scholarly journals Quasi-1500-Year-Cycle Signal in Length-of-Day Change

2021 ◽  
Vol 56 (2) ◽  
pp. 10-17
Author(s):  
Lihua MA
Keyword(s):  
Rotation Rate ◽  
Time Span ◽  
Historical Documents ◽  
Data Series ◽  
Earth’S Rotation ◽  
Time Varying ◽  
Length Of Day ◽  
The Past ◽  
Continuous Sequence

Abstract Length-of-day (LOD) change, i.e., variations in Earth’s rotation rate, includes the long-term slowdown trend, as well as periodic and irregular fluctuations. The current continuous sequence of the LOD change covers a time span of <400 years. Using astronomical records in ancient historical documents, combined with a modern astronomical ephemeris, it is possible to obtain ancient LOD change. Some scholars have given a discontinuous LOD data series for the past 4000 years. In this paper, the author uses the Lomb–Scargle periodogram to study the LOD series and finds a significant quasi-1500-year-cycle signal. Furthermore, with weighted wavelet Z-transform, time-varying characteristics of the cycle in the LOD change are obtained.

Long-term changes in the rotation of the Earth : 700 B.C. to A.D. 1980

1984 ◽  
Vol 313 (1524) ◽  
pp. 47-70 ◽  
Keyword(s):  
Earth’S Rotation ◽  
Earth's Rotation ◽  
Temporal Behaviour ◽  
Tidal Friction ◽  
The Past ◽  
The Earth ◽  
Tidal Changes ◽  
Rotation Of The Earth ◽  
Tidal Variations

Occultations of stars by the Moon, and solar and lunar eclipses are analysed for variations in the Earth’s rotation over the past 2700 years. Although tidal braking provides the dominant, long-term torque, it is found that the rate of rotation does not decrease uniformly as would be expected if tidal friction were the only mechanism affecting the Earth’s rotation. There are also non-tidal changes present that vary on timescales ranging from decades to millennia. The magnitudinal and temporal behaviour of these non-tidal variations are evaluated in this paper.

scholarly journals Characteristics of cold–warm variation in the Hetao region and its surrounding areas in China during the past 5000 years

2010 ◽  
Vol 6 (4) ◽  
pp. 475-481 ◽  
Author(s):  
M.-Q. Li ◽  
Q.-S. Ge ◽  
Z.-X. Hao ◽  
J.-Y. Zheng ◽  
S.-F. He
Keyword(s):  
Climate Changes ◽  
Mean Value ◽  
Data Series ◽  
Proxy Data ◽  
Average Temperature ◽  
The Past ◽  
The Mean ◽  
Temperature Proxy ◽  
Surrounding Areas

Abstract. Using six long-term temperature proxy data series derived from different natural evidences, including pollens and lake-sediments, we reconstructed a temperature series with a 100-yr time resolution for the past 5000 yr in the Hetao region and its surrounding areas. The resulting series suggests that, on a millennial timescale, temperatures in the region were higher than the mean value of the whole series during the 5000~2600 years before present (yr BP) period, and became relatively low comparing with the average temperature of the whole series after 2600 yr BP. Within these two periods, temperature fluctuations comprising numerous short, multi-centennial intervals also existed. A comparison between our reconstructed series and other series in China and across the Northern Hemisphere indicate that, on a long-term scale, cold–warm variations had been in phase across the whole hemisphere during the past 5000 years; on the century to multi-century scale, the beginning and the ending times varied from region to region, thus implying that climate changes did not occur simultaneously in different regions.

Eruption Pattern and a Long-Term Magma Discharge Rate over the Past 100 Years at Kelud Volcano, Indonesia

2019 ◽  
Vol 14 (1) ◽  
pp. 27-39 ◽  
Author(s):  
Fukashi Maeno ◽  
Setsuya Nakada ◽  
Mitsuhiro Yoshimoto ◽  
Taketo Shimano ◽  
Natsumi Hokanishi ◽  
...  
Keyword(s):  
Discharge Rate ◽  
Explosive Eruptions ◽  
Historical Documents ◽  
The Past ◽  
Discharge Rates ◽  
Cumulative Volume ◽  
Magma Discharge ◽  
Mass Discharge ◽  
The Relationship

Kelud Volcano is among the most active volcanoes in Indonesia, with repeated explosive eruptions throughout its history. Here, we reconstructed the relationship between the repose period and the cumulative volume of erupted material over the past 100 years and estimated the long-term magma discharge rate and future eruptive potential and hazards. Tephra data and eruption sequences described in historical documents were used to estimate the volume and mass discharge rate. The volumes of the 1901, 1919, 1951, 1966, 1990, and 2014 eruptions were estimated as 51–296 × 106m3. The mass discharge rates were estimated to be on the order of 107kg/s for the 1919, 1951, and 2014 eruptions and the order of 106kg/s for the 1966 and 1990 eruptions. Based on a linear relationship between the repose period and cumulative erupted mass, the long-term mass discharge rate was estimated as ∼ 1.5 × 1010kg/year, explaining the features of the larger eruptions (1919, 1951, and 2014) but not those of the smaller eruptions (1966 and 1990). This estimate is relatively high compared to other typical basaltic-andesitic subduction-zone volcanoes. This result provides important insights into the evolution of magmatic systems and prediction of future eruptions at Kelud Volcano.

On the time-varying characteristic of the 6-year oscillation signal in length-of-day

2020 ◽  
Author(s):  
Pengshuo Duan ◽  
Cancan Xu ◽  
Xueqing Xu ◽  
Chengli Huang
Keyword(s):  
Harmonic Signal ◽  
Time Span ◽  
Least Square ◽  
Time Varying ◽  
Length Of Day ◽  
Excitation Process ◽  
The Earth ◽  
Geophysical Excitation ◽  
Morlet Wavelet Transform ◽  
The Time Domain

&lt;p&gt;A significant 6-year oscillation (SYO) signal existing in the length-of-day (LOD) variations may reflect the fast dynamics of the Earth cores. The time-varying characteristic (TVC) of this signal may reveal the relevant details on the geophysical excitation process. However, it is still debate about the TVC of the SYO. Our previous works indicated that the SYO signal was showing an obviously decaying trend during 1962~2012 based on the normal Morlet wavelet transform (NMWT) method, while other works did not show the similar decaying result based on the other methods (e.g., the least square fitting- LSF). Here, in order to solve this controversial issue, we revisit the SYO and its TVC. Through a lot of numerical simulation tests, NMWT method is further confirmed to be a good approach to quantitatively recover the target damped harmonic signals from the complex background noises, but the classical LSF method can destroy the original harmonic signal. This work indicates that the unattenuated SYO result obtained by the LSF method is not reliable. In addition, this work further analyzes the LOD data during a longer span (i.e., 1840~2018) and extracts the SYO result in the time domain, the result of which &amp;#160;shows: 1) the amplitude modulation phenomenon of the SYO itself on the longer time span, revealing the relevant excitation information within the Earth system; 2) a decreasing trend of the SYO signal in its amplitude after 1960s, which further supports the current SYO decaying result during 1962~2019. This recovered SYO result during a longer time-span obtained by this work is significant to understand the nature of the SYO change and its excitation process.&lt;/p&gt;

Use of the Kalman filter to reconstruct historical trends in productivity of Bristol Bay sockeye salmon (Oncorhynchus nerka)

2003 ◽  
Vol 60 (7) ◽  
pp. 809-824 ◽  
Author(s):  
Randall M Peterman ◽  
Brian J Pyper ◽  
Brice W MacGregor
Keyword(s):  
Kalman Filter ◽  
Sockeye Salmon ◽  
Oncorhynchus Nerka ◽  
Time Varying ◽  
Historical Trends ◽  
Bristol Bay ◽  
Fish Stocks ◽  
The Past ◽  
Better Than

Fisheries scientists and managers are concerned about potential long-term, persistent changes in productivity of fish stocks that might result from future climatic changes or other alterations in aquatic systems. However, because of large natural variability and measurement error in fisheries data, such changes are usually difficult to detect until long after they occur. Previous research using numerous Monte Carlo simulation trials showed that a Kalman filter performed better than standard estimation techniques in detecting such trends in a timely manner. Therefore, we used historical data along with a Kalman filter that included a time-varying Ricker a parameter to reconstruct changes in productivity (recruits per spawner at a given spawner abundance) of eight Bristol Bay, Alaska, sockeye salmon (Oncorhynchus nerka) stocks over the past 40 years. Productivity generally increased for most stocks but varied widely for others and dramatically decreased in another. Such large changes in productivity are important for management. They greatly affected optimal spawner abundances and optimal exploitation rates, suggesting that in the future, scientists should consider using models with time-varying productivity parameters.

scholarly journals Characteristics of cold-warm variation in the Hetao region and its surrounding areas in China during the past 5000 yr

2010 ◽  
Vol 6 (1) ◽  
pp. 1-18
Author(s):  
M. Li ◽  
Q. Ge ◽  
Z. Hao ◽  
J. Zheng ◽  
S. He
Keyword(s):  
Climate Changes ◽  
Mean Value ◽  
Data Series ◽  
Proxy Data ◽  
Average Temperature ◽  
The Past ◽  
The Mean ◽  
Temperature Proxy ◽  
Surrounding Areas

Abstract. Using six long-term temperature proxy data series derived from different natural evidences, including pollens and lake-sediments, we reconstructed a temperature series with a 100-year time resolution for the past 5000 yr in the Hetao region and its surrounding areas. The resulting series suggests that, on a millennial timescale, temperatures in the region were higher than the mean value of the whole series during the 5000~2600 yr before present (yr BP) period, and became relatively low comparing with the average temperature of the whole series after 2600 yr BP. Within these two periods, temperature fluctuations comprising numerous short, multi-centennial intervals also existed. A comparison between our reconstructed series and other series in China and across the Northern Hemisphere indicate that, on a long-term scale, cold–warm variations had been in phase across the whole hemisphere during the past 5000 yr; on the century to multi-century scale, the beginning and the ending times varied from region to region, thus implying that climate changes did not occur simultaneously in different regions.

scholarly journals As relações africano-brasileiras de longa data: uma análise da investigação histórica sobre o assunto no Brasil * The african-brazilian long term relationship: an analysis of historical research about the subject in Brazil

2015 ◽  
Vol 4 (1) ◽  
pp. 45
Author(s):  
GILBERTO DA SILVA GUIZELIN
Keyword(s):  
International Relations ◽  
Academic Community ◽  
Historical Research ◽  
Historical Documents ◽  
The Past ◽  
Historical View ◽  
Long Time ◽  
History Of ◽  
The Subject

<p><strong>Resumo:</strong> O presente artigo parte do pressuposto de que ao contrário da história das relações contemporâneas entre o Brasil e a África, a história das relações pretéritas entre as duas margens do Atlântico Sul não tem recebido a mesma atenção por parte dos investigadores brasileiros. Acredita-se aqui que tal descompasso investigativo seja fruto de uma visão histórica reducionista, por muito tempo predominante no meio acadêmico nacional, e, por conseguinte, da dificuldade sentida entre os próprios investigadores brasileiros de reunir fontes que lhes permitam recriar, observar e analisar o contexto das relações de longa data entre o Brasil e a África. Ainda assim, ressalta-se aqui que a partir de uma reorientação quanto às perspectivas de investigação é sim possível o desenvolvimento de novos estudos do entrosamento africano-brasileiro mais distante.</p><p><strong>Palavras-chave:</strong> historiografia brasileira; História das Relações Internacionais; relações Africano-Brasileiras.</p><p> </p><p><strong>Abstract:</strong> This article begins by assuming that unlike the history of contemporary relations between Brazil and Africa, the history of the past relations between the two costs of South Atlantic has not received the same attention by Brazilian researchers. It is believed here that this discrepancy is a result of a reductionist historical view,  prevalent for a long time in the national academic community, and therefore by the difficulty felt among the Brazilian researchers themselves to gather historical documents that allow them to re-create, observe and analyze the context of the past relation between Brazil and Africa. Still, it is also emphasized in this article that from a reorientation on the prospects of research the development of new studies on the African -Brazilian long term relationship is indeed possible.</p><p><strong>Keywords:</strong> Brazilian historiography; History of International Relations; African-Brazilian relations.</p>

Enabling Community Well-being Self-Monitoring in the Context of Mining: The Naskapi Nation of Kawawachikamach

2016 ◽  
Vol 1 (2) ◽  
Author(s):  
Robert Klinck ◽  
Ben Bradshaw ◽  
Ruby Sandy ◽  
Silas Nabinacaboo ◽  
Mannie Mameanskum ◽  
...  
Keyword(s):  
Indigenous Peoples ◽  
Well Being ◽  
Aboriginal Community ◽  
Self Monitoring ◽  
Community Engaged Research ◽  
The Past ◽  
Mineral Development ◽  
Iron Deposits ◽  
Term Monitoring

The Naskapi Nation of Kawawachikamach is an Aboriginal community located in northern Quebec near the Labrador Border. Given the region’s rich iron deposits, the Naskapi Nation has considerable experience with major mineral development, first in the 1950s to the 1980s, and again in the past decade as companies implement plans for further extraction. This has raised concerns regarding a range of environmental and socio-economic impacts that may be caused by renewed development. These concerns have led to an interest among the Naskapi to develop a means to track community well-being over time using indicators of their own design. Exemplifying community-engaged research, this paper describes the beginning development of such a tool in fall 2012—the creation of a baseline of community well-being against which mining-induced change can be identified. Its development owes much to the remarkable and sustained contribution of many key members of the Naskapi Nation. If on-going surveying is completed based on the chosen indicators, the Nation will be better positioned to recognize shifts in its well-being and to communicate these shifts to its partners. In addition, long-term monitoring will allow the Naskapi Nation to contribute to more universal understanding of the impacts of mining for Indigenous peoples.

Courting the Youth Vote in 2008: The Obama Effect

2009 ◽  
Vol 5 ◽  
Author(s):  
Lindsey C Bohl
Keyword(s):  
Presidential Elections ◽  
Voter Registration ◽  
The Internet ◽  
The Past ◽  
Several Variables ◽  
High Turnout ◽  
Short And Long Term ◽  
Use Of The Internet ◽  
Youth Vote

This paper examines a few of the numerous factors that may have led to increased youth turnout in 2008 Election. First, theories of voter behavior and turnout are related to courting the youth vote. Several variables that are perceived to affect youth turnout such as party polarization, perceived candidate difference, voter registration, effective campaigning and mobilization, and use of the Internet, are examined. Over the past 40 years, presidential elections have failed to engage the majority of young citizens (ages 18-29) to the point that they became inclined to participate. This trend began to reverse starting in 2000 Election and the youth turnout reached its peak in 2008. While both short and long-term factors played a significant role in recent elections, high turnout among youth voters in 2008 can be largely attributed to the Obama candidacy and campaign, which mobilized young citizens in unprecedented ways.

Sign in / Sign up

Export Citation Format

Share Document