China has a coastline of 18,000 kilometers and a coastal area of about 350,000 square kilometers, with sediment issues being particularly prominent in major river estuaries such as the Yellow River, Yangtze River, Hangzhou Bay, and the Pearl River estuary, where the average annual sediment discharge is more than 500 million to 1.2 billion tons. If we can grasp the movement law of sediment and make good use of it, it will be a huge wealth; otherwise, it will bring great disasters.
Using multi-temporal satellite remote sensing images can not only reflect the distribution and dynamic changes of suspended sediment in large areas of sea, but also determine the range of high sand content during strong wind weather. This information is essential for new port site selection, new channel opening, offshore oil exploitation, and solving old port siltation issues.
Satellite remote sensing information can be used for fisheries marine environment research, mainly:
Inversion of water temperature: the temperature of seawater is closely related to the survival and migration of fish species. Different fish species not only have their own suitable temperature range for survival, but also undergo seasonal migration. Meteorological satellites can provide large-area sea-surface temperature information for fisheries production services.
Flow barrier research: there are different flow systems in the ocean, and there is a large temperature gradient between different flow systems, referred to as flow barriers. After density segmentation processing of the infrared image by computer, the distribution of different flow systems can be clearly reflected, providing indicators for determining the central fishing ground.
Monitoring of small-scale hydrological phenomena in fishing grounds: when a vortex with a diameter of tens to hundreds of kilometers is found in the fishing ground through satellite monitoring, a central fishing ground can be formed near the center of the vortex.
Analysis of chlorophyll concentration: marine fishing resources are based on the annual production of plankton. By measuring the annual production of plankton, the potential fishing resources can be estimated. Marine chlorophyll is an important parameter reflecting the photosynthesis of marine plankton. Meteorological satellites can provide the distribution of relative chlorophyll concentration in the ocean.
With the increasing proportion of the marine economy in the total national economic output value, marine nearshore water pollution is becoming increasingly serious. Traditional monitoring methods for marine nearshore water quality have been unable to meet actual requirements due to small spatial coverage and low observation frequency, and it is urgent to use remote sensing and other high-tech methods to achieve near-real-time and high-frequency monitoring of marine nearshore water quality. Remote sensing satellites can provide water-quality classification images, water temperature, suspended matter, and water pollution status.
The coastal zone is a transitional zone between the continent and the ocean and is also the area on the land most affected by the ocean.
Storm surges: Using satellite remote sensing, typhoons can be tracked and wind fields estimated, and combined with numerical forecasts, storm surges and the total water level and range of influence of storm surges and tidal waves can be announced in advance.
Sea ice and sea fog: Remote sensing is widely used for real-time monitoring of sea ice and sea fog. Using free MODIS data, ice distribution can be inverted to provide warnings for shipping; satellite-based radar altimeters can accurately measure ice thickness and ice volume over the sea, as well as monitor the distribution and movement of sea ice.
Red tide: Abnormal sea-surface color and temperature can be detected by remote sensing, combined with the abnormal spectral characteristics caused by red tide to monitor the center and range of the red tide occurrence area.
Marine oil spills and green algae (tidal wave): Marine oil spills and tide waves have become major ecological environmental issues today, and using satellite remote sensing to extract information on oil spills and tide waves based on image can be an effective means of monitoring their dynamic changes. Remote sensing can not only detect oil pollution but also analyze the location, area, and calculate the direction and drift speed of oil pollution. Tidal waves, as a type of floating object, can be timely monitored for their latest distribution and drift status through remote sensing.
The process of submarine movement in seawater is also a process of interaction between the submarine and the ocean. The physical characteristics of the ocean itself change due to the existence of submarines. Microwave remote sensing, infrared remote sensing, optical remote sensing, and detection of marine biological fluorescence can be used for submarine detection.