Meteorological analysis of "Morning dips" in wind power production across Germany in 2021

Wind power is highly dependent on the large scale weather situation, but additionally, small-scale variations of the boundary layer can have significant effects on the wind power production. In a joint collaboration with Statkraft, the authors analysed the influence of diurnal variations of the boundary layer on the amount of wind power produced across Germany.

Statkraft maintains wind power plants across the country and monitors the power production. A high-resolution data set of wind power production, broken down to the locations of the power plants, has been analysed with respect to small-scale variations of the wind power production. These sudden and often unexpected drops in wind power production are known to occur during daytime, especially in the morning (“morning dip”).

This work uses the data of 2021 to give the frequency of these morning dips across Germany. Their diurnal and seasonal occurrence is analysed as well as the regional occurrence. The occurrence of morning is analysed with respect to different pattern of meteorological conditions.

We found that morning dips are frequent in the warm season, whereas they are almost missing in the winter. Their average diurnal occurrence is dependent on the time of sun rise, and the relative frequency of days with morning dips was largest in the southern and eastern parts of Germany. Sunny conditions were most likely to be associated with morning dips, even when the large-scale flow was only modest. Cloudy and rainy conditions were not favorable for morning dips, even when the large-scale flow was strong. We suppose that morning dips are associated with sharp changes of the wind speed within the boundary layer, and that the change of boundary-layer depth during the morning causes the rapid drop of wind power production in particular on sunny days in the warm season.