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Extrapolation of upwelling irradiance just beneath the ocean surface from the in-water radiometric profile measurements

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海洋湖沼学报(英文) 2023年第5期41卷 1694-1705页

作者： Shaoqi GONG School of Remote Sensing and Geomatics Engineering Nanjing University of Information Science&TechnologyNanjing 210044China

Accurate measurements of upwelling irradiance just beneath the ocean surface,E_(u)(λ,0^(-)),can be used to calculate ocean optical parameters,and further develop retrieval algorithms for remotely sensing water component concentrations.Due to the effects of sea surface waves,perturbation from instrument platform(ship),and instrument self-shading,E_(u)(λ,0^(-))is often difficult to be accurately measured.This study presents a procedure for extrapolating the E_(u)(λ,0^(-))from the in-water radiometric profile measurements.Using the optical profile data from 13 bands(ranging from 381 to 779 nm)measured by 45 casts in the Ligurian Sea during 2003–2009,the E_(u)(λ,0^(-))was extrapolated from in-water upwelling irradiance measurements between the initial shallow depth,Z_(0),and an optimal bottom depth,Z_(1),by three linear models(linear,2-degree polynomial,and exponential)and two nonlinear models(LOESS and spline).The accumulated errors of extrapolated E_(u)(λ,0^(-))at each wavelength for the five models were calculated.It was found that the optimal Z_(1) depth for the linear and exponential models was at the depth of80%of E_(u)(λ,Z_(0)),50%of E_(u)(λ,Z_(0))for the 2-degree polynomial model,40%of E_(u)(λ,Z_(0))for the LOESS model,and 15%of E_(u)(λ,Z_(0))for the spline model.The extrapolated E_(u)(λ,0^(-))derived from the five models was in good agreement with the calculated true E_(u)(λ,0^(-)).In all bands,the 2-degree polynomial model achieved the highest accuracy,followed by the LOESS model.In the short band of 381–559 nm,the linear and exponential models had the third-best performance,and the spline model performed worst within this range.For the red band of 619–779 nm,the accuracies of the exponential and spline models had the third highest performance,and the linear model produced lowest accuracy.Hence,the 2-degree polynomial model was an optimal procedure for extrapolation of E_(u)(λ,0^(-))from the in-water radiometric profile measurements.

关键词： extrapolation upwelling irradiance ocean in-water accuracy

Emerging and Innovative Materials for Hydropower Engineering Applications:Turbines,Bearings,Sealing,Dams and Waterways,and ocean Power

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Engineering 2022年第1期8卷 148-158页

作者： Emanuele Quaranta Peter Davies European Commission Joint Research Centre Ispra 21027Italy Marine Structures Laboratory IFREMER Centre BretagnePlouzané29280France

The hydropower sector is currently experiencing several technological developments.New technologies and practices are emerging to make hydropower more flexible and more sustainable.Novel materials have also been recently developed to increase performance,durability,and reliability;however,no systematic discussions can be found in the literature.Therefore,in this paper,novel materials for hydropower applications are presented,and their performance,advantages,and limitations are discussed.For example,composites can reduce the weight of steel equipment by 50%to 80%,polymers and superhydrophobic materials can reduce head losses by 4%to 20%,and novel bearing materials can reduce bearing wear by 6%.These improvements determine higher efficiencies,longer life span,waste reduction,and maintenance needs,although the initial cost of some materials is not yet competitive with respect to the costs of traditional materials.The novel materials are described here based on the following categories:novel materials for turbines,dams and waterways,bearings,seals,and ocean hydropower.

关键词： Bearing Composite Dam Hydropower Material ocean Seal Turbine

Recent Progress in Applications of the Conditional Nonlinear Optimal Perturbation Approach to Atmosphere-ocean Sciences

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Chinese Annals of Mathematics,Series B 2022年第6期43卷 1033-1048页

作者： Mu MU Kun ZHANG Qiang WANG Department of Atmospheric and oceanic Sciences and Institute of Atmospheric Sciences Fudan UniversityShanghai 200438China CMA-FDU Joint Laboratory of Marine Meteorology Shanghai 200438China Shanghai Frontiers Science Center of Atmosphere-ocean Interaction Shanghai 200438China CAS Key Laboratory of ocean Circulation and Waves Institute of OceanologyChinese Academy of Sciences and Qingdao National Laboratory for Marine Science and TechnologyQingdao 266071China Key Laboratory of Marine Hazards Forecasting Ministry of Natural ResourcesHohai UniversityNanjing 210098China College of oceanography Hohai UniversityNanjing 210098China

The conditional nonlinear optimal perturbation(CNOP for short) approach is a powerful tool for predictability and targeted observation studies in atmosphere-ocean sciences. By fully considering nonlinearity under appropriate physical constraints, the CNOP approach can reveal the optimal perturbations of initial conditions, boundary conditions, model parameters, and model tendencies that cause the largest simulation or prediction uncertainties. This paper reviews the progress of applying the CNOP approach to atmosphere-ocean sciences during the past five years. Following an introduction of the CNOP approach, the algorithm developments for solving the CNOP are discussed.Then, recent CNOP applications, including predictability studies of some high-impact ocean-atmospheric environmental events, ensemble forecast, parameter sensitivity analysis, uncertainty estimation caused by errors of model tendency or boundary condition, are reviewed. Finally, a summary and discussion on future applications and challenges of the CNOP approach are presented.

关键词： Conditional nonlinear optimal perturbation Atmosphere ocean Targeted observation Predictability

Thunderstorm and Lightning Activities over Western Pacific,Northern Indian ocean and South China Sea Along with Their Adjacent Lands

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热带气象学报:英文版 2023年第3期29卷 347-358页

作者：丁嘉欣张义军郑栋姚雯张文娟 Department of Atmospheric and oceanic Sciences Institute of Atmospheric SciencesFudan UniversityShanghai 200438 China Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disaster(CIC-FEMD) Nanjing University of Information Science&TechnologyNanjing 210044 China State Key Laboratory of Severe Weather Chinese Academy of Meteorological SciencesBeijing 100081 China CMA-FDU Joint Laboratory of Marine Meteorology and Shanghai Frontiers Science Center of Atmosphere-ocean Interaction Shanghai 200438 China

The Lightning Imaging Sensor(LIS)and Radar Precipitation Feature(RPF)data are used to investigate the activities and properties of lightning and thunderstorms over a region including the Western Pacific,northern Indian ocean and the South China Sea along with their adjacent lands.The lands feature significantly more frequent lightning flashes and thunderstorms than the oceans,especially the open oceans.The highest densities of lightning and thunderstorm occur over the Strait of Malacca and the southern foothills of the Himalayas.Over the ocean regions,the Bay of Bengal and the South China Sea are characterized by relatively frequent lightning and thunderstorm activities.Larger average spatiotemporal size and optical radiance of flashes can be found over the oceans;specifically,the offshore area features the most significant flash duration,and the open ocean area is characterized by the greatest flash length and optical radiance.The smallest average values of flash properties can be found over and around the Tibetan Plateau(TP).The oceanic thunderstorms tend to have a significantly larger horizontal extent than the continental thunderstorms,with the former and latter having the average area of the regions with radar reflectivity larger than 20 dBZ,generally over 7000 km^(2) and commonly below 6000 km^(2),respectively.The TP thunderstorms show the smallest horizontal extent.Meanwhile,the oceanic thunderstorms exhibit greater 20 dBZ but smaller 40 dBZ top heights than the continental thunderstorms.The average flash frequency and density of the oceanic thunderstorms are typically less than 5 fl min^(-1) and 0.3 fl 100 km^(-2) min^(-1),respectively;in contrast,the corresponding values of continental thunderstorms are greater.It is explored that the regions associated with strong convective thunderstorms are more likely to feature small-horizontal-extent and low-radiance flashes.

关键词： lightning thunderstorm land ocean thunderstorm structure lightning spatiotemporal size and radiance

Some progress on ocean data assimilation in China: Introduction of the special section “ocean Data Assimilation”

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Acta oceanologica Sinica 2022年第2期41卷 1-2页

作者： Huizan Wang Yan Chen Weimin Zhang College of Meteorology and oceanography National University of Defense TechnologyChangsha 410073China

This special section is the scientific legacy of the 13th National ocean Data Assimilation and Numerical Simulation Conference of China,which was held in Changsha,China during December 3–4,2020 with more than 160 participants from 35 units in China.It continued a series of National ocean Data Assimilation conferences which began in 2003,which played an important role in the development of ocean data assimilation in China.In this 13th conference,there were 41 oral presentations and 15 posters,which focused on ocean data assimilation methods,ocean reanalysis data,developments and operational application of ocean data assimilation systems,assimilation of new type ocean observations,ocean targeted observation analysis,coupled data assimilation,ocean models and parameter estimation,etc.This conference was hosted by National University of Defense Technology,and cohosted by the Institute of Atmospheric Physics of Chinese Academy of Sciences,the South China Sea Institute of oceanology of Chinese Academy of Sciences,the Second Institute of oceanography of the Ministry of Natural Resources,ocean University of China,Tianjin University and Hohai University.

关键词： China ocean assimilation

Multi-AUV SOM task allocation algorithm considering initial orientation and ocean current environment

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Frontiers of Information Technology & Electronic Engineering 2019年第3期20卷 330-341页

作者： Da-qi ZHU Yun QU Simon X.YANG Laboratory of Underwater Vehicles and Intelligent Systems Shanghai Maritime University Advanced Robotics and Intelligent Systems Laboratory University of Guelph

There is an ocean current in the actual underwater working environment. An improved self-organizing neural network task allocation model of multiple autonomous underwater vehicles(AUVs) is proposed for a three-dimensional underwater workspace in the ocean current. Each AUV in the model will be competed, and the shortest path under an ocean current and different azimuths will be selected for task assignment and path planning while guaranteeing the least total consumption. First, the initial position and orientation of each AUV are determined. The velocity and azimuths of the constant ocean current are determined. Then the AUV task assignment problem in the constant ocean current environment is considered. The AUV that has the shortest path is selected for task assignment and path planning. Finally, to prove the effectiveness of the proposed method, simulation results are given.

关键词： Autonomous underwater vehicles Self-organizing neural networks Azimuths ocean current

Relationship between sea surface salinity and ocean circulation and climate change

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Science China Earth Sciences 2019年第5期62卷 771-782页

作者： Yan DU Yuhong ZHANG Jiancheng SHI State Key Laboratory of Tropical oceanography South China Sea Institute of Oceanology Chinese Academy of Sciences University of Chinese Academy of Sciences State Key Laboratory of Remote Sensing Science Institute of Remote Sensing and Digital Earth Chinese Academy of Sciences

Based on Argo sea surface salinity(SSS) and the related precipitation(P), evaporation(E), and sea surface height data sets, the climatological annual mean and low-frequency variability in SSS in the global ocean and their relationship with ocean circulation and climate change were analyzed. Meanwhile, together with previous studies, a brief retrospect and prospect of seawater salinity were given in this work. Freshwater flux(E-P) dominated the mean pattern of SSS, while the dynamics of ocean circulation modulated the spatial structure and low-frequency variability in SSS in most regions. Under global warming, the trend in SSS indicated the intensification of the global hydrological cycle, and featured a decreasing trend at low and high latitudes and an increasing trend in subtropical regions. In the most recent two decades, global warming has slowed down, which is called the"global warming hiatus". The trend in SSS during this phase, which was different to that under global warming, mainly indicated the response of the ocean surface to the decadal and multi-decadal variability in the climate system, referring to the intensification of the Walker Circulation. The significant contrast of SSS trends between the western Pacific and the southeastern Indian ocean suggested the importance of oceanic dynamics in the cross-basin interaction in recent decades. ocean Rossby waves and the Indonesian Throughflow contributed to the freshening trend in SSS in the southeastern Indian ocean, while the increasing trend in the southeastern Pacific and the decreasing trend in the northern Atlantic implied a long-term linear trend under global warming. In the future, higher resolution SSS data observed by satellites, together with Argo observations, will help to extend our knowledge on the dynamics of mesoscale eddies, regional oceanography, and climate change.

关键词： Sea surface salinity ocean circulation Climate change Multi-scale interaction

Optimal communication frequency for switching cabled ocean networks with commands carried over the power line

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Frontiers of Information Technology & Electronic Engineering 2019年第10期20卷 1331-1343页

作者： Yan-hu CHEN Yu-jia ZANG Jia-jie YAO Gul MUHAMMAD State Key Laboratory of Fluid Power and Mechatronic Systems Zhejiang UniversityHangzhou 310027China

Cabled ocean networks with tree or ring topologies play an important role in real-time ocean exploration. Due to the time-consuming need for field maintenance, cable switching technology that can actively switch the power on/off on certain branches of the network becomes essential for enhancing the reliability and availability of the network. In this paper, a novel switching-control method is proposed, in which we invert the power transmission polarity and use the current on the power line as the digital signal at low frequency to broadcast information with the address and commands to the network, and the corresponding branching unit (BU) can decode and execute the switching commands. The cable's parasitic parameters, the network scale, and the number of BUs, as the influencing factors of the communication frequency on the power line, are theoretically studied and sim-ulated. An optimized frequency that balances the executing accuracy and rate is calculated and proved on a simulated prototype. The results showed that the cable switching technology with optimized frequency can enhance the switching accuracy and con-figuring rate.

关键词： Cable switching Cabled ocean network Branching unit Transmission line theory Communication frequency

ocean negative carbon emissions: A new UN Decade program

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The Innovation 2022年第5期3卷 48-49页

作者： Jihua Liu Carol Robinson Douglas Wallace Louis Legendre Nianzhi Jiao Institute of Marine Science and Technology Shandong UniversityQingdao 266237China Joint Lab for ocean Research and Education at Dalhousie University Shandong University and Xiamen UniversityQingdao 266237China Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai) Zhuhai 519000China Centre for ocean and Atmospheric Sciences School of Environmental SciencesUniversity of East AngliaNorwich NR47TJUK Department of oceanography Dalhousie UniversityHalifaxNS B3H 4R2Canada Sorbonne Université CNRSLaboratoire d’Océanographie de VillefrancheLOV06230 Villefranche-sur-MerFrance College of ocean and Earth Sciences Xiamen UniversityXiamen 361005China Carbon Neutral Innovation Research Center(CNIR) Xiamen UniversityXiamen 361005China

The Paris Agreement sets the target to limit increases in mean global temperature to well below 2C,preferably to 1.5C,compared with preindustrial levels.Carbon neutrality is the preferred route to reach this target.1 This requires primarily a reduction of CO_(2) emissions to the atmosphere but also an increase of carbon sinks or negative emissions(absorption of atmospheric CO_(2)).The ocean is the largest active carbon pool on Earth,acting as the key regulator to global climate change,and thus has great potential for carbon negative emission.2,3 Recent research demonstrates that the ocean has already absorbed approximately 28%of anthropogenic CO_(2) since the Industrial Revolution,4,5 which indicates that ocean negative carbon emissions could potentially have an important role in achieving the 1.5C or 2.0C goal.Given the urgency and seriousness of the ongoing climate change,it is therefore imperative to explore the potential of enhancing ocean carbon sinks.

关键词： ocean Earth carbon