What is DANA and why does it happen so often lately?

We have just started September, there are still a few days left before the astronomical autumn in the northern hemisphere, but the meteorological weather seems to be already appearing in Spain on a large scale. Isolated upper level depression (DANA) which can lead to episodes of heavy rainfall and a general drop in temperature at many points Peninsula and Balearic Islands. It is curious, because a few years ago we did not even hear about DANA, but recently they have become a very common phenomenon in our country. Is it our perception or is it true that they are increasing?

There are two answers to this question. First, in fact, DANA has always existed, but this is a phenomenon that was previously mentioned together. Other names. This may make us see something new in this, but it is not. It is also true that DANA increasingly in Spain. This is a common occurrence in our climate, but perhaps not as common as of late. This makes them perhaps another consequence of climate change.

And the fact is that there is something to see, although it rains less and less, when it does, it seems that the rains become more torrential. This is the fault of DANA, like the one that will appear now. DANA, which, if it follows the evolution predicted so far, could break records.

What is DANA?

Even though we are already familiar with it, is it clear to us what DANA is?

As explained National Geography AEMET representative, Ruben del Campois a low pressure system that manifests itself primarily in middle and upper layers of the troposphere.

A low pressure system is an area where the atmospheric pressure is less than the ambient air pressure. As for the troposphere, this is the layer of the atmosphere closest to the Earth’s surface, so the effects of this pressure drop are strongly felt. And what are those effects? Before answering this question, let’s take a step-by-step look at how DANA is formed.

The first thing that happens is that the polar jet oscillates. This is a current of very strong winds, formed in the upper layers of the troposphere, circulating from west to east, separating cold polar air from warm tropical air.

As this jet undulates, a kind of suffocation can occur, resulting in a pocket of cold air surrounded by warmer air. Thus, when these two air masses, cold and warm, collide with each other, along with a low pressure zone, precipitation and thunderstorms. It will be DANA.

Unlike what happens to normal storms that constantly move eastward, DANAs can remain stationary in one place for a long time. It generates local precipitationat very specific points that can become very intense.

Are there more now?

By definition, DANA is the same as cold drop. In the past, they were more often called the second form, coined at the end 19th century. The problem is that this term was gradually distorted until any downpour began to be called a cold drop.

That is why the term “DANA” was taken out of the box and still more so. Therefore, it suddenly appeared in our lives as something new, but it was not there.

Putting that aside, it is true that DANA has increased in recent years. A study published in 2020 showed an increase in these phenomena worldwide since the 1960s. This also has an explanation. We can say that we experienced more or less the same DANA, but they were much more intense. It’s hard to know if it’s true blame for climate change. However, climate models suggest that a relationship exists.

These models are made computationally, modeling climate change based on data from the past. Thus, it was observed that in a hypothetical scenario in which not much greenhouse gas emissions, about 4 or 5 DANA are naturally produced in ten years. Instead, given enough greenhouse gases to affect global warming, there are about eight DANAs in the same time period.

So perhaps DANA seems more frequent to us because of the name change, but in a certain sense they more widespread and intense. In fact, unless forecasts change, this weekend could prove to be one of the busiest we’ve ever experienced. Now it’s time to wait and see if the forecast comes true.