LOD Revisited for CSALT

One of the most questioned aspects of the CSALT model of global temperature is the LOD to Temperature factor. This creates a multi-decadal variation in temperature useful for optimizing a multiple-linear regression AGW model dependent on CO2 and other factors.

Lunisolar tides impact variations in Length-of-Day (LOD). So does ENSO and QBO. There is a recursive aspect to these relationships as well, since both LOD and ENSO have the same Chandler wobble match in apparent forcing periodicity. This is what I believe generates a 6-year signal that gets identified routinely in the LOD time-series, such as the latest finding in ref [1] below.

From ref [1], the 6-year signal in LOD series. Counting cycles this is close to an average 6.25 year period, close to the 6.4 year Chandler wobble angular momentum variation.

Its a mystery why the LOD may be considered deterministic/periodic based on how well the lunisolar tides resolve the features, but ENSO is only considered quasi-periodic or nearly chaotic (the latter according to Tsonis), even though they likely arise from common mechanisms. Above all, these phenomena all have that curious tie-in to the seasonally aliased Draconic-monthly lunar cycle.

Now we can add this paper by Marcus [2] to the mix. This is a very detailed look at the correlation between long-range LOD variations (longer than the 6-year variation of Ref [1]) and global surface temperature. His application of a 5-year running mean is essentially similar to a 5-year lag that works as a best fit in the CSALT model. Marcus stops short of assigning a source cause for the LOD-to-Temperature correlation, but the general idea is that angular momentum variations are the forcing terms that slosh the sources of heat to the surface -- "via core-induced rotational and/or related global-scale processes".  (I also have to note that Marcus is an independent researcher, who at one time had an affiliation with NASA JPL.)

From Marcus [2], correlation of LOD against various temperature indices.

All these observations of LOD, ENSO, QBO, Chandler Wobble, Flood Return periods have a strong sense of self-consistency (IMO ultimately tied to lunisolar forcing), but the problem is that the discussions are scattered among different research groups. And even on this blog, the discussions reside in scattered postings (and over at Azimuth Project, also see another lunar connection).  Eventually I will write a longer manuscript to tie it all together much like I did with The Oil Conundrum and my old fossil-fuel depletion blog.

References

[1] Duan, Pengshuo, Genyou Liu, Lintao Liu, Xiaogang Hu, Xiaoguang Hao, Yong Huang, Zhimin Zhang, and Binbin Wang. 2015. “Recovery of the 6-Year Signal in Length of Day and Its Long-Term Decreasing Trend.” Earth, Planets and Space 67 (1): 1.

[2] Marcus, Steven L. 2015. “Does an Intrinsic Source Generate a Shared Low-Frequency Signature in Earth’s Climate and Rotation Rate?” Earth Interactions 20 (4): 1–14. doi:10.1175/EI-D-15-0014.1.

7 thoughts on “LOD Revisited for CSALT

  1. And the lunar cycle may extend to earthquake triggering:
    Spring tides trigger tremors deep on California’s San Andreas fault

    which takes from this PNAS paper written by USGS scientists:

    Fortnightly modulation of San Andreas tremor and low-frequency earthquakes

    "Significance -- The sun and moon exert a gravitational tug on Earth that stretches and compresses crustal rocks. This cyclic stressing can promote or inhibit fault slip, particularly at the deep roots of faults. The amplitude of the solid Earth tide varies over a fortnightly (2-wk) cycle, as the sun and moon change their relative positions in the sky. In this study, we show that deep, small earthquakes on the San Andreas Fault are most likely to occur during the waxing fortnightly tide—not when the tidal amplitude is highest, as might be expected, but when the tidal amplitude most exceeds its previous value. The response of faults to the tidal cycle opens a window into the workings of plate tectonics."

    This is a chart representing the salient features of their argument. Stress builds up over time but the lunar tidal influence provides forcing excursions on ~two-week periods that can cause an earthquake.

    quake

  2. And this important paper, just found:

    Shen, Wenbin, and Cunchao Peng. 2016. “Detection of Different-Time-Scale Signals in the Length of Day Variation Based on EEMD Analysis Technique.” Special Issue: Geodetic and Geophysical Observations and Applications and Implications 7 (3): 180–86. doi:10.1016/j.geog.2016.05.002.

    Great table repro'd here:

    Frequencies and amplitudes of different ΔLOD signals.

    Frequency (cpy) Period Amplitude (ms) Causes/Authors
    39.99 9.13 d 0.12 Solid earth tide/Seize & Schuh (2010) [40]
    26.74..26.74 13.7 d..13.70 d –0.19 Lunar tides/Wahr (1988) [6]Lunar tides/This study
    13.18..13.26 27.7 d..27.50 d –0.19 Lunar tides/Wahr (1988) [6]Lunar tides/This study
    About 2.00..2.10 About 182 d .. 181.80 d About 0.3..0.22 Solar tides and ocean currents/Rosen (1993) [5], Hopfner (1996) [33]Solar tides and ocean currents/This study
    About 1.0..0.99 About 365 d..370.40 d About 0.30.18 Solar tides and ocean currents/Rosen (1993) [5], Hopfner (1996) [33]Solar tides and ocean currents/This study
    About 0.41..0.44 About 2.42yr..2.28yr –0.03 Quasi-biennial oscillation in the stratosphere/Chao B F (1989) [9]Unknown/This study
    About 0.17..0.18 About 6yr..5.48yr About 0.12..0.05 Exchange of angular momentum between the mantle and inner core/Mound & Buffet (2003) [12]Exchange of angular momentum between the mantle and inner core/This study
    0.07 13.69 yr 0.10 Unknown/This study

    “—” denote that the data is unavailable.

    These all complement the forcing periods used in the ENSO model, in particular the last value of 13.69 years fits in well with the 14y value identified as a triaxial wobble term. I posted this to the Azimuth Project forum, but will post to this blog as well.

    • And they reference this work, which I said in a previous post was an essential finding on the strict biennial signal:
      Pan, Y.; Shen, W.-B.; Ding, H.; Hwang, C.; Li, J.; Zhang, T. The Quasi-Biennial Vertical Oscillations at Global GPS Stations: Identification by Ensemble Empirical Mode Decomposition. Sensors 2015, 15, 26096-26114.

      The takeaway message is that all the forcing components that I resolve with the ENSO model, are measured by other means -- either from traditional LOD or from this new high resolution GPS technique.

  3. Pingback: ENSO recovers LOD | context/Earth

Leave a Reply