The research team confronted a long-standing puzzle. Central Europe sits in a climatological transition zone, wedged between the drying Mediterranean and the wetting Nordic countries, and different studies have reached contradictory conclusions about whether the region is becoming wetter or drier. Part of the disagreement stems from the metrics used. The researchers tackled this by employing two complementary drought indices computed over three-month accumulation windows: the Standardized Precipitation Index, which considers rainfall alone, and the Standardized Precipitation Evapotranspiration Index, which also accounts for atmospheric evaporative demand, the combined thirst of the atmosphere for water from soil and vegetation. The gap between these two measures turned out to be the key to the entire story.

To extend the record back to the pre-industrial era, the team harnessed three independent reanalysis datasets, each blending numerical weather models with historical observations. ERA5, the most modern and high-resolution product, assimilates satellites, aircraft, ships and station data but only reaches back to 1940. The Twentieth Century Reanalysis version 3 relies primarily on surface pressure observations and offers temporal consistency from 1836 onward, while the Modern Era Reanalysis incorporates proxy records, documentary sources and early instrumental measurements. Before trusting any of them, the researchers rigorously evaluated each dataset against century-long weather station records from De Bilt, Frankfurt am Main, Paris-Le Bourget and Uccle, using moving-window error metrics and correlation coefficients to identify the periods where each reanalysis could be considered reliable.

The evaluation revealed telling weaknesses. ERA5 showed spurious dryness in its earliest years, likely because upper-air temperature observations were scarce before 1946, while the Twentieth Century Reanalysis displayed excessive wetness before the late 1910s, when the number of assimilated Northern Hemisphere observations jumped sharply. ModE-RA proved dependable from 1844 onward. The final analysis therefore combined reliable windows from each dataset: 1947 to 2023 for ERA5, 1918 to 2015 for the Twentieth Century Reanalysis, and 1844 to 2008 for ModE-RA. Encouragingly, the datasets agreed well with one another, with correlation coefficients for drought-event identification reaching 0.79 between ERA5 and ModE-RA.

The historical perspective delivered some surprising verdicts. The most severe drought in the 180-year record was not the celebrated disaster of 2018 but the great drought of 1921, which persisted for an extraordinary fourteen months in the ModE-RA reconstruction, producing a severity more than double the threshold defining the worst ten percent of events. Comparable clusters of successive dry years to the 2011-2023 period occurred during 1857-1874 and 1947-1960, separated by conspicuously wet intervals in 1912-1920 and 1977-1988. This pronounced multidecadal oscillation means that any assessment of recent trends must reckon with the phase of natural variability, a caution the authors emphasize throughout.

Yet one finding stood out with unsettling clarity. When evaporative demand was included, the 2010s emerged as the driest decade since the pre-industrial era, with 35 drought months in the ERA5 record, nearly a third of the decade, and western Germany locally exceeding 40 drought months. When only precipitation was considered, that same decade looked entirely unremarkable, with just 21 drought months. This divergence is the fingerprint of warming. Since the 1990s, western Central Europe has warmed at 0.42 degrees Celsius per decade, faster than the global average, and the resulting rise in atmospheric evaporative demand has progressively offset the region’s increasing precipitation. In practical terms, droughts that once required a rainfall deficit now can be manufactured, at least in part, by heat alone.

The seasonal anatomy of this shift is equally revealing. Winter and autumn have become wetter, as robust precipitation increases outpace the modest warming-driven rise in evaporative demand during the energy-limited cold season. Summer, by contrast, shows the strongest increase in evaporative demand, which largely cancels out rainfall gains and produces drying in the water-balance index. Most strikingly, spring, historically an intermediate season, has recently tipped toward drying as well, with precipitation rising far below the roughly seven percent per degree expected from basic thermodynamic scaling while evaporative demand climbed more than twice as fast. Spring drying, the analysis shows, is a distinctly recent development, absent from the longer historical record.

To explain these patterns dynamically, the researchers turned to the atmosphere itself. They applied a k-means clustering algorithm to seasonal anomalies of 500 hectopascal geopotential height, the height of the pressure surface roughly five to six kilometers aloft, for every drought event across the Euro-Atlantic sector. Four recurrent circulation patterns emerged: a Baltic High, a British Isles High, a North-South Dipole combining high pressure over Northern Europe with low pressure to the south, and a European High centered directly over the study region. Each carries a distinct hydroclimatic signature. The Baltic High draws warm continental air from the southeast, inflating evaporative demand, while the British Isles High brings cool northerly flow and its droughts are driven almost purely by rainfall deficits. The North-South Dipole dominates winter droughts and, linked to cold easterly air masses, produces the weakest events.

The European High is the villain of the modern chapter. Droughts associated with this pattern, which combines strong anticyclonic subsidence, reduced cloud cover and the largest positive evaporative demand anomalies, are the most intense in the record, particularly over western Belgium and northern France, and they occur predominantly in spring. Crucially, the fraction of droughts tied to the European High has been rising across all reanalyses and both indices, with moderate to high statistical confidence, while associations with the British Isles High and the North-South Dipole have declined since 1947. This dynamical shift dovetails neatly with the observed hydroclimatic trends: the fading winter dipole aligns with winter wetting under increasingly positive North Atlantic Oscillation phases, and the ascending European High provides a coherent explanation for the emergence of spring drying.

The broader implication is that western Central Europe’s droughts are entering a new regime. Severity alone no longer tells the full story, because the 1921 benchmark can still be matched or exceeded by persistence, while the character of droughts, increasingly hot, evaporative and spring-rooted, has shifted beneath the apparent stability of the long-term water balance. The authors note that compound hot and dry conditions, which inflict impacts exceeding either hazard alone, are becoming the regional norm, and that multi-year droughts of the kind seen in 2018 are projected to intensify further as evaporative demand continues to climb. For the roughly 100 million people who live in this economic heartland of Europe, and for the croplands, grasslands and forests it supports, the message of the past 180 years is clear: the droughts of the future will not simply be repeats of the past, and monitoring systems that ignore the atmosphere’s growing thirst risk underestimating the threat.

Subject of Research: Long-term drought variability and associated atmospheric circulation patterns in western Central Europe since 1844

Article Title: Droughts in western Central Europe and associated atmospheric circulation patterns since 1844

Article References: Neimry, E., Goosse, H., & Jonard, M. (2026). Droughts in western Central Europe and associated atmospheric circulation patterns since 1844. Weather and Climate Dynamics, 7(3), 1759-1778. https://doi.org/10.5194/wcd-7-1759-2026

Image Credits: AI Generated

DOI: 10.5194/wcd-7-1759-2026

Keywords: drought, western Central Europe, atmospheric circulation, evaporative demand, climate change, reanalysis, SPEI, anticyclone, European High, multidecadal variability, spring drying, hydroclimate