Mesoscale eddies play a central role in the poleward oceanic heat flux in the Southern Ocean.Previous studies have documented changes in the location of temperature fronts in the Southern Ocean,but little attention ha...Mesoscale eddies play a central role in the poleward oceanic heat flux in the Southern Ocean.Previous studies have documented changes in the location of temperature fronts in the Southern Ocean,but little attention has been paid to changes in the genesis locations of mesoscale eddies.Here,we provide evidence from three decades of satellite altimetry observations for the heterogeneity of the poleward shift of mesoscale activities,with the largest trend of~0.23°±0.05°(10 yr)^(-1) over the Atlantic sector and a moderate trend of~0.1°±0.03°(10 yr)^(-1) over the Indian sector,but no significant trend in the Pacific sector.The poleward shift of mesoscale eddies is associated with a southward shift of the local westerly winds while being constrained by the major topographies.As the poleward shift of westerly winds is projected to persist,the poleward oceanic heat flux from mesoscale eddies may influence future ice melt.展开更多
Mesoscale eddies play a pivotal role in deciphering the intricacies of ocean dynamics and the transport of heat,salt,and nutrients.Accurate representation of these eddies in ocean models is essential for improving mod...Mesoscale eddies play a pivotal role in deciphering the intricacies of ocean dynamics and the transport of heat,salt,and nutrients.Accurate representation of these eddies in ocean models is essential for improving model predictions.In this study,we propose a convolutional neural network(CNN)that combines data-driven techniques with physical principles to develop a robust and interpretable parameterization scheme for mesoscale eddies in ocean modeling.We use a highresolution reanalysis dataset to extract subgrid eddy momentum and then applying machine learning algorithms to identify patterns and correlations.To ensure physical consistency,we have introduced conservation of momentum constraints in our CNN parameterization scheme through soft and hard constraints.The interpretability analysis illustrate that the pre-trained CNN parameterization shows promising results in accurately solving the resolved mean velocity and effectively capturing the representation of unresolved subgrid turbulence processes.Furthermore,to validate the CNN parameterization scheme offline,we conduct simulations using the Massachusetts Institute of Technology general circulation model(MITgcm)ocean model.A series of experiments is conducted to compare the performance of the model with the CNN parameterization scheme and high-resolution simulations.The offline validation demonstrates the effectiveness of the CNN parameterization scheme in improving the representation of mesoscale eddies in the MITgcm ocean model.Incorporating the CNN parameterization scheme leads to better agreement with high-resolution simulations and a more accurate representation of the kinetic energy spectra.展开更多
The Aleutian Low(AL)is a dominant feature of the mean circulation in the North Pacific during the winter season.The background stationary wave,air-sea interaction,and transient eddies over the North Pacific exert dist...The Aleutian Low(AL)is a dominant feature of the mean circulation in the North Pacific during the winter season.The background stationary wave,air-sea interaction,and transient eddies over the North Pacific exert distinct impacts on the interannual variations of the AL intensity and position.In this study,we adopt the quasi-geostrophic geopotential tendency equation to investigate the roles of various physical processes in the maintenance and interannual variations of this system.The results show that absolute vorticity advection plays the most important role in the formation and maintenance of AL intensity,while high-frequency transient eddies contribute most to the meridional and zonal shifts of the AL.The high-frequency transient eddy vorticity forcing affects the AL through the barotropic energy conversion process,and,in turn,the AL enhances the high-frequency transient eddies through the baroclinic energy conversion process,forming a positive feedback.The associated high-frequency eddy kinetic energy anomalies exhibit an eastward movement toward the east coast of North America in the years of an intensified AL,which explains why a strengthened AL is often accompanied by an eastward movement.Furthermore,the energy conversion terms of high-frequency transient eddies are mostly located over the extratropical eastern North Pacific,leading to asymmetric features in the zonal movement of the AL.展开更多
Mesoscale eddies are widespread in the global ocean,significantly influencing the physical,chemical,and biological structures of water column.Based on the CTD data and suspended particulate matter(SPM)data collected a...Mesoscale eddies are widespread in the global ocean,significantly influencing the physical,chemical,and biological structures of water column.Based on the CTD data and suspended particulate matter(SPM)data collected at 36 hydrographic stations during a field cruise in southern Mozambique Channel,combined with satellite altimeter observations,we identified a series of mesoscale eddies traversing the Mozambique Channel.Our hydrographic measurements,coupled with in situ chlorophyll fluorescence data,reveal that these eddies significantly influence thermohaline structure and chlorophyll distribution,which in turn affects primary productivity and SPM concentrations in the upper ocean.The cyclonic eddies facilitate the upwelling of cold subsurface water,leading to a shallowing of the pycnocline and the creation of a low-temperature anomaly with variable salinity anomalies at different depths.Conversely,anticyclonic eddies submerge warm surface water,deepening the pycnocline,and resulting in a high-temperature anomaly accompanied by distinct salinity patterns.Significantly,a coastal anticyclonic eddy was observed to intercept terrestrial material from the Delagoa Bight,redirecting it west of 36°E.This study presents unique and quasi-synchronous CTD datasets capturing mesoscale eddy impacts,and provided valuable insights into SPM variability within the often-neglected southern Mozambique Channel.展开更多
A cyclonic eddy(CE)is often accompanied by an anticyclonic eddy(AE)to the east of Vietnam in the South China Sea(SCS)in summer,but the dipole lifetime and the intrinsic connection between CE and AE are still understud...A cyclonic eddy(CE)is often accompanied by an anticyclonic eddy(AE)to the east of Vietnam in the South China Sea(SCS)in summer,but the dipole lifetime and the intrinsic connection between CE and AE are still understudied.Data from 1993-2021 reveal that the dipole lifetime are significantly correlated with the wind direction and speed in the dipole region.Higher wind speed was found to be associated with more eastward wind direction and tends to longer dipole lifetime.The wind stress work(WW)on the eddy is much stronger in the eastward jet region than in the CE and AE regions.Comparing of results of 12 higher and lower wind speed years reveal that higher wind can produce stronger mean current,WW and barotropic instability(T4)that further enhances eddy kinetic energy(EKE)and dipole lifetime.The correlations between the dipole CE and AE characteristics are insignificant on interannual scales and mostly insignificant on seasonal scales in the surface layer but significant on seasonal scales in the subsurface layers.In addition,the daily mean vertical profiles(0-500 m)of EKE,vorticity and total deformation rate(TD)between CE and AE remain significantly correlated throughout the dipole’s lifetime,which can be a useful criterion for judging if two eddies are a dipole.展开更多
Anticyclonic eddies are widely distributed off Peru,producing obvious effects on climate-environmentsensitive jumbo flying squid Dosidicus gigas.However,how the habitat of D.gigas changes within anticyclonic eddies du...Anticyclonic eddies are widely distributed off Peru,producing obvious effects on climate-environmentsensitive jumbo flying squid Dosidicus gigas.However,how the habitat of D.gigas changes within anticyclonic eddies during El Ni?o events is still unknown.Therefore,this study constructed a habitat model with different weights and screened the optimal performance model using fishery data from September to December during 2015 to 2019,as well as vertical water temperature data(sea surface temperature and 50 m water depth temperature)and surface chlorophyll concentration data(Chl-a).Then,combined with the eddy tracking dataset,the differences in the variation of resource abundance and habitat of D.gigas within the anticyclonic eddy between the 2015 El Ni?o year and the 2019 normal year were further comparatively analyzed based on the optimal habitat model.Compared with the normal year of 2019,the 2015 El Ni?o event occurred with a lower intensity of eddy activity,and both temperature in the fishing ground and near-surface sea water temperature within the anticyclonic eddy became warmer,with a small decrease in Chl-a;the percentage of suitable near-surface water temperature within the anticyclonic eddies decreased significantly,and suitable Chl-a decreased slightly;the suitable habitat for D.gigas was reduced dramatically,which was unfavorable to D.gigas survival.Our finding suggested that that anomalous climatic events can have an impact on eddy strength,as well as on the suitable environment and habitat within the anticyclonic eddies,resulting in variations in the abundance of D.gigas.展开更多
Mesoscale eddies have been suggested to have an impact on biological carbon fixation in the South China Sea （SCS）. However, their overall contribution to primary production during the spring inter-monsoon pe riod is...Mesoscale eddies have been suggested to have an impact on biological carbon fixation in the South China Sea （SCS）. However, their overall contribution to primary production during the spring inter-monsoon pe riod is still unknown. Based on large-scale biological and environmental in situ observations and synchro nous remote sensing data, the distribution patterns of phytoplankton biomass and the primary production, and the role of mesoscale eddies in regulating primary production in different eddy-controlled waters were investigated. The results suggested that the surface chlorophyll a concentrations and water column inte grated primary production （IPP） are significantly higher in cyclonic eddies and lower in the anticyclonic eddies as compared to that in non-eddy waters. Although eddies could affect various environmental factors, such as nutrients, temperature and light availability, nutrient supply is suggested to be the most important one through which mesoscale eddies regulated the distribution patterns of phytoplankton biomass and pri mary production. The estimated IPP in cyclonic and anticyclonic eddies are about 29.5% higher and 16.6% lower than the total average in the whole study area, respectively, indicating that the promotion effect of mesoscale cold eddies on the primary production was much stronger than the inhibition effect of the warm eddies per unit area. Overall, mesoscale eddies are crucial physical processes that affect the biological car bon fixation and the distribution pattern of primary production in the SCS open sea, especially during the spring inter-monsoon period.展开更多
Some life history statistics of the mesoscale eddies of the South China Sea (SCS) derived from altimetry data will be further discussed according their different formation periods. A total of three ATLAS (autonomous t...Some life history statistics of the mesoscale eddies of the South China Sea (SCS) derived from altimetry data will be further discussed according their different formation periods. A total of three ATLAS (autonomous temperature line acquisition system)mooring buoys data will be analyzed to discuss eddies' impact on temperature profiles.They identify that the intraseasonal variation of SCS thermocline is partly controlled by mesoscale eddies.展开更多
Based on the temperature and salinity from the Argo profiling floats and altimeter-derived geostrophic velocity anomaly (GVA) data in the western North Pacific during 2002-2011, the North Pacific Subtropical Mode Wate...Based on the temperature and salinity from the Argo profiling floats and altimeter-derived geostrophic velocity anomaly (GVA) data in the western North Pacific during 2002-2011, the North Pacific Subtropical Mode Water (NPSTMW) distribution is investigated and cyclonic and anti-cyclonic eddies (CEs and AEs) are constructed to study the influence of their vertical structures on maintaining NPSTMW. Combining eddies identified by the GVA data and Argo profiling float data, it is found that the average NPSTMW thickness of AEs is about 60 dbar, which is thicker than that of CEs. The NPSTMW thicker than 150 dbar in AEs accounts for 18%, whereas that in CEs accounts for only 1%. About 3377 (3517) profiles, which located within one diameter of the nearest CEs (AEs) are used to construct the CE (AE). The composite AE traps low-PV water in the center and with a convex shape in the vertical section. The 'trapped depth' of the composite CE (AE) is 300 m (550 m) where the rotational velocity exceeds the transitional velocity. The present study suggests that the anticyclonic eddies are not only likely to form larger amounts of NPSTMW, but also trap more NPSTMW than cyclonic eddies.展开更多
An automatic detection method is employed to identify and track eddies in the Gulf of Mexico. The physical parameters of the eddies, such as lifespan, radius, and distribution position are first examined and used to d...An automatic detection method is employed to identify and track eddies in the Gulf of Mexico. The physical parameters of the eddies, such as lifespan, radius, and distribution position are first examined and used to determine the spatio–temporal evolution of a strong warm eddy separated from the Mexico current. Then, the influence of this strong warm eddy on sound propagation during its lifespan are comprehensively analyzed with the parabolic equation and explained by using the normal mode and ray theories. Additionally, the influence of mesoscale eddies on the redistribution of total depth-integrated energy among the normal modes in the deep water is also discussed. The variation of arrival angle is investigated to explain the spreading acoustic energy caused by eddies. Overall, the results show that warm eddies can change the propagation paths and cause the convergence zone to broaden and approach the sound source. Moreover,the warm eddy can disperse sound energy and cause the total depth-integrated energy to incline to a lower normal mode.Throughout the whole of these three periods(eddy generating, eddy maturing, and eddy terminating), the fluctuation in the transmission loss is up to 30 dB(depending on the relative location of eddy center to the source).展开更多
Using the mesoscale eddy trajectory atlas product derived from satellite altimeter data from 1993 to 2016,this study analyzes statistical characteristics and seasonal variability of mesoscale eddies in the Banda Sea o...Using the mesoscale eddy trajectory atlas product derived from satellite altimeter data from 1993 to 2016,this study analyzes statistical characteristics and seasonal variability of mesoscale eddies in the Banda Sea of the Indonesian seas.The results show that there were 147 mesoscale eddies that occurred in the Banda Sea,of which 137 eddies were locally generated and 10 originated from outside.The total numbers of cyclonic eddies(CEs,clockwise)and anticyclonic eddies(AEs,anticlockwise)are 76 and 71,respectively.Seasonally,the number of CEs(AEs)is twice larger than the number of AEs(CEs)in winter(summer).In winter,CEs are distributed in the southern and AEs in the northern basins,respectively,but the opposite thing occurs in summer,i.e.,the polarities of mesoscale eddies observed at the same location reverse seasonally.The mechanisms of polarity distribution reversal(PDR)of mesoscale eddies are examined with reanalysis data of ocean currents and winds.The results indicate that the basin-scale vorticity,wind stress curl,and the meridional shear of zonal current reverse seasonally,which are favorable to the PDR of mesoscale eddies.The possible generation mechanisms of mesoscale eddies include direct wind forcing,barotropic and baroclinic instabilities,of which the direct wind forcing should play the dominant role.展开更多
Subsurface eddies(SSEs)are common features of the ocean interior.They are particularly abundant in oceanic basins and the vicinity of major intermediate water outfl ows.They are responsible for subsurface transport of...Subsurface eddies(SSEs)are common features of the ocean interior.They are particularly abundant in oceanic basins and the vicinity of major intermediate water outfl ows.They are responsible for subsurface transport of mass,heat,and salt.Analysis of high-resolution general circulation model data has revealed the existence of subsurface anticyclonic eddies(SSAEs)and subsurface cyclonic eddies(SSCEs)in the northwestern tropical Pacifi c Ocean.SSEs are abundant east of the Philippines(0°–22°N,120°E–140°E)and in latitude bands between 9°N–17°N east of 140°E.The composite structure of SSEs was investigated.SSEs had a core at about 400-m water depth and their maximum meridional velocity exceeded 10 cm/s.They exhibited two cores with diff erent salinity polarities in the surface and subsurface.Additionally,spatial distributions of heat transport induced by SSEs in the northwestern tropical Pacifi c were presented for the fi rst time.A net equatorward heat fl ux toward a temperature up-gradient was observed.The analysis of eddy-mean fl ow interactions revealed that the circulation is baroclinically and barotropically unstable at diff erent depths and to diff ering degrees.The energy conversions suggest that both barotropic and baroclinic instabilities are responsible for SSE generation east of the Philippines,whereas baroclinic instability caused by a horizontal density gradient and vertical eddy heat fl ux are important between 9°N and 17°N east of 140°E.Meridional movement of the north equatorial current and the north equatorial undercurrent can contribute to SSE generation in our study region.展开更多
Automated identification and tracking of mesoscale ocean eddies has recently become one research hotspot in physical oceanography. Several methods have been developed and applied to survey the general kinetic and geom...Automated identification and tracking of mesoscale ocean eddies has recently become one research hotspot in physical oceanography. Several methods have been developed and applied to survey the general kinetic and geometric characteristics of the ocean eddies in the South China Sea（SCS）. However, very few studies attempt to examine eddies＇ internal evolution processes. In this study, we reported a hybrid method to trace eddies＇ propagation in the SCS based on their internal structures, which are characterized by eddy centers, footprint borders, and composite borders. Eddy identification and tracking results were represented by a GIS-based spatiotemporal model. Information on instant states, dynamic evolution processes, and events of disappearance, reappearance, split, and mergence is stored in a GIS database. Results were validated by comparing against the ten Dongsha Cyclonic Eddies（DCEs） and the three long-lived anticyclonic eddies（ACEs） in the northern SCS, which were reported in previous literature. Our study confirmed the development of these eddies. Furthermore, we found more DCE-like and ACE-like eddies in these areas from 2005 to 2012 in our database. Spatial distribution analysis of disappearing, reappearing, splitting, and merging activities shows that eddies in the SCS tend to cluster to the northwest of Luzon Island, southwest of Luzon Strait, and around the marginal sea of Vietnam. Kuroshio intrusions and the complex sea floor topography in these areas are the possible factors that lead to these spatial clusters.展开更多
The South China Sea（SCS） is an eddy-active area. Composite analyses based on 438 mesoscale ocean eddies during 2000–2012 revealed the status of the atmospheric boundary layer is influenced remarkably by such eddies...The South China Sea（SCS） is an eddy-active area. Composite analyses based on 438 mesoscale ocean eddies during 2000–2012 revealed the status of the atmospheric boundary layer is influenced remarkably by such eddies. The results showed cold-core cyclonic（warm-core anticyclonic） eddies tend to cool（warm） the overlying atmosphere and cause surface winds to decelerate（accelerate）. More than 5% of the total variance of turbulent heat fluxes, surface wind speed and evaporation rate are induced by mesoscale eddies. Furthermore, mesoscale eddies locally affect the columnar water vapor, cloud liquid water, and rain rate. Dynamical analyses indicated that both variations of atmospheric boundary layer stability and sea level pressure are responsible for atmospheric anomalies over mesoscale eddies. To reveal further details about the mechanisms of atmospheric responses to mesoscale eddies, atmospheric manifestations over a pair of cold and warm eddies in the southwestern SCS were simulated. Eddy-induced heat flux anomalies lead to changes in atmospheric stability. Thus, anomalous turbulence kinetic energy and friction velocity arise over the eddy dipole, which reduce（enhance） the vertical momentum transport over the cold（warm） eddy, resulting in the decrease（increase） of sea surface wind. Diagnoses of the model＇s momentum balance suggested that wind speed anomalies directly over the eddy dipole are dominated by vertical mixing terms within the atmospheric boundary layer, while wind anomalies on the edges of eddies are produced by atmospheric pressure gradient forces and atmospheric horizontal advection terms.展开更多
Using a 19-year altimetric dataset, the mean properties and spatiotemporal variations of eddies in the Kuroshio recirculation region are examined. A total of 2 001 cyclonic tracks and 1 847 anticyclonic tracks were id...Using a 19-year altimetric dataset, the mean properties and spatiotemporal variations of eddies in the Kuroshio recirculation region are examined. A total of 2 001 cyclonic tracks and 1 847 anticyclonic tracks were identifi ed using a geometry-based eddy detection method. The mean radius was 57 km for cyclonic eddies and was 61 km for anticyclonic eddies, respectively, and the mean lifetime was about 10 weeks for both type eddies. There were asymmetric spatial distributions for eddy generation and eddy termination, which were domain-dependent. Mean eddy generation rates were 2.0 per week for cyclonic eddies and were 1.9 per week for anticyclonic eddies. Both type eddies tended to deform during their lifetime and had different propagation characteristics, which mainly propagated westward and southwestward with velocities 4.0–9.9 cm/s, in the Kuroshio recirculation region. Further discussion illustrates that the eddy westward speed maybe infl uenced by the combined effect of vertical shear of horizontal currents and nonlinearity of eddy. To better understand the evolution of eddy tracks, a total of 134 long-lived tracks(lifetime ≥20 weeks) were examined. Comparison between short-span eddies(lifetime ≥4 weeks and <20 weeks) and long-lived eddies is also conducted and the result shows that the short-span and long-lived eddies have similar time evolution. Finally, eddy seasonal variations and interannual changes are discussed. Correlation analysis shows that eddy activity is sensitive to the wind stress curl and meridional gradient of sea surface temperature on interannual timescales. Besides, the strength and orientation of background fl ows also have impacts on the eddy genesis.展开更多
Mesoscale eddies,which are mainly caused by baroclinic effects in the ocean,are common oceanic phenomena in the Northwest Pacific Ocean and play very important roles in ocean circulation,ocean dynamics and material en...Mesoscale eddies,which are mainly caused by baroclinic effects in the ocean,are common oceanic phenomena in the Northwest Pacific Ocean and play very important roles in ocean circulation,ocean dynamics and material energy transport.The temperature structure of mesoscale eddies will lead to variations in oceanic baroclinity,which can be reflected in the sea level anomaly(SLA).Deep learning can automatically extract different features of data at multiple levels without human intervention,and find the hidden relations of data.Therefore,combining satellite SLA data with deep learning is a good way to invert the temperature structure inside eddies.This paper proposes a deep learning algorithm,eddy convolution neural network(ECN),which can train the relationship between mesoscale eddy temperature anomalies and sea level anomalies(SLAs),relying on the powerful feature extraction and learning abilities of convolutional neural networks.After obtaining the temperature structure model through ECN,according to climatic temperature data,the temperature structure of mesoscale eddies in the Northwest Pacific is retrieved with a spatial resolution of 0.25°at depths of 0–1000 m.The overall accuracy of the ECN temperature structure is verified using Argo profiles at the locations of cyclonic and anticyclonic eddies during 2015–2016.Taking 10%error as the acceptable threshold of accuracy,89.64%and 87.25%of the cyclonic and anticyclonic eddy temperature structures obtained by ECN met the threshold,respectively.展开更多
Mesoscale eddies play vital roles in ocean processes.Although previous studies focused on eddy surface features and individual three-dimensional(3D)eddy cases in the northwestern Pacific Ocean,the analysis of unique e...Mesoscale eddies play vital roles in ocean processes.Although previous studies focused on eddy surface features and individual three-dimensional(3D)eddy cases in the northwestern Pacific Ocean,the analysis of unique eddy3D regional characteristics is still lacking.A 3D eddy detection scheme is applied to 9 years(2000-2008)of eddyresolving Regional Ocean Modeling System(ROMS)output to obtain a 3D eddy dataset from the surface to a depth of 1000 m in the northwestern Pacific Ocean(15°-35°N,120°-145°E).The 3D characteristics of mesoscale eddies are analyzed in two regions,namely,Box1(Subtropical Countercurrent,15°-25°N,120°-145°E)and Box2(Southern Kuroshio Extension,25°-35°N,120°-145°E).In Box1,the current is characterized by strong vertical shear and weak horizontal shear.In Box2,the current is characterized by the strong Kuroshio,topographic effect,and the westward propagation of Rossby waves.The results indicate the importance of baroclinic instability in Box1,whereas in Box2,both the barotropic and baroclinic instability are important.Moreover,the mesoscale eddies’properties in Box1 and Box2 are distinct.The eddies in Box1 have larger number and radius but a shorter lifetime.By contrast,Box2 has fewer eddies,which have smaller radius but longer lifetime.Vertically,more eddies are detected at the subsurface than at the surface in both regions;the depth of 650 m is the turning point in Box1.Above this depth,the number of cyclonic eddies(CEs)is larger than that of anticyclonic eddies(AEs).In Box2,the number of CEs is dominant vertically.Eddy kinetic energy(EKE)and mean normalized relative vorticity in Box2are significantly higher than those in Box1.With increasing depth,the attenuation trend of EKE and relative vorticity of Box1 become greater than those of Box2.Furthermore,the upper ocean(about 300 m in depth)contains 68.6%of the eddies(instantaneous eddy).Only 16.6%of the eddies extend to 1000 m.In addition,about87%of the eddies are bowl-shaped eddies in the two regions.Only about 3%are cone-shaped eddies.With increasing depth of the eddies,the proportion of bowl-shaped eddies gradually decreases.Conversely,the coneand lens-shaped eddies are equal in number at 700-1000 m,accounting for about 30%each.Studying the 3D characteristics of eddies in two different regions of the northwestern Pacific Ocean is an important stepping stone for discussing the different eddy generation mechanisms.展开更多
A hybrid coordinate ocean model （ltYCOM） is used to simulate the Kuroshio frontal eddies in the East China Sea （ECS）. The research area is located （20°-32°N, 120°-132°E）. Using tile simulatin...A hybrid coordinate ocean model （ltYCOM） is used to simulate the Kuroshio frontal eddies in the East China Sea （ECS）. The research area is located （20°-32°N, 120°-132°E）. Using tile simulating data, it is figured out that the Kuroshio frontal eddies occur in summer as well as in the other season in this area. The life cycle of the Kuroshio and its frontal eddies is different with the position. The life-cycle of the Kuroshio frontal eddies of the northwest Diaoyu Islands is about 14 d; and the life cycle of the Kuroshio frontal eddies of southwest Yakushima about 20 d. This result extends the in situ researching results greatly. In addition, the vertical impact depth of the Kuroshio frontal eddies is also changing with the position. On the whole, in the ECS, the maximum impact depth of the Kuroshio frontal eddies of the northwest Taiwan Islands is about 75 m; the maximum impact depth of the Kuroshio frontal eddies of the northwest Diaoyu Islands is more than 125 m, but no more than 200 m; and the maximum impact depth of the Kuroshio frontal eddies of southwest Yakushima is up to 100 m.展开更多
Traditional methods of extracting the ocean wave eddy information from remotely sensed imagery mainly use the edge detection technology such as Canny and Hough operators. However, due to the complexities of ocean eddi...Traditional methods of extracting the ocean wave eddy information from remotely sensed imagery mainly use the edge detection technology such as Canny and Hough operators. However, due to the complexities of ocean eddies and image itself, it is sometimes difficult to successfully detect ocean eddies using these methods. A mnltifractal filtering technology is proposed for extraction of ocean eddies and demonstrated using NASA MODIS, SeaWiFS and NOAA satellite data set in the typical area, such as ocean west boundary current. Results showed that the new method has a superior performance over the traditional methods.展开更多
The impact of eddies on the Kuroshio Current in the Luzon Strait (LS) area is investigated by using the sea surface height anomaly (SSHA) satellite observation data and the sea surface height (SSH) assimilation data. ...The impact of eddies on the Kuroshio Current in the Luzon Strait (LS) area is investigated by using the sea surface height anomaly (SSHA) satellite observation data and the sea surface height (SSH) assimilation data. The influence of the eddies on the mean current depends upon the type of eddies and their relative position. The mean current is enhanced (weakened) as the cyclonic (anticyclonic) eddy becomes slightly far from it, whereas it is weakened (enhanced) as the cyclonic (anticyclonic) eddy moves near or within the position of the mean current; this is explained as the eddy-induced meridional velocity and geostrophic flow relationship. The anticyclonic (cyclonic) eddy can increase (decrease) the mean meridional flow due to superimposition of the eddy-induced meridional flow when the eddy is within the region of the mean current. However, when the eddy is slightly far from the mean current region, the anticyclonic (cyclonic) eddy tends to decrease (increase) the zonal gradient of the SSH, which thus results in weakening (strengthening) of the mean current in the LS region.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.42230405,42006029)Science and Technology Plan of Liaoning Province(2024JH2/102400061)+1 种基金Dalian Science and Technology Innovation Fund(2024JJ11PT007)Dalian Science and Technology Pro-gram for Innovation Talents of Dalian(2022RJ06).
文摘Mesoscale eddies play a central role in the poleward oceanic heat flux in the Southern Ocean.Previous studies have documented changes in the location of temperature fronts in the Southern Ocean,but little attention has been paid to changes in the genesis locations of mesoscale eddies.Here,we provide evidence from three decades of satellite altimetry observations for the heterogeneity of the poleward shift of mesoscale activities,with the largest trend of~0.23°±0.05°(10 yr)^(-1) over the Atlantic sector and a moderate trend of~0.1°±0.03°(10 yr)^(-1) over the Indian sector,but no significant trend in the Pacific sector.The poleward shift of mesoscale eddies is associated with a southward shift of the local westerly winds while being constrained by the major topographies.As the poleward shift of westerly winds is projected to persist,the poleward oceanic heat flux from mesoscale eddies may influence future ice melt.
基金The National Key Research and Development Program of China under contract No.2021YFC3101602the National Natural Science Foundation of China under contract Nos 42176017 and 41976019.
文摘Mesoscale eddies play a pivotal role in deciphering the intricacies of ocean dynamics and the transport of heat,salt,and nutrients.Accurate representation of these eddies in ocean models is essential for improving model predictions.In this study,we propose a convolutional neural network(CNN)that combines data-driven techniques with physical principles to develop a robust and interpretable parameterization scheme for mesoscale eddies in ocean modeling.We use a highresolution reanalysis dataset to extract subgrid eddy momentum and then applying machine learning algorithms to identify patterns and correlations.To ensure physical consistency,we have introduced conservation of momentum constraints in our CNN parameterization scheme through soft and hard constraints.The interpretability analysis illustrate that the pre-trained CNN parameterization shows promising results in accurately solving the resolved mean velocity and effectively capturing the representation of unresolved subgrid turbulence processes.Furthermore,to validate the CNN parameterization scheme offline,we conduct simulations using the Massachusetts Institute of Technology general circulation model(MITgcm)ocean model.A series of experiments is conducted to compare the performance of the model with the CNN parameterization scheme and high-resolution simulations.The offline validation demonstrates the effectiveness of the CNN parameterization scheme in improving the representation of mesoscale eddies in the MITgcm ocean model.Incorporating the CNN parameterization scheme leads to better agreement with high-resolution simulations and a more accurate representation of the kinetic energy spectra.
基金partially supported by the National Natural Science Foundation of China(Grant Nos.42088101 and 42175023)the Innovation Group Project of Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai)(Grant No.316323005)the Guangdong Province Key Laboratory for Climate Change and Natural Disaster Studies(Grant No.2020B1212060025)。
文摘The Aleutian Low(AL)is a dominant feature of the mean circulation in the North Pacific during the winter season.The background stationary wave,air-sea interaction,and transient eddies over the North Pacific exert distinct impacts on the interannual variations of the AL intensity and position.In this study,we adopt the quasi-geostrophic geopotential tendency equation to investigate the roles of various physical processes in the maintenance and interannual variations of this system.The results show that absolute vorticity advection plays the most important role in the formation and maintenance of AL intensity,while high-frequency transient eddies contribute most to the meridional and zonal shifts of the AL.The high-frequency transient eddy vorticity forcing affects the AL through the barotropic energy conversion process,and,in turn,the AL enhances the high-frequency transient eddies through the baroclinic energy conversion process,forming a positive feedback.The associated high-frequency eddy kinetic energy anomalies exhibit an eastward movement toward the east coast of North America in the years of an intensified AL,which explains why a strengthened AL is often accompanied by an eastward movement.Furthermore,the energy conversion terms of high-frequency transient eddies are mostly located over the extratropical eastern North Pacific,leading to asymmetric features in the zonal movement of the AL.
基金Supported by the Taishan Scholar Project of Shandong Province (Nos.TS20190913,tsqn202211054)the Fundamental Research Funds for the Central Universities (No.202241007)the Youth Innovation Team Program in Colleges and Universities of Shandong Province (No.2022KJ045)
文摘Mesoscale eddies are widespread in the global ocean,significantly influencing the physical,chemical,and biological structures of water column.Based on the CTD data and suspended particulate matter(SPM)data collected at 36 hydrographic stations during a field cruise in southern Mozambique Channel,combined with satellite altimeter observations,we identified a series of mesoscale eddies traversing the Mozambique Channel.Our hydrographic measurements,coupled with in situ chlorophyll fluorescence data,reveal that these eddies significantly influence thermohaline structure and chlorophyll distribution,which in turn affects primary productivity and SPM concentrations in the upper ocean.The cyclonic eddies facilitate the upwelling of cold subsurface water,leading to a shallowing of the pycnocline and the creation of a low-temperature anomaly with variable salinity anomalies at different depths.Conversely,anticyclonic eddies submerge warm surface water,deepening the pycnocline,and resulting in a high-temperature anomaly accompanied by distinct salinity patterns.Significantly,a coastal anticyclonic eddy was observed to intercept terrestrial material from the Delagoa Bight,redirecting it west of 36°E.This study presents unique and quasi-synchronous CTD datasets capturing mesoscale eddy impacts,and provided valuable insights into SPM variability within the often-neglected southern Mozambique Channel.
基金Supported by the National Natural Science Foundation of China(No.42250710152)the Jiangsu Province Graduate Innovation and Entrepreneurship Project(No.KYCX22_1171)the National Key Research and Development Program of China(No.2023YFC3008200)。
文摘A cyclonic eddy(CE)is often accompanied by an anticyclonic eddy(AE)to the east of Vietnam in the South China Sea(SCS)in summer,but the dipole lifetime and the intrinsic connection between CE and AE are still understudied.Data from 1993-2021 reveal that the dipole lifetime are significantly correlated with the wind direction and speed in the dipole region.Higher wind speed was found to be associated with more eastward wind direction and tends to longer dipole lifetime.The wind stress work(WW)on the eddy is much stronger in the eastward jet region than in the CE and AE regions.Comparing of results of 12 higher and lower wind speed years reveal that higher wind can produce stronger mean current,WW and barotropic instability(T4)that further enhances eddy kinetic energy(EKE)and dipole lifetime.The correlations between the dipole CE and AE characteristics are insignificant on interannual scales and mostly insignificant on seasonal scales in the surface layer but significant on seasonal scales in the subsurface layers.In addition,the daily mean vertical profiles(0-500 m)of EKE,vorticity and total deformation rate(TD)between CE and AE remain significantly correlated throughout the dipole’s lifetime,which can be a useful criterion for judging if two eddies are a dipole.
基金financially supported by the Natural Science Foundation of Shanghai(23ZR1427100)the Shanghai Talent Development Funding for the Project(2021078)+1 种基金the National Key R&D Program of China(2023YFD2401303)the Open Fund of Key Laboratory for Sustainable Utilization of Open-sea Fishery,Ministry of Agriculture and Rural Affairs,P.R.China(LOF 2023-05)
文摘Anticyclonic eddies are widely distributed off Peru,producing obvious effects on climate-environmentsensitive jumbo flying squid Dosidicus gigas.However,how the habitat of D.gigas changes within anticyclonic eddies during El Ni?o events is still unknown.Therefore,this study constructed a habitat model with different weights and screened the optimal performance model using fishery data from September to December during 2015 to 2019,as well as vertical water temperature data(sea surface temperature and 50 m water depth temperature)and surface chlorophyll concentration data(Chl-a).Then,combined with the eddy tracking dataset,the differences in the variation of resource abundance and habitat of D.gigas within the anticyclonic eddy between the 2015 El Ni?o year and the 2019 normal year were further comparatively analyzed based on the optimal habitat model.Compared with the normal year of 2019,the 2015 El Ni?o event occurred with a lower intensity of eddy activity,and both temperature in the fishing ground and near-surface sea water temperature within the anticyclonic eddy became warmer,with a small decrease in Chl-a;the percentage of suitable near-surface water temperature within the anticyclonic eddies decreased significantly,and suitable Chl-a decreased slightly;the suitable habitat for D.gigas was reduced dramatically,which was unfavorable to D.gigas survival.Our finding suggested that that anomalous climatic events can have an impact on eddy strength,as well as on the suitable environment and habitat within the anticyclonic eddies,resulting in variations in the abundance of D.gigas.
基金The CAS Strategic Pilot Science and Technology of China under contract Nos XDA11020205 and XDA05030403the National Project of Basic Sciences and Technology of China under contract Nos 2012FY112400 and 2013FY111200+1 种基金the National Natural Science Foundation of China under contract Nos 41276162,41130855,41276161 and 40906057the Natural Science Foundation of Guangdong Province of China under contract No.S2011040000151
文摘Mesoscale eddies have been suggested to have an impact on biological carbon fixation in the South China Sea （SCS）. However, their overall contribution to primary production during the spring inter-monsoon pe riod is still unknown. Based on large-scale biological and environmental in situ observations and synchro nous remote sensing data, the distribution patterns of phytoplankton biomass and the primary production, and the role of mesoscale eddies in regulating primary production in different eddy-controlled waters were investigated. The results suggested that the surface chlorophyll a concentrations and water column inte grated primary production （IPP） are significantly higher in cyclonic eddies and lower in the anticyclonic eddies as compared to that in non-eddy waters. Although eddies could affect various environmental factors, such as nutrients, temperature and light availability, nutrient supply is suggested to be the most important one through which mesoscale eddies regulated the distribution patterns of phytoplankton biomass and pri mary production. The estimated IPP in cyclonic and anticyclonic eddies are about 29.5% higher and 16.6% lower than the total average in the whole study area, respectively, indicating that the promotion effect of mesoscale cold eddies on the primary production was much stronger than the inhibition effect of the warm eddies per unit area. Overall, mesoscale eddies are crucial physical processes that affect the biological car bon fixation and the distribution pattern of primary production in the SCS open sea, especially during the spring inter-monsoon period.
基金the Ocean University of China,was supported by the Major State Basic Research Program of China under contract Nos G1999043805 ,1999043810.
文摘Some life history statistics of the mesoscale eddies of the South China Sea (SCS) derived from altimetry data will be further discussed according their different formation periods. A total of three ATLAS (autonomous temperature line acquisition system)mooring buoys data will be analyzed to discuss eddies' impact on temperature profiles.They identify that the intraseasonal variation of SCS thermocline is partly controlled by mesoscale eddies.
基金supported by the National Basic Research Program of China(Grant No.2012CB955602)the National Natural Science Foundation of China(Grant Nos.41076005 and 41176009)
文摘Based on the temperature and salinity from the Argo profiling floats and altimeter-derived geostrophic velocity anomaly (GVA) data in the western North Pacific during 2002-2011, the North Pacific Subtropical Mode Water (NPSTMW) distribution is investigated and cyclonic and anti-cyclonic eddies (CEs and AEs) are constructed to study the influence of their vertical structures on maintaining NPSTMW. Combining eddies identified by the GVA data and Argo profiling float data, it is found that the average NPSTMW thickness of AEs is about 60 dbar, which is thicker than that of CEs. The NPSTMW thicker than 150 dbar in AEs accounts for 18%, whereas that in CEs accounts for only 1%. About 3377 (3517) profiles, which located within one diameter of the nearest CEs (AEs) are used to construct the CE (AE). The composite AE traps low-PV water in the center and with a convex shape in the vertical section. The 'trapped depth' of the composite CE (AE) is 300 m (550 m) where the rotational velocity exceeds the transitional velocity. The present study suggests that the anticyclonic eddies are not only likely to form larger amounts of NPSTMW, but also trap more NPSTMW than cyclonic eddies.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11434012 and 41561144006)
文摘An automatic detection method is employed to identify and track eddies in the Gulf of Mexico. The physical parameters of the eddies, such as lifespan, radius, and distribution position are first examined and used to determine the spatio–temporal evolution of a strong warm eddy separated from the Mexico current. Then, the influence of this strong warm eddy on sound propagation during its lifespan are comprehensively analyzed with the parabolic equation and explained by using the normal mode and ray theories. Additionally, the influence of mesoscale eddies on the redistribution of total depth-integrated energy among the normal modes in the deep water is also discussed. The variation of arrival angle is investigated to explain the spreading acoustic energy caused by eddies. Overall, the results show that warm eddies can change the propagation paths and cause the convergence zone to broaden and approach the sound source. Moreover,the warm eddy can disperse sound energy and cause the total depth-integrated energy to incline to a lower normal mode.Throughout the whole of these three periods(eddy generating, eddy maturing, and eddy terminating), the fluctuation in the transmission loss is up to 30 dB(depending on the relative location of eddy center to the source).
基金The National Natural Science Foundation of China under contract No.41776034the Special Project of Global Change and Air and Sea Interaction under contract Nos GASI-IPOVAI-01-02 and GASI-02-SCS-YGST2-02the Guangdong Province First-Class Discipline Plan under contract Nos CYL231419012 and 231819002
文摘Using the mesoscale eddy trajectory atlas product derived from satellite altimeter data from 1993 to 2016,this study analyzes statistical characteristics and seasonal variability of mesoscale eddies in the Banda Sea of the Indonesian seas.The results show that there were 147 mesoscale eddies that occurred in the Banda Sea,of which 137 eddies were locally generated and 10 originated from outside.The total numbers of cyclonic eddies(CEs,clockwise)and anticyclonic eddies(AEs,anticlockwise)are 76 and 71,respectively.Seasonally,the number of CEs(AEs)is twice larger than the number of AEs(CEs)in winter(summer).In winter,CEs are distributed in the southern and AEs in the northern basins,respectively,but the opposite thing occurs in summer,i.e.,the polarities of mesoscale eddies observed at the same location reverse seasonally.The mechanisms of polarity distribution reversal(PDR)of mesoscale eddies are examined with reanalysis data of ocean currents and winds.The results indicate that the basin-scale vorticity,wind stress curl,and the meridional shear of zonal current reverse seasonally,which are favorable to the PDR of mesoscale eddies.The possible generation mechanisms of mesoscale eddies include direct wind forcing,barotropic and baroclinic instabilities,of which the direct wind forcing should play the dominant role.
基金Supported by the National Key Research and Development Plan(Nos.2016YFC1400505SQ,2017YFSF070166)the National Natural Science Foundation of China(No.41676005)the NSFC Innovative Group(No.41421005),the CAS“Huiquan Scholar”,and the CAS Youth Innovation Promotion Association。
文摘Subsurface eddies(SSEs)are common features of the ocean interior.They are particularly abundant in oceanic basins and the vicinity of major intermediate water outfl ows.They are responsible for subsurface transport of mass,heat,and salt.Analysis of high-resolution general circulation model data has revealed the existence of subsurface anticyclonic eddies(SSAEs)and subsurface cyclonic eddies(SSCEs)in the northwestern tropical Pacifi c Ocean.SSEs are abundant east of the Philippines(0°–22°N,120°E–140°E)and in latitude bands between 9°N–17°N east of 140°E.The composite structure of SSEs was investigated.SSEs had a core at about 400-m water depth and their maximum meridional velocity exceeded 10 cm/s.They exhibited two cores with diff erent salinity polarities in the surface and subsurface.Additionally,spatial distributions of heat transport induced by SSEs in the northwestern tropical Pacifi c were presented for the fi rst time.A net equatorward heat fl ux toward a temperature up-gradient was observed.The analysis of eddy-mean fl ow interactions revealed that the circulation is baroclinically and barotropically unstable at diff erent depths and to diff ering degrees.The energy conversions suggest that both barotropic and baroclinic instabilities are responsible for SSE generation east of the Philippines,whereas baroclinic instability caused by a horizontal density gradient and vertical eddy heat fl ux are important between 9°N and 17°N east of 140°E.Meridional movement of the north equatorial current and the north equatorial undercurrent can contribute to SSE generation in our study region.
基金The National Science Foundation of China under contract Nos 41071250 and 41371378the Innovation Projects of the State Key Laboratory of Resource and Environment Information System,Chinese Academy of Sciences,under contract No.088RA500TA
文摘Automated identification and tracking of mesoscale ocean eddies has recently become one research hotspot in physical oceanography. Several methods have been developed and applied to survey the general kinetic and geometric characteristics of the ocean eddies in the South China Sea（SCS）. However, very few studies attempt to examine eddies＇ internal evolution processes. In this study, we reported a hybrid method to trace eddies＇ propagation in the SCS based on their internal structures, which are characterized by eddy centers, footprint borders, and composite borders. Eddy identification and tracking results were represented by a GIS-based spatiotemporal model. Information on instant states, dynamic evolution processes, and events of disappearance, reappearance, split, and mergence is stored in a GIS database. Results were validated by comparing against the ten Dongsha Cyclonic Eddies（DCEs） and the three long-lived anticyclonic eddies（ACEs） in the northern SCS, which were reported in previous literature. Our study confirmed the development of these eddies. Furthermore, we found more DCE-like and ACE-like eddies in these areas from 2005 to 2012 in our database. Spatial distribution analysis of disappearing, reappearing, splitting, and merging activities shows that eddies in the SCS tend to cluster to the northwest of Luzon Island, southwest of Luzon Strait, and around the marginal sea of Vietnam. Kuroshio intrusions and the complex sea floor topography in these areas are the possible factors that lead to these spatial clusters.
基金supported by the National Natural Science Foundation of China (Grant Nos. 41675043 and 41375050)
文摘The South China Sea（SCS） is an eddy-active area. Composite analyses based on 438 mesoscale ocean eddies during 2000–2012 revealed the status of the atmospheric boundary layer is influenced remarkably by such eddies. The results showed cold-core cyclonic（warm-core anticyclonic） eddies tend to cool（warm） the overlying atmosphere and cause surface winds to decelerate（accelerate）. More than 5% of the total variance of turbulent heat fluxes, surface wind speed and evaporation rate are induced by mesoscale eddies. Furthermore, mesoscale eddies locally affect the columnar water vapor, cloud liquid water, and rain rate. Dynamical analyses indicated that both variations of atmospheric boundary layer stability and sea level pressure are responsible for atmospheric anomalies over mesoscale eddies. To reveal further details about the mechanisms of atmospheric responses to mesoscale eddies, atmospheric manifestations over a pair of cold and warm eddies in the southwestern SCS were simulated. Eddy-induced heat flux anomalies lead to changes in atmospheric stability. Thus, anomalous turbulence kinetic energy and friction velocity arise over the eddy dipole, which reduce（enhance） the vertical momentum transport over the cold（warm） eddy, resulting in the decrease（increase） of sea surface wind. Diagnoses of the model＇s momentum balance suggested that wind speed anomalies directly over the eddy dipole are dominated by vertical mixing terms within the atmospheric boundary layer, while wind anomalies on the edges of eddies are produced by atmospheric pressure gradient forces and atmospheric horizontal advection terms.
基金Supported by the National Natural Science Foundation of China(No.41230420)the Knowledge Innovation Program of Chinese Academy of Sciences(No.KZCX3-EW-201)the Basic Research Program of Science and Technology Projects of Qingdao(No.11-14-95-jch)
文摘Using a 19-year altimetric dataset, the mean properties and spatiotemporal variations of eddies in the Kuroshio recirculation region are examined. A total of 2 001 cyclonic tracks and 1 847 anticyclonic tracks were identifi ed using a geometry-based eddy detection method. The mean radius was 57 km for cyclonic eddies and was 61 km for anticyclonic eddies, respectively, and the mean lifetime was about 10 weeks for both type eddies. There were asymmetric spatial distributions for eddy generation and eddy termination, which were domain-dependent. Mean eddy generation rates were 2.0 per week for cyclonic eddies and were 1.9 per week for anticyclonic eddies. Both type eddies tended to deform during their lifetime and had different propagation characteristics, which mainly propagated westward and southwestward with velocities 4.0–9.9 cm/s, in the Kuroshio recirculation region. Further discussion illustrates that the eddy westward speed maybe infl uenced by the combined effect of vertical shear of horizontal currents and nonlinearity of eddy. To better understand the evolution of eddy tracks, a total of 134 long-lived tracks(lifetime ≥20 weeks) were examined. Comparison between short-span eddies(lifetime ≥4 weeks and <20 weeks) and long-lived eddies is also conducted and the result shows that the short-span and long-lived eddies have similar time evolution. Finally, eddy seasonal variations and interannual changes are discussed. Correlation analysis shows that eddy activity is sensitive to the wind stress curl and meridional gradient of sea surface temperature on interannual timescales. Besides, the strength and orientation of background fl ows also have impacts on the eddy genesis.
基金The National Key Research and Development Program of China under contract Nos 2016YFC1402608,2016YFC1400904,2016YFC1400900 and 2019YFD0901000。
文摘Mesoscale eddies,which are mainly caused by baroclinic effects in the ocean,are common oceanic phenomena in the Northwest Pacific Ocean and play very important roles in ocean circulation,ocean dynamics and material energy transport.The temperature structure of mesoscale eddies will lead to variations in oceanic baroclinity,which can be reflected in the sea level anomaly(SLA).Deep learning can automatically extract different features of data at multiple levels without human intervention,and find the hidden relations of data.Therefore,combining satellite SLA data with deep learning is a good way to invert the temperature structure inside eddies.This paper proposes a deep learning algorithm,eddy convolution neural network(ECN),which can train the relationship between mesoscale eddy temperature anomalies and sea level anomalies(SLAs),relying on the powerful feature extraction and learning abilities of convolutional neural networks.After obtaining the temperature structure model through ECN,according to climatic temperature data,the temperature structure of mesoscale eddies in the Northwest Pacific is retrieved with a spatial resolution of 0.25°at depths of 0–1000 m.The overall accuracy of the ECN temperature structure is verified using Argo profiles at the locations of cyclonic and anticyclonic eddies during 2015–2016.Taking 10%error as the acceptable threshold of accuracy,89.64%and 87.25%of the cyclonic and anticyclonic eddy temperature structures obtained by ECN met the threshold,respectively.
基金The National Natural Science Foundation of China under contract Nos NSFC 41806030 and 42076021the China Ocean Mineral Resources Research and Development Association Program under contract No.DY135-E2-3-01+4 种基金the Basic Scientific Research Business Expenses of Zhejiang Provincial Universities under contract No.2020J00007the project of State Key Laboratory of Tropical Oceanography,South China Sea Institute of Oceanology,Chinese Academy of Sciences under contract No.LTO1807the project of Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai)under contract No.SML2020SP007the Innovation Group Project of Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai)under contract No.311020004the Strategic Priority Research Program of Chinese Academy of Sciences under contract No.XDB42000000。
文摘Mesoscale eddies play vital roles in ocean processes.Although previous studies focused on eddy surface features and individual three-dimensional(3D)eddy cases in the northwestern Pacific Ocean,the analysis of unique eddy3D regional characteristics is still lacking.A 3D eddy detection scheme is applied to 9 years(2000-2008)of eddyresolving Regional Ocean Modeling System(ROMS)output to obtain a 3D eddy dataset from the surface to a depth of 1000 m in the northwestern Pacific Ocean(15°-35°N,120°-145°E).The 3D characteristics of mesoscale eddies are analyzed in two regions,namely,Box1(Subtropical Countercurrent,15°-25°N,120°-145°E)and Box2(Southern Kuroshio Extension,25°-35°N,120°-145°E).In Box1,the current is characterized by strong vertical shear and weak horizontal shear.In Box2,the current is characterized by the strong Kuroshio,topographic effect,and the westward propagation of Rossby waves.The results indicate the importance of baroclinic instability in Box1,whereas in Box2,both the barotropic and baroclinic instability are important.Moreover,the mesoscale eddies’properties in Box1 and Box2 are distinct.The eddies in Box1 have larger number and radius but a shorter lifetime.By contrast,Box2 has fewer eddies,which have smaller radius but longer lifetime.Vertically,more eddies are detected at the subsurface than at the surface in both regions;the depth of 650 m is the turning point in Box1.Above this depth,the number of cyclonic eddies(CEs)is larger than that of anticyclonic eddies(AEs).In Box2,the number of CEs is dominant vertically.Eddy kinetic energy(EKE)and mean normalized relative vorticity in Box2are significantly higher than those in Box1.With increasing depth,the attenuation trend of EKE and relative vorticity of Box1 become greater than those of Box2.Furthermore,the upper ocean(about 300 m in depth)contains 68.6%of the eddies(instantaneous eddy).Only 16.6%of the eddies extend to 1000 m.In addition,about87%of the eddies are bowl-shaped eddies in the two regions.Only about 3%are cone-shaped eddies.With increasing depth of the eddies,the proportion of bowl-shaped eddies gradually decreases.Conversely,the coneand lens-shaped eddies are equal in number at 700-1000 m,accounting for about 30%each.Studying the 3D characteristics of eddies in two different regions of the northwestern Pacific Ocean is an important stepping stone for discussing the different eddy generation mechanisms.
基金The State Oceanic Administration Youth Funds of China under contract No.2012403the Public Science and Technology Research Funds Projects of Ocean of China under contract No.201005030+2 种基金the Special Funds for Basic Scientific Research Project of the First Institute of Oceanography,the State Ocean Administration of China under contract No.2010G12Water Marine Remote Sensing Survey and Research of China under contract No.908-01-ST10(Ⅱ)China’s Coastal Marine Optics and Remote Sensing Research under contract No.908-ZC-I-04
文摘A hybrid coordinate ocean model （ltYCOM） is used to simulate the Kuroshio frontal eddies in the East China Sea （ECS）. The research area is located （20°-32°N, 120°-132°E）. Using tile simulating data, it is figured out that the Kuroshio frontal eddies occur in summer as well as in the other season in this area. The life cycle of the Kuroshio and its frontal eddies is different with the position. The life-cycle of the Kuroshio frontal eddies of the northwest Diaoyu Islands is about 14 d; and the life cycle of the Kuroshio frontal eddies of southwest Yakushima about 20 d. This result extends the in situ researching results greatly. In addition, the vertical impact depth of the Kuroshio frontal eddies is also changing with the position. On the whole, in the ECS, the maximum impact depth of the Kuroshio frontal eddies of the northwest Taiwan Islands is about 75 m; the maximum impact depth of the Kuroshio frontal eddies of the northwest Diaoyu Islands is more than 125 m, but no more than 200 m; and the maximum impact depth of the Kuroshio frontal eddies of southwest Yakushima is up to 100 m.
文摘Traditional methods of extracting the ocean wave eddy information from remotely sensed imagery mainly use the edge detection technology such as Canny and Hough operators. However, due to the complexities of ocean eddies and image itself, it is sometimes difficult to successfully detect ocean eddies using these methods. A mnltifractal filtering technology is proposed for extraction of ocean eddies and demonstrated using NASA MODIS, SeaWiFS and NOAA satellite data set in the typical area, such as ocean west boundary current. Results showed that the new method has a superior performance over the traditional methods.
基金supported by the National Basic Research Program of China (Grant Nos. 2007CB411800 and 2005CB422300)the National Natural Science Foundation of China (Grant No. 40921004)
文摘The impact of eddies on the Kuroshio Current in the Luzon Strait (LS) area is investigated by using the sea surface height anomaly (SSHA) satellite observation data and the sea surface height (SSH) assimilation data. The influence of the eddies on the mean current depends upon the type of eddies and their relative position. The mean current is enhanced (weakened) as the cyclonic (anticyclonic) eddy becomes slightly far from it, whereas it is weakened (enhanced) as the cyclonic (anticyclonic) eddy moves near or within the position of the mean current; this is explained as the eddy-induced meridional velocity and geostrophic flow relationship. The anticyclonic (cyclonic) eddy can increase (decrease) the mean meridional flow due to superimposition of the eddy-induced meridional flow when the eddy is within the region of the mean current. However, when the eddy is slightly far from the mean current region, the anticyclonic (cyclonic) eddy tends to decrease (increase) the zonal gradient of the SSH, which thus results in weakening (strengthening) of the mean current in the LS region.
