Photo: Shutterstock The memory of the drought of 2018 in the Netherlands and Western Europe is still fresh. This dry spell may be explained by studying atmospheric air currents. A persistent high-pressure area over the ocean prevented rainfall. That is one perspective. Meteorologist Imme Benedict, who recently obtained her PhD, studied transportation of moisture. Or: which water was retained?
Rhine delta
‘I am interested in how drought occurs’, says Benedict. ‘Can studying the water cycle help us to understand this better? Where does the water normally come from, what sources are involved, and why do these sources fail to a greater or lesser extent during a drought? This makes drought comprehensible, easier to understand, and allows us to learn.’
Benedict focussed on the river basin of the Mississippi and the Rhine. In the Rhine delta, she compared the causes of the dry summers of 2003 and 2018. She studied meteo-data from the past four decades in order to discover where humidity typically originates and how this changes during a drought.
Evaporation
The drought of 2018 clearly shows the effects of a persistent high-pressure area over Western Europe. This blocked the normal supply of humid air from the Atlantic Ocean. Precipitation needed to come from local evaporation, and from moisture that came in from the east. In 2003, that local contribution dropped in the course of the summer: the ground was too dry to evaporate anything at all.
There are still so many processes, such as simulating a persistent high-pressure area, that we need to better understand
Imme Benedict, lecturer at the Meteorology and Air Quality group
Benedict is reluctant to make predictions about future droughts. ‘I understand people are interested in knowing. But there are still so many processes, such as simulating a persistent high-pressure area, that we need to better understand. It is important to focus on this so that we can apply this knowledge to improve the uncertain simulations in the future.’