5:15 PM - 7:15 PM
[AOS12-P04] Observation of mode-2 internal solitary waves in Dongsha Atoll based on multi-source optical remote sensing
Keywords:mode-2 internal solitary waves , multi-source optical remote sensing, South China Sea
Internal solitary waves (ISWs) are widely distributed in marginal seas and continental shelf regions. With the increasing availability of field measurements and satellite remote sensing data, there has been growing attention to the study of high-mode ISWs. In recent years, field measurements of mode-2 ISWs near Dongsha Atoll in the South China Sea (SCS) have been reported, indicating that this region is a potential hotspot. However, mode-2 ISWs are small in scale and have limited sea surface manifestations, making them difficult to detect using satellite imagery. Traditional medium-resolution optical remote sensing satellites are not fully competent for their observation, while modern high-resolution optical remote sensing satellites play a crucial role in detecting mode-2 ISWs.
The synergy of multi-source optical remote sensing satellites addresses the limitations of insufficient temporal and spatial resolution in observing mode-2 ISWs. This study identifies and analyzes mode-2 ISWs near Dongsha Atoll in the SCS using optical remote sensing images acquired by Environmental Disaster Reduction Satellites 2A and 2B (HJ-2A/B), Gaofen-1/6 (GF-1/6), China-Brazil Earth Resource Satellite-04 (CBERS-04), and Terra/Aqua from 2014 to 2023, revealing their distribution and propagation characteristics for the first time. A total of 279 instances of mode-2 ISWs were identified from over 10,000 images, predominantly appearing as solitons and occasionally as wave packets. Wavefronts were constructed by extracting the center elements of stripes using ENVI software, projecting them in ArcGIS, and digitizing their geographic locations to map the northern part of the SCS. Mode-2 ISWs were found within the 120 m to 500 m isobath, primarily concentrated north of Dongsha Atoll, with an average wavefront length of 16.1 km, so most of the wavefronts are straight or slightly convex-type curvature. Statistical analysis of wave propagation reveals that the direction of propagation of mode-2 ISWs is generally perpendicular to the local isobath, and a mode-1 ISW is often observed nearby ahead of the mode-2 ISW. The phase speeds of mode-2 ISWs, estimated using the multi-image comparison method, range from 0.54 to 0.72 m/s. At the same geographic location, the average propagation speed of mode-2 ISW is approximately half that of mode-1 ISW. During the period from April to September, when optical remote sensing data are abundantly available, water depth was identified as the primary factor influencing phase speed. High-resolution optical remote sensing images demonstrated the ability to observe mode-2 ISWs, while the synergy of multi-source satellites enabled near-daily observation of the target sea area, providing robust data support for further research on mode-2 ISWs.
The synergy of multi-source optical remote sensing satellites addresses the limitations of insufficient temporal and spatial resolution in observing mode-2 ISWs. This study identifies and analyzes mode-2 ISWs near Dongsha Atoll in the SCS using optical remote sensing images acquired by Environmental Disaster Reduction Satellites 2A and 2B (HJ-2A/B), Gaofen-1/6 (GF-1/6), China-Brazil Earth Resource Satellite-04 (CBERS-04), and Terra/Aqua from 2014 to 2023, revealing their distribution and propagation characteristics for the first time. A total of 279 instances of mode-2 ISWs were identified from over 10,000 images, predominantly appearing as solitons and occasionally as wave packets. Wavefronts were constructed by extracting the center elements of stripes using ENVI software, projecting them in ArcGIS, and digitizing their geographic locations to map the northern part of the SCS. Mode-2 ISWs were found within the 120 m to 500 m isobath, primarily concentrated north of Dongsha Atoll, with an average wavefront length of 16.1 km, so most of the wavefronts are straight or slightly convex-type curvature. Statistical analysis of wave propagation reveals that the direction of propagation of mode-2 ISWs is generally perpendicular to the local isobath, and a mode-1 ISW is often observed nearby ahead of the mode-2 ISW. The phase speeds of mode-2 ISWs, estimated using the multi-image comparison method, range from 0.54 to 0.72 m/s. At the same geographic location, the average propagation speed of mode-2 ISW is approximately half that of mode-1 ISW. During the period from April to September, when optical remote sensing data are abundantly available, water depth was identified as the primary factor influencing phase speed. High-resolution optical remote sensing images demonstrated the ability to observe mode-2 ISWs, while the synergy of multi-source satellites enabled near-daily observation of the target sea area, providing robust data support for further research on mode-2 ISWs.