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The local typhoon refers to the tropical cyclone formed in the South China Sea. 1949-2014 CMA-STI compiled "best track dataset for tropical cyclone" was chosen in this study, the local typhoon intensity and intensity change characteristics on the scope of the study area (5°-22.5°N, 105°-120.5°E) were discussed. The results showed as follows: (1) The time curves of local typhoon intensity were similar to symmetric funnel-shape, that was changed from weak-strong-weak, intensity change was the most significant before and after 6 h in maximum intensity, and intensity change in summer was quickly than in winter. (2)The local typhoons had one intensified centers, located in the east of Hainan Island coastal area, but which decreased obviously near the south China coastal land area; further analysis showed that the typhoon intensified/weakened area moved with the changing seasons, in the summer it was mainly in the north offshore/nearshore area near 18°-23° N, while in the winter it was close to the west offshore/nearshore area near 10°-18° N, and the average decreased rate in winter was bigger than that in summer. (3) Furthermore, the eastward local typhoon intensity was generally stronger than that of westward, average intensity of summer eastward typhoon was the largest and that of winter westward typhoon intensity was the least; around the maximum intensity, the summer eastward typhoon intensity change was the fastest and winter westward typhoon was the slowest. Summer westward typhoon intensity distribution was stronger in the north, and eastward typhoon intensity distribution formed a northeast belt-shaped. In winter, westward and eastward typhoon intensity distribution was stronger in west. The difference of such spatial distribution was mainly due to the typhoon moving paths with the seasons. (4)The duration time of maritime activity with the intensity and variation in the range was proportional. The shorter maritime activity, the more westward paths, the average intensity was weaker, intensified/weakened centers was much smaller, intensified/weakened rate was slower; conversely, the longer maritime activity, the more eastward paths, the intensity distribution had multicenter, its average intensity was stronger, intensified/weakened center was more concentrated and broad, intensified/weakened rate was faster.

Equatorial Westerly Wind Bursts (WWBs) are characterized by sudden increase of surface westerlies over the equatorial region. Previous studies showed that the WWBs play a fundamental role in triggering and maintaining the El Niño event. In this thesis, we evaluate the simulation of WWBs in the state-of-the-art models from the Coupled Model Intercomparison Project phase5(CMIP5). Most of the models can reproduce the eastward propagation of WWBs in El Niño years, as occurrences of WWBs are strongly dependent on sea surface temperature in the tropical western-central Pacific. The WWBs generally occurs before the development of El Niño. Unlike what was proposed in previous studies, we found that MJO does not significantly increase the likelihood of WWBs in both observations and model simulations.

The sediments from 12.7 m to 17.4 m in the core QG01 which was taken from the west coast of Bohai Bay were analyzed with grain size analysis, XRD and OSL, the characteristics of clay mineral assemblages and used as paleoclimatic proxies were also investigated. The sediments are composed of sandy silt, silty sand, and clayey silt, with the rage 4.11~7.79 Φ. The results show that illite-chlorite-kaolinite-smectite is the main clay mineral assemblage. The KI and the ratio values of “(illite+chlorite)/(kaolinite+smectite)” are used as paleoclimate proxies. The results show that two proxies can reflect the feature of climate change when the trends of the two proxies are corresponding. On the contrary, when the trends of the two proxies do not correspond with each other, they cannot be used as paleoclimatic proxies since the source of sediments may change.

Multibeam sonar data can effectively reflect the features of seafloor topography and its substrates. The shipboard multibeam data were used to characterize the topography, geomorphology and the backscatter intensity characteristics of typical tectono-geographic units of the 60°-61°E segment in Carlsberg Ridge, Northwestern Indian Ocean, aiming to describe the strength of the magmatism and tectonism of the studied ridge segments. Basically, the 60°-61°E segment of Carlsberg Ridge showed symmetrical spreading with discontinuous zone. The Segment I was more influenced by tectonism, with more fractures occurred in the rift valley. The segment axis and nearby backscatter intensity reached -29 dB, with the rift wall height difference over 1 200 m. The segment also had deeper valley bottoms, higher rift valley walls, higher flank/width ratio (78.7-126.2) but less off-axial linear structures. In the rift flank, the normal fault plane was wider and the dip angle was smaller. Compared to the center of the segment, the volcanic activities in segment end had lower eruption frequency but larger eruption scale, and erupted volcanic edifices were larger in the aspect of number and volume. In contrast, the Segment II was dominated by magmatism with axial volcanic ridges and numerous symmetrically developed off-axial linear structures. The segment axis and nearby backscatter intensity reached -35 dB. The rift flank/width ratio was 77.6-116.8. The difference of the rift wall height was less than 500 m. The linear structures had relatively high aspect ratio, and were approximately symmetric on the flank of the rift. It is suggested that multibeam backscatter data combining with the topography analysis can provide quantitative evidence for the study of the strengths of the tectonism and magmatism of the mid-ocean ridge.

Icequakes on Laohugou Glacier No.12 were observed by operating a portable digital seismometer for 9 days in Oct. 2015. Lots of seismic signals relating to glacier dynamic characteristics were found. On the basis of signal frequency and duration time, two types of seismic event can be divided. Short-period icequakes have time duration less than 0.1 s, the frequency domains are among 20-100 Hz and the numbers are up to 6 600 per day. The majority of seismic events are short-period icequakes. Long-period icequakes have time duration from several minutes to several hours, the frequency domains are among 0.1-10 Hz and the numbers are up to 296 during the observation. Comparing the time distribution of short-period icequakes with local air temperature, it is found that once temperature drops, the numbers of short-period icequake increase rapidly. And once temperature rises, the numbers of short-period icequake decrease. The time distributions of short-period icequakes have a diurnal cycle. It is inferred that once air temperature decreases, temperature of glacier ice decreases and as a result, the fracture at the surface of glacier under tensile thermal stress was happened. Using Maxwell Model to calculate glacier stress change, the diurnal cycle of short-period icequakes can be explained.

Salt marsh is one of the major coastal wetland types in the world's temperate and subtropical regions. Taking Yancheng coastal area as an example and using 6 remote sensing satellite images of past 30 years, the temporal and spatial evolution of salt marsh in this area were analyzed by simple vegetation cover index (NDVI) crude extraction and visual interpretation. The influencing factors of these changes were also discussed. The results show that the area of salt marsh has risen and declined sharply at first and then risen slightly in the past 30 years, it has decreased about 18 km² so far. The salt marsh continues to expand outward, the maximum expansion distance reaches 5.5 km. The width of the salt marsh has also changed over time, salt marsh vegetation types have also undergone different degrees of evolution. The landscape index shows that landscape fragmentation is getting worse. Mane, suaeda and reeds have decreased significantly, and plenty of spartina covers the wetland. Among the natural and human factors that affect the temporal and spatial changes of salt marshes, the effects of reclamation activities are the most pronounced.

Particulate biogenic silica (BSi) and chlorophyll a (Chl a) were determined at 61 stations in the Pearl River Estuary and adjacent coastal waters in summer, in order to evaluate spatial variability in biogenic silica and the interference of lithogenic silica (LSi) in the bulk silica leached from the alkaline solution. Our results showed that Chl a concentrations ranged from 0.06 to 8.64 μg·L^-1. Particulate BSi concentrations varied from the detect limit to 14.3 μmol·L^-1, LSi concentrations were 0.00-9.56 μmol·L^-1 and the average ratio of LSi to LSi+BSi was 0.38 mol·mol^-1. The average ratio of Si to Al was 2.42 mol·mol^-1, comparable to the value reported by RAGUENEAU et al(2005). A significant correlation was found between particulate biogenic silica and Chl a, which indicated diatom and phytoplankton biomass in the water column. LSi concentrations varied spatially, with high BSi, LSi and low LSi/(LSi+BSi) ratios in the nearshore area, low BSi, LSi and high LSi/(LSi+BSi) ratios in the offshore waters, low BSi, high LSi and high LSi/(LSi+BSi) ratios in the estuary, high BSi, LSi and high LSi/(LSi+BSi) ratios in the upwelling region. LSi and LSi/(LSi+BSi) ratios in the bottom water were higher than those in the surface water. In addition, some limitations caused by other methodologies of BSi measurements had been discussed.

The potential pressure caused by sea use activities on marine eco-environment in Laizhou Bay was quantitatively evaluated based on GIS and geospatial modeling by combining the spatial distribution of marine ecological red line zone. We firstly identified the spatial distribution patterns of all anthropogenic pressures as well as their potential impact on key marine habitats. The general characteristic of spatial distribution of potential anthropogenic pressure on the eco-environment in Laizhou Bay can be described as that in the offshore area is higher than that in the far-shore area and the sequence from high to low is: the bay-head, the east area, the west area. Overall, the high pressure area is concentrated in the sea area within 10 km and the water depth within 5 m. It is worthy to note that a few of marine ecological red line zones, such as marine special protected areas, natural reserves, and important estuarine ecosystems, have already threatened by pressure caused by sea aquaculture and salt industry. The study reveals the spatial distribution pattern of the potential pressure of sea use activities on the marine ecological environment in Laizhou Bay. Accordingly, a few policy suggestions are also proposed at the end to implement the spatial planning of marine ecological red line zones and regulate utilization of sea area.

The design of compressive cabin which is used in the underwater vehicle requires that the design strength and stability can be improved to the maximum, and the weight can be reduced as much as possible to satisfy the requirements of the overall index. The Design Explorer Module in ANSYS Workbench was used for the fast optimization design of the compressive cabin, and a number of optimal candidate results were obtained at one time. The optimal design scheme was obtained by comparison and analysis. Then, contact analysis was carried out in the form of assembly to ensure that the structure would not fail under the condition of high pressure. Finally, the stability analysis of the cabin structure was carried out to ensure that the structure could not cause instability failure in a large depth environment. The result of this study provides the reference for rapid optimization design, strength and stability checking of the underwater vehicle's compressive cabin.

According to the comparative analysis result of historical heavy metals contents in the surface sediments from the Jiulong River Estuary and Xiamen Bay from 1980s, the average value of heavy metals contents in this sea area was established, and the overview of heavy metals distribution characteristic has been made. Besides, the background level of heavy metal element contents was determined according to the need of potential ecological risk index method, it provides the reference data of average value and background level for further research and evaluation. Combined with the survey data in August, 2016, the integrated risk evaluation results indicated an unoptimistic situation of this sea area, the eastern of Xiamen Sea Area mainly belonged to low ecological risk, Jiulong River Estuary mainly belonged to heavy ecological risk, and the rest of Xiamen Bay mainly belonged to moderate ecological risk.

To explore the effect of polyamines on the growth of diatoms, Chaetoceros sp., Phaeodactylum tricornutum Bohlin and Conticribra weissflogii were cultured indoor by adding spermine, spermidine, putrescine, cadaverine and phenylethylamine as exogenous polyamines. The results show that different polyamines reveal different specificity for the growth of different diatoms at the same temperature. Spermidine promotes the growth of Chaetoceros sp. And cadaverine promotes the growth of P. tricornutum, while spermine inhibit on the growth of P. tricornutum. The polyamines mainly promote the pre-growth of Conticribra weissflogii (before 13 d), and inhibit the growth (after 13 d). The timely and proper addition of polyamines can promote the growth of diatoms effectively and increase the reproductive efficiency of diatoms.

In order to study the effect of typhoon on the cultured Portunus trituberculatus, the changes of T-SOD, CAT, MDA, GSH, ACP and Na⁺, K⁺-ATPase in the hearts, gills and hepatopancreas were detected in 12 hours before and after typhoon “Canhong”(1509) at Xiangshan in July, 2015. The typhoon increased highly significantly the activity of the T-SOD enzyme (p<0.01) and increased significantly CAT enzyme(p<0.05) in the gills. After typhoon, the MDA and GSH content in gills increased insignificantly (p>0.05). T-SOD enzyme activity in the hepatopancreas showed an insignificant trend of decrease (p>0.05) while the CAT enzyme activity showed an insignificant trend of increase (p>0.05), MDA content increased significantly (p<0.05) and the increase of the GSH content was highly significant (p<0.01). In the hearts, the levels of T-SOD, CAT enzyme activity and GSH content increased and the MDA content decreased, but these changes were not significant(p>0.05). In addition, the ACP enzyme activity in the gills and the hearts increased insignificantly(p>0.05), which was reduced but not significantly in the hepatopancreas (p>0.05). The Na⁺, K⁺-ATPase activity in the gills decreased highly significantly (p<0.01), but increased highly significantly in the hepatopancreas (p<0.01) and significantly in the heart (p<0.05) . This study reveals that the typhoon can cause the cultured P. trituberculatus stress response in the short term and solutions are need to take to avoid typhoon damage to cultured P. trituberculatus.