Insúa-Costa et al. (2022) A global perspective on western Mediterranean precipitation extremes

Identification

• Journal: npj Climate and Atmospheric Science
• Year: 2022
• Date: 2022-02-08
• Authors: Damián Insúa-Costa, Martín Senande-Rivera, María Carmen Llasat, Gonzalo Miguez‐Macho
• DOI: 10.1038/s41612-022-00234-w

Research Groups

• CRETUS, Non-linear Physics Group, Universidade de Santiago de Compostela, Galicia, Spain
• Department of Applied Physics, Universitat de Barcelona, Barcelona, Spain

Short Summary

This study simulates 160 extreme precipitation events in the western Mediterranean to clarify moisture origins, revealing that large-scale moisture transport from remote sources is more critical than local evaporation. The findings emphasize a global perspective for understanding and attributing these events in the context of climate change.

Objective

• To definitively clarify the origin of the humidity fueling catastrophic extreme precipitation events in southern Europe and identify regions relevant for attributing these episodes to global warming.
• To determine if extreme precipitation events in the Mediterranean are dominated by local-scale mechanisms or are more connected to processes in other parts of the planet than previously thought.

Study Configuration

• Spatial Scale: Western Mediterranean region (Spain, Andorra, France, Italy) for event detection; simulation domain covers almost the entire Northern Hemisphere (1416 x 362 grid points).
• Temporal Scale: 160 extreme precipitation events from 1980 to 2015; each event simulated for 31 days.

Methodology and Data

• Models used:
  • Weather Research and Forecasting (WRF) model version 3.8.1
  • WRF-WVTs (Eulerian-online moisture tracking technique)
  • Parameterizations: Yonsei University (YSU) for boundary layer, WRF single-moment 6-class (WSM6) for microphysics, Kain–Fritsch for convection.
• Data sources:
  • High-resolution MESCAN gridded precipitation dataset for event detection.
  • ERA5 (5th generation of ECMWF global reanalysis) for initial and boundary conditions.

Main Results

• The average precipitation fraction with source in the Mediterranean Sea is 35%.
• Evapotranspiration over nearby continental Europe contributes an average of 10% to precipitation.
• The North Atlantic accounts for an average of 25% of precipitation.
• The remaining 30% originates from several more distant source regions, including the tropical Pacific or Southern Hemisphere.
• Remote sources contribute, on average, 10% more than local sources to precipitation, reaching almost 60% for the 25 most extreme cases.
• Mediterranean water vapour is more efficiently rained out (35% precipitation from 27.4% total precipitable water) compared to Atlantic water vapour (34.7% precipitation from 39.4% total precipitable water).
• Mediterranean moisture is predominantly found at low atmospheric levels (30–40%), while Atlantic moisture is more significant aloft.
• Tropical moisture exports contribute an average of 17.3% to precipitation, with maximum values exceeding 40%.
• No significant correlation was found between the El Niño-Southern Oscillation (ENSO) index and the moisture contribution from the Atlantic or Pacific to these events.

Contributions

• Provides a definitive and quantitative clarification of moisture origins for extreme precipitation events in the western Mediterranean using a state-of-the-art Eulerian moisture tagging tool.
• Utilizes a large simulation domain and a comprehensive dataset of 160 extreme events, yielding more robust and general conclusions than previous studies.
• Challenges the traditional regional perspective on Mediterranean extreme precipitation, demonstrating the crucial role of global-scale moisture transport and energy redistribution.
• Reveals that the "well-mixed" assumption for atmospheric water vapour is invalid, showing distinct vertical distributions for moisture from different sources.
• Suggests that alterations in remote regions, such as sea surface temperature, can directly influence catastrophic events in the Mediterranean, necessitating a global approach for climate change attribution.

Funding

• Spanish Ministerio de Economia y Competitividad: OPERMO (CGL2017-89859-R), M-CostAdapt (CTM2017-83655-C2-2-R)
• European Union Interreg V POCTEFA project: EFA210/16 PIRAGUA
• CRETUS strategic partnership: AGRUP2015/02
• European Union ERDF (co-funding for the above programs)
• Xunta de Galicia: Predoctoral grant (Programa de axudas á etapa predoutoral 2019, ED481A 2019/112)
• Spanish Ministry of Science, Innovation and Universities: Predoctoral FPI (PRE2018-084425) grant

Citation

@article{InsúaCosta2022global,
  author = {Insúa-Costa, Damián and Senande-Rivera, Martín and Llasat, María Carmen and Miguez‐Macho, Gonzalo},
  title = {A global perspective on western Mediterranean precipitation extremes},
  journal = {npj Climate and Atmospheric Science},
  year = {2022},
  doi = {10.1038/s41612-022-00234-w},
  url = {https://doi.org/10.1038/s41612-022-00234-w}
}