Scientists pay great attention to different-time-scale signals in the lengllh of day （LOD） variations △LOD, which provide signatures of the Earth＇s interior structure, couplings among different layers, and potenti...Scientists pay great attention to different-time-scale signals in the lengllh of day （LOD） variations △LOD, which provide signatures of the Earth＇s interior structure, couplings among different layers, and potential excitations of ocean and atmosphere. In this study, based on the ensemble empirical mode decomposition （EEMD）, we analyzed the latest time series of △LOD data spanning from January 1962 to March 2015. We observed the signals with periods and amplitudes of about 0.5 month and 0.19 ms, 1.0 month and 0.19 ms, 0.5 yr and 0.22 ms, 1.0 yr and 0.18 ms, 2.28 yr and 0.03 ms, 5.48 yr and 0.05 ms, respectively, in coincidence with the results of predecessors. In addition, some signals that were previously not definitely observed by predecessors were detected in this study, with periods and amplitudes of 9.13 d and 0.12 ms, 13.69 yr and 0.10 ms, respectively. The mechanisms of the LOD fluctuations of these two signals are still open.展开更多
The time series of the length of day (LOD) and the observational Pacific sea level during l962.0-1990.0 are used to study the relation between Earth rotation and equatorial oceanic activities.The results show that (i)...The time series of the length of day (LOD) and the observational Pacific sea level during l962.0-1990.0 are used to study the relation between Earth rotation and equatorial oceanic activities.The results show that (i) the sea level is apparently rising at an average rate of about 1.75±.01mm/a during the past 30 years,(ii) there are large-scale eastward and westward water motions in the upper equatorial Pacific zone,which,according to the dynamical analysis of the angular momentum of the large-scale sea water motion in Pacific Ocean related to the Earth rotation axis accounts for about 30% of the change in ititerannual Eatlh rotation rate; (iii) the interannual changes in Earth rotation also cause changes in the distribution of the water mass in equatorial Pacific,and affect the formation of ENSO events.Based on these results,we give a new model for the interaction between equatorial ocean and Earth rotation.展开更多
Earthquakes heavily deform the crust in the vicinity of the fault, which leads to mass redistribution in the earth interior. Then it will produce the change of the Earth＇s rotation （ polar motion and length of day）...Earthquakes heavily deform the crust in the vicinity of the fault, which leads to mass redistribution in the earth interior. Then it will produce the change of the Earth＇s rotation （ polar motion and length of day） due to the change of Earth inertial moment. This paper adopts the elastic dislocation to compute the co-seismic polar motion and variation in length of day （LOD） caused by the 2011 Sumatra earthquake. The Earth＇s rota- tional axis shifted about 1 mas and this earthquake decreased the length of day of 1 p,s, indicating the tendency of earthquakes make the Earth rounder and to pull the mass toward the centre of the Earth. The result of varia- tion in length of day is one order of magnitude smaller than the observed results that are available. We also compared the results of three fault models and find the co-seismic change is depended on the fault model.展开更多
On July 29, 2021, a large earthquake of MW8.2 occurred south of the Alaska Peninsula. To investigate the spatial-temporal changes of crustal stress in the earthquake-stricken area before this event, we selected 159 ea...On July 29, 2021, a large earthquake of MW8.2 occurred south of the Alaska Peninsula. To investigate the spatial-temporal changes of crustal stress in the earthquake-stricken area before this event, we selected 159 earthquakes of 4.7 ≤ MW ≤ 6.9 that occurred in the epicentral region and its surroundings between January 1980 and June 2021 to study the temporal variation and spatial distribution of their apparent stress. In addition, we analyzed the correlation between seismic activities and Earth’s rotation and explored the seismogenic process of this earthquake. The crustal stress rose from January 2008 to December 2016. This period was followed by a sub-instability stage from January 2017 until the occurrence of the MW8.2 earthquake. The average rate of apparent stress change in the first five years of the stress increase period was roughly 2.3 times that in the last four years. The lateral distribution of the apparent stress shows that the areas with apparent stress greater than 1.0 MPa exhibited an expanding trend during the seismogenic process. The maximum apparent stress was located at the earthquake epicenter during the last four years. The distribution of the apparent stress in the E-W vertical cross section revealed that an apparent stress gap formed around the hypocenter during the first five years of the stress increase period, surrounded by areas of relatively high apparent stress. After the Alaska earthquake, most parts of this gap were filled in by aftershocks. The seismic activities during the sub-instability stage exhibited a significant correlation with Earth’s rotation.展开更多
A science plan for future 15 a, 'A Study of Climate Variability and Predictability'(CLIVAR), was published by WMO in 1996. As the plan treated interdecadal climatic variability as a sub-plan, it showed that th...A science plan for future 15 a, 'A Study of Climate Variability and Predictability'(CLIVAR), was published by WMO in 1996. As the plan treated interdecadal climatic variability as a sub-plan, it showed that this problem is very important. By the implementation of 'Tropical Ocean and Global Atmosphere' (TOGA) 10-a plan during 1985—1994, the interdecadal variability that occurred in ENSO (El Nino/Southern Oscillation) ocean-atmosphere interaction has been found. This variability made the traditional ENSO prediction pattern useless展开更多
Ⅰ. INTRODUCTIONSince the strong El Nio event occurred at the end of 1982, which was characterized by the anomalous warming up of the sea surface water in equatorial area of eastern Pacific, the relationship between t...Ⅰ. INTRODUCTIONSince the strong El Nio event occurred at the end of 1982, which was characterized by the anomalous warming up of the sea surface water in equatorial area of eastern Pacific, the relationship between the variation of the rate of Earth rotation and the El Nio event has attracted more and more attention and some significant studies have been made. How-展开更多
Although the Japanese records of central or near central solar eclipses (i.e. the total, annular and total-annular eclipses) are not very old, so long as their documents definitely recording the observational place, d...Although the Japanese records of central or near central solar eclipses (i.e. the total, annular and total-annular eclipses) are not very old, so long as their documents definitely recording the observational place, date and phenomenon of the eclipse or the parameters can be defined through some textual researches even if展开更多
In the study of variation of the earth’s rotation based on the records of some ancientastronomical events, the timing records of ancient astronomical events and phenomena, suchas solar and lunar eclises and lunar occ...In the study of variation of the earth’s rotation based on the records of some ancientastronomical events, the timing records of ancient astronomical events and phenomena, suchas solar and lunar eclises and lunar occultation, are important components of the data.The reliable records, especially those from the countries and regions with advanced an-cient astronomy and timing technology, contain valuable information on the variation展开更多
The relationship between the inter-annual variations of the earth rotation, atmospheric angular momentum (AAM), sunspot number and El Ni(?)o is analyzed. The result shows that the inter-annual variation of the earth r...The relationship between the inter-annual variations of the earth rotation, atmospheric angular momentum (AAM), sunspot number and El Ni(?)o is analyzed. The result shows that the inter-annual variation of the earth rotation responds to the variation of AAM and the preg-nancy of El Ni(?)o timely. Generally, the inter-annual compo-nent of the earth rotation will reach zero in a changing proc-ess that increases from the negative to the positive extreme before El Ni(?)o occurs about half year or more. And the solar activity may have certain influence on the appearance of El Ni(?)o. We consider that El Ni(?)o will possibly appear around the end of 2001.展开更多
We use the method of wavelet transform to analyze the time series of the Earth＇s rotation rate of the EOP （IERS） C04. The result shows that the seasonal （annual and semiannual） variation of the length-of-day （LO...We use the method of wavelet transform to analyze the time series of the Earth＇s rotation rate of the EOP （IERS） C04. The result shows that the seasonal （annual and semiannual） variation of the length-of-day （LOD） has temporal variability in its period length and amplitude. During 1965.0-2001.0, the periods of the semiannual and annual components varied mainly from 175-day to 190-day and from 360-day to 370-day, respectively; while their amplitudes varied by more than 0.2 ms and 0.1 ms, respectively. Analyzing the axial component of atmospheric angular momentum （AAM） during this period, we have found that time-variations of period lengths and amplitudes also exist in the seasonal oscillations of the axial AAM and are in good consistency with those of the seasonal LOD change. The time variation of the axial AAM can explain largely the change of the LOD on seasonal scales.展开更多
It is well known that a variation in the direction of Earth’s rotation axis is a real astronomical phenomenon, named nutation. It is interesting if a variation of this axis can take place only in intensity, in the si...It is well known that a variation in the direction of Earth’s rotation axis is a real astronomical phenomenon, named nutation. It is interesting if a variation of this axis can take place only in intensity, in the simplest theoretical case of only two rigid body dynamics. This paper presents two positions of the Moon during its monthly orbit, where a sudden variation of Earth’s rotation axis in intensity can take place. The duration of this phenomenon is limited in time, maybe an instant or a day, and then a vortex can appear.展开更多
基金supported by National 973 Project China (2013CB733305)National Natural Science Foundation of China (NSFCs) (41174011,41429401,41210006,41128003,41021061)
文摘Scientists pay great attention to different-time-scale signals in the lengllh of day （LOD） variations △LOD, which provide signatures of the Earth＇s interior structure, couplings among different layers, and potential excitations of ocean and atmosphere. In this study, based on the ensemble empirical mode decomposition （EEMD）, we analyzed the latest time series of △LOD data spanning from January 1962 to March 2015. We observed the signals with periods and amplitudes of about 0.5 month and 0.19 ms, 1.0 month and 0.19 ms, 0.5 yr and 0.22 ms, 1.0 yr and 0.18 ms, 2.28 yr and 0.03 ms, 5.48 yr and 0.05 ms, respectively, in coincidence with the results of predecessors. In addition, some signals that were previously not definitely observed by predecessors were detected in this study, with periods and amplitudes of 9.13 d and 0.12 ms, 13.69 yr and 0.10 ms, respectively. The mechanisms of the LOD fluctuations of these two signals are still open.
基金Projeot supported by the National Natural Science Foundation of ChinaNational Key Basic Scientific Research Project
文摘The time series of the length of day (LOD) and the observational Pacific sea level during l962.0-1990.0 are used to study the relation between Earth rotation and equatorial oceanic activities.The results show that (i) the sea level is apparently rising at an average rate of about 1.75±.01mm/a during the past 30 years,(ii) there are large-scale eastward and westward water motions in the upper equatorial Pacific zone,which,according to the dynamical analysis of the angular momentum of the large-scale sea water motion in Pacific Ocean related to the Earth rotation axis accounts for about 30% of the change in ititerannual Eatlh rotation rate; (iii) the interannual changes in Earth rotation also cause changes in the distribution of the water mass in equatorial Pacific,and affect the formation of ENSO events.Based on these results,we give a new model for the interaction between equatorial ocean and Earth rotation.
基金supported by the National Natural Science Foundation of China(41174063)
文摘Earthquakes heavily deform the crust in the vicinity of the fault, which leads to mass redistribution in the earth interior. Then it will produce the change of the Earth＇s rotation （ polar motion and length of day） due to the change of Earth inertial moment. This paper adopts the elastic dislocation to compute the co-seismic polar motion and variation in length of day （LOD） caused by the 2011 Sumatra earthquake. The Earth＇s rota- tional axis shifted about 1 mas and this earthquake decreased the length of day of 1 p,s, indicating the tendency of earthquakes make the Earth rounder and to pull the mass toward the centre of the Earth. The result of varia- tion in length of day is one order of magnitude smaller than the observed results that are available. We also compared the results of three fault models and find the co-seismic change is depended on the fault model.
基金supported by the the Special fund of the Institute of Geophysics,China Earthquake Administration(No.DQJB22Z04).
文摘On July 29, 2021, a large earthquake of MW8.2 occurred south of the Alaska Peninsula. To investigate the spatial-temporal changes of crustal stress in the earthquake-stricken area before this event, we selected 159 earthquakes of 4.7 ≤ MW ≤ 6.9 that occurred in the epicentral region and its surroundings between January 1980 and June 2021 to study the temporal variation and spatial distribution of their apparent stress. In addition, we analyzed the correlation between seismic activities and Earth’s rotation and explored the seismogenic process of this earthquake. The crustal stress rose from January 2008 to December 2016. This period was followed by a sub-instability stage from January 2017 until the occurrence of the MW8.2 earthquake. The average rate of apparent stress change in the first five years of the stress increase period was roughly 2.3 times that in the last four years. The lateral distribution of the apparent stress shows that the areas with apparent stress greater than 1.0 MPa exhibited an expanding trend during the seismogenic process. The maximum apparent stress was located at the earthquake epicenter during the last four years. The distribution of the apparent stress in the E-W vertical cross section revealed that an apparent stress gap formed around the hypocenter during the first five years of the stress increase period, surrounded by areas of relatively high apparent stress. After the Alaska earthquake, most parts of this gap were filled in by aftershocks. The seismic activities during the sub-instability stage exhibited a significant correlation with Earth’s rotation.
文摘A science plan for future 15 a, 'A Study of Climate Variability and Predictability'(CLIVAR), was published by WMO in 1996. As the plan treated interdecadal climatic variability as a sub-plan, it showed that this problem is very important. By the implementation of 'Tropical Ocean and Global Atmosphere' (TOGA) 10-a plan during 1985—1994, the interdecadal variability that occurred in ENSO (El Nino/Southern Oscillation) ocean-atmosphere interaction has been found. This variability made the traditional ENSO prediction pattern useless
文摘Ⅰ. INTRODUCTIONSince the strong El Nio event occurred at the end of 1982, which was characterized by the anomalous warming up of the sea surface water in equatorial area of eastern Pacific, the relationship between the variation of the rate of Earth rotation and the El Nio event has attracted more and more attention and some significant studies have been made. How-
文摘Although the Japanese records of central or near central solar eclipses (i.e. the total, annular and total-annular eclipses) are not very old, so long as their documents definitely recording the observational place, date and phenomenon of the eclipse or the parameters can be defined through some textual researches even if
文摘In the study of variation of the earth’s rotation based on the records of some ancientastronomical events, the timing records of ancient astronomical events and phenomena, suchas solar and lunar eclises and lunar occultation, are important components of the data.The reliable records, especially those from the countries and regions with advanced an-cient astronomy and timing technology, contain valuable information on the variation
基金This work was supported by the National Natural Science Foundation of China (Grant Nos. 19973011 and 19833030).
文摘The relationship between the inter-annual variations of the earth rotation, atmospheric angular momentum (AAM), sunspot number and El Ni(?)o is analyzed. The result shows that the inter-annual variation of the earth rotation responds to the variation of AAM and the preg-nancy of El Ni(?)o timely. Generally, the inter-annual compo-nent of the earth rotation will reach zero in a changing proc-ess that increases from the negative to the positive extreme before El Ni(?)o occurs about half year or more. And the solar activity may have certain influence on the appearance of El Ni(?)o. We consider that El Ni(?)o will possibly appear around the end of 2001.
基金Supported by the National Natural Science Foundation of China
文摘We use the method of wavelet transform to analyze the time series of the Earth＇s rotation rate of the EOP （IERS） C04. The result shows that the seasonal （annual and semiannual） variation of the length-of-day （LOD） has temporal variability in its period length and amplitude. During 1965.0-2001.0, the periods of the semiannual and annual components varied mainly from 175-day to 190-day and from 360-day to 370-day, respectively; while their amplitudes varied by more than 0.2 ms and 0.1 ms, respectively. Analyzing the axial component of atmospheric angular momentum （AAM） during this period, we have found that time-variations of period lengths and amplitudes also exist in the seasonal oscillations of the axial AAM and are in good consistency with those of the seasonal LOD change. The time variation of the axial AAM can explain largely the change of the LOD on seasonal scales.
文摘It is well known that a variation in the direction of Earth’s rotation axis is a real astronomical phenomenon, named nutation. It is interesting if a variation of this axis can take place only in intensity, in the simplest theoretical case of only two rigid body dynamics. This paper presents two positions of the Moon during its monthly orbit, where a sudden variation of Earth’s rotation axis in intensity can take place. The duration of this phenomenon is limited in time, maybe an instant or a day, and then a vortex can appear.
