balanced level of precipitation provides the basis for a wide range of economic
and social activities in Europe. Particularly agriculture, drinking water
supply and inland waterway transport are directly affected. However, the amount
of rain fluctuates strongly from year to year. While it may pour torrentially
in one year, rain may remain absent for weeks in another year. The population
is used to this variability and knows how to deal with it.
chance discovery by an agricultural scientist from Münster, Germany, now
suggests that in certain months rain over Germany and other parts of Europe
follows a pattern that up to now has remained undetected. As part of
agricultural consultation, Ludger Laurenz analyzed decades of rainfall records
of his home weather station in Münster and noticed a constant up and down that
followed an 11-year rhythm – especially in February. After detailed examination
it was clear that this rhythm correlated closely with the activity of the sun:
the well-documented 11-year sunspot cycle.
next teamed up with two colleagues to examine the extent to which the observed
pattern from Münster is reproducible in other parts of Germany and Europe, and
whether the phenomenon also exists for the other months of the year.
Horst-Joachim Lüdecke from the HTW University of Applied Sciences in Saarland
gathered the precipitation data collected in Europe since the beginning of the
20th century. The physicist emeritus then developed a computer algorithm to
determine the similarity of changes in rainfall and solar activity. All 39
European countries and every one of the 12 months of the year were quantified
over a total of 115 years using mathematical correlations.
order to include possible delay effects, the data series of rain and sunspots
were systematically checked for shifts. For this purpose, the time series were
gradually shifted in time against each other like combs and the respective
change of the correlation quality was noted. The multidimensional data obtained
in this way were evaluated for systematic trends by geoscientist Sebastian
Lüning and visualized cartographically. Lüning is associated with the Swiss
Institute of Hydrography, Geoecology and Climate Sciences (IFHGK) and is
specialized in the research of solar climate effects.
mapped out results show that the link between February precipitation and solar
activity originally discovered in Münster is valid for large parts of Central
and Northern Europe and has good statistical significance there. Towards
southern Europe, however, the correlation weakens significantly.
statistical investigation was also able to demonstrate systematic phase shifts
across the continent. In Germany and neighboring countries, February
precipitation was particularly low when the sun was very strong four years
earlier. The delay seems to be due to the slow deep circulation of the
Atlantic, as earlier work had already suggested. On the basis of the
statistically-empirically determined correlation, February 2018 in Germany with
particularly low precipitation can now also be explained, which followed a
particularly high intensity peak of solar activity at the beginning of 2014.
relationships between rainfall and solar activity have been observed in other
months, although somewhat weaker, especially in April, June and July, which
account for a large part of the vegetation period in Central Europe. The result
was a complex interplay of sun and rain in Europe, which showed clear trends over
1000 km and varied strongly from month to month.
study thus confirms the concept of a solar participation in the European
hydroclimatic development, which had already been indicated by a whole series
of local case studies of other authors. The exact mechanism by which the solar
signal influences precipitation is still largely unclear and requires further
solar precipitation effect now mapped out across Europe for the first time
opens up new possibilities for improved medium-term precipitation forecasts.
Agriculture in particular, but also protection measures against extreme weather
damage in connection with heavy rainfall and droughts could benefit from this. The
next step in refining the forecasting methodology is a more precise quantification
of the effects of Atlantic Ocean cycles, which also play an important role in
rainfall, especially in Western Europe.
L., H.-J. Lüdecke, S. Lüning (2019): Influence
of solar activity on European rainfall. J. Atmospheric and
Solar-Terrestrial Physics, 185: 29-42, doi: 10.1016/j.jastp.2019.01.012
pdf version can be downloaded free of charge at the following link until early
via The Global Warming Policy Forum (GWPF)
February 19, 2019 at 06:47AM