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Sustained Ocean Surface Observation Using HF Radar: From Data to Societal Applications II

A special issue of Remote Sensing (ISSN 2072-4292). This special issue belongs to the section "Environmental Remote Sensing".

Deadline for manuscript submissions: 31 July 2024 | Viewed by 1895

Special Issue Editor


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Guest Editor
CETMAR (Centro Tecnológico del Mar), 36208 Pontevedra, Spain
Interests: physical oceanography; coastal oceanography; coastal radars; physical–biological coupling; ocean observing systems; forecast systems; climate change
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

HF radars offer comprehensive, frequent, and detailed information at the interface of the ocean and the atmosphere. These shore-based remote sensing systems have thus evolved into indispensable instruments within operational oceanography, enabling fo the measurement of synoptic, high-frequency and high-resolution data from surface currents, waves, and winds over wide areas. Additionally, their practical applications span across various sectors.

The majority of HF radars deployed over the past two decades have primarily served research and development purposes. Throughout this timeframe, the technology has undergone extensive validation, and at present, HF radar technology has reached a mature stage, especially in terms of surface current data extraction. It is now acknowledged as a fundamental tool for researching and managing coastal environments.

By combining the high-resolution spatial and temporal data provided by HF radar velocities with other in situ or remote sensing measurements and models, our understanding of coastal dynamics can be significantly enhanced. Consequently, this technology can foster economic blue growth while minimizing environmental impacts in coastal areas. For example, HF radars have diverse applications, including monitoring oil spills, aiding in search and rescue efforts, tracking extreme wave events, providing meteorological support, managing marine environments, operating tsunami warning systems, monitoring coastal currents and waves, facilitating routine navigation, supporting commercial fishing, monitoring Harmful Algae Blooms (HABs), assessing marine energy resources, and studying climate change, among other applications.

This Special Issue is the second volume of a previous SI that focused on the societal applications that arise from this technology. It is important to note that the scope of the first Special Issue was more extensive, and therefore was aimed at not just HF radar products. In this new Special Issue, we wish to invite more papers that demonstrate emerging products derived from HF radars in an evolutionary manner, providing useful information not only on intermediate users but also end users (specialist or non-specialist sectors).

Dr. Silvia Piedracoba
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Remote Sensing is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • HF radar
  • multiplatform observations
  • circulation models
  • products and applications
  • downstream services
  • open sea and coastal areas monitoring
  • physical–biological interactions

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Published Papers (2 papers)

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Research

27 pages, 21712 KiB  
Article
Quality Control for Ocean Current Measurement Using High-Frequency Direction-Finding Radar
by Shuqin He, Hao Zhou, Yingwei Tian, Da Huang, Jing Yang, Caijun Wang and Weimin Huang
Remote Sens. 2023, 15(23), 5553; https://doi.org/10.3390/rs15235553 - 29 Nov 2023
Viewed by 782
Abstract
High-frequency radars (HFRs) are important for remote sensing of the marine environment due to their ability to provide real-time, wide-coverage, and high-resolution measurements of the ocean surface current, wave height, and wind speed. However, due to the intricate multidimensional processing demands (e.g., time, [...] Read more.
High-frequency radars (HFRs) are important for remote sensing of the marine environment due to their ability to provide real-time, wide-coverage, and high-resolution measurements of the ocean surface current, wave height, and wind speed. However, due to the intricate multidimensional processing demands (e.g., time, Doppler, and space) for internal data and effective suppression of external noise, conducting quality control (QC) on radar-measured data is of great importance. In this paper, we first present a comprehensive quality evaluation model for both radial current and synthesized vector current obtained by direction-finding (DF) HFRs. In the proposed model, the quality factor (QF) is calculated for each current cell to evaluate its reliability. The QF for the radial current depends on the signal-to-noise ratio (SNR) and DF factor of the first-order Bragg peak region in the range–Doppler (RD) spectrum, and the QF for the synthesized vector current can be calculated using an error propagation model based on geometric dilution of precision (GDOP). A QC method is then proposed for processing HFR-derived surface current data via the following steps: (1) signal preprocessing is performed to minimize the effect of unwanted external signals such as radio frequency interference and ionospheric clutter; (2) radial currents with low QFs and outliers are removed; (3) the vector currents with low QFs are also removed before spatial smoothing and interpolation. The proposed QC method is validated using a one-month-long dataset collected by the Ocean State Monitoring and Analyzing Radar, model S (OSMAR-S). The improvement in the current quality is proven to be significant. Using the buoy data as ground truth, after applying QC, the correlation coefficients (CCs) of the radial current, synthesized current speed, and synthesized current direction are increased by 4.33~102.91%, 1.04~90.74%, and 1.20~62.67%, respectively, and the root mean square errors (RMSEs) are decreased by 2.51~49.65%, 7.86~27.22%, and 1.68~28.99%, respectively. The proposed QC method has now been incorporated into the operational software (RemoteSiteConsole v1.0.0.65) of OSMAR-S. Full article
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18 pages, 3343 KiB  
Article
Assessment of Ocean Circulation Characteristics off the West Coast of Ireland Using HF Radar
by Lei Ren, Guangwei Pan, Lingna Yang, Yaqi Wang, Gang Zheng, Peng Yao, Qin Zhu, Zhenchang Zhu and Michael Hartnett
Remote Sens. 2023, 15(22), 5395; https://doi.org/10.3390/rs15225395 - 17 Nov 2023
Viewed by 737
Abstract
Research on coastal ocean circulation patterns over long time periods is significant for various marine endeavors: environmental protection, coastal engineering construction, and marine renewable energy extraction. Based on sea surface current data remotely observed using a shore-based high frequency radar (HFR) system for [...] Read more.
Research on coastal ocean circulation patterns over long time periods is significant for various marine endeavors: environmental protection, coastal engineering construction, and marine renewable energy extraction. Based on sea surface current data remotely observed using a shore-based high frequency radar (HFR) system for one year (2016), spatiotemporal characteristics of surface flow fields of sea surface flow fields along the west coast of Ireland are studied using harmonic analysis, rotary spectral analysis and representative flow fields over different seasons and the whole year. Coastal surface currents in the study area are strongly affected by tidal dynamics of the M2 constituent, showing significant characteristics of regular semidiurnal tide, such as M2 and S2. The energy spectrum distribution indicates that the tidal constituents M2 and S2 are the dominant periodic energy constituents in a counterclockwise spectrum, which mainly presents rotating flow; the representative diurnal tidal constituents is the constituent K1, and its energy spectrum distribution is mainly clockwise. A comparison between probable maximum current velocity (PMCV) and measured maximum current velocity (MMCV) is presented. It shows that although tidal current characteristics in the study area are significant, the main driving force of the currents at the time of the maximum currents is wind energy. These results provide new insights into a region of huge societal potential at early stages of sustainable economic exploitation where few data currently exist. Full article
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Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

Title: High-Resolution Sea Surface Target Detection Using Bi-Frequency HFSWR
Authors: Dragan Golubović; Miljko Erić; Nenad Vukmirović; Vladimir Orlić
Affiliation: 1. Vlatacom Institute of High Technologies, Belgrade, Serbia 2. University of Belgrade, School of Electrical Engineering, Belgrade, Serbia 3. University of Belgrade, School of Electrical Engineering and Innovation Center of the School of Electrical Engineering, Belgrade, Serbia
Abstract: The monitoring of the sea surface, whether it is the state of the sea or the position of targets (ships) is an up-to-date research topic. In order to determine localization parameters of ships, we propose a high- resolution algorithm for primary signal processing in High Frequency Surface Wave Radar (HFSWR) which operates at two frequencies. The proposed algorithm is based on a high-resolution estimate of the Range–Doppler (RD-HR) map formed at every antenna in the receive antenna array, which is an essential task, because the performance of the entire radar system depends on its estimation. We also propose a new focusing method allowing us to have only one RD-HR map in the detection process, which collects the information from both these carrier frequencies. The goal of the bi-frequency mode of operation is to improve the detectability of targets, because their signals are affected by different Bragg-line interference patterns at different frequencies, as seen on the RD-HR maps during the primary signal processing. Also, the effect of the sea (sea clutter) manifests itself in different ways at different frequencies. Some targets are masked (undetectable) at one frequency, but they become visible at another frequency. By exploiting this, we increase the probability of detection. The bi-frequency architecture (system model) for the localization of sea targets and the novel signal model were presented in the paper. The advantage of bi-frequency mode served as a motivation for testing the detectability of small boats, which is otherwise a very challenging task, primarily because such targets have a small radar reflective surface, they move quickly and often change their direction. Based on experimentally obtained results, it can be observed that the probability of detection of small boats can also be significantly improved by using a bi-frequency architecture.

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