Recent progress of physical oceanography in the South China Sea (SCS) associated with the western boundary current (WBC) and eddies is reviewed in this paper. It includes Argo observations of the WBC, eddy detection in the WBC based on satellite images, cross-continental shelf exchange in the WBC, eddy-current interaction, interannual variability of the WBC, air-sea interaction, the SCS throughflow (SCSTF), among others. The WBC in the SCS is strong, and its structure, variability and dynamic processes on seasonal and interannual time scales are yet to be fully understood. In this paper, we summarize progresses on the variability of the WBC, eddy-current interaction, air-sea interaction, and the SCSTF achieved in the past few years. Firstly, using the drifting buoy observations, we point out that the WBC becomes stronger and narrower after it reaches the central Vietnam coast. The possible mechanisms influencing the ocean circulation in the northern SCS are discussed, and the dynamic mechanisms that induce the countercurrent in the region of northern branch of WBC in winter are also studied quantitatively using momentum balance. The geostropic component of the WBC was diagnosed using the ship observation along 18°N, and we found that the WBC changed significantly on interannual time scale. Secondly, using the ship observations, two anti-cyclonic eddies in the winter of 2003/2004 in the northern SCS, and three anti-cyclonic eddies in the summer of 2007 along 18°N were studied. The results show that the two anti-cyclonic eddies can propagate southwestward along the continental shelf at the speed of first Rossby wave (~0.1 m s 1 ) in winter, and the interaction between the three anti-cyclonic eddies in summer and the WBC in the SCS is preliminarily revealed. Eddies on the continental shelf of northern SCS propagated southeastward with a maximum speed of 0.09 m s 1 , and those to the east of Vietnam coast had the largest kinetic energy, both of which imply strong interaction between eddy activity and WBC in the SCS. Thirdly, strong intraseasonal variability (ISV) of sea surface temperature (SST) near the WBC regions was found, and the ISV signal of SST in winter weakens the ISV signal of latent heat flux by 20%. Fourthly, the long-term change of SCSTF volume transport and its connection with the ocean circulation in the Pacific were discussed.South China Sea, western boundary current, eddy, eddy-current interaction, intraseasonal variability, South China Sea thoughflow Citation:Wang D X, Liu Q Y, Xie Q, et al. Progress of regional oceanography study associated with western boundary current in

Air–sea interaction in the South China Sea (SCS) has direct impacts on the weather and climate of its surrounding areas at various spatiotemporal scales. In situ observation plays a vital role in exploring the dynamic characteristics of the regional circulation and air–sea interaction. Remote sensing and regional modeling are expected to provide high-resolution data for studies of air–sea coupling; however, careful validation and calibration using in situ observations is necessary to ensure the quality of these data. Through a decade of effort, a marine observation network in the SCS has begun to be established, yielding a regional observatory for the air–sea synoptic system. Earlier observations in the SCS were scarce and narrowly focused. Since 2004, an annual series of scientific open cruises during late summer in the SCS has been organized by the South China Sea Institute of Oceanology (SCSIO), carefully designed based on the dynamic characteristics of the oceanic circulation and air–sea interaction in the SCS region. Since 2006, the cruise carried a radiometer and radiosondes on board, marking a new era of marine meteorological observation in the SCS. Fixed stations have been established for long-term and sustained records. Observations obtained through the network have been used to study regional ocean circulation and processes in the marine atmospheric boundary layer. In the future, a great number of multi-institutional, collaborative scientific cruises and observations at fixed stations will be carried out to establish a mesoscale hydrological and marine meteorological observation network in the SCS.

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Abstract. Using an observation data set of temperature and the Simple Ocean Data Assimilation (SODA), the decadal variability of upper ocean heat content (0-400 m; hereafter, OHC) in the South China Sea (SCS) was investigated for the period from 1958 to 2007. Decadal variability was identified as the dominant mode of upper OHC besides the seasonal cycle. According to decreasing or increasing OHC, four periods were chosen to discuss detailed processes behind OHC variability in the SCS; the four periods are

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Phytoplankton blooms often occur in the offshore region northwest of Luzon Islands in winter. Using remote sensing data, including sea-surface temperature, monthly-mean mixed layer depth (MLD), wind speed (SP), and SeaWiFS-derived chlorophyll-a (Chl-a) data from September 1997 to February 2007, we investigate the spatial and interannual variation of the winter phytoplankton in the region along with in situ GTS (the Global Telecommunications System) XBT (Expendable Bathythermograph) data and climatological nitrate and temperature observations from World Ocean Atlas 2005. The results clearly show high winter phytoplankton biomass (i.e. Chl-a) and its interannual variation in the region. The lower Chl-a concentrations (∼0.2 mg m −3 ) appeared often in winters (e.g. 1997 and 1998) when there was weaker wind speed, Ekman pumping velocity (EPV) and entrainment velocity (EV), and shallower MLD; conversely higher Chl-a (>0.5 mg m −3 ) appeared in winters (e.g. 2001 and 2003) when there was higher subsurface temperature, stronger wind speed, EPV and EV, and deeper MLD. It is thought that wind-induced upwelling (Ekman pumping) and entrainment mixing may be important factors leading to the high winter Chl-a, and the wind speed and wind stress curl were good indicators of higher Chl-a; the positive correlation between subsurface temperature (and MLD) and Chl-a represented more warm water intrusion from the Northwest Pacific Ocean into the region in the higher Chl-a years.

Studying the dynamic characteristics, species coexistence and biodiversity conservation mechanisms of subtropical forest ecosystems is important in the study of the quantitative characteristics and spatial gap distribution patterns. Based on census data from the 20 ha dynamics plot of the subtropical evergreen broad-leaved forest in Dinghushan in 2015, we analyzed the geometric characteristics and spatial distribution pattern of gaps in the plot by combining aerial image processing technology of unmanned aerial vehicles and GIS. Results show that the gap fraction is 13.72%, the gap density is 35.75 no./ha, and the average gap area is 38.37 m 2 . Results also show that: (1) The number of gaps in the area is negatively exponentially distributed with the increase of gap area, that is, the gap is small and the marginal effect is not significant. (2) The aver-age area of forest gaps in over-mature forest stands is larger than that in mature forests, while the mature forest is more likely to have more small gaps and fewer large gaps. (3) In different habitats, the distribution of gaps in each habitat shows the same pattern as that found in the whole plot. However, the difference in the valley is significant when compared with other habitats, and gap area and gap density in the valley are larger than other habitats. The ridge gap is also distinctive, and its gap density is lower than other habitats. (4) Gap area is significantly correlated with topographic factors. It was significantly negatively correlated with altitude and convexity, and had a significantly positive correlation with aspect and gradient. Based on these comparative analyses, a monitoring system of forest canopy changes and patterns can be established using drones, to dynamically monitor forest gaps and the undergrowth community.

Without the use of chemical oxidants and metal catalysts, an aqueous electrochemical synthesis of 5trifluoromethyluracil in batch and continuous flow was reported. The green and economically friendly approach employing commercially available CF 3 SO 2 Na as a CF 3 source and cheap (NH 4 ) 2 SO 4 as a supporting electrolyte afforded the 5trifluoromethyluracil in 10 g scale in batch electrolysis. The continuous flow-electrolysis technique was employed to further facilitate the scale-up synthesis of 5-trifluoromethyluracil.