Quantifying the Central European Droughts in 2018 and 2019 With GRACE Follow‐On

• Published in: Geophysical research letters Vol. 47; no. 14
• Main Authors: Boergens, Eva, Güntner, Andreas, Dobslaw, Henryk, Dahle, Christoph
• Format: Journal Article
• Language: English
• Published: Washington John Wiley & Sons, Inc 28.07.2020
• Subjects: Annual variations; Central European drought 2018; Central European drought 2019; Climatology; Drought; GRACE; GRACE (experiment); GRACE‐FO; Gravity; Groundwater; Lakes; Mass; Moisture content; Recovery; Rivers; Satellite observation; Satellites; Soil; Soil water; Soil water storage; Space missions; Spacecraft recovery; Summer; Surface water; Water content; Water deficit; Water masses; Water storage; Central Europe
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2020GL087285

The GRACE‐FO satellites launched in May 2018 are able to quantify the water mass deficit in Central Europe during the two consecutive summer droughts of 2018 and 2019. Relative to the long‐term climatology, the water mass deficits were −112 ± 10.5 Gt in 2018 and −145 ± 12 Gt in 2019. These deficits are 73% and 94% of the mean amplitude of seasonal water storage variations, which is so severe that a recovery cannot be expected within 1 year. The water deficits in 2018 and 2019 are the largest in the whole GRACE and GRACE‐FO time span. Globally, the data do not show an offset between the two missions, which proves the successful continuation of GRACE by GRACE‐FO and thus the reliability of the observed extreme events in Central Europe. This allows for a joint assessment of the four Central European droughts in 2003, 2015, 2018, and 2019 in terms of total water storage deficits. Plain Language Summary During the droughts of 2018 and 2019, Central Europe had a water deficit of about 112 and 145 Gt compared to an average year. As the water storage differences between winter and summer is about 150 Gt, the drought‐related deficit amounts to 73% and 94% of these annual variations. These mass variations can be observed with the twin satellite missions GRACE (Gravity Recovery and Climate Experiment, 2002–2017) and its successor GRACE Follow‐On (launched May 2018). With the satellite observations, the change in the total water storage can be estimated, including ground water, soil water content, and surface waters such as lakes and rivers. During the 21st century, Central Europe experienced four major droughts in 2003, 2015, 2018, and 2019, and we document the severity of the more recent droughts with respect to earlier events. We also find no systematic offset between the GRACE and GRACE‐FO observations, so that the available satellite gravity record extends now over 18 years already. Key Points GRACE‐FO quantifies continental water mass anomalies in continuation of the GRACE mission (2002–2017) GRACE‐FO observes a water storage deficit of 112 and 145 Gt in 2018 and 2019 in Central Europe relative to the average conditions These deficits amount to 73% and 94% of the mean amplitude of seasonal water storage variations, respectively