This paper overviews research progress in observation, theoretical analysis and numerical modeling of submesoscale dynamic processes in the South China Sea(SCS) particularly during recent five years. The submesoscale ...This paper overviews research progress in observation, theoretical analysis and numerical modeling of submesoscale dynamic processes in the South China Sea(SCS) particularly during recent five years. The submesoscale processes are defined according to both spatial and dynamic scales, and divided into four subcategories as submesoscale waves, submesoscale vortexes, submesoscale shelf processes, and submesoscale turbulence. The major new findings are as follows.(1) Systematic mooring observations provide new insights into the solitary waves(ISWs) and the typhoon-forced near-inertial waves(NIWs), of which a new type of ISWs with period of 23 h was observed in the northern SCS(NSCS), and the influences of background vorticity, summer monsoon onset, and deep meridional overturning circulation on the NIWs, as well as nonlinear wave-wave interaction between the NIWs and internal tides, are better understood. On the other hand, satellite altimeter sea surface height data are used to reveal the internal tide radiation patterns and provide solid evidence for that the ISWs in the northeastern SCS originate from the Luzon Strait.(2) Submesoscale offshore jets and associated vortex trains off the Vietnam coast in the western boundary of the SCS were observed from satellite chlorophyll concentration images. Spiral trains with the horizontal scale of 15–30 km and the spacing of 50–80 km were identified.(3) 3-D vertical circulation in the upwelling region east of Hainan Island was theoretically analyzed. The results show that distribution patterns of all the dynamic terms are featured by wave-like structures with horizontal wavelength scale of 20–40 km.(4) Numerical models have been used for the research of submesoscale turbulence. Submesoscale vertical pump of an anticyclonic eddy and the spatiotemporal features of submesoscale processes in the northeastern SCS are well modeled.展开更多
The spatiotemporal features of submesoscale processes （SMPs） in the northeastern South China Sea （SCS） are analyzed based on a high-resolution simulation from 2009 to 2012. The simulation results show that the SMP...The spatiotemporal features of submesoscale processes （SMPs） in the northeastern South China Sea （SCS） are analyzed based on a high-resolution simulation from 2009 to 2012. The simulation results show that the SMPs with a vertical relative vorticity that matches the local planetary vorticity are ubiquitous in the upper ocean of the northeastern SCS. The SMPs distribution shows an asymmetry due to centrifugal instability, with stronger positive vorticity than negative vorticity. Meanwhile, the SMPs demonstrate an obvious seasonal variation. The SMPs are strong and active in winter but weak and inactive in summer. An investigation of the SMPs generation mechanisms reveals that flow straining and mixed layer depth account for this seasonal variation. The strong flow straining and deep mixed layer depth in winter favor the SMP generation via frontogenesis and mixed layer instability.展开更多
Submesoscale activity in the upper ocean has received intense studies through simulations and observations in the last decade,but in the eddy-active South China Sea(SCS)the fine-scale dynamical processes of submesosca...Submesoscale activity in the upper ocean has received intense studies through simulations and observations in the last decade,but in the eddy-active South China Sea(SCS)the fine-scale dynamical processes of submesoscale behaviors and their potential impacts have not been well understood.This study focuses on the elongated filaments of an eddy field in the northern SCS and investigates submesoscale-enhanced vertical motions and the underlying mechanism using satellite-derived observations and a high-resolution(∼500 m)simulation.The satellite images show that the elongated highly productive stripes with a typical lateral scale of∼25 km and associated filaments are frequently observed at the periphery of mesoscale eddies.The diagnostic results based on the 500 m-resolution realistic simulation indicate that these submesoscale filaments are characterized by cross-filament vertical secondary circulations with an increased vertical velocity reaching O(100 m/d)due to submesoscale instabilities.The vertical advections of secondary circulations drive a restratified vertical buoyancy flux along filament zones and induce a vertical heat flux up to 110 W/m^(2).This result implies a significant submesoscale-enhanced vertical exchange between the ocean surface and interior in the filaments.Frontogenesis that acts to sharpen the lateral buoyancy gradients is detected to be conducive to driving submesoscale instabilities and enhancing secondary circulations through increasing the filament baroclinicity.The further analysis indicates that the filament frontogenesis detected in this study is not only derived from mesoscale straining of the eddy,but also effectively induced by the subsequent submesoscale straining due to ageostrophic convergence.In this context,these submesoscale filaments and associated frontogenetic processes can provide a potential interpretation for the vertical nutrient supply for phytoplankton growth in the high-productive stripes within the mesoscale eddy,as well as enhanced vertical heat transport.展开更多
The South China Sea(SCS)is abundant with complex multiscale dynamic processes but their spatiotemporal variations,generation and evolution mechanisms,and mutual interactions remain inadequately understood due to the l...The South China Sea(SCS)is abundant with complex multiscale dynamic processes but their spatiotemporal variations,generation and evolution mechanisms,and mutual interactions remain inadequately understood due to the lack of long-term in situ observations.To explore oceanic multiscale dynamics in the SCS,the SCS Mooring Array(SCSMA)was began to be constructed since 2009.The SCSMA consists of∼40 moorings and is the largest in situ ocean observing system in marginal seas worldwide.The highest spatial resolution of SCSMA is∼1.5 km,and the longest duration of fixed-location observations reaches∼15 years.Long-term observations from the SCSMA have allowed significant advances in the understanding of large-scale circulation,mesoscale eddies,submesoscale processes,internal waves,turbulent mixing,and interactions and energy cascades of different processes.In particular,the full chain of forward energy cascade from large-scale currents to turbulence has been revealed.Different dynamic processes in the SCS constitute a three-dimensional multiscale circulation system which transports materials and tracers in a relay.Here,we first describe the SCSMA and its construction process,and then comprehensively review its relevant advances in multiscale dynamics.Prospects for the SCSMA and its future applications are given at the end.展开更多
基金The National Natural Science Foundation of China under contract Nos 41776034,41376038,40406009,41806123 and 41506034the National Science and Technology Major Project under contract No.2016ZX05057015+1 种基金the Guangdong Province First-Class Discipline Plan under contract No.CYL231419012the Fund of Southern Marine Science and Engineering Guangdong Laboratory(Zhanjiang)under contract No.ZJW-2019-08
文摘This paper overviews research progress in observation, theoretical analysis and numerical modeling of submesoscale dynamic processes in the South China Sea(SCS) particularly during recent five years. The submesoscale processes are defined according to both spatial and dynamic scales, and divided into four subcategories as submesoscale waves, submesoscale vortexes, submesoscale shelf processes, and submesoscale turbulence. The major new findings are as follows.(1) Systematic mooring observations provide new insights into the solitary waves(ISWs) and the typhoon-forced near-inertial waves(NIWs), of which a new type of ISWs with period of 23 h was observed in the northern SCS(NSCS), and the influences of background vorticity, summer monsoon onset, and deep meridional overturning circulation on the NIWs, as well as nonlinear wave-wave interaction between the NIWs and internal tides, are better understood. On the other hand, satellite altimeter sea surface height data are used to reveal the internal tide radiation patterns and provide solid evidence for that the ISWs in the northeastern SCS originate from the Luzon Strait.(2) Submesoscale offshore jets and associated vortex trains off the Vietnam coast in the western boundary of the SCS were observed from satellite chlorophyll concentration images. Spiral trains with the horizontal scale of 15–30 km and the spacing of 50–80 km were identified.(3) 3-D vertical circulation in the upwelling region east of Hainan Island was theoretically analyzed. The results show that distribution patterns of all the dynamic terms are featured by wave-like structures with horizontal wavelength scale of 20–40 km.(4) Numerical models have been used for the research of submesoscale turbulence. Submesoscale vertical pump of an anticyclonic eddy and the spatiotemporal features of submesoscale processes in the northeastern SCS are well modeled.
基金The National Key Research and Development Program of China under contract No.2017YFA0604103the National Basic Research Program(973 Program)of China under contract No.2014CB745003+1 种基金the National Natural Science Foundation of China under contract No.91628302the Startup Foundation for the Introducing Talent of the Nanjing University of Information Science and Technology under contract No.2243141601059
文摘The spatiotemporal features of submesoscale processes （SMPs） in the northeastern South China Sea （SCS） are analyzed based on a high-resolution simulation from 2009 to 2012. The simulation results show that the SMPs with a vertical relative vorticity that matches the local planetary vorticity are ubiquitous in the upper ocean of the northeastern SCS. The SMPs distribution shows an asymmetry due to centrifugal instability, with stronger positive vorticity than negative vorticity. Meanwhile, the SMPs demonstrate an obvious seasonal variation. The SMPs are strong and active in winter but weak and inactive in summer. An investigation of the SMPs generation mechanisms reveals that flow straining and mixed layer depth account for this seasonal variation. The strong flow straining and deep mixed layer depth in winter favor the SMP generation via frontogenesis and mixed layer instability.
基金The National Natural Science Foundation of China under contract Nos 92058201,41776040,41830538 and 41949907the Talents Team Project of Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou)under contract No.GML2019ZD0303the Program of Chinese Academy of Sciences under contract Nos ZDBS-LY-DQC011,ZDRW-XH-2019-2,XDA15020901 and ISEE2021PY01.
文摘Submesoscale activity in the upper ocean has received intense studies through simulations and observations in the last decade,but in the eddy-active South China Sea(SCS)the fine-scale dynamical processes of submesoscale behaviors and their potential impacts have not been well understood.This study focuses on the elongated filaments of an eddy field in the northern SCS and investigates submesoscale-enhanced vertical motions and the underlying mechanism using satellite-derived observations and a high-resolution(∼500 m)simulation.The satellite images show that the elongated highly productive stripes with a typical lateral scale of∼25 km and associated filaments are frequently observed at the periphery of mesoscale eddies.The diagnostic results based on the 500 m-resolution realistic simulation indicate that these submesoscale filaments are characterized by cross-filament vertical secondary circulations with an increased vertical velocity reaching O(100 m/d)due to submesoscale instabilities.The vertical advections of secondary circulations drive a restratified vertical buoyancy flux along filament zones and induce a vertical heat flux up to 110 W/m^(2).This result implies a significant submesoscale-enhanced vertical exchange between the ocean surface and interior in the filaments.Frontogenesis that acts to sharpen the lateral buoyancy gradients is detected to be conducive to driving submesoscale instabilities and enhancing secondary circulations through increasing the filament baroclinicity.The further analysis indicates that the filament frontogenesis detected in this study is not only derived from mesoscale straining of the eddy,but also effectively induced by the subsequent submesoscale straining due to ageostrophic convergence.In this context,these submesoscale filaments and associated frontogenetic processes can provide a potential interpretation for the vertical nutrient supply for phytoplankton growth in the high-productive stripes within the mesoscale eddy,as well as enhanced vertical heat transport.
基金acknowledge support for the construction and operation of the SCSMA by Ministry of Science and Technology National Key Research and Development Program of China(2022RDC2013300,and 2016YFC1402600)National High Technology Research and Development Program of China(2013AA09A502,and 2008AA09A402)+3 种基金National Key Basic Research Program of China(2014CB745000)former State Oceanic Administration of China,Sanya Yazhou Bay Science and Technology City,Laoshan Laboratory(LSKj202201900,and 2018SDKj0101-3)National Natural Science Foundation of China Shiptime Sharing Projects(NORC2024-05,NORC2023-05,NORC2022-05,NORC2021-05,and NORC2019-05)Sanya Oceanographic Laboratory,and Ocean University of China,and the National Natural Science Foundation of China(91028008,91628302,91858203,91958205,42222601,42076027,42076004,41976008,and 41876011).
文摘The South China Sea(SCS)is abundant with complex multiscale dynamic processes but their spatiotemporal variations,generation and evolution mechanisms,and mutual interactions remain inadequately understood due to the lack of long-term in situ observations.To explore oceanic multiscale dynamics in the SCS,the SCS Mooring Array(SCSMA)was began to be constructed since 2009.The SCSMA consists of∼40 moorings and is the largest in situ ocean observing system in marginal seas worldwide.The highest spatial resolution of SCSMA is∼1.5 km,and the longest duration of fixed-location observations reaches∼15 years.Long-term observations from the SCSMA have allowed significant advances in the understanding of large-scale circulation,mesoscale eddies,submesoscale processes,internal waves,turbulent mixing,and interactions and energy cascades of different processes.In particular,the full chain of forward energy cascade from large-scale currents to turbulence has been revealed.Different dynamic processes in the SCS constitute a three-dimensional multiscale circulation system which transports materials and tracers in a relay.Here,we first describe the SCSMA and its construction process,and then comprehensively review its relevant advances in multiscale dynamics.Prospects for the SCSMA and its future applications are given at the end.
