scholarly journals Satellite Observation of the Marine Light-Fishing and Its Dynamics in the South China Sea

2021 ◽  
Vol 9 (12) ◽  
pp. 1394
Author(s):  
Huiting Li ◽  
Yongxue Liu ◽  
Chao Sun ◽  
Yanzhu Dong ◽  
Siyu Zhang
Keyword(s):  
South China Sea ◽  
South China ◽  
Large Scale ◽  
The South China Sea ◽  
Identification System ◽  
The South ◽  
Fishing Activity ◽  
Fishery Resource ◽  
China Sea ◽  
Spatio Temporal

The South China Sea (SCS) is one of the most important fishery resource bases in the world. Marine fisheries, as a crucial component of regional food security and national revenue, raise wide concern about marine ecology, social-economic and political consequences at regional, national and local scales. The large-scale dynamic detection and analysis of fishing activity in the SCS is still unclear because of the accessibility of in-site data, finite automatic identification system (AIS) usage, complex geopolitics and poor additional data coverage. Nighttime light imagery (NTL) derived from low light imaging sensors and the popularity of light fishing in the SCS offers a unique way to unveil fishing activities and its dynamics. In this study, we proposed a set of algorithms for automatic detection of nighttime fishing activity and provided the first large-scale dynamic analysis of nighttime fishing activity in the SCS using monthly Visible Infrared Imaging Radiometer Suite (VIIRS) images between 2012 and 2019. The proposed method effectively minimized the spatio-temporal fluctuations in radiance values of background and their implications to ship detection by integrating high radiance gradient detection and local adaptive thresholding. Further, nighttime fishing activity trajectories were decomposed into trend and seasonal components by using Hilbert-Huang transformation (HHT) to accurately access general trends and the seasonality of nighttime fishing activity in the SCS. The typical subregions analysis, environmental driver analysis, correlation coefficient analysis and hot spot analysis were integrated to characterize the nighttime fishing activity. It appears that the nighttime fishing activity in the SCS exhibited spatio-temporal variability and heterogeneity and was shaped by policy and natural factors such as holidays, annual Chinese fishery moratoria in the Chinese Exclusive Economic Zone (EEZ) and seasonal tropical storm activity.

scholarly journals Analysis of Severe Droughts in Taiwan and its Related Atmospheric and Oceanic Environments

Atmosphere ◽  
2019 ◽  
Vol 10 (3) ◽  
pp. 159 ◽  
Author(s):  
Chih-wen Hung ◽  
Ming-Fu Shih
Keyword(s):  
South China Sea ◽  
South China ◽  
Large Scale ◽  
Drought Index ◽  
The South China Sea ◽  
Severe Drought ◽  
The South ◽  
China Sea ◽  
Dry Conditions ◽  
Oceanic Environments

Drought is one of the important issues in climate studies. A drought index, Taiwan Meteorological Drought index (TMD index), was previously proposed and is applied here to identify historical severe droughts in Taiwan in order to clarify the corresponding large-scale backgrounds as a potential alert to the society in future. Through the TMD index, several historical severe drought cases in Taiwan are detected and characterized by significant seasonal variability in the annual cycle. Composites for large-scale atmospheric and oceanic environments over different periods within the dry season are conducted. From October to December, the colder sea surface temperature (SST) pattern of Pacific Meridional Mode (PMM) and the PMM-induced local anomalous anticyclones over the South China Sea are both in charge of the extremely dry conditions in Taiwan. From January to February, cold SST in the South China Sea and its adjacent oceans dominates local atmospheric conditions above these regions and creates an unfavorable environment for convection systems. From March to May, a massive anomalous anticyclonic circulation centering beside Alaska and extending its properties to East Asia and Taiwan generates a descending environment and in turn suppresses convection systems to develop. Therefore, the extremely dry conditions under this system are expected.

Genetic diversity and large-scale connectivity of the scleractinian coral Porites lutea in the South China Sea

Coral Reefs ◽  
2018 ◽  
Vol 37 (4) ◽  
pp. 1259-1271 ◽  
Author(s):  
Wen Huang ◽  
Ming Li ◽  
Kefu Yu ◽  
Yinghui Wang ◽  
Jingjing Li ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
South China Sea ◽  
South China ◽  
Scleractinian Coral ◽  
Large Scale ◽  
The South China Sea ◽  
The South ◽  
Porites Lutea ◽  
China Sea

Variabilities of sea level components over the South China Sea based on multi-sensor satellite observations

2020 ◽  
Author(s):  
Jin Sha ◽  
Xiaoming Li
Keyword(s):  
South China Sea ◽  
Sea Level ◽  
South China ◽  
Large Scale ◽  
Seawater Temperature ◽  
Warm Pool ◽  
The South China Sea ◽  
The South ◽  
China Sea ◽  
Relative Contribution

<p>Seawater temperature and salinity are the two key parameters related to the regional sea level variability. In this study, the spatial-temporal variabilities of the thermal and halo steric height over the South China Sea (SCS) are investigated using multi-senor satellite remote sensing products, in-situ measurements and reanalysis. The sea surface temperature and salinity products are used to reconstruct the upper layer sea level components, and the relative contribution of these two components are quantified. It is revealed that the thermal and halo components vary in an out-of-phase pattern, and dominant different regions within SCS. Variabilities of the sea level components on different timescale are further analyzed, and the linkage with large scale processes, such as the indo-pacific warm pool, will be presented.</p>

Accurate Quantification of Seamount Volcanism in Abyssal  Sediments Using Gaussian Process Regression

2021 ◽  
Author(s):  
Yanghui Zhao ◽  
Bryan Riel
Keyword(s):  
Pacific Ocean ◽  
South China Sea ◽  
Gaussian Process ◽  
South China ◽  
Large Scale ◽  
Semimajor Axis ◽  
Gaussian Process Regression ◽  
The South China Sea ◽  
The South ◽  
China Sea

<p>Seamounts are isolated, underwater volcanoes with more than 100 m in relief. This kind of volcanism arises from the lithosphere or asthenosphere through fractional melt and is a direct manifestation of the tectonic-magmatic activity of the interior of the earth. While previous studies have quantified the global distribution of seamounts by their physical properties (e.g., height, semimajor axis, angle, etc.), these studies usually (1) assume an elliptical cone to model seamount shape, and (2) neglect the sediment coverage on the seamount, which results in significant uncertainties when comparing properties of seamounts near the continents covered with thick sediments to those in the open ocean covered with thin sediments.</p><p>We apply a large-scale Gaussian Process regression to recover the seamount topography covered by sediments for an accurate distribution of volcanism in the South China Sea basin (with an average thickness of 1.5 km sediments) and the entire Pacific Ocean (with < 300 m thick sediments). Specifically, we first use Tophat filtering to isolate short-spatial-wavelength seamount topography above long-wavelength seafloor. Subsequently, we apply Gaussian Process regression to learn the seamount structure above the seafloor in order to extrapolate the structure beneath the sediment. Lastly, we compute the seamount volume above the sedimentary basement (i.e., top boundary of the oceanic crust) and compare it to the volume above the seafloor. Our results show that for the South China Sea, there is a significant increase in estimated seamount volume above the basement as compared to above the seafloor. For the Pacific Ocean, due to the thin sediment coverage, we observe negligible differences between the two volume estimates. Thus, analysis of seamount properties in marginal basins in the West Pacific with thick sediment coverage can lead to significant underestimation of volcanism intensity if sub-seafloor topography is not accounted for. For these marginal basins, without massive hotspots or apparent evidence of mantle plumes, normal plate tectonic processes are likely responsible for the intensive oceanic volcanism.</p>

scholarly journals Evaluation of the ability of the Chinese stalagmite δ<sup>18</sup>O to record the variation in atmospheric circulation during the second half of the 20th century

2014 ◽  
Vol 10 (3) ◽  
pp. 975-985 ◽  
Author(s):  
S. Nan ◽  
M. Tan ◽  
P. Zhao
Keyword(s):  
Water Vapor ◽  
South China Sea ◽  
South China ◽  
Bay Of Bengal ◽  
North Pacific ◽  
Western North Pacific ◽  
Large Scale ◽  
The South China Sea ◽  
The South ◽  
China Sea

Abstract. The Chinese stalagmite δ18O (δ18Ocs) has provoked debate worldwide over the past few years due to its lack of quantitative calibration, leading us to questions of whether δ18Ocs records a local or large-scale signal and whether δ18Ocs records the signal of a single remote water vapor source or multiple water vapor sources. In this study, we observe all of the δ18Ocs trends within the instrumental period to verify whether they possess a common trend, which could be used as a basis to determine whether the trends reflect the large-scale signal together or whether each trend reflects the local signal. The results show that most of the δ18Ocs experienced a linear increase from 1960 to 1994, which may indicate that the δ18Ocs could record a trend occurring in large-scale atmosphere circulations. We then quantitatively describe the proportion of water vapor transport (WVT) from different source regions. Using the NCEP/NCAR (National Centers for Environmental Protection/National Center for Atmospheric Research) reanalysis data from 1960 to 1994, the ratios of the intensities of three WVTs from the Bay of Bengal, the South China Sea, and the western North Pacific during the summer are calculated. We define RSCS/BOB as the ratio of the WVT intensities from the South China Sea to those from the Bay of Bengal, RWNP/BOB as the ratio of the WVT intensities from the western North Pacific to those from the Bay of Bengal, and RWNP/SCS as the ratio of the WVT intensities from the western North Pacific to those from the South China Sea. The significant decadal increase occurs in the time series of RWNP/BOB and RWNP/SCS, most likely resulting from the strengthening of the WVT from the western North Pacific in the late 1970s due to the western Pacific subtropical high that extended westward. Further analysis indicates that when the equatorial central and eastern Pacific is in the El Niño phase, the sea surface temperature (SST) in the tropical Indian Ocean, the Bay of Bengal, and the South China Sea is high, and the SST at the middle latitudes in the North Pacific is low, then the RWNP/BOB and RWNP/SCS values tend to be high. After the late 1970s, the equatorial central and eastern Pacific have often been in the El Niño phase. Therefore, we confirm that the δ18Ocs primarily records the variation in atmospheric circulation during the second half of the 20th century.

scholarly journals Underwater Topography Detection and Analysis of the Qilianyu Islands in the South China Sea Based on GF-3 SAR Images

2020 ◽  
Vol 13 (1) ◽  
pp. 76
Author(s):  
Longyu Huang ◽  
Jungang Yang ◽  
Junmin Meng ◽  
Jie Zhang
Keyword(s):  
South China Sea ◽  
South China ◽  
Large Scale ◽  
The South China Sea ◽  
Detection Methods ◽  
Shallow Sea ◽  
The South ◽  
Sar Images ◽  
China Sea ◽  
Underwater Topography

Shallow sea underwater topography plays an important role in the development of islands and reefs. The Qilianyu Islands, located in Xisha, South China Sea, are a key area for the development and utilization of the South China Sea. Compared with traditional underwater topography detection methods, synthetic aperture radar (SAR) has the advantages of low cost, short time consumption, and the large-scale detection of shallow water topography. The GF-3 satellite is the first SAR satellite launched by China, and its ability to probe shallow sea topography has never been assessed. To detect the underwater topography of the Qilianyu Islands and test the application of GF-3 SAR data in shallow sea underwater topography detection, this paper implements the SAR shallow sea underwater topography detection model, the tidal information corresponding to the imaging time of the SAR image, and six GF-3 SAR images to detect the underwater topography of the Qilianyu island and reefs. The detection results have been analyzed from different imaging times, different water depths and different polarization modes, and the first four SAR images show promising detection results. The average absolute error (MAE) and average relative error (MRE) of the results are 1.5 m and 14.33%, respectively, which demonstrates that GF-3 SAR images have an impressive performance in underwater topography detection of South China Sea island reefs.

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