The recent flash floods in Spain were primarily caused by a weather phenomenon known as DANA (Depresión Aislada en Niveles Altos) or the “cold drop.” 

What is DANA?

• Definition: DANA, also known as “cold drop” in Spanish, stands for “isolated depression at high altitudes.”
• It is a weather phenomenon that occurs when a pocket of cold air descends over the warmer waters of the Mediterranean Sea. This collision of cold and warm air creates atmospheric instability, causing rapid formation of dense cumulonimbus clouds.
• Polar Jet Stream Influence: The polar jet stream, a fast-moving wind at the boundary between polar and tropical air masses, can break off pockets of cold air that later collide with warm Mediterranean air, triggering DANA.
• Seasonal Occurrence: Common in autumn and spring, particularly in the western Mediterranean regions.
• Increasing Intensity: Due to global warming, these events have become more frequent and intense, and they now affect inland areas not typically hit by such rainfall, like Madrid.

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Impact of DANA

• Intense Rainfall: DANA causes very heavy rainfall in a short period. For instance, regions in Spain have experienced over a month’s worth of rain in a single day, leading to flash floods.
• Flooding and Infrastructure Damage: Due to the massive deluge, DANA leads to widespread flooding, submerging towns, damaging roads, and straining infrastructure. Flash floods are a significant threat in affected areas, especially along the Mediterranean coast.
• Rising Frequency and Intensity: With increasing sea temperatures due to climate change, DANA events have become more frequent, intense, and geographically widespread, sometimes reaching inland areas unaccustomed to heavy rains, such as Madrid.
• Human and Economic Costs: These events often lead to loss of life, displacement of people, and economic damage due to the need for repairs and recovery efforts in affected areas.

Impact of Climate Change on DANA

• Warmer Air Holds More Moisture: With global warming, warmer air can retain more moisture, leading to heavier rainfall events.
• Mediterranean Sea Temperatures: Sea surface temperatures have risen, with the Mediterranean recording its highest-ever temperature in August, adding to the severity of DANA.