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The backscattering coefficient of particles is one of the most important inherent optical parameters of water body, and also is the core parameter of ocean color remote sensing. It is very important to measure the backscattering coefficient data of particles in water accurately in-situ for the construction of water color remote sensing model and the authenticity test of water color remote sensing products. In this study, the consistency of these three kinds of in-situ instruments(HydroScat6, VSF3 and BB9) for measuring backscattering coefficient of water particles were compared and analyzed. The results show that the measurements by these three kinds of instruments have good consistency in clean water, but in the turbid water, the measurements of HydroScat6 and BB9 are higher than those of VSF3, and their deviations are significantly increased. Based on numerical simulations and laboratory measurements, it is found that the shapes of particles affect the consistency of measurements by the three instruments, and the consistency is better for spherical particles than that of field particles.

Ocean chlorophyll-a concentration remote sensing product is important data sources for the studies of ocean primary productivity and carbon sequestration capacity of ocean ecosystems. In order to ensure the data reliability, it is particularly important to verify the accuracy of remote sensing product and analyze the causes of validation errors. In the verification of remote sensing products, due to the existence of spatial variation, the measured data within the remote sensing pixel have different statistical distribution characteristics, and thus produce different statistical error results. In this work, chlorophyll-a concentration remote sensing products derived from MODIS-Aqua, MODIS-Terra, MERIS and SeaWiFS satellite sensors, were quantitatively analyzed on the relationship between spatial variability and validation accuracy. The results of statistical analysis show that spatial variation is one of the direct causes of validation error. The relationship between Mean Absolute Percentage Error (MAPE) and spatial Coefficient of Variation (CV) is in accordance with power exponential model. When CV<0.05, MAPE increases significantly with CV, and when CV>0.15, MAPE changes gently. The validation results of different chlorophyll-a concentration remote sensing products show that SeaWiFS has the highest accuracy, MERIS takes the second place, and MODIS-Terra has the worst accuracy.

The use of remote sensing technology to quickly extract the shorelines of islands is an important technology. An approach of marked watershed based on extended extremum transform was proposed in this study, solving the problems of over-segmentation and poor anti-interference ability of traditional watershed algorithm in high-resolution multispectral satellite data processing. Firstly, the foreground and background markers were established by morphological reconstruction and extended extremum transform to suppress the minimum and maximum gray regions initially, then the gradient image was modified based on above markers, and finally the island shoreline was extracted based on the improved watershed transform method. The typical islands located in the South China Sea region were selected, and the accuracy and reliability of the proposed method were verified using 2017 GF-2 satellite data. The results show that the accuracy of artificial shorelines is higher than 90% within 1 pixel(4 m) for island shorelines, and the accuracy of sandy shorelines is higher than 90% within 1.5 pixels(6 m), confirmed that the proposed method can be used for segmentation of high-resolution multispectral images and extraction of island shoreline.

The underwater glider is an important platform for unmanned motion observation of the ocean. However, it is difficult to maintain the preset net array when multiple underwater gliders cooperate in observation.In this study, an underwater glider group cooperative control algorithm based on Newton mechanical integration was proposed to adjust the motion parameters of the glider group before entering the water according to its asynchronous entering and leaving the water.Based on the force analysis of the underwater glider, the motion state of the underwater glider in the ocean was restored by Newton mechanics integral. The cooperative control algorithm of the underwater glider group was used to constrain the motion of several underwater gliders at the same time, and the simulation experiment was carried out. The results of experiment show that the algorithm can keep the preset net array of multiple underwater gliders well, so that the target sea area can be observed cooperatively.

Aiming at the requirements of the mobile ocean seismograph for high reliability and low power consumption of the control system, a hardware circuit design scheme based on the Cortex-M4 core was proposed. Firstly, the ultra-low-power consumption STM32L4 was selected as the MCU(Microprogrammed Control Unit) to ensure high operating capacity and reduce power consumption; secondly, a targeted two-level voltage reduction scheme was proposed for the ultra-low-power modules, such as MCU and sensor system, to greatly improve the power conversion efficiency of the circuit and a suitable buck chips was selected for the high-power modules such as buoyancy adjustment systems and communication systems to ensure circuit safety and improve the conversion efficiency. Finally, the peripheral circuit was filtered and protected. The reliability of the different modules was verified through tests which prove that the hardware circuit can support the seismograph to achieve the complete observation task and the circuit design is highly reliable.

Based on historical topographic maps, charts and remote sensing images since 1913, 10 periods of coastline data covering Sanmen Bay were obtained and analyzed using GIS and spatial analysis tools. The temporal and spatial evolution characteristics of the coastlines in Sanmen Bay during the last 100 years were investigated. The results show that: (1) The changes of coastlines mainly occurred in the inner bay. The reclamation activities, mainly including harbor construction and island-land connection, led to a total land area increase of 231.42 km². (2) The total length of the coastlines was reduced by magnitudes of 161.99 km and 121.36 km for the mainland and islands, respectively. The average annual change intensity of coastlines changed from -0.05% to -1.85% in the last 100 years and the most intensely changes occurred in 1971-1980 for mainland coasts and 2006-2010 for islands. (3) The straightening of coastlines was caused by meandering cutting as a result of the continuous decrease of natural coastlines. The artificial degree of mainland coastlines continued to increase, which was much higher than that of island coastlines. (4) Population growth, economic development and policy guidance were found to be the main driving forces for the coastline evolution in Sanmen Bay.

As a sign element, a large range, long-term shore dynamic changes in the coastal zones, are of great significance to the research of regional coastal environment and human activities. Used the remote sensing techniques, the variation characteristics of Thailand shoreline from 1990 to 2020 was analyzed, such as length changes, type changes, change rate, and the “sea-land” pattern. The results show that: (1) For 30 years, the length of the shoreline of Thailand had a continuous growth trend, but the growth rate was fast at first and then slow down, which patterns were expressed as two kinds: sea-forward expansion and land-forward erosion. From 1990 to 2015, the expansion trend in the shoreline toward the sea gradually slowed, and the erosive trend in the land was gradually increased. The overall change trend from 2000 to 2015 was mainly erosion, but the overall shoreline change in 2015 was expanded to the sea. (2) Thailand shoreline regional variation was significant, the change in the expansion of the banks such as Leam ChaBang was dramatic, and the erosion change in the northern part of Bangkok Bay was obvious. (3) The main driving force for the expansion of Thailand shoreline was the construction of coastal projects, and the main factors of erosion variations were the ocean environment and extreme climate, while policy management acted on the whole process of straighten changes.

Sea Surface Temperature(SST) is one of the important marine environmental dynamics elements in the cognition and study of the physical properties and evolution of the atmosphere and ocean, and is also an indispensable component in the composition of marine forecasting. The study of the distribution and evolution of SST is of great significance to the marine economy, environmental protection and national defense security. In this study, a statistical forecasting method based on the similarity coefficient was proposed, and a statistical forecasting model based on the similarity coefficient was constructed to realize the single-point time series forecasting of SST. In the medium and long-term experiments of SST forecasting in the South China Sea, this method has better results than those from Optimal Climate Normals forecasting and ARIMA forecasting methods, which proves the effectiveness of this method and provides a new idea for the medium and long-term forecasting of SST.

To understand the trends of the dominant species of macrozoobenthos and their niches in the intertidal zone of islands off sourthern Zhejiang, the interannual changes and succession of macrozoobenthic community structure were analyzed based on the data collected from the November of 1990, 2006, 2010 and 2016 in Nanji Islands, Beilong-Beiji Islands and Dongtou Islands. The results showed that there were 15 dominant species of macrozoobenthos and the top four dominant species were Tetraclita japonica, Septifer virgatus, Thais clavigera and Nodilittorina exigua.The T. japonica had been gradually replaced by S. virgatusin the past 30 years. In terms of geography, the most dominant species in Beilong-Beiji Islands and Dongtou Islands was T. japonica, while in the Nanji Islands was S. virgatus. The niche breadth (B_i) of the dominant species was 0-0.97, and species with B_i greater than 0.70 were T. clavigera, Liolophura japonica, S. virgatus, N. exigua, Capitulum mitella and T. japonica, indicating that these species appeared at many resource sites and had strong adaptability to the environment. Species with B_i less than 0.4 were Trichomya hirsuta, Megabalanus volcano, Septiper excisus,Saccostrea kegaki,Mytilus coruscus and Chthamalus challengeri, indicating these species only appeared at very few resource sites and were weak in resource utilization. The niche overlap value(O_ik) of the dominant species was 0-0.96. The species with B_i greater than 0.70 had higher O_ik, and O_ik were all greater than 0.53. The species with B_i between 0.4-0.7 had O_ik among 0.34-0.66, while the species with B_i less than 0.4 had not necessarily lower O_ik, and their O_ik were among 0 and 0.69, indicating that the species with larger B_i had higher O_ik, but species with small B_i may have high or low O_ik.

The evaluation of mussel loss rate caused by marine disasters is a new scientific proposition produced by the intersection of marine science and fishery science. At the same time, it is also a difficult problem in fishery economics and insurance value accounting. The effect of sea wave disaster on mussel loss rate was studied in this research, adopting the third generation wave model SWAN to calculate the significant wave height. The significant wave height with different return periods around Shengsi sea area was calculated, and the relationship between mussel loss rate and significant wave height in Shengsi sea area was analyzed. The results show that when the effective wave height is up to 3 meters, mussel begin to fall off; when the effective wave height is bigger than 9 meters, the probability of mussel loss rate reaching 100% is high.