### Observational Data
#### 2.1.1 Remote Sensing Data  
Optical remote sensing measures electromagnetic radiation in the visible (roughly 0.4 \(\upmu\)m to 0.7 \(\upmu\)m) and infrared (about 0.7 \(\upmu\)m to 1 mm) bands. Common instruments for optical remote sensing include Moderate Resolution Imaging Spectroradiometer (MODIS), Visible Infrared Imaging Radiometer Suite (VIIIRS), Ocean and Land Color Instrument  
\begin{table}
\begin{tabular}{p{42.7 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline \hline
**Category** & **Subcategory** & **Widely Used Data** & **Source** & **Characteristics** & **Applications** \\ \hline \multirow{6}{*}{ \begin{tabular}{} \end{tabular}  } & \multirow{2}{*}{HF Radar} & NOAA HF Radar & [[https://hrada.ndbc.noaa.gov/](https://hrada.ndbc.noaa.gov/)]([https://hrada.ndbc.noaa.gov/](https://hrada.ndbc.noaa.gov/)) (accessed on National Server & High frequency 3-30 MHz, cover coastal areas) & Surface currents, wind, wave \\  & & & 1 \(\upmu\)m 2025) & & Sound waves & Fisheries \\ \cline{2-5}  & Acoustic & Passive Acoustic & [[https://www.ncbi.nosa.gov/products/passive-acoustic-data](https://www.ncbi.nosa.gov/products/passive-acoustic-data)]([https://www.ncbi.nosa.gov/products/passive-acoustic-data](https://www.ncbi.nosa.gov/products/passive-acoustic-data)) (accessed on 1 July 2025) & & \\  & & & & In Situ Data & \\ \cline{2-5(OLCI) [14; 15], and Geostationary Ocean Color Imager (GOCI), which is the first geostationary ocean color sensor and provides observations essential for monitoring coastal water dynamics, sea ice, and primary productivity [16; 17; 18]. These sensors record reflectance characteristics of the ocean surface and produce multispectral images (MSIs), which provide critical information on ocean properties such as sea ice extent, chlorophyll concentration, and coastal habitats. Moreover, PlanetScope, a satellite constellation operated by Planet Labs and comprising over 130 CubeSats, captures imagery in eight spectral bands at a spatial resolution of 3-5 m per pixel. It has been widely used in coastal applications, such as wetland monitoring and Sargassum inundation detection [19]. By leveraging these data, optical remote sensing enables comprehensive monitoring of marine environments and their dynamics [20; 21]. A key limitation of optical remote sensing is its dependence on clear atmospheric conditions and adequate sunlight for data acquisition [22]. Factors such as cloud cover, aerosols, and water vapor can obstruct light propagation, reducing data quality and availability. In addition, the absence of sunlight during nighttime or polar winters further limits the frequency and consistency of data collection, posing challenges for continuous ocean observation. SAR Microwave remote sensing exploits longer wavelengths (1 mm to 1 m) to penetrate clouds, rain, and fog, enabling all-weather and day or night observations. Among various microwave techniques, Synthetic Aperture Radar (SAR) stands out for its ability to produce high-resolution images of the ocean surface [23]. Commonly used SAR systems include Sentinel-1, RADARSAT, and GaoFen-3 (GF-3) [24; 25; 26]. Sentinel-1, developed by the European Space Agency (ESA), is a radar imaging system initially comprising two satellites, Sentinel-1A and Sentinel-1B, both equipped with C-band SAR sensors. Following the termination of Sentinel-1B in 2022, Sentinel-1C was launched in December 2024 to ensure the continuity of the mission. The RADARSAT program, led by the Canadian Space Agency, includes RADARSAT-2 (launched in 2007) and the RADARSAT Constellation Mission (RCM, launched in 2019), enabling all-weather imaging for applications such as sea ice mapping and ship detection. TerraSAR-X is another widely used SAR mission for sea state monitoring [27]. GF-3, a Chinese satellite launched in 2016, is equipped with C-band SAR systems, offering high-resolution images [28]. These systems are widely used for various applications such as monitoring sea ice, detecting oil spills, observing coastal dynamics, and tracking ocean waves or currents [29].