Three oceanographic surveys were conducted in the coastal waters off central Fujian Province (24°55'?25°13'N, 119°11'?119°32'E) during December 2009, and April and August 2010. The species composition, eco-groups, dominant species and diversity index of the zooplankton in this area were investigated using the survey data, and impact of seasonal variation of water masses on these ecological characters was discussed. A total of 96 species were identified, including 24 in winter, 48 in spring and 72 in summer. From winter to summer, the number of subtropical water species increased gradually and the warm temperate water species decreased gradually. The number of species of offshore species increased gradually and the nearshore species decreased gradually. The dominant species also had obvious seasonal changes. There were three dominant species in winter, three dominant species in spring, and seven dominant species in summer. In winter and spring, dominant species were mainly warm temperate water species, like Calanus sinicus, Paracalanus parvus and Corycaeus affinis. In summer, dominant species were mainly subtropical species, such as Eucalanus subcrassus, Lucifer hanseni and Sagitta ferox. The species diversity of zooplankton was the highest in summer and the lowest in spring. The seasonal changes of these ecological characters were closely related to the seasonal variation of water masses in the Taiwan Strait. The China Coastal Water with low temperature and low salinity and the Strait Warm Current Water with high temperature and high salinity were two main water masses in the Taiwan Strait. The dynamics of these two water masses and their interaction led to the seasonal variations of temperature and salinity of the investigated waters, and further influenced the ecological characters of the zooplankton.

We investigated the metabolic states of plankton communities in the Taiwan Strait and the northern South China Sea by measuring gross primary productivity (GPP), community respiration (CR) and bacterial production (BP) at 16 stations in these areas. GPP averaged 106.6 mmol O₂ m^-2·d^-1 with a standard error of 7.51 mmol O₂ m^-2·d^-1. CR averaged 131.1 mmol O₂ m^-2·d^-1 with a standard error of 5.95 mmol O₂ m^-2·d^-1. Net community productivity varied from -179.0 to 377.6 mmol O₂ m^-2·d^-1with a median value of -40.4 mmol O₂ m^-2·d^-1. Our results showed that the area affected by Qiongdong upwelling was autotrophic. In the areas affected by the Pearl River discharge, the plankton community was also autotrophic. By contrast, other areas including the Taiwan Strait nearshore waters and the South China Sea open waters were heterotrophic. Therefore, community respiration was not entirely determined by the local primary productivity in the study areas. Our results suggest that the spatial transport of organic carbon plays an important role in determining the metabolic state of the plankton community.

In this study, we conducted barotropic detiding of the summertime shipboard ADCP (SADCP) dataset in the southern Taiwan Strait (TWS) from June to September during 2004-2013, employing the widely used spatiotemporal fitting by the least squares method (STF-LSM). The results show that the mean flow derived from STF-LSM and that derived from averaged vectors by dataset gridding both flowed northeastward. Moreover, these two mean flows had similar spatial distribution patterns of strong and weak flows, but their maximum velocities were slightly different: 0.46 and 0.34 m·s^-1 for the former and the latter, respectively. Besides, the strong currents (about 0.3 m·s^-1) were characterized by the narrow mainstream confined around the depth of 30 m off the sea at Dongshan and Longhai as well as the Taiwan Bank (TWB) with drastic topographic change, whereas the weak currents (less than 0.1 m·s^-1) were mainly distributed in the central TWB. Estimation of the volume transport based on the above mentioned mean flows revealed similar results, up to (0.71±0.24) ×10⁶ m³·s^-1. The strong M₂ tidal currents derived from SADCP were near the TWB and extended to the offshore of Dongshan, with a maximum M₂ current amplitude as large as ~0.64 m·s^-1, which was located in the TWB. The cotidal chart for M₂ currents demonstrates the characteristics of progressive wave, which was delayed successively from the southwest to the northeast along the direction of the tidal wave as the wave propagated (about 2 h). Besides, there was a boundary line along northwestward to southeastward direction with ellipticity equal to zero at the offshore of Dongshan. The M₂ currents rotated counterclockwise in the southern region of this boundary line and clockwise in the northern region.

In order to study the trend, shape and tectonic setting of the Changle—Nan’ao fault and Binhai (littoral) fault, the Earthquake Administration of Fujian Province expanded seismic sounding into the southwest Taiwan Strait using large volume air-gun arrays and Ocean Bottom Seismometers (OBSs), which formed a relatively complete observation system in conjunction with onshore explosions and portable seismometers. In this paper, we introduce in detail the six profiles collected between 2013 and 2015, including the observation system, acquisition parameters, and data preprocessing. Due to rational choice of shooting parameters and receiver position, a variety of seismic phases, including Pg, PmP, Pn, Sg, and SmS, can be clearly identified in most common receiver gathers of the portable seismometers and OBSs. By multiple shooting the air-gun array at fixed site, we obtained several stacked common shot gathers, of which the signal-to-noise ratios were as high as those acquisition with ton-level explosions. Compared with the data recorded by onshore seismometers, the data recorded by OBSs have a relative low signal-to-noise ratio, which probably means that the seabed in this area has a higher absorption. In light of low velocity and acute variety of deposition thickness in the southwest Taiwan Strait, we transfer the travel times, which were picked up on the common receiver gathers to shot domain, in order to avoid the errors of sediment model, which resulted in pseudo deep structures.

Time service system is very important for inverting velocity structure of underground media via traveltime tomography. Due to the lack of GPS time access, the time errors (including time service error and time keeping errors) of the Ocean Bottom Seismometer (OBS) mainly come from the inaccuracy of internal quartz crystal oscillator, affected by external environment changes and switching and other factors. The long term practice finds that, some Chinese-made OBSs have large time deviation when recording air gun signals and natural seismic signals. In this study, 53 Chinese OBS records obtained from the crustal structure sea-land exploration experiments in Fujian and Taiwan straits in 2019 were used for time service system correction. To obtain OBS time service error, the consistency test of uninterrupted acquisition before going to the sea, as well as the sloshing caused by the transport ship during transportation, are used to correct the timing error by cross-correlation. For the time keeping error, the deviation between the calculated actual sampling frequency and the theoretical sampling frequency is corrected. The time service system is corrected comprehensively by using naturally occurred earthquakes. It has been demonstrated that the corrected OBS data can improve the accuracy of time record and reduce the error of seismic phase identification and traveltime picking. At the same time, the results of this paper provide important reference for the widespread use of domestic OBS and standardization of domestic OBS data acquisition process.

Using the measured wave data in 2017 in the central Taiwan Strait, we analyze the basic features of wave, including spectral features, and their relationships with wind. The regression relationship among important characteristic wave parameters and the appropriate wave spectrum form are also investigated. The results are as follows. 1) The most frequently occurring wave direction is NE, and the strong wave direction is NNE. The monthly average significant wave height varies from 0.87 to 2.98 m. The wave height is the smallest in July and the highest in December. The wave period has similar inter-month change to wave height. 2) Mixed waves dominated by wind wave and single-peaked spectra make up the majority. The wave height is positively correlated with the wind speed as a whole. Strong wave is mainly generated by typhoons and strong northeast monsoon. 3) There are good linear correlations between mean wave period and most characteristic period parameters. The significant wave height and its corresponding wave period are strongly linearly related in the directions of NNE and NE. 4) Compared with the Jonswap spectrum, the Code spectrum 1 is more reasonable for the fitting of sea wave spectrum in this area. A spectrum in the form of Code spectrum 1 is given, which is fitted by significant wave height and spectral peak period. These results can provide references for ocean engineering design and numerical simulation of wave.

On the ocean bottom seismometer (OBS) wide-angle seismic record section, multiple signals with high energy and good continuity can often be detected. As same as the first arrival phases, multiple phases also can be real reflections of subsurface interfaces, they are generated by the same source signal. However, in the conventional OBS data processing, multiple signs are often deleted as invalid signals, just a few studies are concerned with their properties and applications. By processing the OBS data acquired from Line HXN01 in the southern Taiwan Strait, the secondary phases are identified and picked on eight seismic recording sections. Analysis of the measured data from OBS0106 station reveals that the waveform characteristics and particle motion trajectory of these two phases are very similar, the amplitude of the secondary Ps phases is greater than that of the first arrival phases. Then we determined that the secondary reflecting interface corresponds to the secondary Ps phases by Rayinvr ray tracing simulation. The fitting results of travel time shows that after adding the secondary phases, the ray-coverage density of the shallow sedimentary layer under the station is significantly increased, and the ray-coverage area is also significantly increased, which provides more information for the inversion of sedimentary structure. In addition, the inversion test before and after the addition of the secondary Ps phase was performed on the crustal structure of the theoretical model, and it was found that after the addition of the secondary Ps phase data, the interface depth error of the sedimentary layer improved significantly.

A severe sea fog occurred in the West Side of the Taiwan Strait from 8PM April 19, 2019 to 7AM April 26, 2019. Based on the coastline automatic weather station, the generation and dissipation law of sea fog was studied. Sea fog occurred from 2AM to 8AM, and the closer the generation time is to the early morning, the shorter the duration. Sea fog is mostly generated locally, some stations are formed for the purpose of propagation, and there is little correlation between north and south sea fog. The visibility decreased rapidly before the sea fog occurred and increased rapidly after the fog dissipated. When sea fog formatted LST-T (LST, land surface temperature; T, temperature) between −1.7~2℃, LST-Td (dewpoint temperature, Td) between 1~2.7℃, T-Td between 0.2~1℃. During the sea fog maintenance period, RH (relative humility) ≥ 96%. Under the background of abundant water vapor, the formation and development of sea fog are closely related to wind speed and weakly related to wind direction. Combined with Himawari-8 satellite image and ERA5 reanalysis data, the characteristics of this sea fog process was analyzed. Satellite images show the extent of the process and the characteristics of occurrence and dissipation. Circulation analysis indicated that this sea fog event occurred under the control of weak southwest flow at 500 hPa, while at 850 hPa and 925 hPa Fujian was affected by southwest airflow, bringing abundant water vapor. According to the analysis of the sea and air conditions, the type of sea fog was advection fog.

This paper investigates a five-day fog process on the west coast of the Taiwan Strait, utilizing observational data from an automatic station, microwave radiometer, and wind profile radar in Xiang'an, Xiamen, from March 30 to April 3, 2021. The boundary layer characteristics of the fog are analyzed. Our findings reveal that: (1) Mild precipitation during the fog's development enhanced its intensity; (2) The presence of an inversion layer was crucial for fog maintenance, with its weakening leading to fog dissipation or reduction. Two distinct scenarios were observed in the inversion layer thickness decrease: (i) the inversion layer top remained relatively stable while its bottom rose, and (ii) both the top and bottom of the inversion layer ascended. These variations are associated with temperature changes near the inversion layer top. The first scenario weakened inversion intensity, whereas the second caused complete inversion layer dissipation and subsequent fog dispersal. Additionally, southwest winds transported warm and moist air, supplying the necessary water vapor for fog formation. When surface water vapor was abundant, strong updrafts lifted the fog to form stratiform clouds, with accumulated water vapor eventually leading to precipitation. On one hand, precipitation during the fog process caused ground evaporation, intensifying the fog or paving the way for subsequent precipitation. On the other hand, it consumes atmospheric water vapor, accelerating fog dissipation. Notably, three significant jumps in liquid water content were observed above the inversion layer top during the fog process, each followed by precipitation.