Intradecadal variations in length of day and their correspondence with geomagnetic jerks

Duan, Pengshuo; Huang, Chusheng

doi:10.1038/s41467-020-16109-8

Cited by 28 publications

(37 citation statements)

References 48 publications

(138 reference statements)

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“…The fluctuation characteristics of the SYO and EYO will affect the understanding of their physical mechanisms. To confirm these fluctuation characteristics, we reanalyzed the ∆LOD records used in previous studies (Duan and Huang, 2020a and Holme and de Viron, 2013) and further analyzed the EOPC04 ∆LOD time series based on the classic filter process. Our results show that the results for the SYO from the classic filter process are well consistent with the corresponding results in Holme and de Viron (2013) and Ding (2019) (both studies used a fitting and removing process).…”

Section: Discussionmentioning

confidence: 99%

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New Evidence for the Fluctuation Characteristics of Intradecadal Periodic Signals in Length‐Of‐Day Variation

Ding

Shen

2021

JGR Solid Earth

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The fluctuation characteristics and excitations of the intradecadal changes in the length-of-day variation (∆LOD) were thought to be related to the secular variations in the core geomagnetic field and hence help to constrain the magnetic field strength in the core as well as to understand the mechanism driving the Earth's core-mantle interactions (e.g., R. S. Gross, 2015; Mound & Buffett, 2006). Two periodic signals have been detected from the ∆LOD in the intradecadal period band (i.e., the 5-10 years period band), an approximately six year oscillation (SYO, e.g., Holme & de Viron, 2013; Liao & Greiner-Mai, 1999) and an approximately 8.5 years oscillation (EYO, Ding, 2019). Their fluctuation characteristics are thought to help determine their possible mechanism (e.g., Gillet et al., 2010), but the fluctuation characteristics of these two signals are still controversial. Liao and Greiner-Mai (1999) first found a nearly stable ∼5.8 years oscillation in the 1970-1990 ∆LOD (see their Figure 5a) and suggested that the Southern Oscillation Index may have had some correlation with it. Abarca del Rio et al. (2000) also showed that the 6-7 years oscillation had no stable decreasing trend in the 1900-2000 time span (see their Figures 3 and 5), and its fluctuation characteristic was similar to a

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Section: Discussionmentioning

confidence: 99%

“… a ‘DH_': extracted from Duan and Huang (2020a) (DH20); ‘Hd_': extracted from Holme and de Viron (2013); ‘N_': newly obtained from the EOPC04 or the yearly long‐term ΔLOD by us. …”

Section: Whether the Syo And The Eyo Have Stable Damping Trendsmentioning

confidence: 99%

New Evidence for the Fluctuation Characteristics of Intradecadal Periodic Signals in Length‐Of‐Day Variation

Ding

Shen

2021

JGR Solid Earth

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“…nature. com/ artic les/ s41467-020-16109-8# Sec13), though Duan and Huang (2020) did not give the specific harmonic expression of this ~ 7.2 years signal. Some previous works seemed to show the existence of this ~ 7.0 years signal as well: For example, Vondrák (1977) indicated that two prominent signals (i.e., ~ 8.67 years and ~ 6.75 years) are present on the intradecadal scales in ΔLOD during 1955ΔLOD during .5-1976 based on a filtering approach, while using the traditional Fourier analysis, Silva et al (2012) showed that there are three frequency peaks (i.e., ~ 6.0 years, ~ 7.0 years and ~ 8.5 years) existing in the first-order derivative of LOD (i.e., dLOD/dt) on 5-10 year scales (see Fig.…”

Section: Introductionmentioning

confidence: 93%

“…(e.g., Mound and Buffett 2003;Gillet et al 2010;Holme and de Viron 2013;Duan et al 2018). As Duan and Huang (2020) indicated, the intradecadal variations in LOD during 1962-2019 are more complex than current findings, i.e., besides two primary harmonic components (i.e., ~ 5.9 years and ~ 8.6 years signals with average amplitudes of ~ 0.124 ms and ~ 0.08 ms, respectively), a relatively weaker periodic component with period between 5.9 and 8.6 years also exists. It should be emphasized that Duan and Huang (2020) explicitly referred to the existence of a ~ 7.2 years signal in LOD using the normal Morlet wavelet transformation method (see Page 11 in the Peer Review File of Duan and Huang (2020), which can be downloaded from https:// www.…”

Section: Introductionmentioning

confidence: 99%

“…Consequently, in order to further confirm the existence of this ~ 7.0 years signal mentioned by Duan and Huang (2020) and estimate its related harmonic parameters in a new way (which is different from the methods mentioned above), we need to adopt an effective mathematical harmonic analysis method to accurately analyze the signals on the intradecadal scales.…”

Section: Introductionmentioning

confidence: 99%

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On the ~ 7 year periodic signal in length of day from a frequency domain stepwise regression method

Hsu

Duan

et al. 2021

J Geod

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The intradecadal variations in length-of-day (LOD) and their time-varying characteristics still need to be further studied. Given that the corresponding signal periods on the intradecadal scales are quite close to each other and the span of currently observed ΔLOD data (i.e., 1962–2019, only 57 years) is not long enough, accurate detection of these signals depends on using effective mathematical method. On the basis of the traditional harmonic retrieval model, this work proposes a frequency domain stepwise regression method, which can well identify the periodic components with close periods and recognize the weaker signals to estimate the relevant harmonic parameters (i.e., amplitude, frequency and phase). Furthermore, we apply this method to detection of the actual LOD intradecadal variations, the result of which shows that there are three components (i.e., the ~ 5.9 years, ~ 8.3 years and ~ 7.3 years) existing in LOD intradecadal variations. Here, we firstly give the time-domain harmonic expression of the ~ 7.3 years signal, i.e., $$y\left(t\right)=A\mathrm{cos}\left(\frac{2\pi }{T}\left(t-1962+\psi \right)\right)$$ y t = A cos 2 π T t - 1962 + ψ , where the period $$T=7.33$$ T = 7.33 years, amplitude $$A=0.0413(\pm 0.0099)$$ A = 0.0413 ( ± 0.0099 ) ms, phase $$\psi =-1.58(\pm 0.30)$$ ψ = - 1.58 ( ± 0.30 ) years. The mechanism of this ~ 7.3 years signal needs to be further studied.

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Contributions of oceanic and continental AAM to interannual variation in ΔLOD with the detection of 2020–2021 La Nina event

Zhou

Duan

et al. 2022

J Geod

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As a strong climate element on interannual scales, the El Nino-Southern Oscillation (ENSO) is a major component of global weather and climate change, and it is also closely related to the interannual atmospheric angular momentum (AAM) and length-of-day changes (ΔLOD). Here, we reprocess and compare the interannual variations of AAM, ΔLOD with ENSO indices, with AAM mass and motion terms calculated over land separately from those over the ocean. Three oscillatory components (at ~ 6, ~ 7, ~ 8 years), due to angular momentum changes in Earth's interior, are removed to obtain the interannual ΔLOD solely related to climatic variations. Our results show that the AAM motion term over the ocean contributes the most to interannual ΔLOD, and that the oceanic AAM has larger variability than that over land, especially during the periods of strong ENSO events. After subtracting contributions associated with interior processes, the interannual ΔLOD anomalies corresponding to extreme ENSO events (1982–1983 ~ 0.43, 1997–1998 ~ 0.36, 2015–2016 ~ 0.42 ms) are about half as strong as those found in previous studies (~ 0.91, ~ 0.76, ~ 0.81 ms). Furthermore, we detect an intermediate La Nina event that occurred from August 2020 to May 2021, forcing the interannual ΔLOD to a minimum value of approximately -0.21 ms.

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Intradecadal variations in length of day and their correspondence with geomagnetic jerks

Cited by 28 publications

References 48 publications

New Evidence for the Fluctuation Characteristics of Intradecadal Periodic Signals in Length‐Of‐Day Variation

New Evidence for the Fluctuation Characteristics of Intradecadal Periodic Signals in Length‐Of‐Day Variation

On the ~ 7 year periodic signal in length of day from a frequency domain stepwise regression method

Contributions of oceanic and continental AAM to interannual variation in ΔLOD with the detection of 2020–2021 La Nina event

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