The 2018-2019 European drought sets a new benchmark over 250 years

The 21st-century droughts in Europe are regarded as exceptionally severe
and negatively affecting a wide range of socio-economic sectors due to
increases in temperature together with a lack of precipitation during
the spring/summer months [1]. In this study, we synthesize a space-time
evolution of soil moisture droughts in the period of 1766-2019
to better understand the evolution of large-domain multi-year droughts
reflecting the long-term historical changes in hydroclimate variability across Europe.

Following steps are taken to quantify the prolonged (multi-year) soil
moisture droughts: (1) simulate soil moisture (SM) with
the mesoscale Hydrologic Model (mHM, [2]) forced using several bias-corrected
meteorological merged products [3-5]; (2) estimate
quantile-based soil moisture index (SMI) based on a 254-year long
monthly dataset, which is estimated with a kernel density approach [6];
(3) perform a spatio-temporal clustering algorithm to track droughts
through space and time along their evolution, for a given threshold of
SMI<0.2 [6]; (4) estimate drought statistics such as areal extent,
duration, intensity for all identified soil moisture drought events. 

The results from the period 1766-2019 show that total drought intensity
over Europe has an increasing trend, while the average
drought area remains unchanged.  In terms of total drought magnitude,
the ongoing recent 2018-2019 drought is ranked as the most extreme,
followed by 1920-1922, 1947-1948, 1857-1860, and 1988-1991
events. All these exceptional summer droughts were initiated in spring
primarily as a result of compounding effects of low precipitation and
high temperatures leading to extreme soil water
deficits. The 2018-2019 event exhibits average drought area covering
50% of the study domain, which is same as in 1947-1948. Our analysis
suggests that the 2018-2019 event is a new European drought benchmark,
replacing the well-documented 2003 drought event.

References:

[1] https://doi.org/10.1038/s41598-018-27464-4
[2] https://www.ufz.de/mhm
[3] https://doi.org/10.1007/s00382-007-0257-6
[4] https://doi.org/10.1002/joc.3711
[5] https://doi.org/10.1029/2009JD011799
[6] https://doi.org/10.1175/JHM-D-12-075.1