Barcelonathe word DANA is on everyone’s lips these days after the tragic and catastrophic rainstorm of the last few hours in the Valencian Country and in other areas of the Peninsula. A concept we have become familiar with and associate with extreme weather phenomena, but few people really know its meaning. What exactly is a DANA and why can it become so devastating? Here are the keys to understanding this phenomenon:
What is a DANA?
The DANA concept comes from the acronym isolated depression at high levels. It is a system of low pressure and cold air at a height – at around 9,000 meters – that separates and falls off the wind currents from where it originates. As its name suggests, it remains isolated in the atmosphere and often stagnates with a lot of associated instability, which causes sudden changes in weather in its areas of influence, while relatively few kilometers away we can find a good alone and under the effects of the anticyclone.
Why can a DANA last so many days?
Unlike a regular storm, a DANA can be very stagnant for a few days in a specific area. For example, in this case the Iberian Peninsula has been under the effects of this phenomenon for almost a week. The fact that it is isolated from other depression areas, and sometimes surrounded by anticyclones, means that its movements are erratic and that instability can be maintained for days in the same area. Factors that make the work of weather men and women very difficult when it comes to preparing and fine-tuning weather forecasts.
Why does it cause downpours in specific areas?
Since a DANA moves aimlessly and very erratically, depending on where its core is, it can cause more or less intense rain in one area or another. And here the climatic and orographic conditions of each place also come into play. For example, on Tuesday the core of the DANA was in the Gulf of Cadiz, where it drove warm maritime winds and laden with moisture that, combined with the cold air aloft, were the perfect storm to cause severe downpours in the Valencian Country. Since the core of the phenomenon has been moving with the turn of the winds, the rains have been appearing in different parts of the Peninsula, especially in the Mediterranean.
Why do DANA affect the Mediterranean so much?
A DANA is a common phenomenon in our house that occurs especially between the end of summer and the beginning of autumn. It mainly affects the Mediterranean because at this time of the year the sea is very hot, and when the heat and humidity of the sea collide with the instability and cold air at high altitude, torrential downpours and abundant rains occur in the Mediterranean area. It’s an explosive combination that tends to produce the worst storms.
The climate crisis and DANA
The context of the climate crisis we are living in undoubtedly influences the impact of DANA in our home. The fact that the sea is getting warmer due to global warming plays a key role. The warmer the seawater, the greater the collision with the cold air aloft, and this leads to more torrential rain and more extreme weather events. If episodes as catastrophic as those of the last few hours used to occur every many decades, they can now take place every few years due to the effects of climate change.
Why has this DANA been so exceptional?
The orographic and urban conditions have been the other factors for this DANA to have been so exceptional. In the case of the province of Valencia, the constant winds from the sea towards the land produced rains that, when they collided with the mountains in the interior, generated a train of storms that persisted for hours, leaving more than 500 l/m² or 600 l/m² in a few hours and caused the tragic and historic downpours. The fact that many urban areas were built in flood zones worsened the effects of the rains.
Are ‘DANA’ and ‘cold drop’ the same thing?
A DANA is what used to be known as a freda drop. So the two terms mean the same thing. What happens is that the concept freda drop it became very familiar and distorted at a scientific level, and even generated fear among the population due to its devastating effects. For this reason, it was decided to create the new concept recently DANA.
