Pub Date : 2021-12-30DOI: 10.1080/01490419.2021.2020185
A. Zaki, Mahmoud Magdy, M. Rabah, A. Saber
Abstract For the purpose of marine geoid modeling and many other geodetic and geophysical applications, a marine gravity map around Egypt is established by the integration of gravity data provided by satellite altimetry and shipborne gravimetric observations. Firstly, the collected shipborne data were compared with GO_CONS_GCF_2_TIM_R6 and XGM2019e GGMs and with SSv29.1 and DTU17 altimetry models. Then, a pre-refinement of ship marine surveys was done with a rigorous condition, in which a number of 6525 points have been removed from the dataset. After that, 87709 points were deducted from the pre-filtered shipborne dataset to fit the study area and the cross-validation approach with the kriging interpolation algorithm were applied. A rigorous level of confidence was decided in this step where the points which have differences between the estimated and the observed values more than twice the STD of the residuals were removed until the STD reached a value less than 1 mGal. Finally, the filtered shipborne gravity data were combined with DTU17 (the best evaluation model) using the least-squares collocation technique (LSC). The final gravity map was tested using 8000 randomly chosen shipborne stations, which were not included when applying LSC, revealing the significant enhancement gained after the integration process.
{"title":"Establishing a Marine Gravity Database around Egypt from Satellite Altimetry-Derived and Shipborne Gravity Data","authors":"A. Zaki, Mahmoud Magdy, M. Rabah, A. Saber","doi":"10.1080/01490419.2021.2020185","DOIUrl":"https://doi.org/10.1080/01490419.2021.2020185","url":null,"abstract":"Abstract For the purpose of marine geoid modeling and many other geodetic and geophysical applications, a marine gravity map around Egypt is established by the integration of gravity data provided by satellite altimetry and shipborne gravimetric observations. Firstly, the collected shipborne data were compared with GO_CONS_GCF_2_TIM_R6 and XGM2019e GGMs and with SSv29.1 and DTU17 altimetry models. Then, a pre-refinement of ship marine surveys was done with a rigorous condition, in which a number of 6525 points have been removed from the dataset. After that, 87709 points were deducted from the pre-filtered shipborne dataset to fit the study area and the cross-validation approach with the kriging interpolation algorithm were applied. A rigorous level of confidence was decided in this step where the points which have differences between the estimated and the observed values more than twice the STD of the residuals were removed until the STD reached a value less than 1 mGal. Finally, the filtered shipborne gravity data were combined with DTU17 (the best evaluation model) using the least-squares collocation technique (LSC). The final gravity map was tested using 8000 randomly chosen shipborne stations, which were not included when applying LSC, revealing the significant enhancement gained after the integration process.","PeriodicalId":49884,"journal":{"name":"Marine Geodesy","volume":"45 1","pages":"101 - 120"},"PeriodicalIF":1.6,"publicationDate":"2021-12-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48218934","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-12-16DOI: 10.1080/01490419.2021.2011502
Jichao Wang, Yue Wang
Abstract Significant wave height (SWH) is a vital parameter in marine science research and engineering application. The up-to-date reanalysis product ERA5 SWH brings new possibilities to the long-term analysis. However, a systematic assessment of ERA5 SWH on a large scale is still lacking. This paper presents an evaluation of ERA5 SWH against observations from 103 buoys in the North American Atlantic and Pacific sourced by the National Data Buoy Center over the period 1979 to 2019. Overall, the ERA5 SWH has a good agreement with the in-situ observations, with a bias of −0.058 m, root mean squared error of 0.325 m, correlation coefficient of 0.961 and scatter index of 18.54%. The accuracy of ERA5 SWH is satisfactory under the most typical sea states (0.5 m < SWH < 4 m). The monthly analysis shows the performance of ERA5 SWH in summer is the best. The water depth and offshore distance have also been identified to impact the reliability of ERA5 SWH. Although the statistics vary at different locations, the performances of ERA5 SWH at most stations are reasonable. In addition, an evident improvement in the validity over time is observed, which can be attributed to the assimilation of the altimeter wave height.
{"title":"Evaluation of the ERA5 Significant Wave Height against NDBC Buoy Data from 1979 to 2019","authors":"Jichao Wang, Yue Wang","doi":"10.1080/01490419.2021.2011502","DOIUrl":"https://doi.org/10.1080/01490419.2021.2011502","url":null,"abstract":"Abstract Significant wave height (SWH) is a vital parameter in marine science research and engineering application. The up-to-date reanalysis product ERA5 SWH brings new possibilities to the long-term analysis. However, a systematic assessment of ERA5 SWH on a large scale is still lacking. This paper presents an evaluation of ERA5 SWH against observations from 103 buoys in the North American Atlantic and Pacific sourced by the National Data Buoy Center over the period 1979 to 2019. Overall, the ERA5 SWH has a good agreement with the in-situ observations, with a bias of −0.058 m, root mean squared error of 0.325 m, correlation coefficient of 0.961 and scatter index of 18.54%. The accuracy of ERA5 SWH is satisfactory under the most typical sea states (0.5 m < SWH < 4 m). The monthly analysis shows the performance of ERA5 SWH in summer is the best. The water depth and offshore distance have also been identified to impact the reliability of ERA5 SWH. Although the statistics vary at different locations, the performances of ERA5 SWH at most stations are reasonable. In addition, an evident improvement in the validity over time is observed, which can be attributed to the assimilation of the altimeter wave height.","PeriodicalId":49884,"journal":{"name":"Marine Geodesy","volume":"45 1","pages":"151 - 165"},"PeriodicalIF":1.6,"publicationDate":"2021-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46796619","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-12-15DOI: 10.1080/01490419.2021.2006376
Shailee Patel, Manisha Vithalpura, S. Mallick, S. Ratheesh
Abstract This study investigates the response of a high resolution coupled physical-ecosystem model simulations to initial and boundary conditions (IBCs) from various sources. For this purpose, we used physical parameters from the data sets World Ocean Atlas (WOA09), CSIRO Atlas of Regional Seas (CARS09) and North Indian Ocean Atlas (NIOA). Evaluating model simulated fields with standard validation data suggests that all three experiments could resolve most of the known surface and subsurface features of the Bay of Bengal (BoB) but with considerable differences in salinity and chlorophyll-a (Chl-a) and negligible differences in temperature among model simulations with various IBCs. The modeled Chl-a is well simulated with WOA09 as compared to NIOA and CARS09 data for climatological model simulations, with a correlation of 0.52 for the BoB. Moreover, the vertical distribution of Chl-a is found to be a function of nutrient supply to the base of the euphotic layer and mixed layer. These results significantly highlight the implicit and explicit use of IBCs for better representation of Chl-a concentration in the BoB from a high-resolution coupled model.
{"title":"Impact of Initial and Boundary Conditions on Coupled Model Simulations for Bay of Bengal","authors":"Shailee Patel, Manisha Vithalpura, S. Mallick, S. Ratheesh","doi":"10.1080/01490419.2021.2006376","DOIUrl":"https://doi.org/10.1080/01490419.2021.2006376","url":null,"abstract":"Abstract This study investigates the response of a high resolution coupled physical-ecosystem model simulations to initial and boundary conditions (IBCs) from various sources. For this purpose, we used physical parameters from the data sets World Ocean Atlas (WOA09), CSIRO Atlas of Regional Seas (CARS09) and North Indian Ocean Atlas (NIOA). Evaluating model simulated fields with standard validation data suggests that all three experiments could resolve most of the known surface and subsurface features of the Bay of Bengal (BoB) but with considerable differences in salinity and chlorophyll-a (Chl-a) and negligible differences in temperature among model simulations with various IBCs. The modeled Chl-a is well simulated with WOA09 as compared to NIOA and CARS09 data for climatological model simulations, with a correlation of 0.52 for the BoB. Moreover, the vertical distribution of Chl-a is found to be a function of nutrient supply to the base of the euphotic layer and mixed layer. These results significantly highlight the implicit and explicit use of IBCs for better representation of Chl-a concentration in the BoB from a high-resolution coupled model.","PeriodicalId":49884,"journal":{"name":"Marine Geodesy","volume":"45 1","pages":"166 - 193"},"PeriodicalIF":1.6,"publicationDate":"2021-12-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42505934","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-12-13DOI: 10.1080/01490419.2021.2013355
P. Bonnefond, O. Laurain, P. Exertier, M. Calzas, T. Guinle, N. Picot
Abstract The geodetic Corsica site was set up in 1998 in order to perform altimeter calibration of the TOPEX/Poseidon (T/P) mission and subsequently, Jason-1, OSTM/Jason-2, Jason-3 and more recently Sentinel-6 Michael Freilich (launched on November, 21 2020). The aim of the present study held in June 2015 is to validate a recently developed GNSS-based sea level instrument (called CalNaGeo) that is designed with the intention to map Sea Surface Heights (SSH) over large areas. This has been undertaken using the well-defined geodetic infrastructure deployed at Senetosa Cape, and involved the estimation of the stability of the waterline (and thus the instantaneous separation of a GNSS antenna from water level) as a function of the velocity at which the instrument is towed. The results show a largely linear relationship which is approximately 1 mm/(m/s) up to a maximum practical towing speed of ∼10 knots (∼5 m/s). By comparing to the existing “geoid” map, it is also demonstrated that CalNaGeo can measure a sea surface slope with a precision better than 1 mm/km (∼2.5% of the physical slope). Different processing techniques are used and compared including GNSS Precise Point Positioning (PPP, where the goal is to extend SSH mapping far from coastal GNSS reference stations) showing an agreement at the 1-2 cm level.
科西嘉测量站建立于1998年，目的是对TOPEX/Poseidon (T/P)任务以及随后的Jason-1、OSTM/Jason-2、Jason-3和最近的Sentinel-6 Michael Freilich(于2020年11月21日发射)进行高度计校准。本研究于2015年6月进行，目的是验证最近开发的基于gnss的海平面仪器(称为CalNaGeo)，该仪器旨在绘制大面积的海面高度(SSH)。这是使用部署在塞内托萨角的定义明确的大地测量基础设施进行的，并涉及估计水线的稳定性(因此GNSS天线与水位的瞬时分离)，作为仪器拖曳速度的函数。结果显示了一个很大程度上的线性关系，大约为1毫米/(米/秒)，直到最大实际拖曳速度为~ 10节(~ 5米/秒)。通过与现有的“大地水准面”地图进行比较，还证明CalNaGeo可以以优于1 mm/km(物理坡度的约2.5%)的精度测量海面坡度。使用并比较了不同的处理技术，包括GNSS精确点定位(PPP，其目标是将SSH映射扩展到远离沿海GNSS参考站的地方)，显示出1-2厘米水平的一致性。
{"title":"Validating a New GNSS-Based Sea Level Instrument (CalNaGeo) at Senetosa Cape","authors":"P. Bonnefond, O. Laurain, P. Exertier, M. Calzas, T. Guinle, N. Picot","doi":"10.1080/01490419.2021.2013355","DOIUrl":"https://doi.org/10.1080/01490419.2021.2013355","url":null,"abstract":"Abstract The geodetic Corsica site was set up in 1998 in order to perform altimeter calibration of the TOPEX/Poseidon (T/P) mission and subsequently, Jason-1, OSTM/Jason-2, Jason-3 and more recently Sentinel-6 Michael Freilich (launched on November, 21 2020). The aim of the present study held in June 2015 is to validate a recently developed GNSS-based sea level instrument (called CalNaGeo) that is designed with the intention to map Sea Surface Heights (SSH) over large areas. This has been undertaken using the well-defined geodetic infrastructure deployed at Senetosa Cape, and involved the estimation of the stability of the waterline (and thus the instantaneous separation of a GNSS antenna from water level) as a function of the velocity at which the instrument is towed. The results show a largely linear relationship which is approximately 1 mm/(m/s) up to a maximum practical towing speed of ∼10 knots (∼5 m/s). By comparing to the existing “geoid” map, it is also demonstrated that CalNaGeo can measure a sea surface slope with a precision better than 1 mm/km (∼2.5% of the physical slope). Different processing techniques are used and compared including GNSS Precise Point Positioning (PPP, where the goal is to extend SSH mapping far from coastal GNSS reference stations) showing an agreement at the 1-2 cm level.","PeriodicalId":49884,"journal":{"name":"Marine Geodesy","volume":"45 1","pages":"121 - 150"},"PeriodicalIF":1.6,"publicationDate":"2021-12-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43403790","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-11-12DOI: 10.1080/01490419.2021.1993386
S. D. Dao, Antoine Mallégol, P. Meyer, Mehrdad Mohammadi, S. Loyer
Abstract Hydrographic surveying is a necessary task in the maritime community, which can contribute to maritime security, economic development, scientific research, and environmental protection. Hydrographic surveying is a regular and costly activity; hence, careful hydrographic survey planning is required. Hydrographic survey routing is one of the main tasks in hydrographic survey planning, in which we not only need to find the most interesting maritime area(s) (usually evaluated through a risk measure, aggregating navigation risk, environmental impact, and/or data obsolescence), but also the shortest route to do the hydrographic surveying. In this article, first, we attempt to formulate the hydrographic survey routing problem and then develop an efficient hybrid iterated greedy algorithm to solve the problem. The proposed algorithm consists of three stages, that is, Stage 1 with a memetic algorithm to find a good starting point, Stage 2 with a global greedy algorithm to explore the global search space, and Stage 3 with a local greedy algorithm to exploit the local search space. Five real case studies in France are conducted to validate the performance of the developed algorithm.
{"title":"A Hybrid Iterated Greedy Algorithm for Hydrographic Survey Routing Problem","authors":"S. D. Dao, Antoine Mallégol, P. Meyer, Mehrdad Mohammadi, S. Loyer","doi":"10.1080/01490419.2021.1993386","DOIUrl":"https://doi.org/10.1080/01490419.2021.1993386","url":null,"abstract":"Abstract Hydrographic surveying is a necessary task in the maritime community, which can contribute to maritime security, economic development, scientific research, and environmental protection. Hydrographic surveying is a regular and costly activity; hence, careful hydrographic survey planning is required. Hydrographic survey routing is one of the main tasks in hydrographic survey planning, in which we not only need to find the most interesting maritime area(s) (usually evaluated through a risk measure, aggregating navigation risk, environmental impact, and/or data obsolescence), but also the shortest route to do the hydrographic surveying. In this article, first, we attempt to formulate the hydrographic survey routing problem and then develop an efficient hybrid iterated greedy algorithm to solve the problem. The proposed algorithm consists of three stages, that is, Stage 1 with a memetic algorithm to find a good starting point, Stage 2 with a global greedy algorithm to explore the global search space, and Stage 3 with a local greedy algorithm to exploit the local search space. Five real case studies in France are conducted to validate the performance of the developed algorithm.","PeriodicalId":49884,"journal":{"name":"Marine Geodesy","volume":"45 1","pages":"75 - 100"},"PeriodicalIF":1.6,"publicationDate":"2021-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48302724","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-11-08DOI: 10.1080/01490419.2021.1992546
D. M, V. S., S. S. A., M. K
Abstract A shoreline change analysis has been carried out for the coastal stretch from Ennore creek to Karungali village located along the southeast coast of India. This 15 km-long coastal stretch had undergone significant changes such as erosion and accretion concerning infrastructure developments and leading to large impact on the livelihood of the community. To assess the shoreline changes, the analysis of multi-temporal satellite images has been carried out. A historical trend is established for the study period from 1991 to 2019. The analysis has been made in three timelines considering various developing activities. There was no significant coastal infrastructure development during 1991 to 1999; however, between 1999 and 2009, a major port, pier, and a groyne field were constructed. Additionally, a port was established between 2009 and 2019. Erosion was observed on the coast from Kattupalli to Karungali at a rate of −16.85 m/yr since 2009, while the coast on the south of Ennore port is accreting at the rate of +12.43 m/yr during the same period. The near-future projection using a linear regression model shows further erosion in the coast under similar conditions. The results of this study provide a baseline data for future anthropogenic activities along this coast.
{"title":"Historical Shoreline Analysis and Field Monitoring at Ennore Coastal Stretch along the Southeast Coast of India","authors":"D. M, V. S., S. S. A., M. K","doi":"10.1080/01490419.2021.1992546","DOIUrl":"https://doi.org/10.1080/01490419.2021.1992546","url":null,"abstract":"Abstract A shoreline change analysis has been carried out for the coastal stretch from Ennore creek to Karungali village located along the southeast coast of India. This 15 km-long coastal stretch had undergone significant changes such as erosion and accretion concerning infrastructure developments and leading to large impact on the livelihood of the community. To assess the shoreline changes, the analysis of multi-temporal satellite images has been carried out. A historical trend is established for the study period from 1991 to 2019. The analysis has been made in three timelines considering various developing activities. There was no significant coastal infrastructure development during 1991 to 1999; however, between 1999 and 2009, a major port, pier, and a groyne field were constructed. Additionally, a port was established between 2009 and 2019. Erosion was observed on the coast from Kattupalli to Karungali at a rate of −16.85 m/yr since 2009, while the coast on the south of Ennore port is accreting at the rate of +12.43 m/yr during the same period. The near-future projection using a linear regression model shows further erosion in the coast under similar conditions. The results of this study provide a baseline data for future anthropogenic activities along this coast.","PeriodicalId":49884,"journal":{"name":"Marine Geodesy","volume":"45 1","pages":"47 - 74"},"PeriodicalIF":1.6,"publicationDate":"2021-11-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41709499","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-10-19DOI: 10.1080/01490419.2021.1992547
Wenlong Yang, S. Xue, Yixu Liu
Abstract The computational efficiency of underwater acoustic positioning based on the ray tracing is mainly limited to a great amount of calculation of ray inverse problem. We propose two kinds of p-order secant methods to improve the efficiency of traditional method, and the proposed methods can be regarded as a generalization of the traditional secant method from two points to p points for rapidly solving the inverse problem. In the proposed methods, the calculation information in previous iterations is utilized to fit a polynomial model to speed up the algorithm convergence. In the first-kind method, the inverse problem is calculated by solving a polynomial equation approximating the function mapping from the emission angle to the radial distance of the ray. In the second-kind method, the inverse problem is however directly solved by approximating the function mapping from the radial distance to the emission angle. As the first-kind method needs to solve a p-order polynomial equation, the practicability of this method is limited to the complexity of solving the high-order equation, while the second-kind method can directly approximate the solution of the inverse problem, which is more practical and flexible. The proposed methods have been verified in deep-sea trial. It shows that, the proposed methods can precisely produce the solution of the acoustic ray inverse problem within one iteration, and the computational efficiency of proposed method is about 6 times faster than that of the traditional method.
{"title":"P-Order Secant Method for Rapidly Solving the Ray Inverse Problem of Underwater Acoustic Positioning","authors":"Wenlong Yang, S. Xue, Yixu Liu","doi":"10.1080/01490419.2021.1992547","DOIUrl":"https://doi.org/10.1080/01490419.2021.1992547","url":null,"abstract":"Abstract The computational efficiency of underwater acoustic positioning based on the ray tracing is mainly limited to a great amount of calculation of ray inverse problem. We propose two kinds of p-order secant methods to improve the efficiency of traditional method, and the proposed methods can be regarded as a generalization of the traditional secant method from two points to p points for rapidly solving the inverse problem. In the proposed methods, the calculation information in previous iterations is utilized to fit a polynomial model to speed up the algorithm convergence. In the first-kind method, the inverse problem is calculated by solving a polynomial equation approximating the function mapping from the emission angle to the radial distance of the ray. In the second-kind method, the inverse problem is however directly solved by approximating the function mapping from the radial distance to the emission angle. As the first-kind method needs to solve a p-order polynomial equation, the practicability of this method is limited to the complexity of solving the high-order equation, while the second-kind method can directly approximate the solution of the inverse problem, which is more practical and flexible. The proposed methods have been verified in deep-sea trial. It shows that, the proposed methods can precisely produce the solution of the acoustic ray inverse problem within one iteration, and the computational efficiency of proposed method is about 6 times faster than that of the traditional method.","PeriodicalId":49884,"journal":{"name":"Marine Geodesy","volume":"46 1","pages":"3 - 15"},"PeriodicalIF":1.6,"publicationDate":"2021-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44242204","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-09-11DOI: 10.1080/01490419.2021.1974132
A. Mandal, Aditya Chaudhary, N. Agarwal, Rashmi Sharma
Abstract In this study interior plus Surface Quasi-Geostrophic (isQG) methodology is used to reconstruct subsurface density anomaly using sea surface temperature (SST), sea surface salinity (SSS) and sea surface height (SSH). The study is carried out in the Arabian Sea and Bay of Bengal of the Northern Indian ocean region. isQG is first tested for identical twin experiments, where the surface data and the stability profile (N2) were taken from a numerical ocean model. The root mean square error (RMSE) between isQG and model density anomalies lie within the error bars of model density anomaly in most of the levels. The impact of expected errors in synthetic observations of SST and SSS on isQG retrieved density anomalies was studied and it is found that error in SSS results in greater RMSE in isQG density anomaly profile in the Arabian sea than in the Bay of Bengal. isQG method is then applied to the satellite observations of SST, SSS and SSH and retrieved density profiles are then compared with model outputs and in-situ observations from RAMA buoy for the year 2019. The comparison indicates seasonal dependency and effect of N2 on the performance of isQG method.
{"title":"Sub-Surface Ocean Structure from Satellite Surface Observations in the North Indian Ocean","authors":"A. Mandal, Aditya Chaudhary, N. Agarwal, Rashmi Sharma","doi":"10.1080/01490419.2021.1974132","DOIUrl":"https://doi.org/10.1080/01490419.2021.1974132","url":null,"abstract":"Abstract In this study interior plus Surface Quasi-Geostrophic (isQG) methodology is used to reconstruct subsurface density anomaly using sea surface temperature (SST), sea surface salinity (SSS) and sea surface height (SSH). The study is carried out in the Arabian Sea and Bay of Bengal of the Northern Indian ocean region. isQG is first tested for identical twin experiments, where the surface data and the stability profile (N2) were taken from a numerical ocean model. The root mean square error (RMSE) between isQG and model density anomalies lie within the error bars of model density anomaly in most of the levels. The impact of expected errors in synthetic observations of SST and SSS on isQG retrieved density anomalies was studied and it is found that error in SSS results in greater RMSE in isQG density anomaly profile in the Arabian sea than in the Bay of Bengal. isQG method is then applied to the satellite observations of SST, SSS and SSH and retrieved density profiles are then compared with model outputs and in-situ observations from RAMA buoy for the year 2019. The comparison indicates seasonal dependency and effect of N2 on the performance of isQG method.","PeriodicalId":49884,"journal":{"name":"Marine Geodesy","volume":"44 1","pages":"573 - 592"},"PeriodicalIF":1.6,"publicationDate":"2021-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43475134","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-07-27DOI: 10.1080/01490419.2021.1954111
M. El-Alfy, Dina H. Darwish, Afifi I. Basiony, A. Elnaggar
Abstract Sensitivity to pollution in Burullus Lake was estimated based on the proximity analysis. The category of sensitivity was based on six factors including: agricultural areas, industrial areas, drains, Elboughaz, urban areas and fish farms. A statistical model was developed to estimate trophic state index (TSI) based on laboratory measurements of water samples at two different periods of time (Mach 2020 and June 2020) (R2 = 0.96 and 0.94, respectively). The important factors that were considered at the first period were chlorophyll, phosphate PO4 and oxidizable organic matter OOM. In the second period, the considered factors were ammonia NH4, silicates SiO4, and dissolved oxygen (DO). The category of TSI varied from oligotrophic to hyper-eutrophic conditions in March 2020, whereas it varied from eutrophic to hyper-eutrophic in June 2020. The eutrophication condition was higher in June than in March. This may be attributed to the huge amount of wastewaters, their contaminant load and season. The compatibility between sensitivity model and the obtained results in March 2020 was about 54.5%, whereas it was about 27.3% in June 2020. This reveals that the lake is highly sensitive to pollution and therefore it needs to be monitored regularly.
{"title":"GIS-Based Study on the Environmental Sensitivity to Pollution and Susceptibility to Eutrophication in Burullus Lake, Egypt","authors":"M. El-Alfy, Dina H. Darwish, Afifi I. Basiony, A. Elnaggar","doi":"10.1080/01490419.2021.1954111","DOIUrl":"https://doi.org/10.1080/01490419.2021.1954111","url":null,"abstract":"Abstract Sensitivity to pollution in Burullus Lake was estimated based on the proximity analysis. The category of sensitivity was based on six factors including: agricultural areas, industrial areas, drains, Elboughaz, urban areas and fish farms. A statistical model was developed to estimate trophic state index (TSI) based on laboratory measurements of water samples at two different periods of time (Mach 2020 and June 2020) (R2 = 0.96 and 0.94, respectively). The important factors that were considered at the first period were chlorophyll, phosphate PO4 and oxidizable organic matter OOM. In the second period, the considered factors were ammonia NH4, silicates SiO4, and dissolved oxygen (DO). The category of TSI varied from oligotrophic to hyper-eutrophic conditions in March 2020, whereas it varied from eutrophic to hyper-eutrophic in June 2020. The eutrophication condition was higher in June than in March. This may be attributed to the huge amount of wastewaters, their contaminant load and season. The compatibility between sensitivity model and the obtained results in March 2020 was about 54.5%, whereas it was about 27.3% in June 2020. This reveals that the lake is highly sensitive to pollution and therefore it needs to be monitored regularly.","PeriodicalId":49884,"journal":{"name":"Marine Geodesy","volume":"44 1","pages":"554 - 572"},"PeriodicalIF":1.6,"publicationDate":"2021-07-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/01490419.2021.1954111","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41760911","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-06-24DOI: 10.1080/01490419.2021.1943576
Minzhang Hu, T. Jin, Weiping Jiang, Yonghai Chu, Hanjiang Wen, Jiancheng Li
Abstract New bathymetry models in the northwestern Pacific Ocean are presented at 1 arc-minute and 15 arc-second resolution. The latest version of the altimetric vertical gravity gradient (VGG) anomalies from Scripps Institute of Oceanography, ∼7 million single-beam depths from the National Centers for Environmental Information, and ∼80 GB of multibeam grids from the Japan Agency for Marine-Earth Science and Technology are used. The ship-board depths are used to constrain bathymetry at wavelengths longer than 200 km, and calibrate the local topography to VGG ratio at 15–200 km wavelength bands. The VGG is used to predict bathymetry at 15 ∼ 200 km wavelength bands. The spectrum analysis results show that the 1 arc-minute model has more power than models predicted from gravity anomalies at wavelengths shorter than 100 km. The standard deviation of differences between the 1 arc-minute model and ship-board depths is 44.76 m, and it is 102.842 m comparing to the SIO topo_20.1.nc model. The accuracy of the new 1 arc-minute model has been improved significantly from our last bathymetry model, BAT_VGG, and has a better accuracy than that of the DTU18, GEBCO_08, and ETOPO1 models. The accuracy of the 15 arc-second model is consistent with that of SRTM + V2.1 and GEBCO_2020.
{"title":"Bathymetry Model in the Northwestern Pacific Ocean Predicted from Satellite Altimetric Vertical Gravity Gradient Anomalies and Ship-Board Depths","authors":"Minzhang Hu, T. Jin, Weiping Jiang, Yonghai Chu, Hanjiang Wen, Jiancheng Li","doi":"10.1080/01490419.2021.1943576","DOIUrl":"https://doi.org/10.1080/01490419.2021.1943576","url":null,"abstract":"Abstract New bathymetry models in the northwestern Pacific Ocean are presented at 1 arc-minute and 15 arc-second resolution. The latest version of the altimetric vertical gravity gradient (VGG) anomalies from Scripps Institute of Oceanography, ∼7 million single-beam depths from the National Centers for Environmental Information, and ∼80 GB of multibeam grids from the Japan Agency for Marine-Earth Science and Technology are used. The ship-board depths are used to constrain bathymetry at wavelengths longer than 200 km, and calibrate the local topography to VGG ratio at 15–200 km wavelength bands. The VGG is used to predict bathymetry at 15 ∼ 200 km wavelength bands. The spectrum analysis results show that the 1 arc-minute model has more power than models predicted from gravity anomalies at wavelengths shorter than 100 km. The standard deviation of differences between the 1 arc-minute model and ship-board depths is 44.76 m, and it is 102.842 m comparing to the SIO topo_20.1.nc model. The accuracy of the new 1 arc-minute model has been improved significantly from our last bathymetry model, BAT_VGG, and has a better accuracy than that of the DTU18, GEBCO_08, and ETOPO1 models. The accuracy of the 15 arc-second model is consistent with that of SRTM + V2.1 and GEBCO_2020.","PeriodicalId":49884,"journal":{"name":"Marine Geodesy","volume":"45 1","pages":"24 - 46"},"PeriodicalIF":1.6,"publicationDate":"2021-06-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/01490419.2021.1943576","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43223102","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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