Recent European drying and its link to prevailing large-scale atmospheric patterns
Sigrid J Bakke1,2, Monica Ionita3,4, Lena M Tallaksen5
1Department of Geosciences, University of Oslo, Oslo, Norway. sijb@nve.no.
Scientific Reports
|December 11, 2023
Summary
European droughts are linked to rising atmospheric pressure. Studies show increased high-pressure systems (geopotential height at 500mb) correlate with drier conditions (Standardised Precipitation-Evapotranspiration Index), with future projections indicating this trend will continue.
Area of Science:
- Atmospheric Science
- Climate Science
- Meteorology
Background:
- Europe has experienced severe droughts in recent decades, notably in 2018 and 2022, causing significant societal, environmental, and economic disruptions.
- While the connection between atmospheric circulation and meteorological drought is recognized, in-depth research linking historical drought index changes with large-scale atmospheric patterns in Europe is lacking.
Purpose of the Study:
- To investigate the relationship between historical changes in large-scale atmospheric patterns and meteorological drought indicators across Europe.
- To analyze trends in geopotential height at 500mb (Z500) and the Standardised Precipitation-Evapotranspiration Index (SPEI) for different European climate regions during the growing season.
Main Methods:
- Analyzed geopotential height at 500mb (Z500) and Standardised Precipitation-Evapotranspiration Index (SPEI) data from 1979 to 2021 for North, West, Central-East, and Mediterranean climate regions.
- Calculated correlations and co-occurrences between Z500 and SPEI to assess the link between high-pressure systems and drought.
- Utilized CMIP6 climate models to project future Z500 changes under low-end (SSP126) and high-end (SSP585) emission scenarios.
Main Results:
- Significant trends of increasing Z500 (higher pressure) and decreasing SPEI (drier conditions) were observed in West Europe (spring) and Central-East Europe (summer) from 1979-2021.
- A strong linkage between Z500 and SPEI was confirmed through significant correlations and high co-occurrences (69-96%) of drought and high-pressure anomalies since 1900.
- Future projections suggest anomalously high-pressure systems will become the norm, potentially exceeding 2018/2022 levels under high-emission scenarios, although model uncertainties exist.
Conclusions:
- Historical data reveal significant trends in European atmospheric circulation, strongly correlating with observed drying trends.
- Anomalously high-pressure systems are projected to become more frequent, increasing drought risk across Europe.
- Current climate models (CMIP6 ensemble) face limitations in accurately reproducing the spatial heterogeneity of historical circulation changes, leading to uncertainty in future drought projections.
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