Book a demoTorrential Flooding in Spain: Is Climate Change Amplifying DANA Events?
Extreme weather in Spain
The Meteorologiclal Setup
Last month, a “Cut-Off Low” (COL) or “DANA” in Spanish (Depresión Aislada en Niveles Altos, #WMO 2024), remained nearly stationary over Spain’s interior, bringing torrential rainfall and consequential catastrophic flooding, particularly around Valencia. This phenomenon resulted in extensive damage, tragic loss of hundreds of lives, significant disruption to communities and infrastructure, and long-term economic impact for the region.
According to Martín León (2003), a DANA is a high-altitude closed depression that becomes fully isolated from the general atmospheric circulation (Jet Stream) and moves independently. It can remain stationary or move retrograde (east to west). The presence of cold air in upper levels associated with this depression, combined with warm, moist Mediterranean air near the surface, creates significant atmospheric instability. This instability fuels intense convection, leading to torrential rainfall along Spain’s Mediterranean coast.
On October 29, 2024, AEMET (Agencia Estatal de Meteorología) recorded an unprecedented rainfall intensity in Turís: 184.6 mm fell within just one hour, totalling nearly 771.8 mm (30 inches) over 24 hours. In a mere three hours, some areas received nearly an entire year’s worth of rainfall, emphasising the storm’s extreme nature.
Figure 1 illustrates the synoptic situation from October 24 to November 1, 2024, highlighting the development of a DANA (cut-off low) over the Iberian Peninsula. An Atlantic “vaguada” (trough) was blocked by high-pressure systems, deepened significantly, and eventually detached from the main westerly flow. This process resulted in an isolated low-pressure system that drew in unstable, moisture-laden air with high convective potential, particularly affecting southern and eastern Spain.
Figure 1: This map shows a weather forecast from ECMWF/IFS, depicting 500 hPa geopotential height with dark blue contour lines, temperature at 500 hPa with a dashed line, and 6-hour accumulated precipitation using a color gradient from blue to red to indicate increasing rainfall. The DANA appears as a distinct circular area of low geopotential height with a colder area in the center.
Extreme Precipitation: Is It Intensifying Due to Anthropogenic Climate Change?
While DANA events are not uncommon in Spain, recent research indicates that they may be intensifying. For instance, Oria Iriarte (2021) highlighted increasing frequencies and intensities of extreme precipitation events in the Mediterranean region. Her analysis found upward trends at the extremes of precipitation distributions (Figure 2), suggesting that very heavy, widespread rains are becoming more frequent.
Figure 2 shows the PDF of accumulated daily precipitation, illustrating shifts in frequency and intensity at a Mediterranean coastal station. A comparison between the periods 1965-1992 and 1992-2020 reveals that both the P98 and P99.5 precipitation intensities have increased, suggesting a rise in the intensity of extreme precipitation events.
Figure 2: The Probability Density Function (PDF) for accumulated daily precipitation (mm) at the Oria Iriarte station (2021) shows the 98th and 99.5th percentiles for two periods: 1965-1992 (red) and 1992-2020 (green). The shift of the curve to the right and upwards between the two periods suggests an increase in both the intensity and frequency of extreme precipitation events.
Furthermore, the World Weather Attribution (WWA) programme recently published a report highlighting preliminary research carried out right after the DANA event indicating that torrential rains in southern Spain are now approximately 12% more intense and nearly twice as likely compared to what they would have been in the pre-industrial climate. However, it is essential to note that these findings, while insightful, are preliminary. This study was based on observational data rather than a complete climate model attribution study, which would offer more robust evidence of causation. When it comes to accumulated rainfall, recent findings from another attribution study based on observational data , ClimateMeter, suggest that these events, which often result in severe flooding, are now up to 7 mm/day wetter in present conditions compared to historical values.
The need for Attribution Studies
DANA events are complex meteorological phenomena, and establishing a direct causal link to climate change requires careful analysis. While the analysis outlined above suggests a connection between human-induced climate change and the intensification of extreme precipitation events in the Mediterranean Sea, definitive conclusions will require more comprehensive attribution studies.
Outlook
As climate risks continue to escalate, comprehensive studies are needed to fully understand the role of human influence in intensifying extreme weather events. Already severe DANA events in the Mediterranean may become increasingly common and destructive if warming trends continue. Companies, governments, and communities need robust climate intelligence to prepare for these events and mitigate their impacts. This underscores the importance of climate risk modeling and sustainable planning.
Sources
- Martín León, F. (2003). Las gotas frías / DANAS: Ideas y conceptos básicos. Instituto Nacional de Meteorología.
- Oria Iriarte, 2021. AEMET Blog. https://aemetblog.es/2021/05/02/esta-aumentando-la-frecuencia-o-la-intensidad-de-las-precipitaciones-extremas-en-el-mediterraneo/
- WWA, 2024. Extreme Downpours Increasing in Southern Spain. https://www.worldweatherattribution.org/extreme-downpours-increasing-in-southern-spain-as-fossil-fuel-emissions-heat-the-climate/
- ClimateMeter, 2024. Southeast Spain Floods. https://www.climameter.org/20241029-south-east-spain-floods
Share the word
.png)
