The lunar nodal cycle and its effects on climate

Posted: October 16, 2013 by tallbloke in solar system dynamics

The k2p blog

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…

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  1. tchannon says:

    An error there is mentioning atmospheric tide.

    As I recall but can’t cite (might have been Lindzen) there was surprise when a lunar atmospheric tide was not present (barely detectable) but unexpectedly a thermal tide is present. Why was figured out.
    Close your eyes on the authors

    I was curious about this so I did try to find what is going on in datasets. All very small. An effect is quite easy to find in good barometric data but critically presupposes the barometer has perfect thermal compensation, an unwise assumption.

    Now for some fun. The ground moves too. That alone is measurable, caution is needed over tiny effects.
    Enjoy, seismometer 840 metres down a borehole where temperature is very stable.

    I’m not saying the paper is wrong.

  2. suricat says:

    Thanks for a way into this thread TC. 🙂 TB made the ‘read more’ link ‘elsewhere’! 😦

    Best regards, Ray.

  3. tchannon says:

    Fooled me for ages suricat when I first came across that horror tall bloke.

    A bug in WordPress makes adding “more” at best unreliable on reblog, ghastly facility.

    NOTE: Two workarounds.

    1. click on the title

    2. if present, click on the balloon with comment count. )for zero I think you need 1(

    And I seem to be reversing )(

  4. Ian Wilson says:

    T Channon,

    The atmosphere has a strong semi-diurnal (and diurnal?) cycle in atmospheric pressure caused by the daily heating of atmosphere by short wave radiation (UV/visible/IR) from the Sun. This thermal atmospheric pressure cycles dominates any ground level atmospheric pressure measurements.

    Given that the wet/dry adiabatic lapse rate fixes the temperature profile in the troposphere, you would expect that the general bulk heating of the atmosphere during the day would produce roughly equal pressure changes with altitude over the mid to lower troposphere ( less than 5 – 8 km in altitude). This is what you see at the link:

    In addition, since the heat capacity of the troposphere decrease with decreasing height, you would expect that any excess heating of the atmosphere due to water vapour would be greatest in the upper troposphere. Hence, you should see enhanced semi-diurnal (and diurnal ?) pressure changes at ~ 15 km (in the tropics) because of excess heating caused by clouds. Again this is what is observed at the cited link.

    Finally, in the lower stratosphere you have significant thermal pressure enhancements above about 20 kilometers cause by excessive heating of the atmosphere caused by ozone absorption. And again, this is what’s observed in the cited link.

    The Semi-diurnal (and diurnal?) Lunar tides in the Earth’s atmosphere are very weak compared to the thermal semi-diurnal tides caused by the Sun. Fortunately, the magnitude of the lunar atmospheric tides increase with altitude. This means that (while small) they a detectable above about 3 km up to about 8 km, especially if you look at long time scales.

    Here is a quote from my paper confirming the detection of Lunar atmospheric tides at 27.3 and 13.6 days by Li and his collaborators.

    The Open Atmospheric Science Journal, 2012, 6, 49-60
    Lunar Tides and the Long-Term Variation of the Peak Latitude Anomaly
    of the Summer Sub-Tropical High Pressure Ridge over Eastern Australia
    Ian R.G. Wilson

    Click to access 49TOASCJ.pdf

    “However, Li [3], Li and Zong [4] and Li et al. [5] have shown that, contrary to currently accepted tidal theories, cyclical changes in lunar tidal forcing produce 27.3 day and 13.6 day periodic atmospheric tides. They detect these atmospheric tides in the tropical troposphere at heights above the 700 hPa isobaric surface (~ 3000m). Furthermore, Li et al. [5] claim that the changes in lunar tidal forcing that are
    responsible for the lunar-driven atmospheric tides, are the same as those that are collectively responsible for the periodic changes in the Earth’s length-of-day (LOD), on fortnightly to seasonal timescales.”

    [3] Li G. 27.3-day and 13.6-day atmospheric tide and lunar forcing on
    atmospheric circulation. Adv Atmos Sci 2005; 22(3): 359-74.

    [4] Li G, Zong H. 27.3-day and 13.6-day atmospheric tide. Science in
    China (D) 2007; 50(9): 1380-95.

    [5] Li G, Zong H, Zhang Q. 27.3-day and average 13.6-day periodic
    oscillations in the earth’s rotation rate and atmospheric pressure
    fields due to celestial gravitation forcing. Adv Atmos Sci 2011;
    28(1): 45-58.

    In addition, my paper is about the detection of lunar atmospheric tides over Eastern Australia with periods of 9.3 (= half the 18.6 year nodical period) and 3.8 years.

    The detection by Li et al. of 27.3 and 13.6 day atmospheric lunar tides is confirmed by Krahenbuhl et al. 2011

    “Support for the findings of Li et al. [7] is provided by Krahenbuhl et al. [8] who have shown that the 27.3 day lunar atmospheric tides can influence the short-term midlatitude general circulation pattern by deforming the highlatitude Rossby long-waves. They also find that these tidal effects have their greatest influence in the upper troposphere of both hemispheres.”

    Krahenbuhl DS, Pace MB, Cerveny RS, Balling Jr RC. Monthly
    lunar declination extremes’ influence on tropospheric circulation
    patterns. J Geophys Res 2011; 116: D23121- 6.

    And finally, you have our 2013 paper:

    Wilson, I.R.G. and Sidorenkov, N.S., Long-Term Lunar Atmospheric Tides in the
    Southern Hemisphere, The Open Atmospheric Science Journal, 2013, 7, 51-76

    Click to access TOASCJ130415001.pdf

    which has the followoing abstract:

    The longitudinal shift-and-add method is used to show that there are N=4 standing wave-like patterns in the summer (DJF) mean sea level pressure (MSLP) and sea-surface temperature (SST) anomaly maps of the Southern Hemisphere between 1947 and 1994. The patterns in the MSLP anomaly maps circumnavigate the Earth in 36, 18, and 9 years. This indicates that they are associated with the long-term lunar atmospheric tides that are either being driven by the 18.0 year Saros cycle or the 18.6 year lunar Draconic cycle. In contrast, the N=4 standing wave-like patterns in the SST anomaly maps circumnavigate the Earth once every 36, 18 and 9 years between 1947 and 1970 but then start circumnavigating the Earth once every 20.6 or 10.3 years between 1971 and 1994. The latter circumnavigation times indicate that they are being driven by the lunar Perigee-Syzygy tidal cycle. It is proposed that the different drift rates for the patterns seen in the MSLP and SST anomaly maps between 1971 and 1994 are the result of a reinforcement of the lunar Draconic cycle by the lunar Perigee-Syzygy cycle at the time of Perihelion. It is claimed that this reinforcement is part of a 31/62/93/186 year lunar tidal cycle that produces variations on time scales of 9.3 and 93 years. Finally, an N=4 standing wave-like pattern in the MSLP that circumnavigates the Southern Hemisphere every 18.6 years will naturally produce large extended regions of abnormal atmospheric pressure passing over the semi-permanent South Pacific subtropical high roughly once every ~ 4.5 years. These moving regions of higher/lower than normal atmospheric pressure will increase/decrease the MSLP of this semi-permanent high pressure system, temporarily increasing/reducing the strength of the East-Pacific trade winds. This may led to conditions that preferentially favor the onset of La Nina/El Nino

    Do you think that there might be some mention of the 18.6 year nodical cycle in there somewhere???

  5. Ian Wilson says:

    This paper by Muller might also be of some interest:

  6. Ian Wilson says:

    Here is another one,

    A unified approach to orbital, solar, and lunar forcing based on the Earth’s latitudinal insolation/temperature gradient. Basil A.S. Davis, Simon Brewer
    Quaternary Science Reviews
    Volume 30, Issues 15–16, July 2011, Pages 1861–1874

  7. tallbloke says:

    Ian, thanks for the links, enough to keep us busy there for a good long while.

  8. J.Seifert says:

    Congratulations to the authors!
    This lunar node pulls the atmosphere up with gravitational force, thus changing the path
    of the NAO air fluxes….As high/low pressure systems with/without rain being pulled
    by lunar forces on the Southern Hemisphere, the same lunar force acts on the NHem…..
    Here we have the explanation, why Northerly winds increased over the UK….as result
    of the action of the lunar node. JS