Posts Tagged ‘18.6 year cycle’

The lunar nodal cycle and its effects on climate

July 27, 2013

A paper has just been published in the International Journal of Climatology showing that the lunar nodal cycle influences “the low-frequency summer rainfall variability over the plains to the east of subtropical Andes, in South America, through long-term sea surface temperature (SST) variations induced by the nodal amplitude of diurnal tides over southwestern South Atlantic (SWSA).”

Eduardo Andres Agosta, The 18.6-year nodal tidal cycle and the bi-decadal precipitation oscillation over the plains to the east of subtropical Andes, South America, International J of Climatology, DOI: 10.1002/joc.3787

Abstract: This work shows statistical evidence for lunar nodal cycle influence on the low-frequency summer rainfall variability over the plains to the east of subtropical Andes, in South America, through long-term sea surface temperature (SST) variations induced by the nodal amplitude of diurnal tides over southwestern South Atlantic (SWSA). In years of strong (weak) diurnal tides, tide-induced diapycnal mixing makes SST cooler (warmer) together with low (high) air pressures in the surroundings of the Malvinas/Falklands Islands in the SWSA, possibly through mean tropospheric baroclinicity variations. As the low-level tropospheric circulation anomalies directly affect the interannual summer rainfall variability, such an influence can be extended to the bi-decadal variability present in the summer rainfall owing to the nodal modulation effect observed in the tropospheric circulation. The identification of the nodal periodicity in the summer rainfall variability is statistically robust.

The lunar nodal cycle is not something that is very well known but it is another celestial cycle which is clearly not to be ignored. Naturally the IPCC takes no notice of solar cycles, planetary cycles or lunar cycles and all these are lumped into what could be considered “natural variability”.

(Sourced from Wikipedia)

The lunar orbit is inclined by about 5 degrees on the ecliptic. The moon  therefore can lie up to about 5 degrees north or south of the ecliptic. The ecliptic is the plane of the apparent path of the Sun on the celestial sphere, and is coplanar with both the orbit of the Earth around the Sun and the apparent orbit of the Sun around the Earth.

File:Lunar eclipse diagram-en.svg

Lunar eclipse orbital diagram: wikipedia

The lunar nodes precess around the ecliptic, completing a revolution (called a draconitic or nodical period, the period of nutation) in 6793.5 days or 18.5996 years.

The effects of the 18.6 year lunar nodal cycle on climate on tides and geological sediments and on weather and climate have long been of interest (though not apparently for the IPCC).

Nanocycles Method is the English translation of the title of a book published in Russian by Professor of Geology S Afanasiev of Moscow University in 1991,ISBN 5–7045–0109–0.

From “Nanocycles Method” by S Afanasiev, 1991

The lunar node cycle, which is presently 18.6 years, affects the rainfall on a 9.3 year cycle and this shows up as varying thickness layers of deposits, or varves, in geological formations. 

However the moon’s orbit is gradually getting larger over time and so its period is slowing down. The rate of movement of the nodes is also decelerating and Prof Afanasiev has determined the accurate nodal cycle period for the whole of the last 600 million years.

The cycle of the lunar node is important in affecting the weather because it plays a part in determining tides in the atmosphere, oceans and solid body of the earth. The atmospheric tides affect rainfall which in turn affects river flows and hence the deposition of geological varves, or annual deposits in geological layers. ….. 

At the present time, with a nodal cycle of 9.3 years, successive nodal cycles begin 0.3 years later in the seasons each cycle. Therefore after 3 or 4 cycles the nodal cycle start return to the same time of year again. The average period of the cycle when the nodal cycle comes at the same time of year is 9.3/0.3 or 31 years. Specific occurrences of nearly the same season, within 0.1 year, will occur after 28, 65 and 93 years and so on. 

…. Because the lunar nodal cycle period has changed from 9.147 years to 9.298 years in the last 1.0 million years, the secondary cycle has varied from 62.12 years to 31.21 years. If this cycle can be measured in a deposit to an accuracy of 1 year then it allows the dating of the deposit to an accuracy of +/-0.03 million years.

A small selection of papers dealing with the effects of the 18.6 year lunar nodal cycle is given below:

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