Spectral power density derived from cross-correlation of Tmax and sun-hours data from UK Met. Office Durham station.
Both Tmax and d/dt(Tmax) were cross-correlated with sun-hours data. The derivative gave slightly sharper defined peaks and was preferred for reading the peak values.
Graph annotation are approximate only. Values below were read off at higher resolution.
1.853 2.682 3.118 3.4945 3.796 4.894 6.686 8.25 11.24
p1=2.682; pc=3.4945; p2= 4.894
3.465 * 11.868 ; triplet asymmetry: -0.849 %
p1= 3.118; pc= 3.796; p2= 4.894
3.809 * 17.184 ; triplet asymmetry: 0.345 %
It may be coincidental but the first triplet has a modulating frequency that matches the orbital period of Jupiter to 4 significant figures.
pJ = 11.8624 years
Derived frequencies are calculated as follows:
Explanatory notes on amplitude modulation triplets: