Rip currents are narrow and concentrated seaward-directed flows and play an important role on coastal morphodynamics, mass transport and swimmer safety. As the intersecting wave field caused by wave reflection of coastal structures is not uniform alongshore, the flow characteristics and spatial distribution of rip currents are different from those of uniform intersecting waves on an open coast. The reflection of waves on cross-shore coastal structures will lead to longshore standing waves, and rip currents will occur in the area of standing wave nodes because of the small wave height, which is one of the generation mechanisms for rip currents. In this study, the characteristics of rip current systems near a coastal structure on a barred beach are given by a laboratory experiment. The influence of the longshore variation of wave height on the flow balance of each rip current unit is discussed. The results showed that the existence of structure drives a longshore current away from the structure and causes the water exchange between each rip current unit. The lateral currents between rip current units are found to make contributions to the rip current transport of each rip current unit and the contributions mainly depend on the relative position of the unit to the structure.

Jiaomen outlet is a typical river network bifurcated estuary and an important channel for flood discharge and sediment discharge of the Zhujiang River. The change of diversion ratio in bifurcated Jiaomen outlet is crucial to the geomorphological evolution, flood control and navigation safety of the Zhujiang River Delta. This study designed a series of flume experiments, and selected sensitivity analysis parameter which includes the water depth of bifurcated channel and bifurcated angle to explores the evolution of the flow division ratio of the river network type bifurcated estuary with the above factors. The dimension of the physical model is based on the recent geomorphic morphology of Jiaomen outlet. The result show that, on the basis of the stability of the section feature of the bifurcated channel, the flow division ratio of Fuzhou Channel depicts a good correlation with the flow velocity ratio between Humen and Jiaomen, and is less affected by the absolute flow velocity of the two outlets. Subsequently, the sensitivity experiment result indicate that the flow division ratio is negatively correlated with the water depth of Jiaomen South Channel and positively correlated with the water depth of Fuzhou Channel, and when the bifurcation angle is between 30° and 65°, the flow division ratio is negatively correlated with the bifurcation angle, but when the bifurcation angle is between 65° and 75°, the positive and negative correlation between the flow division ratio and the bifurcation angle changes around the velocity ratio V = 0.7. Then, the sensitivity of the increase or decrease of the flow division ratio to the above each variable can be obtained by quantifying the sensitivity experiment result. The research results can provide reference for artificial regulation project of Jiaomen outlet.

Using reanalysis sea surface data and in-situ high-resolution observations in spring, summer 2018, and summer 2019, this study analyzes the 3D structure and seasonal variation of temperature fronts in the shelf sea west of Guangdong. The results show that the sea surface temperature (SST) fronts reach the strongest intensity up to 0.049°C/km in winter, with the largest occurrence probability of 75% and coverage of 66 km. The SST fronts weaken in spring and summer, and almost disappear in autumn. The average offshore distance of the front is 50 km in winter and 23.1 km in summer. The in-situ observations show a strong thermal front in coastal areas shallower than 20 m in both spring and summer. The front gets weaker and closer to the coast in deeper layers and is associated with warm coastal water and cold shelf water. In shelf areas deeper than 20 m, the fronts in the subsurface layer are stronger than in the surface layer and shift shoreward in deeper layers. The correlation coefficient and information flow between the surface wind and frontal parameters reveal that the surface wind stress curl and along-coast wind are the most important factors affecting the surface thermal front. These thermal fronts also have interannual variations, with maximum intensity in La Niña years with negative PDO and minimum intensity in El Niño years with positive PDO.

Grain size, composition of elements and clay minerals, and AMS¹⁴C dating of samples of upmost 100 cm in Core CJ09-03 in the Southwest Arabian Sea were analysied, and provenance, the sedimentary evolution and the restricting factors in the study area since 45 ka BP were discussed. The composition of major elements and rare earth elements show that, the sediment in the study area has obvious terrigenous properties Graph of (La/Sm)_UCC-(Gd/Yb)_UCC and the composition of clay minerals show that the sources of the sediments in the study area are relatively complex, which include the Thar Desert, the Northeast Africa, the Southwest Asia and the Arabian Peninsula. Based on the index of δ¹⁵N from literatures, and indexs of chemical weathering index of illite, K/Al, 1−CaCO₃(%), the sedimentary evolution of the Southwest Arabian Sea since 45 ka BP can be divided into four stages: the Last Glacial period, the Last Glacial Maximum periond, the Deglaciation period and the Holocene period. The provenance in different stages are different, which is mainly influenced by the sea level changes and the strength of the Indian monsoon.

Multispectral images are greatly affected by factors such as clouds, fog, and solar flares, which makes it difficult to automatically extract high-precision green tides under complex weather conditions. Based on the multi-spectral images of my country’s HY-1C/D satellite CZI payload, using data mining technology to explore the difference in data distribution between green tide areas and non-green tide areas, we propose a high-precision and fully automatic green tide extraction method , which can be applied to HY-1C/D CZI sensor data. First of all, the thick cloud area is removed by preliminary extraction rules to achieve preliminary classification. Then, the correctly classified green tide samples and non-green tide samples were used as positive and negative samples respectively, and these samples were used as experimental data to train the decision tree model, and the automatic extraction rules of green tide were obtained according to the model. Finally, 5 strategies for correcting misclassifications were designed to achieve fully automatic extraction of green tides. In order to verify the effectiveness of the method, we collected 25 images of the green tide outbreak period in the Yellow Sea in 2021 for automatic detection experiments, and compared the experimental results with traditional index methods (NDVI, VB-FAH) and deep learning methods (ResNet50, U-Net). The results showed that the method outperformed other methods in terms of accuracy, Kappa coefficient, F1-Score, and MIoU. The accuracy of green tide extraction was higher in areas with thick clouds, thin clouds, cloudless clouds, cloud spots, and flares.

Using Tropical Rainfall Measurement Mission 3B42 rainfall data, this study tracks pathways of Tropical Intraseasonal Oscillations (MJO) from a Lagrange perspective, analyses their distribution in the Maritime Continent (100°−120°E) and further discusses its mechanism. Identifying a raining area with above 12 mm in 24 hours precipitation as a MJO convective region and using its centroid as MJO convective center, pathways of MJO are tracked and a set of pathways is given. Because eastward propagating MJO events happen mostly in boreal winter, this study focuses on the distribution of pathways of MJO events in boreal winter. The results show that if measured by precipitation MJO moves through the Maritime Continent mostly near the equator (5°S−5°N), which is different from past research results that MJO detours to the south of the Maritime Continent measured by using outgoing long wave radiation (OLR) as a index. Besides, the conclusion that the precipitation associated with MJO moves through the Maritime Continent mostly near the equator is independent of background climate patterns like ENSO or IOD. The analysis of the mechanism shows that pathways of the precipitation associated with MJO through the Maritime Continent are mostly regulated by strong latent heat flux anomalies and are inconsistent with regions with warm sea surface temperature anomalies, which leads to different pathways of MJO moving through the Maritime Continent from different perspectives of precipitation and OLR.

Rossby normal mode as a solution of the boundary problem is a key part of the dynamics in the South China Sea. With the usage of multiscale window transform, a recently developed decomposition tool for multiscale processes, mesoscale-eddy fields analogous to Rossby normal modes are separated from the satellite observation of the South China Sea. The eddies are dominated by a group with lifetime of 3 months, which belongs to an oscillating mode with period of 6 months and wavelength of 250 km. To explore the external influence on this mode, we apply an information flow-based causality analysis that has been rigorously established from first principles in physics. It is found that both the Kuroshio intrusion and monsoon, believed to be two primary forcings of the South China Sea circulations, are causal to the Rossby normal mode within one period. Specifically, the Kuroshio intrusion mainly affects the 1/2π and 3/2π phases, while the monsoon the 3/4π phase. Further analysis reveals that the transition between penetration and leaping of the Kuroshio at the Luzon Strait is key to the mode development. Under this circumstance, the leaking and looping branches are almost of equal intensity, facilitating the generation of cyclonic and anticyclonic eddies west of the Luzon Strait, and hence the Rossby normal mode. The monsoon over the South China Sea, on the other hand, shows the greatest influence at its mature phases. The Gulf of Thailand is a key region for the monsoon to affect the Rossby normal mode in the South China Sea, indicating that local forcing plays an important role in exciting a global mode.

The shoreline change is the most direct factor in studying landform erosion and deposition. The Huanghe River Delta is the world’s fastest-growing delta, and understanding its coastline changes and evolution trends is crucial to regional ecological environment protection, marine resource development, and infrastructure construction. In this study, we combined modified normalized difference water index (MNDWI) and multi-year water frequency index (MWFI) to analyze water quality in typical years from 1976 to 2021, based on previous research. We visually interpreted 207 remote sensing images to obtain an annual coastline that makes the obtained coastline more scientific and representative. We then analyzed the temporal and spatial evolution and stability characteristics of the coastline through quantitative calculations to explore the Qingshuigou sub-delta coastline of the Yellow River’s evolution mechanism since 1976. Our main findings are as follows: (1) In general, the evolution of Qingshuigou sub-delta coastline shows a trend of rapid sedimentation towards the sea, followed by fluctuations and stability. We can divide it into “rapid development” and “slow development,” with the “dynamic equilibrium” in between, taking 1996 and 2002 as nodes. (2) Over the past 45 years, the stability of the coastline in the study area has continued to increase. The coastline of the section of the coastline and the abandoned estuary section of Qingshuigou is relatively active, and its coastline stability index is generally lower than 0.5. (3) The migration of the sedimentation and erosion center of the land delta corresponds to the estuary location’s change, especially the migration of the sedimentation center, which has a positive relationship in the longitude direction between the change of the estuary position and the position of the estuary, R² = 0.690 4. (4) The Huanghe River’s sediment reduction into the sea, the relocation of the estuary position, and human activities have a significant impact on the delta coastline’s development and evolution. In the long run, the Huanghe River’s silt into the sea is still continuously reducing, and the future of the delta is still facing the threat of erosion.

Airborne Laser Bathymetry (ALB) as an established surveying procedure is certainly operated in blue-green region (532 nm) for penetrating the water column to collect depth. Alongside geometric information accepted widely, ALB typically record the radiometric properties (backscattering intensity) about sensed targets and assist with accurate strips registration, fine ground (sediment) cover classification, and advanced geometric modelling. However, due to the design limitations of Automatic Gain Control (AGC), there is a delay in gain value adjustment, particularly prominent in island and coastal areas with more high-return and low-return targets such as exposed rocks and water, which throws the issue of intensity compensation abnormality into stark relief. In response to this issue, a local weighted intensity correction method based on bidirectional movement is designed. Firstly, effective intensity is extracted by index sharing and elevation information. Then, the emission angles are used to divide the scan line and serve as the judgment unit, and the Kolmogorov-Smirnov test is used to identify the abnormal area. Finally, intensity correction is performed by joint weighting of adjacent scan lines and neighborhood intensity, where the joint weighting can ensure the intensity details while eliminating the deviation from the neighborhood intensity. In addition, a unique bidirectional moving strategy is introduced to weaken the decline of strength correction accuracy caused by insufficient correction accumulation. Experiments have illustrated that this approach can effectively solve the AGC compensation anomaly problem, and compared to the pre-correction, the average absolute percentage error of the corrected intensity data decreased by about 0.27, the root mean square error decreased by about 693, and the intensity deviation of the abnormal area was controlled within 26 DN (Digital Number), thus obtaining a high-quality intensity image.

fruitless (fru) gene plays an important role in courtship, mating behavior and reproductive development of insectsand crustaceans. Artemia is not only the crucial live food in fish and crustacean larviculture, but also an ideal experimental organism for biological study. In this experiment, the open reading frame (ORF) of fru gene was obtained from the transcriptome of Artemia franciscana and analyzed bioinformatically. qPCR was used to study the expression characteristics of this gene at different stages of gonad development in the Artemia, and its function was explored by RNAi microinjection. Bioinformatics analysis showed that the ORF length of fru gene was 1 215 bp, which contains 404 amino acids, while its molecular weight and isoelectric point were 45.19 kDa and 5.28, and it was an acidic hydrophilic protein with no signal peptide or transmembrane structure; structural domain prediction showed that there are two structural domains of fru, BTB_POZ and HTH. The secondary structure is dominated by α-helix and irregular coil, and the tertiary structure corresponds to it. The qPCR results showed that the expression of fru gene showed a significant increase in late embryos stage, and its expression was significantly higher than that of early oocyte, later oocyte and early embryo stages in the ovary (P < 0.01); while the expression of fru gene also increased in immature stage of the testis, and its expression was significantly higher than that of early, middle and late maturation stages (P < 0.01). After RNA interference, we found that there was a significant decrease in the expression of the fru gene (P < 0.01), and all the offspring produced were cysts. This suggests that the fru gene has an important effect on reproduction and development of A. franciscana, and may be a key factor influencing the reproductive mode of Artemia. Through this study, we obtained important information about the role of fru gene in the reproductive development of Artemia and their related molecular mechanisms, which can help us better understand this important biological process.