Monitoring absolute vertical land motions and absolute sea-level changes from GPS and tide gauges data over French Polynesia

In this study,we estimate the absolute vertical land motions at three tidal stations with collocated Global Navigation Satellite System(GNSS)receivers over French Polynesia during the period 2007-2020,and obtain,as ancillary results,estimates of the absolute changes in sea level at the same locations.To verify our processing approach to determining vertical motion,we first modeled vertical motion at the International GNSS Service(IGS)THTI station located in the capital island of Tahiti and compared our estimate with previous independent determinations,with a good agreement.We obtained the following estimates for the vertical land motions at the tide gauges:Tubuai island,Austral Archipelago-0.92±0.17 mm/yr,Vairao village,Tahiti Iti:-0.49±0.39 mm/yr,Rikitea,Gambier Archipelago-0.43±0.17 mm/yr.The absolute variations of the sea level are:Tubuai island,Austral Archipelago 5.25±0.60 mm/yr,Vairao village,Tahiti Iti:3.62±0.52 mm/yr,Rikitea,Gambier Archipelago 1.52±0.23 mm/yr.We discuss these absolute values in light of the values obtained from altimetric measurements and other means in French Polynesia.

基于TiDE-PatchTST模型的柑橘冷藏效率时序预测模型优化

柑橘低温贮藏过程中果实温度波动是引发果品品质安全风险与增加制冷能耗的关键因素,同时果品品质与制冷能耗也是评判柑橘冷藏效率的重要评价指标,实现两者动态预测可为科学预知与精准优化柑橘冷藏效率提供可靠支持。本文提出一种基于PatchTST的柑橘冷藏效率时序预测模型。首先,基于自注意力机制和独立预测方法(Channel independent,CI)构建基础PatchTST模型;其次,通过融合基础PatchTST模型与TiDE模型中的协变量特征提取模块,实现对多元时序数据集中全部序列的特征提取,并有效改进模型预测精度;最后,基于皮尔森相关性分析方法定量分析冷库制冷参数与能耗、柑橘温度的相关性,确定TiDE-PatchTST模型输入参数,并基于5000组实验数据实现多种模型训练与测试,对比验证TiDE-PatchTST模型的准确性与优越性。结果表明,基于TiDE-PatchTST模型的冷库能耗预测值与实验值平均绝对误差(MAE)和均方根误差(RMSE)分别为3.645 W·h和10.421 W·h,柑橘温度预测值与实验值的MAE和RMSE分别为0.034℃和0.042℃,相比Transformer模型,能耗预测的MAE和RMSE最高分别下降41.43%和39.27%,柑橘温度预测的MAE和RMSE最高分别下降46.03%和28.81%。本研究可为柑橘冷藏过程温度波动与能耗动态感知与优化调控等提供可靠方法支持与参考。

Combination of Tsoft and ET34-ANA-V80 software for the preprocessing and analysis of tide gauge data in French Polynesia

Since 2008 a network of five sea-level monitoring stations was progressively installed in French Polynesia.The stations are autonomous and data,collected at a sampling rate of 1 or 2 min,are not only recorded locally,but also transferred in real time by a radio-link to the NOAA through the GOES satellite.The new ET34-ANA-V80 version of ETERNA,initially developed for Earth Tides analysis,is now able to analyze ocean tides records.Through a two-step validation scheme,we took advantage of the flexibility of this new version,operated in conjunction with the preprocessing facilities of the Tsoft software,to recover co rrected data series able to model sea-level variations after elimination of the ocean tides signal.We performed the tidal analysis of the tide gauge data with the highest possible selectivity(optimal wave grouping)and a maximum of additional terms(shallow water constituents).Our goal was to provide corrected data series and modelled ocean tides signal to compute tide-free sea-level variations as well as tidal prediction models with centimeter precision.We also present in this study the characteristics of the ocean tides in French Polynesia and preliminary results concerning the non-tidal variations of the sea level concerning the tide gauge setting.

Evolutive Trend of Water Level in the Ebrie Lagoon by Reconstitution of the Tide Gauge Time Series in Front of the Abidjan Coastline (Côte d’Ivoire)

The latest Intergovernmental Panel on Climate Change (IPCC) report shows that sea-level rise, which has been accelerated since the 19th century resulting to the global warming, threatens coastal areas with high population growth. A Global Sea Level Observing System (GLOSS) assessment highlighted the lack of data in Africa, and in Côte d’Ivoire in particular. In order to estimate the evolutionary trend of sea level along the Ivorian coast, and to draw up preventive plans to protect properties and populations, we digitized 65 years of historical tidegrams recorded in the Ebrie Lagoon, using the “Surfer” and “Nunieau” software, then processed them using “T-Tide” and “U-Tide” software. The average levels were calculated using the Demerliac filter from complete daily (day and night) recordings for providing a usable database of 31 years of hourly lagoon data from 1979 to 2015. Our results show that a mean water level in lagoon is 1.04 m. The evolutionary trend in sea level, estimated in the lagoon via the Vridi canal, during the rainy season is the most significant at 2.93 mm/year. This is followed by the dry season, with a trend of 2.89 mm/year. The flood season trend is 2.78 mm/year. This suggests that marine water inflows dominate continental inflows. Our results highlight the vulnerability of Côte d’Ivoire’s coasts to the risk of marine submersion.

Eutrophication of Jiangsu Coastal Water and Its Role in the Formation of Green Tide

Since 2007,the large-scale green tide caused by Ulva prolifera(U.prolifera)have occurred as a recurrent phenomenon in the southern Yellow Sea of China.Field surveys and satellite remote sensing showed that the small scattered patches of green tide algae were first observed along the Porphyra agriculture area of the Subei Shoal in late April.In this study,we attempted to identify the role of eutrophication in the origin of the green tide in the Subei Shoal and its adjacent area.Subei Shoal and its adjacent area are characterized by rich nutrients,especially NO_(3)^(-)-N,NH_(4)^(+)-N,PO_(4)^(3-)-P,and other bioavailable components(such as urea-N and amino acids).In the spring of 2017,the average concentrations of NO_(3)^(-)-N were 19.01±11.01μmolL^(-1),accounting for 86.68%of the dis-solved inorganic nitrogen(DIN).In addition,the average concentration of NH4^(+)-N was 2.51±1.60μmolL^(-1).PO_(4)^(3-)-P had an average concentration of 0.14±0.13μmolL-1.The average concentrations of urea-N and total hydrolyzed amino acids(THAA)were 1.73±1.36μmolL^(-1)and 1.33±0.80μmolL^(-1),respectively.Rich nutritive substances play a key role in the rapid production of U.prolifera and make the Jiangsu coastal water an incubator for green tide.

Analysis on the causes of massive stranding of Yellow Sea green tide on Lianyungang and Rizhao coasts in 2022

In 2022,Yellow Sea green tide caused by Ulva prolifera reached a historic minimum and the coastal areas of Shandong Peninsula were less affected.However,the largest amount of seaweed biomass has been washed ashore on Lianyungang and Rizhao coasts since 2015.We studied the development pattern of Yellow Sea green tide in 2022,and analyzed the key environmental factors on the growth and drifting,then discussed the possible reasons that resulted in the massive stranding of green tide biomass in Lianyungang and Rizhao.Results show under the combined influence of the east to southeast winds and currents with shoreward anomalies,green tide drifted to the coastal waters between Shandong and Jiangsu provinces and the distribution areas located westward compared with previous years(2008–2021).Floating U.prolifera rafts from the coastal waters of Binhai and Sheyang drifted continuously into the coastal waters of Lianyungang and Rizhao,providing important supplements for Yellow Sea green tide.Because green tide in 2022 distributed close to the coastal waters,the abundant nutrients might support their continuous high growth rate.In addition,the amount of rainfall around Shandong Peninsula from late June to early July were significantly higher than in previous years,which might promote the development of green tide to some extent.

Unification of Gravitational and Strong Interaction Fields Using Partial Gauge Symmetry

We propose the new field potential by maintaining both the symmetry of the scalar gauge and the conservation law keeping N?ether’s theorem, while disregarding the symmetry of the vector gauge. The new potential forms like the well-type potential where a particle behaves almost freely but is very hard to escape without external energy, which can be interpreted as local confinement and asymptotic freedom. By assuming a 2-dimensional metric tensor in 4-dimensional space-time, we suggest the existence of 3 kinds of particles that resemble QCD with 3 color charges. We also show that the mass term exists but comes to zero and derive the charge and spin values. We can regard the particle with this new potential as a gluon, and the interaction in this well-type potential as a strong interaction for the properties of mass, charge, spin, and its behavior. We suggest the eight-fold way with this new particle, which is similar to the existing method based on SU (3) symmetry. Even though the strong interaction has been analyzed in the standard model and string theory, we build a new consistent model based on the theory of relativity including Riemann geometry, and show the unification of gravitational and strong interactional field.

Genome-wide SNP markers provided insights into the reproductive strategy and genetic diversity of the green tide causative species Ulva prolifera in China

Ulva prolifera is the causative species of the annually occurring large-scale green tides in China since 2007.Its specific biological features on reproductivity strategies,as well as intra-species genetic diversity,are still largely unknown,especially at the genome level,despite their importance in understanding the formation and outbreak of massive green tides.In the present study,the restriction site-associated DNA genotyping approach(2b-RAD)was adopted to identify the genome-wide single-nucleotide polymorphisms(SNPs)of 54 individual thalli including samples collected from Subei Shoal in 2019 and Qingdao coast from 2019 to 2021.SNPs genotype results revealed that most of the thalli in 2019 and 2020 were haploid gametophytes,while only half of the thalli were gametophytes in 2021,indicating flexibility in the reproductive strategies for the formation of the green tides among different years and the dominance of asexual and vegetative reproductive mode for the floating period.Besides,population analysis was conducted,and it revealed a very low genetic diversity among samples from Subei Shoal and the Qingdao coast in the same year and a higher divergence among samples in different years.The results showed the efficiency of 2b-RAD in the exploration of SNPs in U.prolifera and provided the first genome-wide scale evidence for the origin of the large-scale green tides on the Qingdao coast.This study improved our understanding of the reproductive strategy and genetic diversity of the green tide causative species and will help further reveal the biological causes of the green tide in China.

Estimation and verification of green tide biomass based on UAV remote sensing

Since 2007,the Yellow Sea green tide has broken out every summer,causing great harm to the environment and society.Although satellite remote sensing(RS)has been used in biomass research,there are several shortcomings,such as mixed pixels,atmospheric interference,and difficult field validation.The biomass of green tide has been lacking a high-precision estimation method.In this study,high-resolution unmanned aerial vehicle(UAV)RS was used to quantitatively map the biomass of green tides.By utilizing experimental data from previous studies,a robust relationship was established to link biomass to the red-green-blue floating algae index(RGB-FAI).Then,the lab-based model for green tide biomass from visible images taken by the UAV camera was developed and validated by field measurements.Re sults show that the accurate and cost-effective method is able to estimate the green tide biomass and its changes in given local waters of the near and far seas.The study provided an effective complement to the traditional satellite RS,as well as high-precision quantitative techniques for decision-making in disaster management.

Research on the strain gauge mounting scheme of track wheel force measurement system based on high-speed wheel/rail relationship test rig

Purpose-This paper aims to analyze the stress and strain distribution on the track wheel web surface and study the optimal strain gauge location for force measurement system of the track wheel.Design/methodology/approach-Finite element method was employed to analyze the stress and strain distribution on the track wheel web surface under varying wheel-rail forces.Locations with minimal coupling interference between vertical and lateral forces were identified as suitable for strain gauge installation.Findings-The results show that due to the track wheel web’s unique curved shape and wheel-rail force loading mechanism,both tensile and compressive states exit on the surface of the web.When vertical force is applied,Mises stress and strain are relatively high near the inner radius of 710 mm and the outer radius of 1110mmof the web.Under lateral force,high Mises stress and strain are observed near the radius of 670mmon the inner and outer sides of the web.As the wheel-rail force application point shifts laterally toward the outer side,the Mises stress and strain near the inner radius of 710 mm of the web gradually decrease under vertical force while gradually increasing near the outer radius of 1110 mm of the web.Under lateral force,the Mises stress and strain on the surface of the web remain relatively unchanged regardless of the wheel-rail force application point.Based on the analysis of stress and strain on the surface of the web under different wheel-rail forces,the inner radius of 870 mm is recommended as the optimal mounting location of strain gauges for measuring vertical force,while the inner radius of 1143 mm is suitable for measuring lateral force.Originality/value-The research findings provide valuable insights for determining optimal strain gauge locations and designing an effective track wheel force measurement system.

Observation about the Classical Electromagnetic Gauge Transformation and Its Quantum Correspondence

Using the Landau and symmetric gauges for the vector potential of a constant magnetic field and the quantum problem of a charged particle moving on a flat surface, we show the classical electromagnetic gauge transformation does not correspond to a one-dimensional unitary group transformation U(1) of the wave function for the quantum case. In addition, with the re-examination of the relation between the magnetic field B and its vector potential A, we found that, in order to have a consistent formulation of the dynamics of the charged particle with both expressions, we must have that B=∇×A if and only if B≠0.

Assimilated Tidal Results of Tide Gauge and TOPEX/POSEIDON Data over the China Seas Using a Variational Adjoint Approach with a Nonlinear Numerical Model

In order to obtain an accurate tide description in the China Seas, the 2-dimensional nonlinear numerical Princeton Ocean Model （POM） is employed to incorporate in situ tidal measurements both from tide gauges and TOPEX/POSEIDON （T/P） derived datasets by means of the variational adjoint approach in such a way that unknown internal model parameters, bottom topography, friction coefficients and open boundary conditions, for example, are adjusted during the process. The numerical model is used as a forward model. After the along-track T/P data are processed, two classical methods, i.e. harmonic and response analysis, are implemented to estimate the tide from such datasets with a domain covering the model area extending from 0° to 41°N in latitude and from 99°E to 142°E in longitude. And the results of these two methods are compared and interpreted. The numerical simulation is performed for 16 major constituents. In the data assimilation experiments, three types of unknown parameters （water depth, bottom friction and tidal open boundary conditions in the model equations） are chosen as control variables. Among the various types of data assimilation experiments, the calibration of water depth brings the most promising results. By comparing the results with selected tide gauge data, the average absolute errors are decreased from 7.9 cm to 6.8 cm for amplitude and from 13.0° to 9.0° for phase with respect to the semidiurnal tide M2 constituent, which is the largest tidal constituent in the model area. After the data assimilation experiment is performed, the comparison between model results and tide gauge observation for water levels shows that the RMS errors decrease by 9 cm for a total of 14 stations, mostly selected along the coast of China's Mainland, when a one-month period is considered, and the correlation coefficients improve for most tidal stations among these stations.

Accuracy assessment of global ocean tide models in the South China Sea using satellite altimeter and tide gauge data

In this study,to meet the need for accurate tidal prediction,the accuracy of global ocean tide models was assessed in the South China Sea(0°–26°N,99°–121°E).Seven tide models,namely,DTU10,EOT11 a,FES2014,GOT4.8,HAMTIDE12,OSU12 and TPXO8,were considered.The accuracy of eight major tidal constituents(i.e.,Q1,O1,P1,K1,N2,M2,S2 and K2)were assessed for the shallow water and coastal areas based on the tidal constants derived from multi-mission satellite altimetry(TOPEX and Jason series)and tide gauge observations.The root mean square values of each constituent between satellite-derived tidal constants and tide models were found in the range of 0.72–1.90 cm in the deep ocean(depth>200 m)and 1.18–5.63 cm in shallow water area(depth<200 m).Large inter-model discrepancies were noted in the Strait of Malacca and the Taiwan Strait,which could be attributable to the complicated hydrodynamic systems and the paucity of high-quality satellite altimetry data.In coastal regions,an accuracy performance was investigated using tidal results from 37 tide gauge stations.The root sum square values were in the range of 9.35–19.11 cm,with the FES2014 model exhibiting slightly superior performance.

Evaluation of vertical crustal movements and sea level changes around Greenland from GPS and tide gauge observations

To better monitor the vertical crustal movements and sea level changes around Greenland,multiple data sources were used in this paper,including global positioning system(GPS),tide gauge,satellite gravimetry,satellite altimetry,glacial isostatic adjustment(GIA).First,the observations of more than 50 GPS stations from the international GNSS service(IGS)and Greenland network(GNET)in 2007–2018 were processed and the common mode error(CME)was eliminated with using the principal component analysis(PCA).The results show that all GPS stations show an uplift trend and the stations in southern Greenland have a higher vertical speed.Second,by deducting the influence of GIA,the impact of current Gr IS mass changes on GPS stations was analysed,and the GIA-corrected vertical velocity of the GPS is in good agreement with the vertical velocity obtained by gravity recovery and climate experiment(GRACE).Third,the absolute sea level change around Greenland at 4 gauge stations was obtained by combining relative sea level derived from tide gauge observations and crustal uplift rates derived from GPS observations,and was validated by sea level products of satellite altimetry.The results show that although the mass loss of Gr IS can cause considerable global sea level rise,eustatic movements along the coasts of Greenland are quite complex under different mechanisms of sea level changes.

Validation of Sea Level Data in the East Asian Marginal Seas: Comparison between TOPEX/POSEIDON Altimeter and In-Situ Tide Gauges

In an effort to assess the reliability of satellite altimeter systems, the authors conduct a comparative analysis of sea level data that were collected from the TOPEX/POSEIDON (T/P) altimeter and 10 tide gauges (TG) near the satellite passing ground tracks. The analysis is made using datasets collected from marginal sea regions surrounding the Korean Peninsula at T/P cycles of 2 to 230, which correspond to October 1992 to December 1998. Proper treatment of tidal errors is a very critical step in data processing because the study area has very strong tide. When the T/P data are processed, the procedures of Park and Gamberoni (1995) are adapted to reduce errors associated with the tide. When the T/P data are processed in this way, the alias periods of M2, S2, and K1 constituents are found to be 62.1, 58.7, and 173 days repectively. The compatibility of the T/P and TG datasets are examined at various filtering periods. The results indicate that the low-frequency signals of the T/P data can be interpreted more safely with longer filtering periods (such as up to the maximum selected value of 200 days). When RMS errors for the 200-day low-pass filter period are compared with all 10 tidal stations, the values span the range of 2.8 to 6.7 cm. The results of a correlation analysis for this filtering period also show a strong agreement between the T/P and TG datasets across all stations investigated (e.g.,p- values consistently less than 0.001). Hence according to the analysis, the conclusion is made that the analysis of surface sea level using satellite altimeter data can be made safely with reasonably extended filtering periods such as 200 days.

The Time Series Spectral Analysis of Satellite Altimetry and Coastal Tide Gauges and Tide Modeling in the Coast of Caspian Sea

This study endeavors to deal with the least square spectral analysis on the time series, to find present significant frequencies, to analyze 40 tide components using harmonic methods and to show relationship between discovered frequencies and 40 components of tide. For the purpose of collecting data of altimetry satellites of Topex/Poseidon (T/P), Jason 1, Jason 2 and coastal tide gauges of Bandar Anzali, Noshahr, and Nekah were utilized. In this time series formed by cross over points of altimetry satellite and then using least square spectral analysis on time series derived from altimetry satellite and coastal tide gauges the significant components were found and annual, biannual, and monthly components were discovered. Then, analysis of 40 tide components was conducted using harmonic method to find the amplitude and phase. It represented that solar annual (Sa) plays the most significant role on Caspian Sea corresponded to the least square spectral analysis of the time series. The results shows that the annual (Sa) and semi-annual Solar (Ssa) constituents on all of the ports listed have the highest amplitude in comparison with the other constituents which are respectively 16 cm, 18 cm and 15 cm for annual constituent and 2.8 cm, 5.4 cm and 3.7 cm for semi-annual constituent.

Observation on Height Changes of Chinese Tide Gauges by GPS

The height changes of tide gauges directly influence sea level observation. For research of sea level variation in large region or globe, the land vertical displacement must be considered. Two sessions of GPS and absolute gravity observations in 2001 and 2003 are used to determine the horizontal and vertical motion of China coast in ITRF2000 and Eurasia frame. The difference between results of continuous observation and periodic observation is discussed.

Absolute sea level variability of Arctic Ocean in 1993–2018 from satellite altimetry and tide gauge observations

Arctic absolute sea level variations were analyzed based on multi-mission satellite altimetry data and tide gauge observations for the period of 1993–2018.The range of linear absolute sea level trends were found-2.00 mm/a to 6.88 mm/a excluding the central Arctic,positive trend rates were predominantly located in shallow water and coastal areas,and negative rates were located in high-latitude areas and Baffin Bay.Satellite-derived results show that the average secular absolute sea level trend was(2.53±0.42)mm/a in the Arctic region.Large differences were presented between satellite-derived and tide gauge results,which are mainly due to low satellite data coverage,uncertainties in tidal height processing and vertical land movement(VLM).The VLM rates at 11 global navigation satellite system stations around the Arctic Ocean were analyzed,among which 6 stations were tide gauge colocated,the results indicate that the absolute sea level trends after VLM corrected were of the same magnitude as satellite altimetry results.Accurately calculating VLM is the primary uncertainty in interpreting tide gauge measurements such that differences between tide gauge and satellite altimetry data are attributable generally to VLM.

Determination of the Absolute Rate of Sea Level by Using GPS Reference Station and Tide Gauge Data

The absolute rate of mean sea level of Xiamen area is derived from the data of Xiamen tide gauge station and Xiamen GPS fiducial station of crustal movement observation network of China（CMONC）. The height variation is discussed deeply in this paper, h is shown that height has periodic variations. So the rate of vertical land movement can not be precisely obtained only from several GPS campaigns. It is pointed out that the vertical crustal movement of tide gauge station should be monitored by using long-term continuous GPS observations.

Feasibility Analysis of Performance Validation for Satellite Altimeters Using Tide Gauge and Deep-ocean Bottom Pressure Recorder

Independent of traditional approach of satellite altimeter calibration, the feasibility of altimeter validation using tide gauge located on solitary island at open sea (TGSI) and deep-ocean bottom pressure recorder (DBPR) separately is initially studied. Bias of Jason-3 sea surface height (SSH) and relative SSH bias (Δbias) between Jason-2 and Jason-3 is calculated using the data of tide gauge on Harvest oil platform, tide gauge No. 1890000 and DBPR No. 21419. The standard deviations of calculated SSH bias sequence are 3.98 cm, 2.87 cm and 8.61 cm respectively, and Δbias (Jason-3—Jason-2) is -3.62± 2.17 cm , -2.58±1.97 cm and -2.60±1.30 cm respectively. Comparing to the results reported by international calibration sites, the results show that Jason-3 SSH is 3.0 cm lower than that of Jason-2, the selected DBPR is appropriate to the calculation of relative SSH bias between Jason-2 and Jason-3, but it is not suitable for calibration or validation of single satellite, TGSI is appropriate to both.