Drobinski et al. (2016) Scaling precipitation extremes with temperature in the Mediterranean: past climate assessment and projection in anthropogenic scenarios

Identification

• Journal: Climate Dynamics
• Year: 2016
• Authors: Philippe Drobinski, Nicolas Da Silva, Gérémy Panthou, Sophie Bastin, Caroline Müller, Bodo Ahrens, Marco Borga, Dario Conte, Giorgia Fosser, Filippo Giorgi, Ivan Güttler, Vassiliki Kotroni, Laurent Li, Efrat Morin, Barış Önol, Pere Quintana Seguí, Raquel Romera, Csaba Zsolt Torma
• DOI: 10.1007/s00382-016-3083-x

Research Groups

• LMD/IPSL, CNRS and École Polytechnique, Université Paris-Saclay, France
• LSCE/IPSL, CNRS and CEA, Université Paris-Saclay, France
• LATMOS/IPSL, UVSQ, UPMC Univ. Paris 06, CNRS/INSU, Université Paris-Saclay, Sorbonne Universités, France
• LadHyX, CNRS and Ecole Polytechnique, Université Paris-Saclay, France
• Institute for Atmospheric and Environmental Sciences, Goethe-University Frankfurt, Germany
• Department of Land and Agroforest Environments, University of Padova, Italy
• CMCC, Lecce, Italy
• Météo-France/CNRM, CNRS/GAME, Toulouse, France
• Abdus Salam International Centre for Theoretical Physics (ICTP), Trieste, Italy
• Meteorological and Hydrological Service of Croatia (DHMZ), Zagreb, Croatia
• Institute for Environmental Research and Sustainable Development, National Observatory of Athens, Greece
• Geography Department, The Hebrew University of Jerusalem, Israel
• Department of Meteorology, Aeronautics and Astronautics Faculty, Istanbul Technical University, Turkey
• Observatori de l’Ebre, Universitat Ramon LLull - CSIC, Spain
• Environmental Sciences Institute, University of Castilla-La Mancha, Spain

Short Summary

This study assesses the scaling relationship between precipitation extremes and temperature (P-T scaling) in the Mediterranean using an ensemble of regional climate models (RCMs) from HyMeX/MED-CORDEX. The P-T scaling exhibits a robust "hook shape" (Clausius–Clapeyron (CC) scaling at low temperatures, negative slope at high temperatures), but projections show that the overall change in extremes under the RCP8.5 scenario follows the CC law, implying that the Mediterranean Sea acts as a moisture source maintaining constant relative humidity despite regional warming.

Objective

• To investigate the spatial variability of the "observed" scaling of precipitation extremes with temperature across the diverse Mediterranean basin (coastal, plains, mountains, arid/mid-latitude climates).
• To quantify the uncertainty associated with the simulated "observed" and "projected" scalings of precipitation extremes using RCM ensembles.
• To assess the sensitivity of the simulated scaling to model resolution and ocean–atmosphere coupling effects.
• To determine how the "observed" scaling in the present climate and the "projected" scaling in anthropogenic scenarios differ, and to understand the underlying physical mechanisms.

Study Configuration

• Spatial Scale: Mediterranean region, assessed using gridded data (0.25° E-OBS) and RCM simulations (0.44°, 0.18°, 0.11° horizontal resolution) covering the entire basin, validated against in-situ station data from Croatia, France, Israel, Italy, Spain, and Greece.
• Temporal Scale: Present climate assessment period (1979–2008 or 1989–2008, historical runs) and future climate projection period (2070–2100) under the RCP8.5 scenario. Analysis uses daily and sub-daily (down to 10 minutes) precipitation accumulation times.

Methodology and Data

• Models used: Ensemble of Regional Climate Models (RCMs) from the HyMeX and MED-CORDEX programs, including ALADIN V5.2, CCLM, RegCM V4.3, WRF V3.1.1, LMDZ V4. Coupled atmosphere-ocean simulations used NEMO-MED8 or NEMO-MED12.
• Data sources:
  • Observations: E-OBS gridded dataset (version 10, 0.25° resolution) for daily temperature and precipitation; in-situ measurements from surface weather stations for sub-daily analysis.
  • Reanalysis/Forcing: ERA-Interim reanalysis (used for RCM boundary forcing for present-day simulations).
  • Scenarios: CMIP5 Global Climate Model (GCM) outputs (used for RCM boundary forcing for historical and RCP8.5 future projections).
• Methodology: Precipitation–temperature pairs were binned by daily mean 2 m air temperature (100 samples per bin). The 99th percentile of precipitation intensity was calculated for each bin. An exponential regression was applied to determine the slope of the P-T relationship, comparing it against the Clausius–Clapeyron (CC) scaling (approximately 7 % K$^{-1}$).

Main Results

• Present-Day Scaling (1979–2008): The P-T scaling exhibits a robust "hook shape" across the Mediterranean in both observations and RCM simulations. The slope is close to CC-scaling (approximately 7 % K$^{-1}$) at low temperatures and systematically negative (sub-CC scaling) at high temperatures.
• Temperature Break Variability: The temperature break (the point where the slope sharply changes) varies spatially, ranging from approximately 20 °C in the western Mediterranean (Spain, France) to less than 10 °C in Greece. In arid regions (e.g., Israel), the slope is negative across all temperatures.
• Model Sensitivity: The P-T scaling is insensitive to atmosphere–ocean coupling. Resolution (0.44° vs. 0.11°) only slightly affects the scaling at high temperatures for short accumulation times, primarily by influencing the duration of convective events.
• Future Projections (2070–2100, RCP8.5): The temperature break shifts to higher temperatures by 4–5 K, which corresponds to the mean regional temperature change due to global warming.
• CC Law Applicability: Despite the present-day hook shape, the future P-T scaling curve can be accurately recovered by adjusting the historical curve using the CC law and the projected temperature shift.
• Moisture Source Implication: This successful adjustment implies that relative humidity remains nearly constant in the future Mediterranean climate, counteracting the expected drying trend. This is attributed to the Mediterranean Sea acting as a significant moisture source, maintaining atmospheric water vapor content consistent with CC-scaling. Conversely, more continental regions (e.g., Central Europe) show a significant decrease in relative humidity at high temperatures.

Contributions

• Provides the first multi-model, multi-resolution assessment of P-T scaling across the entire Mediterranean using the HyMeX/MED-CORDEX framework.
• Robustly confirms the spatial variability of the "hook shape" P-T scaling and quantifies the west-to-east gradient of the temperature break.
• Demonstrates that while the observed P-T scaling deviates from CC at high temperatures, the projected change in precipitation extremes follows the thermodynamic CC constraint (7 % K$^{-1}$) when accounting for the regional warming shift.
• Offers a physical explanation for the maintenance of relative humidity in the warming Mediterranean (moisture advection from the Mediterranean Sea), contrasting this with continental regions where relative humidity decreases significantly at high temperatures.

Funding

• HyMeX program (HYdrological cycle in The Mediterranean EXperiment) through INSU-MISTRALS support.
• Med-CORDEX program (COordinated Regional climate Downscaling EXperiment—Mediterranean region).
• French National Research Agency (ANR) projects REMEMBER (Contract ANR-12-SENV-001) and STARMIP (contract ANR-12-JS06-0005).
• IPSL group for regional climate and environmental studies (HPC resources of IDRIS, allocation i2011010227).
• Spanish Economy and Competitivity Ministry and European Regional Development Fund (Grants CGL2010-18013, CGL2007-66440-C04-02, CGL2013-47261-R).
• Croatian Science Foundation, project CARE, No. 2831.
• Chair for Sustainable Development at Ecole Polytechnique.
• GEWEX program (World Climate Research Program) cross-cutting activity on sub-daily precipitation.

Citation

@article{Drobinski2016Scaling,
  author = {Drobinski, Philippe and Silva, Nicolas Da and Panthou, Gérémy and Bastin, Sophie and Müller, Caroline and Ahrens, Bodo and Borga, Marco and Conte, Dario and Fosser, Giorgia and Giorgi, Filippo and Güttler, Ivan and Kotroni, Vassiliki and Li, Laurent and Morin, Efrat and Önol, Barış and Quintana‐Seguí, Pere and Romera, Raquel and Torma, Csaba Zsolt},
  title = {Scaling precipitation extremes with temperature in the Mediterranean: past climate assessment and projection in anthropogenic scenarios},
  journal = {Climate Dynamics},
  year = {2016},
  doi = {10.1007/s00382-016-3083-x},
  url = {https://doi.org/10.1007/s00382-016-3083-x}
}

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