the globe, maintain that data provided by the phones’ sensors could be used to track and anticipate flash floods and other catastrophes that take human lives.

“The sensors in our smartphones are constantly monitoring our environment, including gravity, the earth’s magnetic field, atmospheric pressure, light levels, humidity, temperatures, sound levels and more,” says Prof. Colin Price of TAU’s Porter School of the Environment and Earth Sciences, who led the research. “Vital atmospheric data exists today on some three to four billion smartphones worldwide. This data can improve our ability to accurately forecast the weather and other natural disasters that are taking so many lives every year.”

He collaborated with TAU master’s degree student Ron Maor and doctoral student Hofit Shachaf for the study, which was recently published in the Journal of Atmospheric and Solar-Terrestrial Physics.

Flash floods are unpredictable and potentially deadly forces. Earlier this year, a flash flood that struck near the Dead Sea in April, killed 10 students from the Bnei Zion pre-military academy in Tel Aviv.

It took over five years to get the first billion smartphone subscribers in 2012 and less than two years to get the next billion subscribers. These numbers, together with the quality of the sensors, are expected to increase significantly in the next decade, while the cost of the phones is expected to drop dramatically.

Smartphones measure raw data, such as atmospheric pressure, temperatures and humidity, to assess atmospheric conditions. To understand how the smartphone sensors work, the researchers placed four smartphones under controlled conditions around TAU’s large campus and analyzed the data to detect phenomena such as “atmospheric tides,” which are similar to ocean tides. They also analyzed data from a UK-based app called WeatherSignal.

The tides in the atmosphere are produced by the absorption of solar radiation by water vapor in the troposphere and by ozone in the stratosphere. Similar to tides in the oceans, the atmosphere also has tides. However, unlike tides in the oceans driven by gravitational forces of the sun and moon, atmospheric tides are thermally driven by the periodic absorption of solar radiation throughout the atmosphere. This primarily involves the absorption of ultraviolet radiation by stratospheric ozone and of infrared radiation by water vapor in the troposphere (up to 15 kilometers above Earth).

Price said there are only 10,000 official weather stations around the world –infinitesimal compared to the huge number of smartphones being used. “The amount of information we could be using to predict weather patterns, especially those that offer little to no warning, is staggering,” he insists.

“In Africa, for example, there are millions of phones but only very basic meteorological infrastructures. Analyzing data from 10 phones may be of little use, but using millions of phones would be a game changer. Smartphones are getting cheaper, with better quality and more availability to people around the world.”

The same smartphones may be used to provide real-time weather alerts through a feedback loop, Price continued. The public can provide atmospheric data to the “cloud” via a smartphone application. This data would then be processed into real-time forecasts and returned to the users with a forecast or a warning to those in danger zones.

The study may lead to better monitoring and predictions of hard-to-predict flash floods. “We’re observing a global increase in intense rainfall events and downpours, and some of these cause flash floods,” Price concluded. “The frequency of these intense floods is increasing. We can’t prevent these storms from happening, but soon we may be able to use the public’s smartphone data to generate better forecasts and give these forecasts back to the public in real-time via their phones.”

The largest increase in smartphones is expected to be in the Middle East and Africa, where ownership is expected to rise by more than 200% in the next six years. Asia is likely to have 1.7 billion more smartphone users over the next five years.

In the past few years, a growing number of research groups have tried to use smartphone data for scientific research. In the Netherlands, they have been used to study air pollution, while in the US, smartphone pressure data have been used to improve weather. British scientists have used the devices to map temperature variability, while in California, a seismic network called MyShake has been developed using the accelerometers in smartphones.

But the TAU study is the first to investigate the ability of smartphones to study and monitor atmospheric tides. “We propose considering these sensors for monitoring and studying the atmosphere and environment,” they conclude. “This source of big data may result in significant advances in our ability to monitor and study atmospheric processes in the future.”

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