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1.
This study presents predicts ocean tidal loading (OTL) effects using a Green’s function approach and validates a novel tidal
model for Taiwan. Numerical integration of OTL is performed using the Gauss quadrature method and a local tidal model for
the inner zone and a global model for the outer zone. Observed time series of GPS-derived vertical displacements and gravity
variations (3–7 days) at five co-located GPS-gravimeter stations along the South East China and Taiwan coasts were utilized
to assess the accuracy of the proposed models and two other models. The OTL-induced gravity variations are 3–16 μgal and the
vertical site displacements are 13–27 mm. Generally, an OTL model using a mixed global and local tidal model generates better
agreement with the observations than an OTL model using a global tidal model only. However, containing a local model inside
a global model does not always produce a good agreement with the observations. The relatively large discrepancies between
modeled and observed OTL values at some stations indicate that there is a need for an improved local tidal model in the study
area.
An erratum to this article can be found at 相似文献
2.
We present sea level observations derived from the analysis of signal-to-noise ratio (SNR) data recorded by five coastal GPS stations. These stations are located in different regions around the world, both in the northern and in the southern hemisphere, in different multipath environments, from rural coastal areas to busy harbors, and experience different tidal ranges.The recorded SNR data show periodic variations that originate from multipath, i.e. the interference of direct and reflected signals. The general assumption is that for satellite arcs facing the open sea, the rapid SNR variations are due to reflections off the sea surface. The SNR data recorded from these azimuth intervals were analyzed by spectral analysis with two methods: a standard analysis method assuming a static sea level during a satellite arc and an extended analysis method assuming a time dependent sea level during a satellite arc.The GPS-derived sea level results are compared to sea level records from co-located traditional tide gauges, both in the time and in the frequency domain. The sea level time series are highly correlated with correlation coefficients to the order of 0.89–0.99. The root-mean-square (RMS) difference is 6.2 cm for the station with the lowest tidal range of 165 cm and 43 cm for the station with the highest tidal range of 772 cm. The relative accuracy, defined as the ratio of RMS and tidal range, is between 2.4% and 10.0% for all stations.Comparing the standard analysis method and the extended analysis method, the results based on the extended analysis method agree better with the independent tide gauge records for the stations with a high tidal range. For the station with the highest tidal range (772 cm), the RMS is reduced by 47% when using the extended analysis method. Furthermore, the results also indicate that the standard analysis method, assuming a static sea level, can be used for stations with a tidal range of up to about 270 cm, without performing significantly worse than the extended analysis method.Tidal amplitudes and phases are derived by harmonic analysis of the sea level records. Again, a high level of agreement is observed between the tide gauge and the GPS-derived results. Comparing the GPS-derived results, the results based on the extended analysis method show a higher degree of agreement with the traditional tide gauge results for stations with larger tidal ranges. Spectral analysis of the residuals after the harmonic analysis reveals remaining signal power at multiples of the draconitic day. This indicates that the observed SNR data are to some level disturbed by additional multipath signals, in particular for GPS stations that are located in harbors. 相似文献
3.
The synthetic tidal parameters with high spatial resolution for gravity over China and its neighbor area are con- structed with Earth’s tidal model and ocean tide loading calculated using TPXO7 global ocean tide model as well as tidal data over China seas. The comparison between synthetic parameters and ones observed by spring gravime- ters at some seismic network stations and Hong Kong station and one observed by super-conducting gravimeter at Wuhan station shows that the average differences in amplitude factors and phases are smaller than 0.005 and 0.5° respectively; and that the discrepancies between observational and synthetic parameters are dependent on gravim- etric technique in that the synthetic parameters are in well agreement with the superconducting gravimetric obser- vations. This also indicates that the synthetic result is a good estimation for tidal gravity, and the numerical results in the present paper not only can provide ground and space gravimetry such as absolute gravimetry with correction model of tidal gravity, but also provide effective tidal parameters over areas where no observation is carried out. 相似文献
4.
In the English Channel, extreme surge heights did not occur at the time of extreme high tides during the last decades and
maximum recorded heights usually do not exceed the maximum astronomical tide by more than a few decimetres. To understand
whether this lack of coincidence may be due to specific phenomena or only to chance, we have studied hourly tide records lasting
a few decades from nine English and nine French stations as well as air pressure and wind data from nearby meteorological
observatories. Among the case studies of moderate flooding at several coastal stations occurring during spring tide, we have
selected those of 24–25/10/1980 and of 30/01/1983 to 02/02/1983 as representative of a normal situation without any special
chance. The third case study 26–28/02/1990 was potentially more dangerous because of the storm intensity and duration; however,
by chance, surge peaks occurred near the low tide. Finally, the propagation of the surge peak of 15–16/10/1987, which reached
the maximum height recorded during all the instrumental period at several stations, has been followed all along the English
Channel, using the hourly records of 12 tide-gauge stations and of 16 meteorological stations. The surge peak of this great
storm, probably the strongest in the last two centuries, occurred everywhere at high tide and spread with the same velocity
of the tidal wave. Fortunately, no major flooding occurred because it was the day after a neap tide. In conclusion, some good
fortune has saved the low coastal areas of the English Channel from major floods during the last decades. However, the occurrence
of the peak of a strong storm surge arriving near the western entrance of the Channel at the time of a great astronomical
high tide is a possible event that could be devastating along both sides of the Channel coasts.
Main parts of this paper have been presented orally in June 2005 at the joint INQUA–IGCP 495 Meeting “Dunkerque 2005” and
in February 2006 at the ASLO-TOS-AGU “Ocean Sciences Meeting” (Honolulu, HI). 相似文献
5.
Temporal variations in free core nutation period 总被引：1，自引：0，他引：1
Based on the nearly diurnal resonance in the tidal gravity observations,the temporal variations in period of the Earth's free core nutation (FCN) are investigated by using the tidal gravity observations of 18-year duration recorded continu-ously with a superconducting gravimeter (SG) at Brussels. The effects of the global oceanic tide loading and local barometric pressure on the SG observations have been removed by using eleven high-precision global digital models of oceanic tides and barometric pressure me... 相似文献
6.
The earth tide is usually ignored in orogenesis (geosynclinal activity) and magmatic activity. We believe that the role of
earth tide in crustal movement should not be ignored. The elemental dynamic analysis of origin of magma chamber under dissipative
tidal heating model and orogenic process driven by alternating earth tidal force is depicted.
The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,15, 508–513, 1993.
Xue-Min AI and Liang CHI also worked for this project.
This work was supported by the Laboratory of Dynamical Geodesy, Academia Sinica.
Translated from Chinese into English by Liang CHI. 相似文献
7.
SHRI R. S. CHUGH M.A. 《水文科学杂志》2013,58(2):10-17
Summary The Hooghly is a tidal river and Calcutta one of the most important ports of India is situated on it. The tidal effect stretches to over 175 miles length up to Nabadwip where two nonperennial rivers Bhagirathi and Jalangi, both taking off at different sites from the Gangesmeet and discharge their rain water (freshets) into the Hoogly all through the summer months. Other rivers join it also downstream. Annual tide tables are published for three places on the river viz Sagar, Diamond Harbour and Garden Reach. In this paper lunitidal intervals, durations of rise and fall, mean high water, mean low water, mean tide level and mean sea level planes and mean ranges have been shown to go through periodic seasonal changes. It has been shown that different tidal planes have changed differently in the intrior of the river indicating changes in tidal regimes and in the river bed. Whereas variations in yearly sea levels since 1882 have not been appreciable at Sagar, these at Garden Reach have changed considerable at indicating sometimes an improvement in the channel, other times worsening of the channel. Four 19 yearly cycles of mean sea-level at Garden Reach have been analysed to give phaselags different from Zero and large variations in amplitudes. To carry this study further one period of 19 years each for Sagar, Madras and Vishakhapatnam on East Coast and 4 periods each for Bombay and Aden in the Arabian Sea have also been analysed to see the possibility of nodal variations being constant in amplitude and phase over large areas of the ocean. 19-yearly cycles in the differences between MTL &; MSL have been examined for Bombay, Madras and Garden Reach. The effects of freshets on various planes have been analysed and the curves of annual freshets and MTLs at Garden Reach are found to run closely parallel. The variations in yearly high water and law water planes above MTLs of the corresponding years after corrections for the longitude of the moons' node have been found to be inappreciable. Theoretical extreme high water and low water planes have been found to be more extreme than actually recorded planes which are very near M.H.W.S. and M.L.W.S. planes indicating there are no predominant effects of winds and storms on the tides in the river. The mean ranges at Garden Reach have been found to be steadily increasing. Theoretical effects of increase in range and lowering of MSL on MHW and MLW plane has been found to agree with actual values. Monthly average temperatures and salinities show distinct annual cycles. High temperatures occur at the same times as low salinities and high mean sea levels. Vertical density structure may be responsible for a large part of annual variation in the sea level at Sagar which is a region of particular interest on account of opposite influences of seasonal monsoons, drainage of rivers and oceanic currents. Seasonal variations in average monthly pressure have been related to variations in mean sea levels and it is found that as the pressures decrease, the height of MSL increases. Tide in Hooghly has been found to be progressive type of wave. Rates of travel of tidal streams outside Sagar and rates of streams in the river have been given also, stating the effects of freshets on tidal streams. Bores in Hooghly have been examined. Shapes of tidal curves and profile of the bore at Garden Reach have been drawn. Rates of propagation of the bore from Doodsons' formulae have been compared with actual values and a remarkable agreement has been found. The rise of tide in 10 minutes and 30 minutes which is the time taken for the steep rise to disappear has been correlated with range of tide and a useful table has been included. Tides in Hooghly are predicted by applying harmonic shallow water corrections to open sea primary predictions at Sagar. As the freshets are unpredictable an approximate relationship has been worked out between the departures of actual freshets from num freshets of the years of analyses and departures of actual from predicted tides. From a knowledge of actual freshets the predictions can be corrected almost, daily. A large number of tables and only the essential graphs have been included to illustrate the contents. 相似文献
8.
T. Sato S. Miura Y. Ohta H. Fujimoto W. Sun C.F. Larsen M. Heavner A.M. Kaufman J.T. Freymueller 《Journal of Geodynamics》2008,46(3-5):78
We analyzed gravity data obtained in Juneau and global positioning system (GPS) data obtained from three PBO sites in southeastern Alaska (SE-AK), which are part of a US research facility called ‘EarthScope’, and we compared the obtained tidal amplitudes and phases with those estimated from the predicted tides including both effects of the body tide and ocean tide. Global tide models predict the ocean tides in this region of complex coastline and bathymetry. To improve the accuracy of prediction, we developed a regional ocean tide model in SE-AK.Our comparison results suggest: (1) by taking into account the ocean tide effect, the amplitude differences between the observation and the predicted body tide is remarkably reduced for both the gravity and displacement (e.g. for the M2 constituent, 8.5–0.3 μGal, and 2.4–0.1 cm at the AB50 GPS site in Juneau in terms of the vector sum of three components of the north–south, east–west and up–down), even though the ocean tide loading is large in SE-AK. (2) We have confirmed the precise point positioning (PPP) method, which was used to extract the tidal signals from the original GPS time series, works well to recover the tidal signals. Although the GPS analysis results still contain noise due to the atmosphere and multipath, we may conclude that the GPS observation surely detects the tidal signals with the sub-centimeter accuracy or better for some of the tidal constituents. (3) In order to increase the accuracy of the tidal prediction in SE-AK, it is indispensable to improve the regional ocean tide model developed in this study, especially for the phase. 相似文献
9.
本文对琼中台连续重力观测数据进行收集整理并处理,基于处理后的数据,进行了潮汐分析和非潮汐分析。潮汐分析采用VAV调和分析方法;非潮汐分析则分别进行了零漂改正、固体潮改正、气压改正和海潮改正。其中,零漂改正采用一般多项式拟合零漂的方法;气压改正采用VAV软件;海潮改正运用SPOTL程序,以NAO.99b潮汐模型计算了琼中台海潮负荷值。最终获得了改正后的琼中台重力非潮汐变化,结果表明琼中台的重力气压导纳值为-0.34×10-8m/s2/mbar,气压改正幅度约为10×10-8m/s2,海潮改正幅度约为5×10-8m/s2。改正后,琼中台重力非潮汐变化数据,比仅进行零漂固体潮改正后的重力非潮汐变化数据中的潮汐信号更加微弱,说明进行海潮改正后的效果是明显的,该方法可进一步去除其中的潮汐信号。 相似文献
10.
Temporal and spatial variability in the Guadalquivir estuary: a challenge for real-time telemetry 总被引：1，自引：1，他引：0
Gabriel Navarro Francisco Javier Gutiérrez Manuel Díez-Minguito Miguel Angel Losada Javier Ruiz 《Ocean Dynamics》2011,61(6):753-765
Meteorological, hydrological, and hydrodynamic data for 3 years (2008–2010) have been used to document and explain the temporal
and spatial variability of the physical–biogeochemical interactions in the Guadalquivir River Estuary. A real-time, remote
monitoring network has been deployed along the course of the river between its mouth and Seville to study a broad range of
temporal scales (semidiurnal, diurnal, fortnightly, and seasonal). This network consists of eight hydrological monitoring
stations capable of measuring temperature, conductivity, dissolved oxygen, turbidity, and chlorophyll fluorescence at four
depths. In addition, six stations have been deployed to study hydrodynamics, obtaining 20-cell water column current profiles,
and there is a meteorological station at the river mouth providing data for understanding atmospheric interactions. Completing
this data-gathering network, there are several moorings (tide gauges, current/wave sensors, and a thermistor chain) deployed
in the estuary and river mouth. Various sources of physical forcing, such as wind, tide-associated currents, and river discharge,
are responsible for the particular temporal and spatial patterns of turbidity and salinity found in the estuary. These variables
force the distribution of biogeochemical variables, such as dissolved oxygen and chlorophyll fluorescence. In particular,
episodes of elevated turbidity (when suspended particle matter concentration >3,000 mg/l) have been detected by the network,
together with episodes of declining values of salinity and dissolved oxygen. All these patterns are related to river discharge
and tidal dynamics (spring/neap and high/low tide). 相似文献
11.
利用理论和实验重力固体潮模型,充分考虑全球海潮和中国近海潮汐的负荷效应,建立了中国大陆的精密重力潮汐改正模型.结果表明,采用不同的固体潮模型会对重力潮汐结果产生相对变化幅度小于0.06％的差异;在沿海地区海潮负荷的影响约为整个潮汐的4％,而中部地区约为1％,其中中国近海潮汐模型的影响约占整个海潮负荷的10%,内插或外推潮波的负荷约占海潮负荷的3％.通过比较实测的重力数据表明,本文给出的重力潮汐改正模型的精度远远优于0.5×10-8 m·s-2,说明了本文构建的模型的实用性,可为中国大陆高精度重力测量提供有效参考和精密的改正模型. 相似文献
12.
13.
中国数字地震观测网络"十五"计划期间,在全国布设约40台我国自主研发的YRY-4型分量式钻孔应变仪.现已取得一批固体潮观测数据,计算M2波潮汐因子的结果表明,潮汐因子的相对精度最高达到了0.001.在此基础上,发现各观测点潮汐响应(潮汐因子)与理论模型比较有很大的离散性及有规律的方位各向异性.本文提出断层隔离是造成各台站潮汐因子偏离理论值及方位各向异性的主要原因.有限元断层地块模型应变方位响应与台站实测方位响应的一致,支持了这一观点.潮汐响应各向异性现象有望在地质构造研究、城市断层探测、地块活动微动态、地震烈度区划等研究领域发挥作用.也可为GPS等空间大地测量观测数据改进潮汐位移修正,提供参考. 相似文献
14.
选取河北省5个形变台站的观测资料,利用Venedikov调和分析法计算河北省境内M_S4.0以上的潮汐因子、相位等参数,发现应变潮汐因子对地震都有多则半年,少则几周的异常期。宽城台对河北省境内发生M_S4.0以上的地震中,震中距较其他台站最近(震中距最远为350km、最近为100km),资料较好,故在综合分析河北应变台站的基础上,重点选取宽城台的应变潮汐因子对河北2005—2015年地震案例进行简要分析,发现该台对地震的对应率达到60%,虚报率40%,漏报率极低只有14%,前兆异常可信度较高,可作为前兆异常的参考。 相似文献
15.
16.
Transverse micro‐erosion meter (TMEM) stations were installed in rock slabs from shore platforms in eastern Canada. The slabs were put into artificial sea water for 1, 6 or 11 hours, representing high, mid‐ and low tidal areas, respectively. The TMEMs were used to record changes in surface elevation as the rocks dried during the remainder of the 12 h of a semi‐diurnal tidal cycle. A similar technique was used on the same rock types at intertidal TMEM stations in the field, as the rocks dried during low tide. Argillite and basalt surface contraction was from 0 to 0·04 mm: there was little surface expansion. Sandstones contracted by up to 0·03 mm in the field, but there was almost no contraction in the laboratory. Argillite and basalt contraction tended to be greatest in the upper intertidal zone, and to increase with rates of longer‐term surface downwearing, but there was little relationship with rock hardness or air temperature and humidity. Changes in elevation at the same points at TMEM stations in the laboratory and field were quite consistent from one tidal cycle to the next, but there were considerable variations within single tidal cycles between different points within each station. The data suggest that contraction within the elevational zone that is normally submerged twice a day by the tides is by alternate wetting and drying. Short‐term changes in elevation are generally low compared with annual rates of downwearing owing to erosion, but they may generate stresses that contribute to rock breakdown. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
17.
Effect of earth tide on deep well water level 总被引：2，自引：0，他引：2
On the basis of the partial differential equations of the water level in a deep well that is affected by the bulk strain tide,
the boundary conditions of permeating each other between aquifer and well are considered. The solutions of the equations have
been obtained by the superposition principle, inpulse theorem and separation of the variations. Some suitable values are given
to the parameters of well aquifer in the solutions. By means of the numerical calculation the relations among the well tide
coefficients and phase lag phenomenon of response of the well level to earth tides is well interpreted. The parametric studies
and the obtained graphs show that the more the radius of casing in a well, the porosity of an aquifer and the bulk compressibility
for solid matrix of an aquifer, the less the transmissibility of an aquifer, then the less the tidal coefficient of well level,
while the more the phase lag for well level to respond to the tide is. The response of the well level to the tide of longer
period is better than the shorter period events.
The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,13, 66–75, 1991. 相似文献
18.
In this study, we compare simulated storm surges run on the two-dimensional operational storm surge/tide forecast system (regional
tide/storm surge model (RTSM), based on Princeton ocean model) of the Korean Meteorological Administration and the three-dimensional
regional ocean modeling system (ROMS), using observational data from 30 coastal tidal stations of three typhoons that struck
Korea in 2007. A maximum positive bias of 6.8 cm was found for Typhoon Manyi predicted by ROMS, while a maximum negative bias
of −7.4 cm was shown for Typhoon Nari predicted by RTSM. For all three typhoons, the total averaged root mean square error
was 10 cm for the two models. Although the statistical results for the storm surge comparison between the observations and
RTSM predictions were better than those for ROMS, with the exception of Typhoon Nari, the spatial and temporal variations
of ROMS were larger than those of RTSM. 相似文献
19.
Parts of the consecutive apparent resistivity monitoring stations of China have recorded clear diurnal variations. The relative amplitudes of diurnal variations at these stations range from 1.3‰ to 5.8‰. The daily accuracies of apparent resistivity observation are better than 1‰, because the background electromagnetic noise is rather low at these stations. Therefore, the diurnal variations of apparent resistivity recorded at these stations are real phenomena. The diurnal variation shapes can be divided into two opposite types according to their characteristics. One type is that the apparent resistivity data decreases during the daytime but increases during the nighttime(Type 1). The other type is the apparent resistivity data increases during the daytime but decreases during the nighttime(Type 2). There is a correspondence between the diurnal and annual variation patterns of apparent resistivity. For the monitoring direction with diurnal variation of Type 1, the apparent resistivity decreases in summer and increases in winter. However, for the monitoring direction with diurnal variation of Type 2, the apparent resistivity increases in summer and decreases in winter.
We take an analysis on the mechanism of apparent resistivity diurnal variation, combining the influence factors of water-bearing medium's resistivity, the electric structure of stations, and the apparent resistivity sensitivity coefficient(SC)theory. Intuitively, diurnal variation of apparent resistivity is caused by diurnal variation of medium resistivity in the measured area. The diurnal variation of medium resistivity will inevitably be caused by the factors with diurnal variation. Among the possible factors, there is diural variation in earth tide and temperature.
Our analysis displays that apparent resistivity diurnal variation is not caused by the usually-believed earth tide, but by the ground temperature difference between daytime and nighttime. The earth tide strain is too small to cause remarkable effects on the apparent resistivity data. On the other hand, the daily tide strain has two peak-valley variations, and its phase and amplitude has a period of approximate 28 days. However, the apparent resistivity data do not show these corresponding features to earth tide. Furthermore, the detection range of current apparent resistivity stations is within a depth of several hundred meters. Within this depth range, the medium deformation caused by solid tide can be regarded as uniform change. Therefore, all monitoring directions and all stations will have the same pattern of diurnal variation.
In general, the temperature increases in the daytime but decreases in the nighttime. For most water-bearing rock and soil medium, its resistivity decreases as temperature increases and increases as temperature decreases. Diurnal temperature difference affects about 0.4m of soil depth. Therefore, resistivity of this surface thin soil layer decreases in the daytime while increases in the nighttime. Under layered medium model, SC of each layer represents its contribution to the apparent resistivity. For the stations with positive SC of surface layer, apparent resistivity decreases in the daytime but increases in the nighttime. While for the stations with negative SC of surface layer, apparent resistivity diurnal variations display the opposite shape. 相似文献
20.
Climate warming and its impact on natural regional boundaries in China in the 1980s 总被引：11，自引：1，他引：10
The global climate warming accelerated in the 1980s has become a focus in the world. Based on the month by month and year by year temperature data from 160 representative stations throughout the country during 1951-1999, this paper analyses annual and four seasons' temperature variations of China since the 1980s. It was found out that the non-equalibrium response with relative great regional and seasonal differences is represented in the country's climate warming. In regional changes a trend of "warm in the north and cold in the south" occurs whereas in seasonal changes, the characters of "warm in winter and cool in summer" present. Significant verification of the temperature variations conducted in terms of mathematical statistics reveals that a confidence level of over 95% has been basically reached in areas north of the Yangtze River. Meanwhile, according to data of diurnal mean temperature steadily passing through accumulated temperature ≥10℃ from 335 stations since 1951 or since the founding of the stations in the early 1950s to 1999, comparative analysis of the data of the last 19 years with that of the first 30 years was conducted and the accumulated temperature ≥10℃ and the variation range of the persistent number of days ≥10℃ were obtained. It was concluded that a general northward shift of central subtropics, north subtropics, warm temperate zone, mesothermal zone and frigid temperate zone of eastern China was observed. The northward shift of north subtropics and warm temperate zone was obvious but changes of south subtropics and marginal tropics were insignificant. In western China, in addition to southwestern Yunnan, the Qinghai-Tibet Plateau and western Inner Mongolia where the temperature zones of each either shifted northward or trended to move upward, not much changes were found in other areas or they shifted southward slightly and declined. 相似文献