This paper reviews the progress in our understanding of the atmospheric response to midlatitude oceanic fronts and eddies,emphasizing the Kuroshio-Oyashio Extension(KOE)region.Oceanic perturbations of interest consist...This paper reviews the progress in our understanding of the atmospheric response to midlatitude oceanic fronts and eddies,emphasizing the Kuroshio-Oyashio Extension(KOE)region.Oceanic perturbations of interest consist of sharp oceanic fronts,temperature anomalies associated with mesoscale eddies,and to some extent even higher-frequency submesoscale variability.The focus is on the free atmosphere above the boundary layer.As the midlatitude atmosphere is dominated by vigorous transient eddy activity in the storm track,the response of both the time-mean flow and the storm track is assessed.The storm track response arguably overwhelms the mean-flow response and makes the latter hard to detect from observations.Oceanic frontal impacts on the mesoscale structures of individual synoptic storms are discussed,followed by the role of oceanic fronts in maintaining the storm track as a whole.KOE fronts exhibit significant decadal variability and can therefore presumably modulate the storm track.Relevant studies are summarized and intercompared.Current understanding has advanced greatly but is still subject to large uncertainties arising from inadequate data resolution and other factors.Recent modeling studies highlighted the importance of mesoscale eddies and probably even submesoscale processes in maintaining the storm track but confirmation and validation are still needed.Moreover,the atmospheric response can potentially provide a feedback mechanism for the North Pacific climate.By reviewing the above aspects,we envision that future research shall focus more upon the interaction between smaller-scale oceanic processes(fronts,eddies,submesoscale features)and atmospheric processes(fronts,extratropical cyclones etc.),in an integrated way,within the context of different climate background states.展开更多
Features of the interannual variability of the spring Wyrtki Jet in the tropical Indian Ocean are revealed using observation data and model output.The results show that the jet has signifi cant interannual variation,w...Features of the interannual variability of the spring Wyrtki Jet in the tropical Indian Ocean are revealed using observation data and model output.The results show that the jet has signifi cant interannual variation,which has a signifi cant correlation with winter El Niño Modoki index(R=0.62).During spring after an El Niño(La Niña)Modoki event,the Wyrtki Jet has a positive(negative)anomaly,forced by a westerly(easterly)wind anomaly.The result of a linear-continuously stratifi ed model shows that the fi rst two baroclinic modes explain most of the interannual variability of the spring Wyrtki Jet(~70%)and the third to fi fth modes together account for approximately 30%.Surface wind anomalies in the tropical Indian Ocean are related to the Walker circulation anomaly associated with El Niño/La Niña Modoki.The interannual variability of the spring Wyrtki Jet has an evident impact on sea surface salinity transport before the onset phase of the summer monsoon in the Indian Ocean.展开更多
Interannual variability(IAV)in the barrier layer thickness(BLT)and forcing mechanisms in the eastern equatorial Indian Ocean(EEIO)and Bay of Bengal(BoB)are examined using monthly Argo data sets during 2002–2017.The B...Interannual variability(IAV)in the barrier layer thickness(BLT)and forcing mechanisms in the eastern equatorial Indian Ocean(EEIO)and Bay of Bengal(BoB)are examined using monthly Argo data sets during 2002–2017.The BLT during November–January(NDJ)in the EEIO shows strong IAV,which is associated with the Indian Ocean dipole mode(IOD),with the IOD leading the BLT by two months.During the negative IOD phase,the westerly wind anomalies driving the downwelling Kelvin waves increase the isothermal layer depth(ILD).Moreover,the variability in the mixed layer depth(MLD)is complex.Affected by the Wyrtki jet,the MLD presents negative anomalies west of 85°E and strong positive anomalies between 85°E and 93°E.Therefore,the BLT shows positive anomalies except between 86°E and 92°E in the EEIO.Additionally,the IAV in the BLT during December–February(DJF)in the BoB is also investigated.In the eastern and northeastern BoB,the IAV in the BLT is remotely forced by equatorial zonal wind stress anomalies associated with the El Ni?o-Southern Oscillation(ENSO).In the western BoB,the regional surface wind forcing-related ENSO modulates the BLT variations.展开更多
Mesoscale eddy generation mechanisms in the eastern South China Sea(ESCS) are investigated using altimetry observations and solutions of a nonlinear, 1?-layer reduced-gravity model. We estimate the relative roles of t...Mesoscale eddy generation mechanisms in the eastern South China Sea(ESCS) are investigated using altimetry observations and solutions of a nonlinear, 1?-layer reduced-gravity model. We estimate the relative roles of the wind forcing in the interior South China Sea(SCS) and the remote forcing from the western tropical Pacific(WTP)in eddy generation in the ESCS. Model solutions show that the high-frequency wind in the interior SCS is the primary forcing for eddies, which explains about 54% of the mesoscale eddies generated in the ESCS. Signals from the WTP also play an important role. Wind-driven equatorial signals reach the west coast of Luzon Island through the Sibutu Passage and Mindoro Strait. The reflected Rossby waves from the west coast of Luzon Island propagate westward, become unstable, and turn into eddies. The signals driven by high-frequency wind from the WTP explain about 40% of the mesoscale eddies generated in the ESCS. The high-frequency wind forcing in both the SCS and the WTP is important for eddy generation in the ESCS.展开更多
The unbalanced submesoscale motions and their seasonality in the northern Bay of Bengal(BoB)are investigated using outputs of the high resolution regional oceanic modeling system.Submesoscale motions in the forms of f...The unbalanced submesoscale motions and their seasonality in the northern Bay of Bengal(BoB)are investigated using outputs of the high resolution regional oceanic modeling system.Submesoscale motions in the forms of filaments and eddies are present in the upper mixed layer during the whole annual cycle.Submesoscale motions show an obvious seasonality,in which they are active during the winter and spring but weak during the summer and fall.Their seasonality is associated with the mixed layer instability that depends on the mixed layer depth(MLD).During the winter,the MLD provides a much greater reservoir of the available potential energy,which promotes mixed layer instability to develop active submesoscale motions.The variations of MLD are likely modulated by the larger scale motions and the influxes of freshwater.Further investigations imply that the MLD and the stratified barrier layer are combined to determine the vertical structure of the submesoscale motions.The shallow MLD and strong stratification below during the summer and fall seem to prevent the downward extension of submesoscale motions.But in spring when the weak stratification exists,the penetration depth exceeds the base of the barrier layer.展开更多
An analysis of a 68-year monthly hindcast output from an eddy-resolving ocean general circulation model reveals the relationship between the interannual variability of the Kerama Gap transport(KGT)and the Kuroshio/Ryu...An analysis of a 68-year monthly hindcast output from an eddy-resolving ocean general circulation model reveals the relationship between the interannual variability of the Kerama Gap transport(KGT)and the Kuroshio/Ryukyu Current system.The study found a significant difference in the interannual variability of the upstream and downstream transports of the East China Sea-(ECS-)Kuroshio and the Ryukyu Current.The interannual variability of the KGT was found to be of paramount importance in causing the differences between the upstream and downstream ECS-Kuroshio.Additionally,it contributed approximately 37%to the variability of the Ryukyu Current.The interannual variability of the KGT was well described by a two-layer rotating hydraulic theory.It was dominated by its subsurface-intensified flow core,and the upper layer transport made a weaker negative contribution to the total KGT.The subsurface flow core was found to be mainly driven by the subsurface pressure head across the Kerama Gap,and the pressure head was further dominated by the subsurface density anomalies on the Pacific side.These density anomalies could be traced back to the eastern open ocean,and their propagation speed was estimated to be about 7.4 km/d,which is consistent with the speed of the local first-order baroclinic Rossby wave.When the negative(positive)density anomaly signal reached the southern region of the Kerama Gap,it triggered the increase(decrease)of the KGT towards the Pacific side and the formation of an anticyclonic(cyclonic)vortex by baroclinic adjustment.Meanwhile,there is an increase(decrease)in the upstream transport of the entire Kuroshio/Ryukyu Current system and an offshore flow that decreases(increases)the downstream Ryukyu Current.展开更多
Seasonal and interannual variability of ocean bottom pressure(OBP)in the Southern Ocean was investigated using Gravity Recovery and Climate Experiment(GRACE)data and a Pressure Coordinate Ocean Model(PCOM)based on mas...Seasonal and interannual variability of ocean bottom pressure(OBP)in the Southern Ocean was investigated using Gravity Recovery and Climate Experiment(GRACE)data and a Pressure Coordinate Ocean Model(PCOM)based on mass conservation.By comparing OBP,steric sea level,and sea level,it is found that at high latitudes the OBP variability dominates the sea level variability at seasonal-to-decadal time scales.The diagnostic OBP based on barotropic vorticity equation has a good correlation with the observations,indicating that wind forcing plays an important role in the variability of the OBP in the Southern Ocean.The unique interannual patterns of OBP in the Southern Ocean are closely associated with El Niño-Southern Oscillation(ENSO)and Southern Annular Mode(SAM).Regression analysis indicates that ENSO and SAM influence the OBP through altering the Ekman transport driven by surface wind.The leading pattern of OBP from PCOM are very similar to observations.Sensitive experiments of PCOM show that surface wind forcing explains the observed OBP variability quite well,confirming the importance of wind forcing and related oceanic processes.In the eastern South Pacific,the averaged OBP shows a decrease(increase)trend before(after)2011,reflecting the reverse trend in westerly wind.In the South Indo-Atlantic Ocean,the averaged OBP has a weak increase trend during 2003–2016.展开更多
Using a gridded array for real-time geostrophic oceanography(Argo)program float dataset,the features of upperocean salinity stratification in the tropical Pacific Ocean are studied.The salinity component of the square...Using a gridded array for real-time geostrophic oceanography(Argo)program float dataset,the features of upperocean salinity stratification in the tropical Pacific Ocean are studied.The salinity component of the squared Brunt-V?is?l?frequency N2(NS2)is used to represent salinity stratification.Layer-max NS2(LMN),defined as the NS2 maximum over the upper 300 m depth,and halocline depth(HD),defined as the depth where the NS2 maximum is located,are used to specifically describe the intensity of salinity stratification.Salinity stratification in the Topical Pacific Ocean has both spatial and temporal variability.Over the western and eastern equatorial Pacific,the LMN has a large magnitude with a shallow HD,and both have completely opposite distributions outside of the equatorial region.An obvious seasonal cycle in the LMN occurs in the north side of eastern equatorial Pacific and freshwater flux forcing dominates the seasonal variations,followed by subsurface forcing.At the eastern edge of the western Pacific warm pool around the dateline,significant interannual variation of salinity stratification occurs and is closely related to the El Ni?o Southern Oscillation event.When an El Ni?o event occurs,the precipitation anomaly freshens sea surface and the thermocline shoaling induced by the westerly wind anomaly lifts salty water upward,together contribute to the positive salinity stratification anomaly over the eastern edge of the warm pool.The interannual variations in ocean stratification can slightly affect the propagation of first baroclinic gravity waves.展开更多
We introduce a new method, the piecewise Reynolds mean(PREM), for decomposing the flow velocity into the mean-flow and eddy-flow parts in the time domain for subsequent calculation of the mean flow kinetic energy(MKE)...We introduce a new method, the piecewise Reynolds mean(PREM), for decomposing the flow velocity into the mean-flow and eddy-flow parts in the time domain for subsequent calculation of the mean flow kinetic energy(MKE) and eddy kinetic energy(EKE). Compared with conventional methods like the Reynolds mean and running mean(RUM), PREM has the advantage of exact balance between the MKE and EKE, without the additional residual kinetic energy(RKE), while retaining time-dependent mean-flow. It is mathematically simple and computationally lightweight, depending on a pre-defined separation scale for the mean-flow and eddies. Based on satellite observations and the separation scale of 1 year, we compare PREM with RUM, as well as another newly proposed method, the eddy detection and extraction(EDEX). The latter is based on objective identification of mesoscale eddies and eddy anomaly extraction algorithms, and is therefore only suitable for mesoscale eddy energetics, but independent of separation scales. It is shown that compared with RUM, PREM gives larger mean EKE and stronger interannual variability. In strong-current and eddy-rich regions, the two methods differ the most(max: Kuroshio Extension, root-mean-sqaure-difference = 60.3 J/m^(3));but in areas with weak current and eddy, the difference accounts for the largest fraction of total EKE(max: south of the Aleutian Islands, 208%). EKE estimated by the two methods is out of phase(min correlation coefficient = 0.38). The mean EKE and standard deviation from the EDEX method resemble the PREM with 1-year separation scale, but is generally smaller in magnitude.展开更多
In this study,convolutional long short-term memory(ConvLSTM)model is used to predict sea level anomaly(SLA)in the Kuroshio Extension(KE)region,utilizing daily satellite altimetry data(1993-2016).The model captures reg...In this study,convolutional long short-term memory(ConvLSTM)model is used to predict sea level anomaly(SLA)in the Kuroshio Extension(KE)region,utilizing daily satellite altimetry data(1993-2016).The model captures regional averaged SLA variability,achieving a correlation coefficient of 0.98 for prediction horizon up to 23 d.Propagating features of Rossby waves are also reproduced in the prediction model.While in spatial,discrepancies between predicted SLA and observed SLA are quite large,especially in regions with strong eddy activities.Incorporating equation of motion for the 11/2-layer reduced-gravity model,the performance of the model has a significant improvement spatially and temporally.Challenges persist in high-variability regions,underscoring the need for advanced models.This study highlights ConvLSTM’s potential for SLA forecasting with wind driven physical constraints,offering insights into wind-driven and eddy-influenced processes in the KE region.展开更多
In this paper,we study chaotic behavior of the(N+1)-body planar ring problem.Firstly,based on the perturbation theory of integrable Hamiltonian systems,we utilize mass ratio as a disturbance parameter so that this rin...In this paper,we study chaotic behavior of the(N+1)-body planar ring problem.Firstly,based on the perturbation theory of integrable Hamiltonian systems,we utilize mass ratio as a disturbance parameter so that this ring problem is regarded as a perturbation of the two-body problem.Then,by applying the extended Melnikov method,we address that there are transversal homoclinic orbits in the ring problem.Afterwards,since the standard Smale–Birkhoff homoclinic theorem cannot be directly applied to the case of a degenerate saddle,we construct an invertible map f satisfying Conley–Moser condition and finally conclude that the ring problem possesses chaotic behavior of the Smale horseshoe type.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.41906001)the Natural Science Foundation of Jiangsu Province(Grant No.BK20190501)the Fundamental Research Funds for the Central Universities(Grant No.B210202137)。
文摘This paper reviews the progress in our understanding of the atmospheric response to midlatitude oceanic fronts and eddies,emphasizing the Kuroshio-Oyashio Extension(KOE)region.Oceanic perturbations of interest consist of sharp oceanic fronts,temperature anomalies associated with mesoscale eddies,and to some extent even higher-frequency submesoscale variability.The focus is on the free atmosphere above the boundary layer.As the midlatitude atmosphere is dominated by vigorous transient eddy activity in the storm track,the response of both the time-mean flow and the storm track is assessed.The storm track response arguably overwhelms the mean-flow response and makes the latter hard to detect from observations.Oceanic frontal impacts on the mesoscale structures of individual synoptic storms are discussed,followed by the role of oceanic fronts in maintaining the storm track as a whole.KOE fronts exhibit significant decadal variability and can therefore presumably modulate the storm track.Relevant studies are summarized and intercompared.Current understanding has advanced greatly but is still subject to large uncertainties arising from inadequate data resolution and other factors.Recent modeling studies highlighted the importance of mesoscale eddies and probably even submesoscale processes in maintaining the storm track but confirmation and validation are still needed.Moreover,the atmospheric response can potentially provide a feedback mechanism for the North Pacific climate.By reviewing the above aspects,we envision that future research shall focus more upon the interaction between smaller-scale oceanic processes(fronts,eddies,submesoscale features)and atmospheric processes(fronts,extratropical cyclones etc.),in an integrated way,within the context of different climate background states.
基金Supported by the National Key R&D Program of China(No.2018YFA0605702)the National Natural Science Foundation of China(Nos.41876002,41776002)the Fundamental Research Funds for the Central Universities(Nos.2017B04714,2017B04114)。
文摘Features of the interannual variability of the spring Wyrtki Jet in the tropical Indian Ocean are revealed using observation data and model output.The results show that the jet has signifi cant interannual variation,which has a signifi cant correlation with winter El Niño Modoki index(R=0.62).During spring after an El Niño(La Niña)Modoki event,the Wyrtki Jet has a positive(negative)anomaly,forced by a westerly(easterly)wind anomaly.The result of a linear-continuously stratifi ed model shows that the fi rst two baroclinic modes explain most of the interannual variability of the spring Wyrtki Jet(~70%)and the third to fi fth modes together account for approximately 30%.Surface wind anomalies in the tropical Indian Ocean are related to the Walker circulation anomaly associated with El Niño/La Niña Modoki.The interannual variability of the spring Wyrtki Jet has an evident impact on sea surface salinity transport before the onset phase of the summer monsoon in the Indian Ocean.
基金The National Key R&D Program of China under contract No.2018YFA0605702the National Natural Science Foundation of China under contract Nos 41522601,41876002 and 41876224the Fundamental Research Funds for the Central Universities under contract Nos 2017B04714 and 2017B4114。
文摘Interannual variability(IAV)in the barrier layer thickness(BLT)and forcing mechanisms in the eastern equatorial Indian Ocean(EEIO)and Bay of Bengal(BoB)are examined using monthly Argo data sets during 2002–2017.The BLT during November–January(NDJ)in the EEIO shows strong IAV,which is associated with the Indian Ocean dipole mode(IOD),with the IOD leading the BLT by two months.During the negative IOD phase,the westerly wind anomalies driving the downwelling Kelvin waves increase the isothermal layer depth(ILD).Moreover,the variability in the mixed layer depth(MLD)is complex.Affected by the Wyrtki jet,the MLD presents negative anomalies west of 85°E and strong positive anomalies between 85°E and 93°E.Therefore,the BLT shows positive anomalies except between 86°E and 92°E in the EEIO.Additionally,the IAV in the BLT during December–February(DJF)in the BoB is also investigated.In the eastern and northeastern BoB,the IAV in the BLT is remotely forced by equatorial zonal wind stress anomalies associated with the El Ni?o-Southern Oscillation(ENSO).In the western BoB,the regional surface wind forcing-related ENSO modulates the BLT variations.
基金The National Natural Science Foundation of China under contract Nos 41522601,41876002,41876224 and4170060064the Fundamental Research Funds for the Central Universities under contract Nos 2017B04714 and 2017B4114
文摘Mesoscale eddy generation mechanisms in the eastern South China Sea(ESCS) are investigated using altimetry observations and solutions of a nonlinear, 1?-layer reduced-gravity model. We estimate the relative roles of the wind forcing in the interior South China Sea(SCS) and the remote forcing from the western tropical Pacific(WTP)in eddy generation in the ESCS. Model solutions show that the high-frequency wind in the interior SCS is the primary forcing for eddies, which explains about 54% of the mesoscale eddies generated in the ESCS. Signals from the WTP also play an important role. Wind-driven equatorial signals reach the west coast of Luzon Island through the Sibutu Passage and Mindoro Strait. The reflected Rossby waves from the west coast of Luzon Island propagate westward, become unstable, and turn into eddies. The signals driven by high-frequency wind from the WTP explain about 40% of the mesoscale eddies generated in the ESCS. The high-frequency wind forcing in both the SCS and the WTP is important for eddy generation in the ESCS.
基金The National Key R&D Program of China under contract No.2018YFA0605702the National Natural Science Foundation of China under contract Nos 41876002 and 41776002。
文摘The unbalanced submesoscale motions and their seasonality in the northern Bay of Bengal(BoB)are investigated using outputs of the high resolution regional oceanic modeling system.Submesoscale motions in the forms of filaments and eddies are present in the upper mixed layer during the whole annual cycle.Submesoscale motions show an obvious seasonality,in which they are active during the winter and spring but weak during the summer and fall.Their seasonality is associated with the mixed layer instability that depends on the mixed layer depth(MLD).During the winter,the MLD provides a much greater reservoir of the available potential energy,which promotes mixed layer instability to develop active submesoscale motions.The variations of MLD are likely modulated by the larger scale motions and the influxes of freshwater.Further investigations imply that the MLD and the stratified barrier layer are combined to determine the vertical structure of the submesoscale motions.The shallow MLD and strong stratification below during the summer and fall seem to prevent the downward extension of submesoscale motions.But in spring when the weak stratification exists,the penetration depth exceeds the base of the barrier layer.
基金The Fundamental Research Funds for the Central Universities under contract No.B220201024.
文摘An analysis of a 68-year monthly hindcast output from an eddy-resolving ocean general circulation model reveals the relationship between the interannual variability of the Kerama Gap transport(KGT)and the Kuroshio/Ryukyu Current system.The study found a significant difference in the interannual variability of the upstream and downstream transports of the East China Sea-(ECS-)Kuroshio and the Ryukyu Current.The interannual variability of the KGT was found to be of paramount importance in causing the differences between the upstream and downstream ECS-Kuroshio.Additionally,it contributed approximately 37%to the variability of the Ryukyu Current.The interannual variability of the KGT was well described by a two-layer rotating hydraulic theory.It was dominated by its subsurface-intensified flow core,and the upper layer transport made a weaker negative contribution to the total KGT.The subsurface flow core was found to be mainly driven by the subsurface pressure head across the Kerama Gap,and the pressure head was further dominated by the subsurface density anomalies on the Pacific side.These density anomalies could be traced back to the eastern open ocean,and their propagation speed was estimated to be about 7.4 km/d,which is consistent with the speed of the local first-order baroclinic Rossby wave.When the negative(positive)density anomaly signal reached the southern region of the Kerama Gap,it triggered the increase(decrease)of the KGT towards the Pacific side and the formation of an anticyclonic(cyclonic)vortex by baroclinic adjustment.Meanwhile,there is an increase(decrease)in the upstream transport of the entire Kuroshio/Ryukyu Current system and an offshore flow that decreases(increases)the downstream Ryukyu Current.
基金The National Key R&D Program of China under contract No.2018YFA0605703the National Natural Science Foundation of China under contract Nos 41876002 and 41876224.
文摘Seasonal and interannual variability of ocean bottom pressure(OBP)in the Southern Ocean was investigated using Gravity Recovery and Climate Experiment(GRACE)data and a Pressure Coordinate Ocean Model(PCOM)based on mass conservation.By comparing OBP,steric sea level,and sea level,it is found that at high latitudes the OBP variability dominates the sea level variability at seasonal-to-decadal time scales.The diagnostic OBP based on barotropic vorticity equation has a good correlation with the observations,indicating that wind forcing plays an important role in the variability of the OBP in the Southern Ocean.The unique interannual patterns of OBP in the Southern Ocean are closely associated with El Niño-Southern Oscillation(ENSO)and Southern Annular Mode(SAM).Regression analysis indicates that ENSO and SAM influence the OBP through altering the Ekman transport driven by surface wind.The leading pattern of OBP from PCOM are very similar to observations.Sensitive experiments of PCOM show that surface wind forcing explains the observed OBP variability quite well,confirming the importance of wind forcing and related oceanic processes.In the eastern South Pacific,the averaged OBP shows a decrease(increase)trend before(after)2011,reflecting the reverse trend in westerly wind.In the South Indo-Atlantic Ocean,the averaged OBP has a weak increase trend during 2003–2016.
基金The National Key R&D Program of China under contract No.2018YFA0605702the National Natural Science Foundation of China under contract Nos 41876002 and 41776002the Fundamental Research Funds for the Central Universities under contract Nos 2017B04714 and 2017B4114
文摘Using a gridded array for real-time geostrophic oceanography(Argo)program float dataset,the features of upperocean salinity stratification in the tropical Pacific Ocean are studied.The salinity component of the squared Brunt-V?is?l?frequency N2(NS2)is used to represent salinity stratification.Layer-max NS2(LMN),defined as the NS2 maximum over the upper 300 m depth,and halocline depth(HD),defined as the depth where the NS2 maximum is located,are used to specifically describe the intensity of salinity stratification.Salinity stratification in the Topical Pacific Ocean has both spatial and temporal variability.Over the western and eastern equatorial Pacific,the LMN has a large magnitude with a shallow HD,and both have completely opposite distributions outside of the equatorial region.An obvious seasonal cycle in the LMN occurs in the north side of eastern equatorial Pacific and freshwater flux forcing dominates the seasonal variations,followed by subsurface forcing.At the eastern edge of the western Pacific warm pool around the dateline,significant interannual variation of salinity stratification occurs and is closely related to the El Ni?o Southern Oscillation event.When an El Ni?o event occurs,the precipitation anomaly freshens sea surface and the thermocline shoaling induced by the westerly wind anomaly lifts salty water upward,together contribute to the positive salinity stratification anomaly over the eastern edge of the warm pool.The interannual variations in ocean stratification can slightly affect the propagation of first baroclinic gravity waves.
基金The National Natural Science Foundation of China under contract No.42276002the Fund of State Key Laboratory of Tropical Oceanography,South China Sea Institute of Oceanography,Chinese Academy of Sciences under contract No.LTO2201the Fund of Key Laboratory of Marine Hazards Forecasting,Ministry of Natural Resources,China under contract No.LOMF2201。
文摘We introduce a new method, the piecewise Reynolds mean(PREM), for decomposing the flow velocity into the mean-flow and eddy-flow parts in the time domain for subsequent calculation of the mean flow kinetic energy(MKE) and eddy kinetic energy(EKE). Compared with conventional methods like the Reynolds mean and running mean(RUM), PREM has the advantage of exact balance between the MKE and EKE, without the additional residual kinetic energy(RKE), while retaining time-dependent mean-flow. It is mathematically simple and computationally lightweight, depending on a pre-defined separation scale for the mean-flow and eddies. Based on satellite observations and the separation scale of 1 year, we compare PREM with RUM, as well as another newly proposed method, the eddy detection and extraction(EDEX). The latter is based on objective identification of mesoscale eddies and eddy anomaly extraction algorithms, and is therefore only suitable for mesoscale eddy energetics, but independent of separation scales. It is shown that compared with RUM, PREM gives larger mean EKE and stronger interannual variability. In strong-current and eddy-rich regions, the two methods differ the most(max: Kuroshio Extension, root-mean-sqaure-difference = 60.3 J/m^(3));but in areas with weak current and eddy, the difference accounts for the largest fraction of total EKE(max: south of the Aleutian Islands, 208%). EKE estimated by the two methods is out of phase(min correlation coefficient = 0.38). The mean EKE and standard deviation from the EDEX method resemble the PREM with 1-year separation scale, but is generally smaller in magnitude.
基金The National Natural Science Foundation of China under contract No.42276014Jiangsu Natural Resources Development Special Fund(Marine Science and Technology Innovation)under contract No.JSZRKJ202403.
文摘In this study,convolutional long short-term memory(ConvLSTM)model is used to predict sea level anomaly(SLA)in the Kuroshio Extension(KE)region,utilizing daily satellite altimetry data(1993-2016).The model captures regional averaged SLA variability,achieving a correlation coefficient of 0.98 for prediction horizon up to 23 d.Propagating features of Rossby waves are also reproduced in the prediction model.While in spatial,discrepancies between predicted SLA and observed SLA are quite large,especially in regions with strong eddy activities.Incorporating equation of motion for the 11/2-layer reduced-gravity model,the performance of the model has a significant improvement spatially and temporally.Challenges persist in high-variability regions,underscoring the need for advanced models.This study highlights ConvLSTM’s potential for SLA forecasting with wind driven physical constraints,offering insights into wind-driven and eddy-influenced processes in the KE region.
基金supported by the National Natural Science Foundation of China(Grant No.11601257)Natural Science Foundation of Hebei Province(Grant Nos.A2019202342,A2023202041)。
文摘In this paper,we study chaotic behavior of the(N+1)-body planar ring problem.Firstly,based on the perturbation theory of integrable Hamiltonian systems,we utilize mass ratio as a disturbance parameter so that this ring problem is regarded as a perturbation of the two-body problem.Then,by applying the extended Melnikov method,we address that there are transversal homoclinic orbits in the ring problem.Afterwards,since the standard Smale–Birkhoff homoclinic theorem cannot be directly applied to the case of a degenerate saddle,we construct an invertible map f satisfying Conley–Moser condition and finally conclude that the ring problem possesses chaotic behavior of the Smale horseshoe type.
基金supported by the National Key Research and Development Program of China (2018YFA0605700)supported by the Joint Research Centre for Southern Hemisphere Oceans Research (CSHOR)between the Qingdao National Laboratory for Marine Science and Technology (QNLM)and the Commonwealth Scientific and Industrial Research Organisation (CSIRO)+10 种基金supported by the Australian Research Council Special Research Initiative for Securing Antarctica’s Environmental Future (SR200100005)supported by the National Natural Science Foundation of China (41876231)supported by the National Natural Science Foundation of China (42230405 and 41976006)the National Natural Science Foundation of China (41876008 and 41730534)supported by the National Natural Science Foundation of China (41830538)the Program of Impact and Response of Antarctic Seas to Climate Change (IRASCC 01-01-01A)supported by the National Key Research and Development Program of China (2020YFA0608801)the Youth Innovation Promotion Association of Chinese Academy of Sciences (2021205)supported by the National Science Foundation (AGS-1934392)supported by the National Science Foundation (OCE-2048336)the International Partnership Program of Chinese Academy of Sciences (183311KYSB20200015)。
