% Conclusion and Outlook

The amplitude of the 6, 7 and 8-day-week is more or less the same for one measured value in all periods. This indicates a random process.

The simulation shows the importance of dynamics or different processes not studied here. So it looks like the difference between weekdays is caused by the dynamics.

Nevertheless if there is an anthropogenic 7-day cycle effect it must be very small and it would be more or less impossible to find this signal. One method that has not used so far is to build an \ac{ARMA}-model.

The results presented here indicate, that a weekly cycle in climatology is random. The \PM{1} and \PM{10} values however provide a clearly significant 7-day course.

The simulations---that initially were created to have a plausibility control of the statistical tests---show additionally how important the dynamics are for weather. The case study for the summer 2007 further clarifies this issue.

In our opinion several studies that have been done on weekly cycles in climatology, apply a basic approach of methods which is not appropriate to detect a weekly cycle. However, this does not mean that it is absolutely impossible to detect one somewhere on this planet (this Masterthesis just focused only on measurements in Switzerland).

It would be interesting to analyse measurements from highly industrialised regions or big cities with a huge air pollution with a \KW{} test and  a \WDT{}. A comparison with simulations would  likewise be very useful---next time maybe with methods a little more sophisticated. Another method is to build an \ac{ARMA}-model.
% Evtl. weitere based suchungen mit ARMA-Modellen!!!
% http://de.wikipedia.org/wiki/ARMA-Modell

Another aspect that might be interesting to consider more precisely are measurements in higher altitudes, like on the Jungfraujoch. The suspended matter measurements from the Jungfraujoch station (since 1998) do yield a significant weekly cycle, while the \PM{10}-data (only since 2006) do not. This result can be coincidence, but we also found several possible explanations, why this could the case.

Now, doing \ac{PM} measurements in different altitudes over industrialised regions or megametropolises could be a way to find out whether weekly periodicities in climatology are possible or not. But maybe even one could not detect a 7-day cycle on the ground in \ac{PM}, due to activities taking place 7 days a week around-the-clock.

For now we can just speak for Switzerland and say that, if there is a an anthropogenically induced 7-day cycle, it must be so small that it would be more or less impossible to detect.

To address the open questions in this and other studies, further research is needed.