What is DANA, the strange meteorological phenomenon that has caused deadly floods in Spain?

A strange weather phenomenon known as DANA has caused catastrophic flash flooding in Valencia, Spain, this week. More than 155 people have died and dozens remain missing in what meteorologists call one of the worst natural disasters in recent memory.

On Tuesday (October 29), some areas received a year’s worth of rain in just a few hours, causing massive flooding that devastated entire towns and left thousands of people stranded. In some areas, Precipitation reached up to 20 inches of rain (500 liters per square meter).).

The cause of this disastrous weather is a phenomenon forming in the Mediterranean called Depression Isolated at High Levels (DANA), a Spanish phrase that translates to isolated depression at high levels. It was the most serious DANA recorded in the 21st century, comparable to the catastrophic “Pantanada de Todos” in 1982according to the Spanish State Meteorological Agency (Aemet).

What is a DANA?

DANAs are intensified versions of what is known as a “cold blob,” which occurs when a mass of warm air collides with a stagnant mass of cold air at an altitude of about 29,500 feet (9,000 meters).

In the upper atmosphere there is a very strong current of wind that surrounds the Earth like a belt. Sometimes this current begins to oscillate, looking more like a snake than a belt. When this happens, the oscillation can become “stuck,” allowing the cold air mass to stay in one place. On this occasion it occurred over the southeast of Spain.

A DANA occurs when this cold air meets very warm air near the surface, especially over the warm waters of the Mediterranean. This combination creates a significant temperature difference between the different layers of the atmosphere, which in turn causes hot air to rise easily and become saturated with water vapor.

If this contrast in temperatures is combined with the humidity and energy of the Mediterranean, which is very warm after the summer months, the result is strong storms and torrential rains.

“The winds may not be as violent as those of a hurricane, but in terms of precipitation and intensity they can even exceed them. These events can cause property damage and loss of life as significant as those of an average hurricane.” hurricane“,” Jorge Olcinadirector of the Climatology Laboratory at the University of Alicante told LiveScience.

A boy clears debris on a flooded street full of crashed cars

The storm dropped a year’s worth of rain in a matter of hours, causing severe property damage and killing more than 155 people. (Image credit: Anadolu via Getty Images)

Iago Pérez, a geoscientist at the University of Oxford, described DANA as one of the most dangerous meteorological phenomena in Spain, noting that they “release enormous amounts of water in a very short time.”

DANAs form only over Spain, but similar weather patterns, called extratropical cyclones, form in the Atlantic off Uruguay and Argentina, the researchers said.

On October 29, DANA flew over the same area for more than 12 hours, making it the most intense day of the year. Meteorological event, which is expected to continue with less intensity until Sunday. (November 3).

DANA use hot water as “fuel”, meteorologist Mar Gomez he told LiveScience.

DANA found water temperatures of around 72 degrees Fahrenheit (22 degrees Celsius) off the coast of Valencia, while the usual temperature for this time of year is around 70 F (21 C). That difference may seem small, but it is enough to provide additional energy to the storm system. This can “cause a cascade of rain in a very short period,” Olcina said. “These rains can be characterized as monsoonal.”

What does climate change have to do with this?

Gómez and Olcina agree that the severity of this week’s DANA is directly related to climate change. Pérez, however, believes that attributing the phenomenon to global warming requires a deeper analysis.

He Mediterranean Sea It is one of the marine basins that has warmed the most in recent decades. It acts as a “moisture and energy transmission ribbon,” Olcina said. Since the 1980s, the average temperature of the Mediterranean has risen 2.7 F (1.5 C), nearly double the increase in air temperatures in the region during the same period. “Since 2020, summers on the Iberian Peninsula have recorded record temperatures and this year sea surface temperatures have exceeded 29 degrees,” Olcina said.

This warming has altered the DANA calendar, since The Mediterranean is now starting to warm up in May and retains that heat until November. In comparison, during the 1980s and 1990s, this phenomenon generally occurred in September and October. Currently, it is estimated that 15% to 20% more DANA are formed each year compared to six decades ago.

For researchers, this episode offers important lessons, starting with the need to improve early warning communication protocols.

“When there are fatalities, something is not going well. Communication and anticipation of these events must be enhanced,” said Gómez.

Climate change is likely to drive more frequent intense and exceptional rainfall. This underlines the urgent need to adapt prevention and protection systems and to restructure vulnerable areas to reduce the risks associated with increasingly extreme weather, Olcina said.

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