Benetó et al. (2026) Exploring shifts in extreme precipitation and synoptic forces across the Iberian Peninsula: A regionalized perspective

Identification

• Journal: Weather and Climate Extremes
• Year: 2026
• Date: 2026-06-26
• Authors: Pau Benetó, José Antonio Valiente, Samira Khodayar
• DOI: 10.1016/j.wace.2026.100929

Research Groups

Mediterranean Center for Environmental Studies (CEAM)

Short Summary

This study conducts a comprehensive regionalization analysis of extreme precipitation events (EPEs) across the Iberian Peninsula for 1951-2021, identifying eight coherent regions and their evolving atmospheric drivers. It reveals two distinct evolutionary pathways: Atlantic regions show a moderate (5-10 %) intensification of EPEs linked to increased surface flows, while Mediterranean regions exhibit a marked (15-25 %) extremization associated with vorticity intensification at 500 hPa, both alongside substantial atmospheric moistening.

Objective

• To identify the dominant synoptic conditions associated with regionalized EPEs across different sectors of the Iberian Peninsula.
• To evaluate how the relationships between synoptic conditions and EPEs are changing under current climate change conditions.

Study Configuration

• Spatial Scale: Iberian Peninsula, including Peninsular Spain and Balearic Islands, regionalized into eight precipitation-coherent regions. Synoptic analysis domain: 30°N to 55°N and 30°W to 10°E.
• Temporal Scale: 1951-2021, with analyses often using 30-year moving periods to assess climatological characteristics and trends.

Methodology and Data

• Models used:
  • Precipitation regionalization: Multistep, connectivity-based approach using Pearson's correlation, a connectedness criterion, weighted centroid computation, and HDBSCAN (density-based clustering).
  • Synoptic classification: 16-grid Jenkinson-Collison (JC) method, extended to 500 hPa geopotential height, classifying atmospheric conditions based on vorticity (Z), flow strength (F), and flow direction (D).
  • Trend analysis: Mann-Kendall (MK) test and Sen's slope.
• Data sources:
  • Daily precipitation: ROCIO_IBEB dataset (5 km spatial resolution) from the Spanish Meteorological Agency (AEMET).
  • Atmospheric variables: ERA5 reanalysis dataset (0.25° horizontal resolution) for mean sea level pressure (MSLP), geopotential height (GEOP) and air temperature (TEMP) at 500 hPa, and total column water vapor (TCWV).

Main Results

• Eight precipitation-coherent regions were identified across the Iberian Peninsula: Galicia (GA), Cantabrian (CA), Mijares-Turia (MT), Ebro (EB), Segura (SE), Guadalquivir (GQ), Guadiana (GD), and Duero-Tajo (DT).
• EPEs show an overall intensification in most regions (1951-2021), with maximum annual magnitudes increasing 2 to 5 times more than mean magnitudes.
• Atlantic regions (GA, DT, GQ): Show a moderate (5-10 %) intensification of EPEs. This is linked to a weakening and northward displacement of upper-level atmospheric perturbations (decreasing 500 hPa vorticity in DT and GA) but an increase in surface flows (GA). A generalized moistening is observed, with a 5-8 % frequency increase for daily mean TCWV values above 16 mm.
• Mediterranean regions (EB, MT, SE): Exhibit a marked (15-25 %) extremization of EPEs. This is associated with vorticity intensification at 500 hPa (MT shows >10 % decadal increase in vorticity at surface and 500 hPa) and surface flow intensification (EB shows a 4 % decadal increase). A substantial increase in moisture is found for the moistest air masses (e.g., EB: 6 mm increase for the 99.9th percentile of TCWV).
• Cantabrian (CA) region: Displays transitional behavior with increased EPE frequency and marked extremization, mainly due to local intensification. This is linked to a 500 hPa flow intensification (3.2 % decadal increase) driven by increasing geopotential gradients, despite minimal changes in TCWV.
• The intensification of EPEs is mainly associated with local precipitation intensity in southern Mediterranean regions (MT, SE) and CA, whereas in GA and EB, it is primarily driven by an increase in the affected area.

Contributions

• Provides the first comprehensive, regionalized analysis of EPEs and their evolving synoptic conditions across the Iberian Peninsula using an objective regionalization approach.
• Identifies distinct regional pathways for EPE evolution (Atlantic, Mediterranean, and transitional Cantabrian) and their specific atmospheric drivers (thermodynamic vs. dynamic factors).
• Highlights the critical importance of regionalized approaches for understanding precipitation extremes in topographically complex regions, offering insights for targeted early warning systems and localized climate adaptation strategies.
• Employs a novel methodology that weights synoptic conditions by EPE magnitude and regional specificity, providing a more relevant analysis of drivers for high-impact events.

Funding

• Research project EVER_PROMETEO [CIPROM/2022/37]
• Mediterranean Center for Environmental Studies (CEAM) partly supported by Generalitat Valenciana

Citation

@article{Benetó2026Exploring,
  author = {Benetó, Pau and Valiente, José Antonio and Khodayar, Samira},
  title = {Exploring shifts in extreme precipitation and synoptic forces across the Iberian Peninsula: A regionalized perspective},
  journal = {Weather and Climate Extremes},
  year = {2026},
  doi = {10.1016/j.wace.2026.100929},
  url = {https://doi.org/10.1016/j.wace.2026.100929}
}