Rico-Bordera et al. (2026) Emerging Links between Droughts, Heatwaves and Extreme Precipitation in a Western Mediterranean Hotspot: Evidence of Intensifying Compound and Sequential Hazards

Identification

• Journal: Earth Systems and Environment
• Year: 2026
• Date: 2026-02-21
• Authors: Belén Rico-Bordera, Pau Benetó, Samira Khodayar
• DOI: 10.1007/s41748-026-01053-2

Research Groups

• Mediterranean Center for Environmental Studies (CEAM)

Short Summary

This study analyzes the increasing occurrence and impacts of compound and sequential climate events (heatwaves, droughts, forest fires, and extreme precipitation) in the Western Mediterranean Valencian Community from 1979 to 2021, revealing a rising frequency of concurrent hazard days and an increasing influence of Mediterranean Sea warming on autumn flood risks.

Objective

• To deepen the understanding of the compounding and sequential effects of extreme heat, drought, and heavy rainfall hazards in the Valencian Community, a climate change hotspot.
• To evaluate whether high-resolution local findings align with broader regional studies conducted at a coarser resolution.

Study Configuration

• Spatial Scale: Valencian Community (eastern Spain) and adjacent Western Mediterranean Sea, with a resolution of 0.05° (approximately 5 km) for temperature and precipitation, and 5.5 km for wind. Forest fire data was transformed to a 5 km resolution grid.
• Temporal Scale: Daily data from 1979 to 2021 for most hazards, with forest fire data from 1993 to 2021. Analysis focused on summer (June-July-August, JJA) for heatwaves, droughts, and forest fires, and autumn (September-October-November, SON) for extreme precipitation.

Methodology and Data

• Models used:
  • Standardized Precipitation Evapotranspiration Index (SPEI) using Hargreaves method for drought identification.
  • Linear models for trend calculation of AHW days, MHW intensity, and drought magnitude/duration.
  • Non-parametric Mann-Kendall (MK) test and Sen's slope for EPE trends.
  • Pearson's correlation coefficient for lagged correlations between variables.
  • Normalized Information Flow (NIF) for assessing causality strengths.
• Data sources:
  • Temperature and Precipitation: Optimal interpolation Observational grid for Iberian Peninsula and Balearic Islands (ROCIO-IBEB) dataset (AEMET) at 0.05° resolution.
  • Sea Surface Temperature (SST): ERA5 reanalysis dataset (ECMWF) at 0.25° resolution.
  • Forest Fires: Cartography from the Valencian Cartographic Institute (ICV) as vectorial data.
  • Wind: Copernicus European Regional ReAnalysis (CERRA) dataset at 5.5 km resolution.

Main Results

• The frequency of concurrent hazard days (droughts, atmospheric heatwaves, marine heatwaves, forest fires) in the Valencian Community increased by approximately 2.2 days per decade.
• Atmospheric heatwaves (AHWs) and marine heatwaves (MHWs) showed statistically significant increasing linear trends in frequency of 1.6 days per year per decade and 17 days per year per decade, respectively, during summer. MHWs also showed a significant intensification of 0.5 °C per decade.
• Drought conditions, indicated by negative SPEI values, increased in annual mean duration and intensity over the past two decades, with a non-significant mean magnitude linear trend of approximately 3% per decade.
• Droughts are a key driver of summer wildfires, with over 50% of forest fires (FFs) preceded by consecutive drought conditions in the 10-day period prior to occurrence.
• Approximately 71% of large FFs (burned area > 1 ha) occurred under AHW and/or drought conditions, with 38.5% compounding with both, 22% exclusively with droughts, and 11% exclusively with AHWs. Moderate wind speeds (above 5 m/s), particularly dry Ponent winds (SW to NW), compounded with almost 24% of FFs.
• Extreme precipitation events (EPEs) exceeding 60 mm/day in autumn (SON) increased in frequency by almost 50% and mean intensity by 19% in the period 2001-2021 compared to 1979-2000.
• Normalized Information Flow (NIF) analysis revealed an increasing influence (up to 12% at p-value < 0.05) of Mediterranean Sea warming (SST anomalies) on extreme autumn precipitation, suggesting an increasing influence of MHWs on autumnal flood risks, particularly in pre-coastal and inland areas.
• Strong correlations (r = 0.515) and positive feedback (0.565) were found between land-surface maximum temperature anomalies (TXa) and sea-surface temperature anomalies (SSTa), with SSTa increasingly influencing TXa along the coast.

Contributions

• First integrated, local-scale assessment in the Valencian Community combining AHWs, droughts, MHWs, and EPEs with observed forest fire records.
• Provides novel insights into the sequential effects of compound climate hazards, highlighting growing interconnections between droughts, heatwaves, and precipitation extremes.
• Demonstrates for the first time in the region that a warming Mediterranean Sea is amplifying coastal summer air temperatures and significantly influencing autumn precipitation intensity, including over inland areas.
• Identifies emerging climate hotspots along coastal sectors of Alicante and Castellón with intensifying vulnerability to multiple extremes.
• Proposes a comprehensive, spatially resolved methodology with daily frequency for hazard detection and characterization, crucial for strengthening early-warning systems and developing adaptive strategies.

Funding

• Consellería de Medio Ambiente, Infraestructuras y Territorio [CEAMMeteoATD GVA]
• Research project EVER_PROMETEO [CIPROM/2022/37]

Citation

@article{RicoBordera2026Emerging,
  author = {Rico-Bordera, Belén and Benetó, Pau and Khodayar, Samira},
  title = {Emerging Links between Droughts, Heatwaves and Extreme Precipitation in a Western Mediterranean Hotspot: Evidence of Intensifying Compound and Sequential Hazards},
  journal = {Earth Systems and Environment},
  year = {2026},
  doi = {10.1007/s41748-026-01053-2},
  url = {https://doi.org/10.1007/s41748-026-01053-2}
}