Ocean Observations

A special issue of Journal of Marine Science and Engineering (ISSN 2077-1312). This special issue belongs to the section "Ocean Engineering".

Deadline for manuscript submissions: closed (1 October 2024) | Viewed by 5009

Special Issue Editor


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Guest Editor
Department of Marine Environmental Informatics, National Taiwan Ocean University, Keelung 202301, Taiwan
Interests: remote sensing; physical oceanography; global change; satellite oceanography

Special Issue Information

Dear Colleagues,

Oceans cover more than 70% of the world's surface. Ocean observation is vital for informing marine scientific research; maritime safety; and marine engineering, planning, and construction. Developments in ocean observation instruments and technology have led to faster, more accurate, and more comprehensive ocean observations. However, ocean observation instruments are often limited by battery capacity, data storage, and transmission, and cannot conduct effective observations.

By combining energy storage systems with the development in ocean energy, the needs of ocean observation systems may be met. This Special Issue of “Ocean Observations” welcomes (but is not limited to) papers on various ocean observation results and their applications, developments in ocean observation instruments and technology, ocean energy, etc.

Prof. Dr. Chung-Ru Ho
Guest Editor

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Keywords

  • ocean observation 
  • maritime safety 
  • marine engineering 
  • maritime planning 
  • maritime construction 
  • ocean observation instruments and technology 
  • battery capacity 
  • data storage 
  • ocean energy ocean observation systems 
  • ocean observation results 
  • ocean observation applications

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Published Papers (6 papers)

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Research

18 pages, 7384 KiB  
Article
Characteristics Analysis of Acoustic Doppler Current Profile Measurements in Northeast Taiwan Offshore
by Chung-Ru Ho, Kai-Ho Cheng, Zhe-Wen Zheng, Hung-Jen Lee and Tai-Wen Hsu
J. Mar. Sci. Eng. 2024, 12(9), 1632; https://doi.org/10.3390/jmse12091632 - 12 Sep 2024
Viewed by 483
Abstract
A comprehensive study was conducted at a wave energy device test site located off the northeastern coast of Taiwan to assess the influence of oceanic currents on experimental equipment. A bottom-mounted 600 kHz acoustic Doppler current profiler, equipped with integrated temperature and pressure [...] Read more.
A comprehensive study was conducted at a wave energy device test site located off the northeastern coast of Taiwan to assess the influence of oceanic currents on experimental equipment. A bottom-mounted 600 kHz acoustic Doppler current profiler, equipped with integrated temperature and pressure sensors, was deployed at a depth of approximately 31 m. This study, spanning from 6 June 2023 to 11 May 2024, recorded ocean current profiles by assembling data from 50 pings every 10 min, with a resolution of one meter per depth layer. The findings reveal that variations in water levels were predominantly influenced by the M2 tidal constituent, followed by the O1, K1, and S2 tides. Notably, seawater temperature fluctuations at the seabed were modulated by tides, especially the M2 tide. A significant drop in seawater temperature was also observed as the typhoon passed through the south of Taiwan. In terms of sea surface currents, the measured maximum current speed was 71.89 cm s−1, but the average current speed was only 15.47 cm s−1. Tidal currents indicated that the M4 and M2 tides were the most significant, with semimajor axes and inclination angles of 8.48 cm s−1 and 102.60°, and 7.00 cm s−1 and 97.76°, respectively. Seasonally, barotropic tidal currents were the strongest in winter. Additionally, internal tides were identified, with the first baroclinic mode being dominant. The zero-crossing depths varied between 14 and 18 m. During the summer, the M2 baroclinic tidal current displayed characteristics of the second baroclinic mode, with zero-crossing depths at approximately 7 m and 22 m. This node aligns with results from the empirical orthogonal function analysis and correlates with the depths’ significant shifts in seawater temperature as measured by a conductivity, temperature, and depth instrument. Despite the velocities of internal tides not being strong, the directional variance between surface and bottom flows presents critical considerations for the deployment and operation of moored wave energy devices. Full article
(This article belongs to the Special Issue Ocean Observations)
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26 pages, 15518 KiB  
Article
Sequential Two-Mode Fusion Underwater Single-Photon Lidar Imaging Algorithm
by Tian Rong, Yuhang Wang, Qiguang Zhu, Chenxu Wang, Yanchao Zhang, Jianfeng Li, Zhiquan Zhou and Qinghua Luo
J. Mar. Sci. Eng. 2024, 12(9), 1595; https://doi.org/10.3390/jmse12091595 - 9 Sep 2024
Viewed by 612
Abstract
Aiming at the demand for long-range and high-resolution imaging detection of small targets such as submerged submarine markers in shallow coastal waters, research on single-photon lidar imaging technology is carried out. This paper reports the sequential two-mode fusion imaging algorithm, which has a [...] Read more.
Aiming at the demand for long-range and high-resolution imaging detection of small targets such as submerged submarine markers in shallow coastal waters, research on single-photon lidar imaging technology is carried out. This paper reports the sequential two-mode fusion imaging algorithm, which has a strong information extraction capability and can reconstruct scene target depth and reflection intensity images from complex signal photon counts. The algorithm consists of four steps: data preprocessing, extremely large group value estimation, noise sieving, and total variation smoothing constraints to image the target with high quality. Simulation and test results show that the imaging performance and imaging characteristics of the method are better than the current high-performance first-photon group imaging algorithm, indicating that the method has a great advantage in sparse photon counting imaging, and the method proposed in this paper constructs a clear depth and reflectance intensity image of the target scene, even in the 50,828 Lux ambient strong light and strong interference, the 0.1 Lux low-light environment, or the underwater high-attenuation environment. Full article
(This article belongs to the Special Issue Ocean Observations)
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13 pages, 1229 KiB  
Article
Advanced Capacitor-Based Battery Equalizer for Underwater Vehicles
by Kun-Che Ho
J. Mar. Sci. Eng. 2024, 12(8), 1357; https://doi.org/10.3390/jmse12081357 - 9 Aug 2024
Viewed by 590
Abstract
As maritime technology advances, exploration of the oceans has progressively moved from surface exploration to underwater ventures. Unmanned underwater vehicles (UUVs), now prevalent for such exploration, effectively reduce human labor and lower operational costs. These vehicles rely on an internal Battery Storage System [...] Read more.
As maritime technology advances, exploration of the oceans has progressively moved from surface exploration to underwater ventures. Unmanned underwater vehicles (UUVs), now prevalent for such exploration, effectively reduce human labor and lower operational costs. These vehicles rely on an internal Battery Storage System (BSS) that sustains device operation by extending operational duration and providing stable voltage. Typically arranged in series, BSSs face challenges due to differences in the chemical characteristics of individual batteries, which lead to discrepancies in battery voltages and cause imbalances during charge and discharge cycles. This results in varied utilization rates among the batteries and uneven aging of the battery pack, potentially decreasing operational efficiency and increasing failure rates, thus reducing reliability and safety. Considering the harsh environmental conditions and maintenance difficulties associated with underwater operations, this paper proposes a robust solution: a balancing system featuring a modular switch with electrical isolation. Through theoretical analysis and circuit simulation, this study constructs and tests a novel prototype of a capacitor-based equalizer circuit with electrical isolation, verifying its feasibility. Full article
(This article belongs to the Special Issue Ocean Observations)
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15 pages, 17356 KiB  
Article
Multidimensional Evaluation of Altimetry Marine Gravity Models with Shipborne Gravity Data from a New Platform Marine Gravimeter
by Bo Wang, Lin Wu, Pengfei Wu, Qianqian Li, Lifeng Bao and Yong Wang
J. Mar. Sci. Eng. 2024, 12(8), 1314; https://doi.org/10.3390/jmse12081314 - 3 Aug 2024
Cited by 1 | Viewed by 700
Abstract
With the development of satellite altimetry technology and the application of new altimetry satellites, the accuracy and resolution of altimeter-derived gravity field models have improved over the last decades. Nowadays, they are close enough to shipborne gravimetry. In this paper, multi-source shipborne gravity [...] Read more.
With the development of satellite altimetry technology and the application of new altimetry satellites, the accuracy and resolution of altimeter-derived gravity field models have improved over the last decades. Nowadays, they are close enough to shipborne gravimetry. In this paper, multi-source shipborne gravity data in the South China Sea were taken to evaluate the accuracies of two high-precision altimeter-derived marine gravity field models (SS V30.1, DTU17). In these shipborne gravity data, there are dozens of routes’ ship gravimetry data, obtained from the National Geophysical Data Center (NGDC); data were tracked from a marine survey with a commercial marine gravimeter (type KSS31M), and data were tracked from a marine gravimetry campaign that was conducted with a newly developed platform gravimeter (type JMG) in the South China Sea in September 2020. After various data filtering, processing, and calibrations, the shipborne gravity data were validated with crossover points analysis. Then, the processed shipborne data were employed to evaluate the accuracy of the altimeter-derived marine gravity field models. During this procedure, the quality of JMG shipborne gravity data was compared with the results of KSS31M and NGDC data. Analysis and evaluation results show that the crossover points verification accuracies of KSS31M and JMG are 0.70 mGal and 1.61 mGal, which are much better than the accuracy of NGDC, which is larger than 8.0 mGal. In the area where the bathymetry changes slowly, the root mean square error values between altimetry gravity models and KSS31M data are respectively 3.28 mGal and 4.54 mGal, and those of the JMG data are respectively 2.94 mGal and 2.60 mGal. According to the above results, we can conclude that the JMG has the same 1–2 mGal accuracy level as KSS31M and can meet the measurement requirements of marine gravity. Full article
(This article belongs to the Special Issue Ocean Observations)
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22 pages, 17643 KiB  
Article
Response of Shallow-Water Temperature and Significant Wave Height to Sequential Tropical Cyclones in the Northeast Beibu Gulf
by Xiaotong Chen, Lingling Xie, Mingming Li, Ying Xu and Yulin Wang
J. Mar. Sci. Eng. 2024, 12(5), 790; https://doi.org/10.3390/jmse12050790 - 8 May 2024
Viewed by 926
Abstract
Using shallow-water buoy observations, reanalysis data, and numerical models, this study analyzes the variations in sea temperature and significant wave height (SWH) caused by two sequential tropical cyclones (TCs) ‘Lionrock’ and ‘Kompasu’ in October 2021 in the northeast Beibu Gulf, South China Sea. [...] Read more.
Using shallow-water buoy observations, reanalysis data, and numerical models, this study analyzes the variations in sea temperature and significant wave height (SWH) caused by two sequential tropical cyclones (TCs) ‘Lionrock’ and ‘Kompasu’ in October 2021 in the northeast Beibu Gulf, South China Sea. The results show that the sea surface temperature (SST) cooling of the nearshore waters was larger than the offshore water in the basin of the gulf, with the cooling amplitude and rate decreasing and the cooling time lagging behind wind increasing from coast to offshore. The near-surface temperature at the buoy station had a maximum decrease of 2.8 °C after ‘Lionrock’, and the decrease increased slightly to 3 °C after the stronger wind of ‘Kompasu’. The total decrease of 4.6 °C indicates that the sequential TCs had a superimposed effect on the cooling of the Beibu Gulf. The heat budget analysis revealed that the sea surface heat loss and the Ekman pumping rate in the nearshore waters during ‘Kompasu’ (−535 W/m2 and 5.8 × 10−4 m/s, respectively) were significantly higher than that (−418 W/m2 and 4 × 10−4 m/s) during ‘Lionrock’. On the other hand, the SST cooling (−1.2 °C) during the second TC is smaller than (−1.6 °C) the first weaker TC in the gulf basin, probably due to the deepening of the mixed layer. During the observation period, the waves in the Beibu Gulf were predominantly wind-driven. The maximum SWHs reached 1.58 m and 2.3 m at the bouy station near shore during the two TCs, and the SWH variation was highly correlated to the wind variation with a correlation of 0.95. The SWH increases from the nearshore to offshore waters during the TCs. The SAWN and ARCIRC coupled model results suggest that wave variations in the Beibu Gulf are primarily influenced by water depth, bottom friction, and whitecapping. Two days after the TCs, sea surface cooling and high waves appeared again due to a cold air event. Full article
(This article belongs to the Special Issue Ocean Observations)
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18 pages, 5414 KiB  
Article
Dynamic Doppler Characteristics of Maritime Airborne Corner Reflector
by Lingang Wu, Shengliang Hu, Chengxu Feng, Yasong Luo, Zhong Liu and Li Lin
J. Mar. Sci. Eng. 2024, 12(5), 727; https://doi.org/10.3390/jmse12050727 - 27 Apr 2024
Viewed by 784
Abstract
The maritime airborne corner reflector (ACR) is a radar reflector that can measure wind speed in an unknown sea area in real time over a long distance. To improve our understanding of how the ACR works, we investigated the Doppler characteristics of the [...] Read more.
The maritime airborne corner reflector (ACR) is a radar reflector that can measure wind speed in an unknown sea area in real time over a long distance. To improve our understanding of how the ACR works, we investigated the Doppler characteristics of the ACR for the first time from a dynamic perspective. First, we constructed a radar echo signal model of the ACR. Then, we obtained the dynamic Doppler characteristics through pulse Doppler processing and discussed the special phenomenon of Doppler broadening. Finally, we proposed a rectangular window decomposition method to analyze the inner principle of the Doppler broadening phenomenon in more detail. In conclusion, this study provides valuable insights into the Doppler characterization of an ACR from a dynamic viewpoint, which contributes to enriching the basic theory of this equipment. Full article
(This article belongs to the Special Issue Ocean Observations)
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