Motivated by the wide applications of empirical global ocean tide models in Earth science,particularly in shallow waters and coastal regions,we proposed an updated global ocean tide model representing all major diurna...Motivated by the wide applications of empirical global ocean tide models in Earth science,particularly in shallow waters and coastal regions,we proposed an updated global ocean tide model representing all major diurnal and semidiurnal tidal constituents.We integrated the development technique of the Technical University of Denmark(DTU10)model and calculated the residual tides using the intermediary FES2012 model.We utilized all available Topex/Poseidon,Jason-1,Ocean Surface Topography Mission(OSTM)/Jason-2 primary and tandem missions to develop the new model.To reduce the discrepancies between the model and in situ measurements estimated S2 tide constituent,the ERA-Interim model was selected for dry tropospheric correction of altimetry data.The newly developed model with an improved spatial resolution from 1/8°×1/8°to 1/16°×1/16°was assessed and compared against contemporary global ocean tide models using in situ measurements in coastal regions,continental shelf waters,marginal seas,and deep waters.The results demonstrate improvements in shallow waters and coastal regions,particularly in representative coastal re-gions such as the Northwest European Shelf and East Asian Marginal Seas.Moreover,the model performs well in simulating S_(2) and K_(2) tides with root mean square differences of 0.355 and 0.234 cm,respectively,against in situ measurements in deep waters world-wide.Compared with that of DTU10,the root sum square of the new model for the eight main tidal constituents decrease by 8.4%to 0.997 cm.展开更多
With the rapid development of modern Interferometric Synthetic Aperture Radar(InSAR)missions,SAR instruments with wider coverage can be used to monitor the ground surface deformation from regional to global scale.Howe...With the rapid development of modern Interferometric Synthetic Aperture Radar(InSAR)missions,SAR instruments with wider coverage can be used to monitor the ground surface deformation from regional to global scale.However,the ocean tide loading(OTL)displacement is becoming a primary source of errors.It contributes to a long-wavelength signal in InSAR interferograms,leading to errors from millimeter to centimeter-level in InSAR deformation monitoring,especially over coastal areas.Although the state-of-the-art has applied ocean tide models to mitigate the errors,the difference between them and their impact on InSAR measurements are rarely discussed.In this paper,we compare representative ocean tide models and investigate their effects in the correction of OTL errors.We found that(i)the modeled OTL displacements from different models show little difference over interiors far from the ocean,while disagreement becomes larger over coastal areas;(ii)the magnitude of OTL artifacts may be greater than the atmospheric delays in some coastal areas,and the correction using ocean tide models can effectively attenuate the OTL effects for large-scale InSAR measurements;(iii)when correcting the OTL errors for InSAR measurements,the global model TPXO and FES are recommended because of their better overall performance,while the NAO model performs the worst.The local models with high spatial resolution can help improve the capability of coarse global models in complex topographic areas.展开更多
By using 11 global ocean tide models and tidal gauge data obtained in the East China Sea and South China Sea, the influence of the ocean loading on gravity field in China and its neighbor area is calculated in this pa...By using 11 global ocean tide models and tidal gauge data obtained in the East China Sea and South China Sea, the influence of the ocean loading on gravity field in China and its neighbor area is calculated in this paper. Furthermore, the differences between the results from original global models and modified models with local tides are discussed based on above calculation. The comparison shows that the differences at the position near the sea are so large that the local tides must be taken into account in the calculation. When the global ocean tide models of CSR4.0, FES02, GOT00, NAO99 and ORI96 are chosen, the local effect for M2 is less than 0.10 × 10-8 m·s-2 over the area far away from sea. And the local effect for O1 is less than 0.05 × 10-8 m·s-2 over that area when choosing AG95 or CSR3.0 models. This numerical result demonstrates that the choice of model is a complex problem because of the inconsistent accuracy of the models over the areas of East and South China Seas.展开更多
Global Positioning System （GPS） has been widely used to estimate the total zenith tropo- spheric delay （ZTD） and precipitable water vapour （PWV） for weather prediction and at- mospheric research as a continuous ...Global Positioning System （GPS） has been widely used to estimate the total zenith tropo- spheric delay （ZTD） and precipitable water vapour （PWV） for weather prediction and at- mospheric research as a continuous and all-weather technique. However, estimations of ZTD and PWV are subject to effects of geophysical models with large uncertainties, particularly imprecise ocean tide models of inland seas in Turkey. In this paper, GPS data from Jan. 1, 2010 to Dec. 31, 2011 are processed using GAMIT/GLOBK at four co-located GPS stations （ISTN, ERZR, SAMN, and IZMI） with Radiosonde from the Turkish Met-Office together with several nearby IGS stations. Four widely used ocean tide models are adopted to evaluate their effects on GPS-estimated PWV, such as IERS recommended FES2004, NAO99b, CSR4.0 and GOT00. Five different strategies are taken without ocean tide model and with four ocean tide models, respectively, which are used to evaluate ocean tide models effects on GPS-estimated PWV through comparing with co-located Radiosonde. Results showed that ocean tide models have greatly affected the estimation of the pre- cipitable water vapour at stations near coasts. The ocean tide model FES2004 gave the best results when compared to Radiosonde with ＋2.12 mm in PWV at stations near coastline. While other ocean tides models agree each other at millimeter level in PWV. However, at inland GPS stations, ocean tide models have less effect on GPS-estimated PWV.展开更多
The HY-2A satellite,which is equipped with a radar altimeter and was launched on August 16,2011,is the first Chinese marine dynamic environmental monitoring satellite.Extracting ocean tides is one of the important app...The HY-2A satellite,which is equipped with a radar altimeter and was launched on August 16,2011,is the first Chinese marine dynamic environmental monitoring satellite.Extracting ocean tides is one of the important applications of the radar altimeter data.The radar altimeter data of the HY-2A satellite from November 1,2011 to August 16,2014 are used herein to extract global ocean tides.The constants representing the tidal constituents are extracted by HY-2A RA data with harmonic analysis based on the least squares method.Considering tide aliasing issues,the analysis of the alias periods and alias synodic periods of different tidal constituents shows that only the tidal constituents M_(2),N_(2),and K_(2)are retrieved precisely by the HY-2A RA data.The derived tidal constants of the tidal constituents M_(2),N_(2)and K_(2)are compared to those of tidal gauge data and the TPXO tide model results.The comparison between the derived results and the tidal gauge data shows that the RMSEs of the tidal amplitude and phase lag are 9.6 cm and 13.34°,2.4 cm and 10.47°,and 8.1 cm and 14.19°for tidal constituents M_(2),N_(2),and K_(2),respectively.The comparisons of the semidiurnal tides with the TPXO model results show that tidal constituents have good consistency with the TPXO model results.These findings confirm the good performance of HY-2A RA for retrieving semidiurnal tides in the global ocean.展开更多
Previous studies show that the calculated loading effects from global ocean tide models do not match actual measurements of gravity attraction and loading effects in Southeast Asia.In this paper,taking advantage of a ...Previous studies show that the calculated loading effects from global ocean tide models do not match actual measurements of gravity attraction and loading effects in Southeast Asia.In this paper,taking advantage of a unique network of gravity tidal stations all over the Chinese mainland,we compare the observed and modeled tidal loading effects on the basis of the most recent global ocean tide models.The results show that the average efficiencies of the ocean tidal loading correction for O_(1),K_(1),M_(2) are 77%,7 s3%and 59%,respectively.The loading correction efficiencies using recent ocean tidal models are better than the 40 years old Schwiderskis model at coastal stations,but relative worse at stations far from ocean.展开更多
Ocean semi-diurnal tides are suggested qualitatively to be more accurately explained by the vertical tide generating forces of the sun and moon, not by the historically standard horizontal components. It is proposed t...Ocean semi-diurnal tides are suggested qualitatively to be more accurately explained by the vertical tide generating forces of the sun and moon, not by the historically standard horizontal components. It is proposed that the sea level elevations created sequentially at the eastern and then western ocean coastal boundaries propagate seaward as shallow water sur</span><span style="font-family:Verdana;font-size:12px;">face gravity waves and interact without mutual disturbance. In that manner two tides per day</span><span style="font-family:Verdana;font-size:12px;"> are created. Horizontal tide forces generate horizontal ocean currents with speeds of 5 mph at the most. Shallow water tide waves move at about 500 mph in open waters and therefore come much closer to being in tune with the sun and moon transiting across the sky.展开更多
Ocean tide loading(OTL)displacements of eight principal constituents at 12 sites in Hong Kong were determined using more than eight years of continuous GPS observations.Parameters of the OTL displacements were estimat...Ocean tide loading(OTL)displacements of eight principal constituents at 12 sites in Hong Kong were determined using more than eight years of continuous GPS observations.Parameters of the OTL displacements were estimated using daily GPS solutions obtained with precise point positioning(PPP)technique.The results were compared with predictions from seven latest global ocean tide models.Gravity measurements of OTL in Hong Kong were also used to validate the GPS results.The study shows that the results from both the GPS and gravity measurements agree best with the GOT4.7 and NAO99b models,when the K1 and K2 constituents are excluded.The agreements between the GPS and the model estimates are generally at sub-millimeter level in both the horizontal and vertical directions,except for S2,K2 and K1 constituents that have relatively larger errors.After removing the systematic biases between the GPS and the model estimates,the misfits of M2,S2,N2,O1,P1 and Q1 at all sites are within 0.5 and 1.0 mm in the horizontal and the vertical directions,respectively,whereas K1 and K2 show relatively larger misfits of up to 2.3 mm.Both the GPS and the gravity S2 estimates have large biases with unknown reasons when compared with the modeled values,which needs to be further investigated.The study demonstrates that GPS is capable of estimating the OTL displacements with the same accuracy as the model predictions,especially for coastal areas.展开更多
Currently,aliasing error of temporal signal model becomes the main factor constraining the accuracy of temporal gravity field.In provision of three types of satellite formations,i.e.,GRACE-type,Pendulum-type and n-s-C...Currently,aliasing error of temporal signal model becomes the main factor constraining the accuracy of temporal gravity field.In provision of three types of satellite formations,i.e.,GRACE-type,Pendulum-type and n-s-Cartwheel-type,which are suitable for gravity mission and composed of observation in different directions,here we design two cases and conduct a simulation experiment on the feasibility to apply satellite formations for eliminating the influence from the aliasing error of ocean tide models.The result of our experiment shows that,when the aliasing error is disregarded,n-s-Cartwheel formation can provide the best conditions for gravity field determination,which,compared with GRACE-type,can improve the accuracy by 43%.When aliasing error of the ocean tide model acts as the main source of error,the satellite formation applied in dynamic method for gravity field inversion cannot eliminate aliasing or improve the accuracy of gravity field.And due to its higher sensitivity to the high-degree variation of gravity field,the Cartwheel-type formation,which includes the radial observation,can result in the gravity field containing more high-frequency signals for the ocean tide model error,and lead to a dramatically larger error.展开更多
The movement of global ocean circulation in the Earth’s main magnetic field generates a measurable induced magnetic field(about 2 nT at geomagnetic satellite altitudes).However,this ocean circulation-induced magnetic...The movement of global ocean circulation in the Earth’s main magnetic field generates a measurable induced magnetic field(about 2 nT at geomagnetic satellite altitudes).However,this ocean circulation-induced magnetic field has not been previously estimated or incorporated into geomagnetic field models,potentially causing leakage into the core field model.Here,we present a method to account for the circulation-induced magnetic field during geomagnetic field modeling.First,a forward model of the circulation-induced magnetic field is constructed by numerically solving electromagnetic induction equations based on a realistic ocean circulation model.Then,this forward model is subtracted from the observed data.Finally,the core and lithospheric fields,magnetospheric and Earth’s mantle-induced fields,and the ocean tide-induced magnetic field are co-estimated.Applying our method to over 20 years of MSS-1,Swarm,CryoSat-2,and CHAMP satellite magnetic data,we derive a new multisource geomagnetic field model(MGFM).We find that incorporating a forward model of the circulation-induced magnetic field marginally improves the fit to the data.Furthermore,we demonstrate that neglecting the circulation-induced magnetic field in geomagnetic field modeling results in leakage into the core field model.The highlights of the MGFM model include:(i)a good agreement with the widely used CHAOS model series;(ii)the incorporation of magnetic fields induced by both ocean tides and circulation;and(iii)the suppression of leakage of the circulation-induced magnetic field into the core field model.展开更多
This paper describes the ocean loading tides corrections of GPS stations in Antarctica, such as the Great Wall station and Zhongshan station. Based on the theory of ocean loading tides, the displacement corrections of...This paper describes the ocean loading tides corrections of GPS stations in Antarctica, such as the Great Wall station and Zhongshan station. Based on the theory of ocean loading tides, the displacement corrections of ocean loading tides on GPS stations in Antarctica are calculated by using the CRS4.0 ocean loading tides model. These corrections are also applied to GPS data proc-essing. The GPS data are analyzed by the GAMIT software with and without these corrections. We compared and analyzed the GPS baseline components to get the differences. The results show that the ocean tidal displacement corrections have obvious effects upon GPS baseline components. Therefore, we should not ignore the ocean loading tides corrections of GPS stations in Antarctica to obtain precise and reliable results.展开更多
The performance of a z-level ocean model, the Modular Ocean Model Version 4（MOM4）, is evaluated in terms of simulating the global tide with different horizontal resolutions commonly used by climate models. The perfo...The performance of a z-level ocean model, the Modular Ocean Model Version 4（MOM4）, is evaluated in terms of simulating the global tide with different horizontal resolutions commonly used by climate models. The performance using various sets of model topography is evaluated. The results show that the optimum filter radius can improve the simulated co-tidal phase and that better topography quality can lead to smaller rootmean square（RMS） error in simulated tides. Sensitivity experiments are conducted to test the impact of spatial resolutions. It is shown that the model results are sensitive to horizontal resolutions. The calculated absolute mean errors of the co-tidal phase show that simulations with horizontal resolutions of 0.5° and 0.25° have about 35.5% higher performance compared that with 1° model resolution. An internal tide drag parameterization is adopted to reduce large system errors in the tidal amplitude. The RMS error of the best tuned 0.25° model compared with the satellite-altimetry-constrained model TPXO7.2 is 8.5 cm for M_2. The tidal energy fluxes of M_2 and K_1 are calculated and their patterns are in good agreement with those from the TPXO7.2. The correlation coefficients of the tidal energy fluxes can be used as an important index to evaluate a model skill.展开更多
The global oceanic/atmospheric tides exert decelerating/accelerating secular torques on the Earth rotation. We developed new formulations to accurately calculate amounts of two kinds of secular tidal torques. After Me...The global oceanic/atmospheric tides exert decelerating/accelerating secular torques on the Earth rotation. We developed new formulations to accurately calculate amounts of two kinds of secular tidal torques. After Melchior, we found that an additional factor 1+k-l = 1.216, which has been formerly neglected, must be multiplied unto the tidal torque integral. By using our refined formulations and the recent oceanic/atmospheric global tide models, we found that:(i) semidiurnal oceanic lunar/solar tides exert decelerating torques of about-4.462 × 10^(16)/-0.676 × 10^(16) Nm respectively and(ii) atmospheric S_2 tide exerts accelerating torque of 1.55 × 10^(15) Nm. Former estimates of the atmospheric S_2 tidal torque were twice as large as our estimate due to improper consideration of loading effect. We took the load Love number for atmospheric loading effect from Guo et al.(2004). For atmospheric loading of spherical harmonic degree two, the value of k′=-0.6031 is different from that for ocean loading as k′ =-0.3052,while the latter is currently used for both cases-ocean/atmospheric loading-without distinction. We discuss(i) the amount of solid Earth tidal dissipation(which has been left most uncertain) and(ii) secular changes of the dynamical state of the Earth-Moon-Sun system. Our estimate of the solid Earth tidal torque is-4.94×10^(15) Nm.展开更多
Using tidal potential solar thermal-radiating energy current and the nonlinear effect of the gravity tide as the input function, moreover, considering the ocean tidal species as the input function of the loading effec...Using tidal potential solar thermal-radiating energy current and the nonlinear effect of the gravity tide as the input function, moreover, considering the ocean tidal species as the input function of the loading effect of ocean tide, we make the lumped response analysis of the observational tilt tide in one year. The tilt gravitational tide, the load tide, the radiational tide and the nonlinear tide with the same frequeny are separated off. It is shown that the load tide and the gravitational tide are the same quantity grade, the load tide may spread into inland far away; the solar thermal-radiation has an effect on the tilt tide; there is a little nonlinear tide in the tilt tide, but the nonlinear tide of the ocean tide has the stronger loading effect on the tilt tide than the nonlinear tide brought about by the gravitational tide itself; the lag interval, △τ=41 (h), is the best value in the response analysis. In addition, the harmonic analyses of the tilt tide and the separated tilt tides are made respectively by using j.v model, and their ellipse factors are calculated.展开更多
Ocean surface waves are strongly forced by high wind conditions associated with winter storms in the Sea of Japan. They are also modulated by tides and storm surges. The effects of the variability in surface wind forc...Ocean surface waves are strongly forced by high wind conditions associated with winter storms in the Sea of Japan. They are also modulated by tides and storm surges. The effects of the variability in surface wind forcing, tides and storm surges on the waves are investigated using a wave model, a high-resolution atmospheric mesoscale model and a hydrodynamic ocean circulation model. Five month-long wave model simulations are inducted to examine the sensitivity of ocean waves to various wind forcing fields, tides and storm surges during January 1997. Compared with observed mean wave parameters, results indicate that the high frequency variability in the surface wind filed has very great effect on wave simulation. Tides and storm surges have a significant impact on the waves in nearshores of the Tsushima-kaihyS, but not for other regions in the Sea of Japan. High spatial and temporal resolution and good quality surface wind products will be crucial for the prediction of surface waves in the JES and other marginal seas, especially near the coastal regions.展开更多
The tide-induced mixing plays an important role in the regulation of ocean circulation.Numerical simulation of continental shelf circulation is found to exhibit an unreasonable vertical thermohaline structure without ...The tide-induced mixing plays an important role in the regulation of ocean circulation.Numerical simulation of continental shelf circulation is found to exhibit an unreasonable vertical thermohaline structure without consideration of tide effects.In this study,we establish a harmonic analyzed parameterization of tide-induced（HAT） mixing,by which means to derive time-depended function of mixing coefficient based on harmonic analysis of the vertical mixing coefficient.By employing HAT mixing parameterization scheme,a series of numerical experiments are conducted for the Yellow Sea.Numerical results show that an ocean circulation model with the HAT mixing involved is capable of reproducing the reasonable thermohaline structure of the Yellow Sea Cold Water Mass,similar to structures produced by explicit tidal forcing on the open boundary.The advantage of the HAT method is its faster computation time,compared with models that directly resolve explicit tidal motion.The HAT parameterization for the tide-induced mixing has potential to improve both the accuracy and efficiency of ocean circulation and climate models.展开更多
By analyzing a data set collected using a moored instrument array and CTD during TOGA-COARE, it is found that there exist remarkable internal tides in the western equatorial Pacific Ocean around 1°45′S, 156°...By analyzing a data set collected using a moored instrument array and CTD during TOGA-COARE, it is found that there exist remarkable internal tides in the western equatorial Pacific Ocean around 1°45′S, 156°E, whose horizontal wavenumber （wavelength）, vertical wavenumber, h 156° orizontal propagation speed and vertical propagation speed are 3.3×10^-2 km^-1 （210 km）, - 1.6×10^-3m, 2.0 m/s and -3.8 cm/s, respectively, that is, the waveform propagates downwards slantingly. Moreover, the propagating direction rotates statistically clockwise as the depth increases and its cause is unclear.展开更多
The global distributions of eight principal tidal constituents, M2, S2, K1, O1, N2, K2, P1, and Q1, are derived using TOPEX/Poseidon and JASON-1（T/P-J） satellite altimeter data for 16 a. The intercomparison of the d...The global distributions of eight principal tidal constituents, M2, S2, K1, O1, N2, K2, P1, and Q1, are derived using TOPEX/Poseidon and JASON-1（T/P-J） satellite altimeter data for 16 a. The intercomparison of the derived harmonics at 7000 subsatellite track crossover points shows that the root mean square （RMS） values of the tidal height differences of the above eight constituents range from 1.19 cm to 2.67 cm, with an average of about 2 cm. The RMS values of the tidal height differences between T/P-J solutions and the harmonics from ground measurements at 152 tidal gauge stations for the above constituents range from 0.34 cm to 1.08 cm, and the relative deviations range from 0.031 to 0.211. The root sum square of the RMS differences of these eight constituents is 2.12 cm, showing the improvement of the present model over the existing global ocean tidal models. Based on the obtained tidal model the global ocean tidal energetics is studied and the global distribution of the tidal power input density by tide-generating force of each constituent is calculated, showing that the power input source regions of semidiurnal tides are mainly concentrated in the tropical belt between 30S and 30N, while the power input source regions of diurnal tides are mainly concentrated off the tropic oceans. The global energy dissipation rates of the M2, S2, K1, O1, N2, P1, K2 and Q1 tides are 2.424, 0.401, 0.334, 0.160, 0.113, 0.035, 0.030 and 0.006 TW, respectively. The total global tidal dissipation rate of these eight constituents amounts to 3.5 TW.展开更多
基金supported by the open funding of the Technology Innovation Center for South China Sea Re-mote Sensing,Surveying and Mapping Collaborative Ap-plication,Ministry of Natural Resources,P.R.China(No.RSSMCA-2024-B001)the National Natural Science Foundation of China(Nos.T2261149752 and 42476172).
文摘Motivated by the wide applications of empirical global ocean tide models in Earth science,particularly in shallow waters and coastal regions,we proposed an updated global ocean tide model representing all major diurnal and semidiurnal tidal constituents.We integrated the development technique of the Technical University of Denmark(DTU10)model and calculated the residual tides using the intermediary FES2012 model.We utilized all available Topex/Poseidon,Jason-1,Ocean Surface Topography Mission(OSTM)/Jason-2 primary and tandem missions to develop the new model.To reduce the discrepancies between the model and in situ measurements estimated S2 tide constituent,the ERA-Interim model was selected for dry tropospheric correction of altimetry data.The newly developed model with an improved spatial resolution from 1/8°×1/8°to 1/16°×1/16°was assessed and compared against contemporary global ocean tide models using in situ measurements in coastal regions,continental shelf waters,marginal seas,and deep waters.The results demonstrate improvements in shallow waters and coastal regions,particularly in representative coastal re-gions such as the Northwest European Shelf and East Asian Marginal Seas.Moreover,the model performs well in simulating S_(2) and K_(2) tides with root mean square differences of 0.355 and 0.234 cm,respectively,against in situ measurements in deep waters world-wide.Compared with that of DTU10,the root sum square of the new model for the eight main tidal constituents decrease by 8.4%to 0.997 cm.
基金This work was supported by the Natural Science Foundation of China(grant Nos.42074008,41804005,42174018).
文摘With the rapid development of modern Interferometric Synthetic Aperture Radar(InSAR)missions,SAR instruments with wider coverage can be used to monitor the ground surface deformation from regional to global scale.However,the ocean tide loading(OTL)displacement is becoming a primary source of errors.It contributes to a long-wavelength signal in InSAR interferograms,leading to errors from millimeter to centimeter-level in InSAR deformation monitoring,especially over coastal areas.Although the state-of-the-art has applied ocean tide models to mitigate the errors,the difference between them and their impact on InSAR measurements are rarely discussed.In this paper,we compare representative ocean tide models and investigate their effects in the correction of OTL errors.We found that(i)the modeled OTL displacements from different models show little difference over interiors far from the ocean,while disagreement becomes larger over coastal areas;(ii)the magnitude of OTL artifacts may be greater than the atmospheric delays in some coastal areas,and the correction using ocean tide models can effectively attenuate the OTL effects for large-scale InSAR measurements;(iii)when correcting the OTL errors for InSAR measurements,the global model TPXO and FES are recommended because of their better overall performance,while the NAO model performs the worst.The local models with high spatial resolution can help improve the capability of coarse global models in complex topographic areas.
基金The Key Knowledge Innovation Project (KZCX3-SW-131), the Hundred Talents Program of Chinese Academy of Sciences and the National Natural Science Foundation of China (40374029)
文摘By using 11 global ocean tide models and tidal gauge data obtained in the East China Sea and South China Sea, the influence of the ocean loading on gravity field in China and its neighbor area is calculated in this paper. Furthermore, the differences between the results from original global models and modified models with local tides are discussed based on above calculation. The comparison shows that the differences at the position near the sea are so large that the local tides must be taken into account in the calculation. When the global ocean tide models of CSR4.0, FES02, GOT00, NAO99 and ORI96 are chosen, the local effect for M2 is less than 0.10 × 10-8 m·s-2 over the area far away from sea. And the local effect for O1 is less than 0.05 × 10-8 m·s-2 over that area when choosing AG95 or CSR3.0 models. This numerical result demonstrates that the choice of model is a complex problem because of the inconsistent accuracy of the models over the areas of East and South China Seas.
文摘Global Positioning System （GPS） has been widely used to estimate the total zenith tropo- spheric delay （ZTD） and precipitable water vapour （PWV） for weather prediction and at- mospheric research as a continuous and all-weather technique. However, estimations of ZTD and PWV are subject to effects of geophysical models with large uncertainties, particularly imprecise ocean tide models of inland seas in Turkey. In this paper, GPS data from Jan. 1, 2010 to Dec. 31, 2011 are processed using GAMIT/GLOBK at four co-located GPS stations （ISTN, ERZR, SAMN, and IZMI） with Radiosonde from the Turkish Met-Office together with several nearby IGS stations. Four widely used ocean tide models are adopted to evaluate their effects on GPS-estimated PWV, such as IERS recommended FES2004, NAO99b, CSR4.0 and GOT00. Five different strategies are taken without ocean tide model and with four ocean tide models, respectively, which are used to evaluate ocean tide models effects on GPS-estimated PWV through comparing with co-located Radiosonde. Results showed that ocean tide models have greatly affected the estimation of the pre- cipitable water vapour at stations near coasts. The ocean tide model FES2004 gave the best results when compared to Radiosonde with ＋2.12 mm in PWV at stations near coastline. While other ocean tides models agree each other at millimeter level in PWV. However, at inland GPS stations, ocean tide models have less effect on GPS-estimated PWV.
基金The National Key Research and Development Program of China under contract No.2016YFC1401801.
文摘The HY-2A satellite,which is equipped with a radar altimeter and was launched on August 16,2011,is the first Chinese marine dynamic environmental monitoring satellite.Extracting ocean tides is one of the important applications of the radar altimeter data.The radar altimeter data of the HY-2A satellite from November 1,2011 to August 16,2014 are used herein to extract global ocean tides.The constants representing the tidal constituents are extracted by HY-2A RA data with harmonic analysis based on the least squares method.Considering tide aliasing issues,the analysis of the alias periods and alias synodic periods of different tidal constituents shows that only the tidal constituents M_(2),N_(2),and K_(2)are retrieved precisely by the HY-2A RA data.The derived tidal constants of the tidal constituents M_(2),N_(2)and K_(2)are compared to those of tidal gauge data and the TPXO tide model results.The comparison between the derived results and the tidal gauge data shows that the RMSEs of the tidal amplitude and phase lag are 9.6 cm and 13.34°,2.4 cm and 10.47°,and 8.1 cm and 14.19°for tidal constituents M_(2),N_(2),and K_(2),respectively.The comparisons of the semidiurnal tides with the TPXO model results show that tidal constituents have good consistency with the TPXO model results.These findings confirm the good performance of HY-2A RA for retrieving semidiurnal tides in the global ocean.
基金funded by The National Natural Science Foundation of China(No.41774015,41704135 and U1939204)National Key Research and Development Project of China(No.2018YFE0206100,2017YFC1500204)。
文摘Previous studies show that the calculated loading effects from global ocean tide models do not match actual measurements of gravity attraction and loading effects in Southeast Asia.In this paper,taking advantage of a unique network of gravity tidal stations all over the Chinese mainland,we compare the observed and modeled tidal loading effects on the basis of the most recent global ocean tide models.The results show that the average efficiencies of the ocean tidal loading correction for O_(1),K_(1),M_(2) are 77%,7 s3%and 59%,respectively.The loading correction efficiencies using recent ocean tidal models are better than the 40 years old Schwiderskis model at coastal stations,but relative worse at stations far from ocean.
文摘Ocean semi-diurnal tides are suggested qualitatively to be more accurately explained by the vertical tide generating forces of the sun and moon, not by the historically standard horizontal components. It is proposed that the sea level elevations created sequentially at the eastern and then western ocean coastal boundaries propagate seaward as shallow water sur</span><span style="font-family:Verdana;font-size:12px;">face gravity waves and interact without mutual disturbance. In that manner two tides per day</span><span style="font-family:Verdana;font-size:12px;"> are created. Horizontal tide forces generate horizontal ocean currents with speeds of 5 mph at the most. Shallow water tide waves move at about 500 mph in open waters and therefore come much closer to being in tune with the sun and moon transiting across the sky.
基金supported by the Research Grants Council(RGC)of the Hong Kong Special Administrative Region(Grant Nos.PolyU5157/05E,PolyU5161/06E)the Scientific Research Foundation of The Hong Kong Polytechnic University(Grant No.GY-F81)the Fundamental Research Funds for the Central Universi-ties(Grant Nos.SWJTU09BR029,SWJTU09BR031)
文摘Ocean tide loading(OTL)displacements of eight principal constituents at 12 sites in Hong Kong were determined using more than eight years of continuous GPS observations.Parameters of the OTL displacements were estimated using daily GPS solutions obtained with precise point positioning(PPP)technique.The results were compared with predictions from seven latest global ocean tide models.Gravity measurements of OTL in Hong Kong were also used to validate the GPS results.The study shows that the results from both the GPS and gravity measurements agree best with the GOT4.7 and NAO99b models,when the K1 and K2 constituents are excluded.The agreements between the GPS and the model estimates are generally at sub-millimeter level in both the horizontal and vertical directions,except for S2,K2 and K1 constituents that have relatively larger errors.After removing the systematic biases between the GPS and the model estimates,the misfits of M2,S2,N2,O1,P1 and Q1 at all sites are within 0.5 and 1.0 mm in the horizontal and the vertical directions,respectively,whereas K1 and K2 show relatively larger misfits of up to 2.3 mm.Both the GPS and the gravity S2 estimates have large biases with unknown reasons when compared with the modeled values,which needs to be further investigated.The study demonstrates that GPS is capable of estimating the OTL displacements with the same accuracy as the model predictions,especially for coastal areas.
基金supported by the National Basic Research Program of China(Grant No.2013CB733302)the Basic Research Project of Institute of Earthquake Science,China Earthquake Administration(Grant Nos.2013IES0203,2014IES010102)the National Natural Science Foundation of China(Grant No.41304018)
文摘Currently,aliasing error of temporal signal model becomes the main factor constraining the accuracy of temporal gravity field.In provision of three types of satellite formations,i.e.,GRACE-type,Pendulum-type and n-s-Cartwheel-type,which are suitable for gravity mission and composed of observation in different directions,here we design two cases and conduct a simulation experiment on the feasibility to apply satellite formations for eliminating the influence from the aliasing error of ocean tide models.The result of our experiment shows that,when the aliasing error is disregarded,n-s-Cartwheel formation can provide the best conditions for gravity field determination,which,compared with GRACE-type,can improve the accuracy by 43%.When aliasing error of the ocean tide model acts as the main source of error,the satellite formation applied in dynamic method for gravity field inversion cannot eliminate aliasing or improve the accuracy of gravity field.And due to its higher sensitivity to the high-degree variation of gravity field,the Cartwheel-type formation,which includes the radial observation,can result in the gravity field containing more high-frequency signals for the ocean tide model error,and lead to a dramatically larger error.
基金supported by the National Natural Science Foundation of China(42250101,42250102)the Macao Foundation.
文摘The movement of global ocean circulation in the Earth’s main magnetic field generates a measurable induced magnetic field(about 2 nT at geomagnetic satellite altitudes).However,this ocean circulation-induced magnetic field has not been previously estimated or incorporated into geomagnetic field models,potentially causing leakage into the core field model.Here,we present a method to account for the circulation-induced magnetic field during geomagnetic field modeling.First,a forward model of the circulation-induced magnetic field is constructed by numerically solving electromagnetic induction equations based on a realistic ocean circulation model.Then,this forward model is subtracted from the observed data.Finally,the core and lithospheric fields,magnetospheric and Earth’s mantle-induced fields,and the ocean tide-induced magnetic field are co-estimated.Applying our method to over 20 years of MSS-1,Swarm,CryoSat-2,and CHAMP satellite magnetic data,we derive a new multisource geomagnetic field model(MGFM).We find that incorporating a forward model of the circulation-induced magnetic field marginally improves the fit to the data.Furthermore,we demonstrate that neglecting the circulation-induced magnetic field in geomagnetic field modeling results in leakage into the core field model.The highlights of the MGFM model include:(i)a good agreement with the widely used CHAOS model series;(ii)the incorporation of magnetic fields induced by both ocean tides and circulation;and(iii)the suppression of leakage of the circulation-induced magnetic field into the core field model.
基金the National 863 Program of China (No.2007AA12Z312)
文摘This paper describes the ocean loading tides corrections of GPS stations in Antarctica, such as the Great Wall station and Zhongshan station. Based on the theory of ocean loading tides, the displacement corrections of ocean loading tides on GPS stations in Antarctica are calculated by using the CRS4.0 ocean loading tides model. These corrections are also applied to GPS data proc-essing. The GPS data are analyzed by the GAMIT software with and without these corrections. We compared and analyzed the GPS baseline components to get the differences. The results show that the ocean tidal displacement corrections have obvious effects upon GPS baseline components. Therefore, we should not ignore the ocean loading tides corrections of GPS stations in Antarctica to obtain precise and reliable results.
基金The National Natural Science Foundation of China(NSFC)-Shandong Joint Fund for Marine Science Research Centers under contract No.U1406404the National Natural Science Foundation of China under contract No.41406027+1 种基金the National Basic Research Program(973 Program)of China under contract No.2010CB950300the Project of Comprehensive Evaluation of Polar Areas on Global and Regional Climate Changes under contract No.CHINARE04-04
文摘The performance of a z-level ocean model, the Modular Ocean Model Version 4（MOM4）, is evaluated in terms of simulating the global tide with different horizontal resolutions commonly used by climate models. The performance using various sets of model topography is evaluated. The results show that the optimum filter radius can improve the simulated co-tidal phase and that better topography quality can lead to smaller rootmean square（RMS） error in simulated tides. Sensitivity experiments are conducted to test the impact of spatial resolutions. It is shown that the model results are sensitive to horizontal resolutions. The calculated absolute mean errors of the co-tidal phase show that simulations with horizontal resolutions of 0.5° and 0.25° have about 35.5% higher performance compared that with 1° model resolution. An internal tide drag parameterization is adopted to reduce large system errors in the tidal amplitude. The RMS error of the best tuned 0.25° model compared with the satellite-altimetry-constrained model TPXO7.2 is 8.5 cm for M_2. The tidal energy fluxes of M_2 and K_1 are calculated and their patterns are in good agreement with those from the TPXO7.2. The correlation coefficients of the tidal energy fluxes can be used as an important index to evaluate a model skill.
基金supported by the Space Geodesy Technology Development Program of Korea Astronomy and Space Science Institutesupported by the NSFC(grant Nos.41631072,41721003,41574007 and 41429401)the Discipline Innovative Engineering Plan of Modern Geodesy and Geodynamics(grant No.B17033)
文摘The global oceanic/atmospheric tides exert decelerating/accelerating secular torques on the Earth rotation. We developed new formulations to accurately calculate amounts of two kinds of secular tidal torques. After Melchior, we found that an additional factor 1+k-l = 1.216, which has been formerly neglected, must be multiplied unto the tidal torque integral. By using our refined formulations and the recent oceanic/atmospheric global tide models, we found that:(i) semidiurnal oceanic lunar/solar tides exert decelerating torques of about-4.462 × 10^(16)/-0.676 × 10^(16) Nm respectively and(ii) atmospheric S_2 tide exerts accelerating torque of 1.55 × 10^(15) Nm. Former estimates of the atmospheric S_2 tidal torque were twice as large as our estimate due to improper consideration of loading effect. We took the load Love number for atmospheric loading effect from Guo et al.(2004). For atmospheric loading of spherical harmonic degree two, the value of k′=-0.6031 is different from that for ocean loading as k′ =-0.3052,while the latter is currently used for both cases-ocean/atmospheric loading-without distinction. We discuss(i) the amount of solid Earth tidal dissipation(which has been left most uncertain) and(ii) secular changes of the dynamical state of the Earth-Moon-Sun system. Our estimate of the solid Earth tidal torque is-4.94×10^(15) Nm.
基金The paper is funded by the 7.5 Key ScienceTechnology Project(87-02-07)of the National Mapping Bureau
文摘Using tidal potential solar thermal-radiating energy current and the nonlinear effect of the gravity tide as the input function, moreover, considering the ocean tidal species as the input function of the loading effect of ocean tide, we make the lumped response analysis of the observational tilt tide in one year. The tilt gravitational tide, the load tide, the radiational tide and the nonlinear tide with the same frequeny are separated off. It is shown that the load tide and the gravitational tide are the same quantity grade, the load tide may spread into inland far away; the solar thermal-radiation has an effect on the tilt tide; there is a little nonlinear tide in the tilt tide, but the nonlinear tide of the ocean tide has the stronger loading effect on the tilt tide than the nonlinear tide brought about by the gravitational tide itself; the lag interval, △τ=41 (h), is the best value in the response analysis. In addition, the harmonic analyses of the tilt tide and the separated tilt tides are made respectively by using j.v model, and their ellipse factors are calculated.
基金This research was supported by a grant from the 0ffice of Naval Research of United States under the Sea of Japan Departmental Research Initiatite of N00014-98-1-0236a project from the National Natural Science Foundation of China under contract No.40506006.
文摘Ocean surface waves are strongly forced by high wind conditions associated with winter storms in the Sea of Japan. They are also modulated by tides and storm surges. The effects of the variability in surface wind forcing, tides and storm surges on the waves are investigated using a wave model, a high-resolution atmospheric mesoscale model and a hydrodynamic ocean circulation model. Five month-long wave model simulations are inducted to examine the sensitivity of ocean waves to various wind forcing fields, tides and storm surges during January 1997. Compared with observed mean wave parameters, results indicate that the high frequency variability in the surface wind filed has very great effect on wave simulation. Tides and storm surges have a significant impact on the waves in nearshores of the Tsushima-kaihyS, but not for other regions in the Sea of Japan. High spatial and temporal resolution and good quality surface wind products will be crucial for the prediction of surface waves in the JES and other marginal seas, especially near the coastal regions.
基金The National Key Research and Development Program of China under contract No.2017YFC1404201the National Natural Science Foundation of China(NSFC)under contract Nos 41606040 and 41606036+1 种基金the NSFC-Shandong Joint Fund for Marine Science Research Centers under contract No.U1606405the National High Technology Research and Development Program(863 Program)of China under contract No.2013AA09A506
文摘The tide-induced mixing plays an important role in the regulation of ocean circulation.Numerical simulation of continental shelf circulation is found to exhibit an unreasonable vertical thermohaline structure without consideration of tide effects.In this study,we establish a harmonic analyzed parameterization of tide-induced（HAT） mixing,by which means to derive time-depended function of mixing coefficient based on harmonic analysis of the vertical mixing coefficient.By employing HAT mixing parameterization scheme,a series of numerical experiments are conducted for the Yellow Sea.Numerical results show that an ocean circulation model with the HAT mixing involved is capable of reproducing the reasonable thermohaline structure of the Yellow Sea Cold Water Mass,similar to structures produced by explicit tidal forcing on the open boundary.The advantage of the HAT method is its faster computation time,compared with models that directly resolve explicit tidal motion.The HAT parameterization for the tide-induced mixing has potential to improve both the accuracy and efficiency of ocean circulation and climate models.
基金supported by the National Natural Science Foundation of China under contract Nos 49676275 and 49976002the Microwave Imaging National Key Laboratory Foundation under contract No.51442020103JW1002.
文摘By analyzing a data set collected using a moored instrument array and CTD during TOGA-COARE, it is found that there exist remarkable internal tides in the western equatorial Pacific Ocean around 1°45′S, 156°E, whose horizontal wavenumber （wavelength）, vertical wavenumber, h 156° orizontal propagation speed and vertical propagation speed are 3.3×10^-2 km^-1 （210 km）, - 1.6×10^-3m, 2.0 m/s and -3.8 cm/s, respectively, that is, the waveform propagates downwards slantingly. Moreover, the propagating direction rotates statistically clockwise as the depth increases and its cause is unclear.
基金The National Natural Science Foundation of China under contract No. 40676009 and 40606006the Basic Research Project of Qingdao Science and Technology Program under contract No. 11-1-4-98-jch
文摘The global distributions of eight principal tidal constituents, M2, S2, K1, O1, N2, K2, P1, and Q1, are derived using TOPEX/Poseidon and JASON-1（T/P-J） satellite altimeter data for 16 a. The intercomparison of the derived harmonics at 7000 subsatellite track crossover points shows that the root mean square （RMS） values of the tidal height differences of the above eight constituents range from 1.19 cm to 2.67 cm, with an average of about 2 cm. The RMS values of the tidal height differences between T/P-J solutions and the harmonics from ground measurements at 152 tidal gauge stations for the above constituents range from 0.34 cm to 1.08 cm, and the relative deviations range from 0.031 to 0.211. The root sum square of the RMS differences of these eight constituents is 2.12 cm, showing the improvement of the present model over the existing global ocean tidal models. Based on the obtained tidal model the global ocean tidal energetics is studied and the global distribution of the tidal power input density by tide-generating force of each constituent is calculated, showing that the power input source regions of semidiurnal tides are mainly concentrated in the tropical belt between 30S and 30N, while the power input source regions of diurnal tides are mainly concentrated off the tropic oceans. The global energy dissipation rates of the M2, S2, K1, O1, N2, P1, K2 and Q1 tides are 2.424, 0.401, 0.334, 0.160, 0.113, 0.035, 0.030 and 0.006 TW, respectively. The total global tidal dissipation rate of these eight constituents amounts to 3.5 TW.
