New Technique May Predict Extreme Rainfall and Flooding in Andes Mountains

There may be a new way to predict disasters. Scientists have developed a new technique that builds upon a mathematical comparison that can be used for any time series data and could be applied to extreme events in all sorts of complex systems.

When it comes to extreme events, there's no better example than the monsoon in South America. This weather system hits the region from December to February, bringing moist, warm air from the tropical Atlantic. When this air travels westward, the wind is blocked by the steep Andes mountains and turn southward. The warm air masses, loaded with moisture, can meet cold and dry winds in the south and leads to torrential rainfall. This, in turn, can cause floods. Predicting this event, though, is harder than you might think; however, scientists may have now found a way.

"Current weather forecast models cannot capture the intensity of the most extreme rainfall events, yet these events are of course the most dangerous, and can have severe impacts for the local population, for example major floods or even landslides," said Niklas Boers, the lead author of the new study, in a news release. "Using complex networks analysis, we now found a way to predict such events in the South American Andes."

The researchers analyzed close to 50,000 high-resolution weather data time series dating from the 15 years since high quality satellite data became available. This showed then that the huge rainfall clusters start off in the area around Buenos Aires, but then travel toward the Andes where they can cause extreme rainfall events. With their new technique, the scientists found that they were able to correctly predict 90 percent of extreme rainfall events during El Niño conditions, and 60 percent of those occurring under any other conditions.

"While the findings were hard to derive, local institutions can now apply them quite easily by using readily available data, which helps a lot," said Jose A. Marengo, co-author of the new study. "Major rainfall events can result in floods which for instance in early 2007 alone produced estimated costs of more than 400 million U.S. dollars in the region. It is now up to the affected countries to adapt their disaster preparation planning."

The findings could be huge in terms of predicting these extreme rainfall events. This, in turn, could help with preparedness and reduce the amount of damage that floods cause.

The findings are published in the journal Nature Communications.