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Detection of different-time-scale signals in the length of day variation based on EEMD analysis technique 被引量:5
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作者 Wenbin Shen Cunchao Peng 《Geodesy and Geodynamics》 2016年第3期180-186,共7页
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
关键词 Earth rotation Variation of length of day Ensemble empirical mode decomposition Periodic signals LOD fluctuation mechanism
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Introducing atmospheric angular momentum into prediction of length of day change by generalized regression neural network model 被引量:9
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作者 王琪洁 杜亚男 刘建 《Journal of Central South University》 SCIE EI CAS 2014年第4期1396-1401,共6页
The general regression neural network(GRNN) model was proposed to model and predict the length of day(LOD) change, which has very complicated time-varying characteristics. Meanwhile, considering that the axial atmosph... The general regression neural network(GRNN) model was proposed to model and predict the length of day(LOD) change, which has very complicated time-varying characteristics. Meanwhile, considering that the axial atmospheric angular momentum(AAM) function is tightly correlated with the LOD changes, it was introduced into the GRNN prediction model to further improve the accuracy of prediction. Experiments with the observational data of LOD changes show that the prediction accuracy of the GRNN model is 6.1% higher than that of BP network, and after introducing AAM function, the improvement of prediction accuracy further increases to 14.7%. The results show that the GRNN with AAM function is an effective prediction method for LOD changes. 展开更多
关键词 general regression neural network(GRNN) length of day atmospheric angular momentum(AAM) function prediction
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Spatial and Temporal Variations of Atmospheric Angular Momentum and Its Relation to the Earth Length of Day 被引量:3
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作者 杨萍 石文静 +2 位作者 肖子牛 董仕 任菊章 《Journal of Meteorological Research》 SCIE 2014年第1期150-161,共12页
The characteristics of atmospheric-angular-momentum (AAM) and length-of-day (LOD) on different timescales are investigated in this paper, on the basis of the NECP/NCAR reanalysis data and an LOD dataset for 1962-2... The characteristics of atmospheric-angular-momentum (AAM) and length-of-day (LOD) on different timescales are investigated in this paper, on the basis of the NECP/NCAR reanalysis data and an LOD dataset for 1962-2010. The variation and overall trend of the AAM anomaly (AAMA) at different latitudes are presented, and the relationship between AAMA and LOD is discussed. The AAMAs in different latitude regions exhibit different patterns of variation, and the AAMA in the tropics makes a dominant contribution to the global AAMA. In the tropics, the AAMA propagates poleward to the extratropical regions. It is confirmed that a downward propagation of the AAMA occurs in the lower stratosphere. Correlation analysis shows that the relationship between AAMA and LOD varies significantly on different timescales. Specifically, the tropical AAMA is positively correlated with LOD on short timescales, but they are not obviously correlated on long timescales. This indicates that the interaction between AAM and the earth's angular momentum follows the conservative restriction on short timescales, but the influence of the earth angular momentum on that of the atmosphere depends on the interaction process on long timescales. 展开更多
关键词 atmospheric angular momentum spatial and temporal variations propagation characteristics length of day
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Interannual variations in length of day and atmospheric angular momentum, and their seasonal associations with El Ni^o/Southern Oscillation-like sea surface temperature patterns
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作者 Yuefeng LI Ziniu XIAO +3 位作者 Wenjing SHI Qi ZHONG Qiguang WANG Huanlian LI 《Frontiers of Structural and Civil Engineering》 SCIE EI CSCD 2017年第4期751-764,共14页
This study examines the seasonal connections between the interannual variations in LOD (length of day)/ AAMglobe (the relative atmospheric angular momentum for the whole globe) and the ENSO-like SST (El Nifio/ So... This study examines the seasonal connections between the interannual variations in LOD (length of day)/ AAMglobe (the relative atmospheric angular momentum for the whole globe) and the ENSO-like SST (El Nifio/ Southern Oscillation-like sea surface temperature) pattern and corresponding zonal and vertical circulations. Consistent with previous studies, the ENSO-like SST impact the following season LOD/AAMglobe, with the strongest correlations in DJF (December, January, and February), when it is likely to be the peak E1 Nino/La Nifia period. Lag correlations between the interannual variations in LOD/AAMglobe and surface temperature, and the interannual variations in LOD and both zonal circulation and vertical airflow around the equator, consistently indicate that the LOD/AAMglobe reflect the potential impacts of variations in the Earth's rotation rate on the following season's sea surface temperatures (SST) over the tropical central and eastern pattern is located). Pacific (where the ENSO-like SST Moreover, the centers of strongest variation in the AAMcolumn (the relative atmospheric angular momentum for an air column and the unit mass over a square meter) are located over the mid-latitudinal North Pacific in DJF and MAM (March, April, and May), and over the mid-latitudinal South Pacific in JJA (June, July, and August) and SON (September, October, and November). This suggests that the AAMcolumn over the mid-latitudinal Pacific around 30°N (30~S) dominate the modulation of Earth's rotation rate, and then impact the variations in LOD during DJF and MAM (JJA and SON). 展开更多
关键词 four season features interannual variation length of day atmospheric angular momentum ENSO-likeSST pattern
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Interannual variations in the length of day and ENSO events in 1982-1983 and 1997-1998
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作者 郑大伟 廖新浩 +4 位作者 赵志弘 李志林 丁晓利 周永宏 陈永奇 《Science China Mathematics》 SCIE 2001年第1期128-136,共10页
The length of day series during the period of 1962.0-2000.0, the atmospheric angular momentum and the Southern Oscillation Index are adopted to analyze the relationships among the EN-SO events that have occurred since... The length of day series during the period of 1962.0-2000.0, the atmospheric angular momentum and the Southern Oscillation Index are adopted to analyze the relationships among the EN-SO events that have occurred since 1960, the changes in the length of day and the atmospheric angular momentum. Attention is particularly given to the different effects of the 1982-1983 and 1997-1998 ENSO events on the variations of Earth rotation. The synthetic excitation effects of multi-scale atmospheric oscillations on the anomalous variations of the interannual rates of Earth rotation are revealed by means of the time-frequency spectrum of the wavelet transform. 展开更多
关键词 change in length of day atmospheric angular momentum ENSO events.
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Effect of day length and temperature on the pollen fertility in photo(thermo)-sensitive genic male-sterile rice
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作者 HUANG Qinglui and TANG Xihua,Shanghai Inst of Piant physiology,Acad Sinica,Xhanghai 200032,China 《Chinese Rice Research Newsletter》 1996年第2期4-5,共2页
The effect of day length and temperature on the pollen fertility of five photoperiod-sensitive genic male-sterile japonica rice lines (PGMSR) and three temperature-sensitive genic malesterile indica rice lines (TGMSR)... The effect of day length and temperature on the pollen fertility of five photoperiod-sensitive genic male-sterile japonica rice lines (PGMSR) and three temperature-sensitive genic malesterile indica rice lines (TGMSR) were investigated in phytotron. The light source used for illumination was xenon lamp, and the light intensity which plant accepted on the leaf surface was 300—350μmol photons ms. The results indicated that pollens of PGMSR 7001S and E47S aborted completely whereas a little part of 31116S pollens appeared normal under long day photoperiod (LD,25℃,15h) (Table 1). High temperature (HT, 30℃, 12h) and lower temperature (LT, 展开更多
关键词 length Effect of day length and temperature on the pollen fertility in photo sensitive genic male-sterile rice THERMO
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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 被引量:1
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作者 李国庆 宗海锋 张庆云 《Advances in Atmospheric Sciences》 SCIE CAS CSCD 2011年第1期45-58,共14页
Variation in length of day of the Earth (LOD, equivalent to the Earth's rotation rate) versus change in atmospheric geopotential height fields and astronomical parameters were analyzed for the years 1962-2006. This... Variation in length of day of the Earth (LOD, equivalent to the Earth's rotation rate) versus change in atmospheric geopotential height fields and astronomical parameters were analyzed for the years 1962-2006. This revealed that there is a 27.3-day and an average 13.6-day periodic oscillation in LOD and atmospheric pressure fields following lunar revolution around the Earth. Accompanying the alternating change in celestial gravitation forcing on the Earth and its atmosphere, the Earth's LOD changes from minimum to maximum, then to minimum, and the atmospheric geopotential height fields in the tropics oscillate from low to high, then to low. The 27.3-day and average 13.6-day periodic atmospheric oscillation in the tropics is proposed to be a type of strong atmospheric tide, excited by celestial gravitation forcing. A formula for a Tidal Index was derived to estimate the strength of the celestial gravitation forcing, and a high degree of correlation was found between the Tidal Index determined by astronomical parameters, LOD, and atmospheric geopotential height. The reason for the atmospheric tide is periodic departure of the lunar orbit from the celestial equator during lunar revolution around the Earth. The alternating asymmetric change in celestial gravitation forcing on the Earth and its atmosphere produces a "modulation" to the change in the Earth's LOD and atmospheric pressure fields. 展开更多
关键词 atmospheric tide intraseasonal atmospheric oscillation length of day (LOD) lunar declination astro-meteorology
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Multichannel singular spectrum analysis of the axial atmospheric angular momentum 被引量:4
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作者 Leonid Zotov N.S.Sidorenkov +2 位作者 Ch.Bizouard C.K.Shum Wenbin Shen 《Geodesy and Geodynamics》 2017年第6期433-442,共10页
Earth's variable rotation is mainly produced by the variability of the AAM(atmospheric angular momentum). In particular, the axial AAM component X_3, which undergoes especially strong variations,induces changes in ... Earth's variable rotation is mainly produced by the variability of the AAM(atmospheric angular momentum). In particular, the axial AAM component X_3, which undergoes especially strong variations,induces changes in the Earth's rotation rate. In this study we analysed maps of regional input into the effective axial AAM from 1948 through 2011 from NCEP/NCAR reanalysis. Global zonal circulation patterns related to the LOD(length of day) were described. We applied MSSA(Multichannel Singular Spectrum Analysis) jointly to the mass and motion components of AAM, which allowed us to extract annual, semiannual, 4-mo nth, quasi-biennial, 5-year, and low-frequency oscillations. PCs(Principal components) strongly related to ENSO(El Nino southern oscillation) were released. They can be used to study ENSO-induced changes in pressure and wind fields and their coupling to LOD. The PCs describing the trends have captured slow atmospheric circulation changes possibly related to climate variability. 展开更多
关键词 Earth's variable rotation Atmospheric circulation AAM(Atmospheric angular momentum) MSSA(Multichannel singular spectrum analysis) ENSO(El Nino southern oscillation) LOD(length of day
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