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To accurately simulate the typhoon track and intensity, the WRF model was used to compare the sensitivity of different microphysical processes parameterization and cumulus convection parameterization on typhoon track and intensity simulation. The ensemble prediction method was been considered on the effect of the track and intensity error of typhoon Kai-tak. Four microphysical parameterization schemes and three cumulus convection parameterization schemes were selected to simulate for the track and intensity of Typhoon Kai-tak. The results show that different parameterization schemes have obvious influence on the simulation results of the track and intensity of typhoon. The parameterization scheme of cumulus convection is more sensitive than the parameterization scheme of microphysical process. Based on the ensemble prediction method of disturbing members based on different parameterization schemes, the simulation accurate of typhoon track and intensity is improved obviously. The error of typhoon track increases little with time, and the result is better than the simulation results of all twelve single schemes. From the aspect of typhoon intensity, the trend of typhoon intensity based on the ensemble prediction method is consistent with the actual result, which is better than the most of the test schemes. The results show that the ensemble prediction model constructed with different microphysical parameterization schemes and cumulus convection parameterization schemes can improve the simulation of typhoon track and intensity, reducing the track uncertainty produced by different parameterization schemes, which can provide a scientific reference for improving the forecasting ability of typhoon.

Various types of ocean detection data with high spatial and temporal resolution provides possibilities for the application of signal decomposition and machine learning algorithms. In order to establish an effective sea surface temperature (SST) prediction model, the high time resolution of the SST and the fusion of products were used in this study, introducing the ensemble empirical mode decomposition (EEMD) in the field of signal processing and autoregressive integrated moving average model (ARIMA) in the field of machine learning. Firstly, the SST data were decomposed into several frequency sequences by EEMD method, which was the most suitable for decomposing natural signals. After that the ARIMA was used to predict the sequence of frequencies, and then the predicted results of each sequence were combined. Compared with the previous method of directly using SST data to build prediction model, this method achieves higher accuracy because of its abundant data, and provides a new way for better SST prediction.

Low salinity lens is a common mesoscale phenomenon in the continental shelf outside the Pearl River Estuary, and its appearance will affect the underwater acoustic waveguide. The structure characteristics of low salinity lenses were analyzed based on the CTD profiles in the northern shelf of the South China Sea. Based on the normal mode and ray model, the two-dimensional waveguide environment was established, the characteristics of sound transmission in the low salinity lenses environment were studied under different sound source conditions. The results show that the low salinity lens will become the acoustic channel in the upper layer of sea water, and the transmission loss at 15 km is about 15 dB less than that without low salinity lens. Although the channel thickness of low salinity lens is usually smaller than surface acoustic channel, the large salinity gradient can effectively trap energy in the acoustic channel. When the sound source whose frequency is higher than the cut-off frequency is placed in a low-salt lens, the acoustic channel can help the long-distance propagation of sound.

Three special polymetallic oxides were taken from the Challenger Deep of Mariana Trench. They were at the initial stage compared to the normal polymetallic nodules. Samples were taken for mineralogical and geochemical analyses, such as X-ray diffraction(XRD) and Mossbauer spectra. Major, trace and rare earth elements(REE) were also measured for all the samples. The results showed that: (1)Compared to the normal polymetallic nodules, the mineralogy of samples were dominated by quartz, plagioclase and clay minerals, but vernadite and todorokite were deficient, which were often seen in polymetallic nodules. (2)Data obtained by Mossbauer spectra indicated that the iron phases were akaganeite(91.6%) and lepidocrocite(8.4%), we suggested it was due to the transmutation from lepidocrocite to akaganeite, a more stable mineral. (3)Higher contents of SiO₂ and Al₂O₃ were found in the samples, but lower contents of Mn, Fe, Cu, Co, Ni in contrast. They were caused by the contamination of pelagic clay and short duration of sorption. (4)Due to the short time for absorption, value of ΣREE was about 0.4×10^-3 in the samples, consumedly lower than that in the normal nodules, of which ΣREE content was usually higher than 1.0×10^-3. The absent of the positive Ce anomaly was due to the reducing bottom-water redox condition and the active hydrothermal fluid.

The contents and distribution of Glycerol Dialkyl Glycerol Tetraethers (GDGTs) in 15 surface sediment samples from Ross Sea, Antarctica were analyzed. Besides, the source of GDGTs and environmental implications of TEX₈₆ were disscussed. The results show that the content of GDGTs is from 93.67 to 2 663.37 ng/g with the isoprenoid GDGTs accounts for 90.33%98.56%, which are much more higher than those of branched GDGTs. Isoprenoid GDGTs have significant positive correlation with branched GDGTs (R²=0.88,p<0.01). The result indicates that isoprenoid GDGTs come from marine Archaea while branched GDGTs are mainly from bacteria in sea waters and sediments. Correlation analysis with the WOA database shows that the TEX^L₈₆ index reconstructed temperatures are of significant positive correlation with the sea surface temperatures in summer in the study area. Thus,the TEX^L₈₆ could be used as a potential index for paleo-SST reconstruction in the Ross Sea.

The study of the impact of landscape pattern changes on ecosystem service value in the island areas plays a positive role in understanding the landscape difference between lands and islands, properly utilizing land resources in the island areas, and steadily developing the regional ecosystem. Based on the land use data in 1995, 2005 and 2015 respectively, the characteristics of changes in landscape patterns and ecosystem service value of the Zhoushan Archipelago from 1995 to 2015 were analyzed, as well as the correlation between landscape index and ecosystem service value. The results are shown as follows: (1)The areas of waters, cities and villages in the Zhoushan Archipelago have been continuously increasing while the areas of other landscapes have been continuously declining, which shows the continuously deepened degree of fragmentation, complexity and diversity of landscape patterns. (2)The ecosystem service value presents an uptrend after a decline, increasing by 376.6 million yuan. Other values have been dropping except that the values of water supply, environment purification and hydrological regulation have been in an overall uptrend. Areas with a comparatively high and low value have been continuously increasing, while areas with a value ranging from 5 to 15 million yuan show a slight reduction. (3)The total value of ecosystem services is significantly positively correlated with the complexity and diversity of landscape patches, but significantly negatively correlated with the aggregation index and contagion index of landscapes.

Li⁺-doped nano-CNTS-TiO₂ composite photocatalyst (Li⁺/CNTS-TiO₂ composite photocatalyst) was prepared by sol-gel method using CNTS-TiO₂ as precursor. The sample was characterized by X-ray diffraction and Scanning electron microscope methods. The photocatalytic degradation of marine diesel was carried out using the 3% Li⁺/CNTS-TiO₂ composite photocatalyst. The effects of different factors, such as the amount of Li⁺ doping, calcination temperature, dosage of 3% Li⁺/CNTS-TiO₂ composite photocatalyst, initial diesel concentration, photocatalytic reaction time and H₂O₂ concentration were investigated under visible light conditions. According to the analysis of orthogonal test results, the optimum process conditions for degradation of marine diesel pollution with 3% Li⁺/CNTS-TiO₂ composite nano-photocatalyst were as follows: calcination temperature of 3% Li⁺/CNTS-TiO₂ composite nano-photocatalyst at 600 ℃, photocatalytic reaction time at 3 h, dosage of 3% Li⁺/CNTS-TiO₂ at 0.1 g/L, initial concentration of degraded diesel at 0.4 g/L, concentration of H₂O₂ at 0.6 g/L. Using these conditions, the degradation rate could reach more than 95%. At the same time, the photocatalyst was applied and tested. The test results showed that the photocatalyst degradation effect was excellent, and the degradation rate was up to 91.87%.

The strait channels are densely covered in the sea area of Zhoushan Islands, and the instability of the slopes of the strait channels is generally developed and varied in scale. The frequent subaqueous landslides pose a greater threat to coastal engineering facilities such as submarine cables and port terminals. In December 2012, the sub-bottom profiles were detected in the sea area of Liuheng Island. Three main acoustic reflection interfaces and four formation units were divided, and the upper three formations were Holocene sedimentary layers. Six subaqueous landslides were found, which were scattered along the coast of Liuheng Island or adjacent to the strait channel slope. The landslides structure were whole landslide, and some of them were multi-step. From the scale of the subaqueous landslides, the volumes were between 1.6×10⁵ to 2.7×10⁷ m³, with 2 super-large landslides, 3 large landslides and 1 medium landslide. According to the correlation between the interface and the landslide body, it was speculated that the subaqueous landslides occurred in the late Holocene since 2.5 ka.

Hydraulic jet trenching technology has been widely used in submarine pipeline and optical cable embedding engineering. However, jet trenching construction in stiff clay is difficult. In order to elucidate the mechanism of soil breaking, the physical simulation experiment of submerged vertical jet trenching was carried out. During the process of soil breaking, it is found that there are some differences between the development characteristics of scour hole in soft clay and stiff clay. Shear-compression stress is the main factor of soil breaking in stiff clay and the breaking mode in stiff clay can be explained by the Prandtl foundation ultimate bearing capacity theory. Based on this, the model of jet to break hardpan is established, and the diameter of hole's neck is proposed to replace the diameter of scour hole as a prediction index.

The characteristics of the tidal and residual currents were investigated via the harmonic analysis based on the 31-day duration current observations at S station near the main channel of Tianjin Port. Effects of the local wind on the surface residual currents were explored in combination with the simultaneous wind velocities data. It is found that: (1)Tianjin Port belongs to the weak-current sea area, and the average velocity of the surface currents is about 31.4 cm/s. The current velocity generally decreases from the top to the bottom, and the main current direction is along the northwest-southeast. (2)The sea area is dominated by the regular semidiurnal tidal currents with a significant to-and-fro movement. The dominant tide component is M₂, and the shallow water tide is also remarkable over there. The flood currents velocities are larger than the ebb currents. (3)The average residual currents during the observation period are between 2.8 cm/s and 13.8 cm/s. The current velocity decreases as the depth increases, and the main current direction is along the northwest. The residual currents in the surface layer of the station are dramatically affected by the local wind, and the southeast wind shifts the residual currents to northwest.

Waters and sediments in coastal waters are important sites for nutrient translocation. By sampling the Bohai Sea waters and sediments in August 2016, the spatial distribution characteristics of different forms of nutrients in the waters and sediments of the Bohai Bay were analyzed. In addition, the migration and transformation of nutrients in waters and sediments were studied. The results show that nutrients in Bohai Bay waters are higher in the nearshore area of the west coast and lower in the open sea areas far from the coastline, showing a clear concentration gradient. It shows that the contribution of man-made activities to the nutrient content in the water body in coastal waters is obvious. Nutrients in waters are mainly in inorganic forms, and inorganic nitrogen and inorganic phosphorus account for 76.65% and 76.46% of the total. Nitrogen and phosphorus in sediments show similar spatial distribution of nutrients in waters. However, the main form of nitrogen is organic nitrogen, while the content of inorganic phosphorus also drops to 30.42%. This shows that the nitrogen and phosphorus in Bohai Bay waters mainly enter the sediments through the assimilation of organic compounds in waters by the organism. Part of inorganic phosphorus enter the sediments through the adsorption form, but the effect of nitrogen entering the sediments from the water body through adsorption is not obvious.