What is DANA? » Yale Climate Connection

DANA is still ongoing over Spain, with very strong storms also occurring along the coast of Andalusia, Castellon and Catalonia. The impact of the meteorological phenomenon known as an isolated upper-altitude depression (DANA) has killed more than 210 people in the Spanish province of Valencia and caused immeasurable damage to the Spanish Mediterranean region.

The incident was the worst disaster the country has experienced in its recent history. Thousands of Spaniards arrived in Valencia over the weekend to assist local residents. Many have criticized the government for being slow to respond to help residents in the worst-hit areas.

What is DANA?

DANA should not be confused with troughs, as the latter are essentially areas where isobars (lines of constant pressure) show V-shaped deformation and typically disappear as they move eastward, whereas DANA is almost static and moves eastward. Any direction, depending on the pressure of the dominant air mass. These substances tend to dissipate when a temperature similar to that of the surrounding air is reached.

While these extreme events happen all the time, they are currently becoming more intense and unpredictable. As climate changes due to carbon emissions, its evolution and development are becoming more rapid. Earth's polar regions are warming faster than the rest of the world, reducing the temperature differences that drive jet streams. On average, the Arctic is warming four times faster than the tropics, which has direct consequences for atmospheric circulation and these extreme events.

The atmospheric circulation consists of five jet streams, known in English as “Jetstreams”: two polar regions, two mid-latitude regions, and one tropical region, all moving around the Earth from west to east. These airflows are often used in air navigation to save fuel.

This airflow is located in the layer of the atmosphere that marks the transition between the troposphere and the stratosphere, at an altitude between 8 and 15 kilometers (5 and 9 miles). In the troposphere (from the surface to about 12 kilometers or 7 miles), while in the stratosphere, temperatures increase with altitude, between 12 and 50 kilometers (7 and 31 miles).

These powerful air currents are like undulating rivers, with curvature and undulations, and their winds blow from west to east at speeds of 129 to 225 km/h (80 to 140 mph), although at times they can reach speeds in excess of 500 km/h. Hour.

Due to the fluctuations in the jet stream, in some cases they can become “jammed” and isolated from normal airflow, forming what is known as an isolated upper-level low, or dana. This creates a closed clockwise circulation and traps cold air, forming cumulonimbus clouds that act like a large pocket of water.

As DANA, commonly known as cold droplets, move over land, warm air from summer or fall convection comes into contact with this mass of cold water, causing the humidity accumulated in the clouds to drop rapidly, producing precipitation. As a result, urban flooding, river flooding, etc. This phenomenon has caused disasters, such as the one in Valencia, Spain.

This is a relatively typical phenomenon in the Spanish Levante, as it refers to the Valencia region as well as Murcia, Malaga and Almeria. Typically, this phenomenon occurs in late summer and early fall, when a combination of low pressure and “pocket” air creates a temperature difference between the upper levels and the ground, creating vertical air currents due to differences in air density and forming clouds.

Rescue operations are continuing and more victims are expected to be found. Such events are likely to become more frequent due to climate change, so preparation is needed at both the individual and government levels.