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Subthermocline eddies carrying the Indonesian Throughflow water observed in the southeastern tropical Indian Ocean

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Acta Oceanologica Sinica 2023年第5期42卷 1-13页

作者： Guangbing Yang quanan zheng Xuejun Xiong First Institute of Oceanography and Key Laboratory of Marine Science and Numerical ModelingMinistry of Natural ResourcesQingdao 266061China Laboratory for Regional Oceanography and Numerical Modeling Pilot National Laboratory for Marine Science and Technology(Qingdao)Qingdao 266237China Shandong Key Laboratory of Marine Science and Numerical Modeling Qingdao 266061China Department of Atmospheric and Oceanic Science University of MarylandCollege Park 20742USA

We observed a subthermocline eddy(STE)with a cold and fresh core during an observation cruise along a transect of 10°S in the southeastern tropical Indian Ocean(SETIO)in December 2017.The vertical scale,speed radius,and maximum swirl velocity of the STE were about 200 m,55 km,and 0.5 m/s,respectively.The mean Rossby number and Burger number of the STE were then estimated to be about−0.7 and 2.4,indicating the STE was a submesoscale coherent vortex.The STE core water had characteristics of the Indonesian Throughflow(ITF)water and was distinct from that of surrounding areas.By examining Argo float data,another STE was well captured by five successive profiles of the same Argo float.Both STEs showed significant temperature and salinity anomalies at theσ0=26.0-26.5 kg/m3 surfaces.With the assumption that the low-salinity ITF water parcels could be carried only by surface eddies and the STEs,the Argo profiles,which detected low-salinity ITF water and were located outside a surface eddy,were believed to be inside an STE and were used to analyze the distribution,origin,and generation mechanism of the STE.The results suggested that the STEs carrying ITF water may be generated under topography-current interaction at the eastern coastal waters or under front-induced subduction in the area away from coastal waters.Those STEs may be widely distributed in the SETIO and may play a role in ITF water parcel transport.

关键词： subthermocline eddy southeastern tropical Indian Ocean Indonesian Throughflow submesoscale coherent vortex

Assessment of theoretical approaches to derivation of internal solitary wave parameters from multi-satellite images near the Dongsha Atoll of the South China Sea

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Acta Oceanologica Sinica 2022年第6期41卷 137-145页

作者： Huarong Xie Qing Xu quanan zheng Xuejun Xiong Xiaomin Ye Yongcun Cheng Key Laboratory of Marine Hazards Forecasting of Ministry of Natural Resources Hohai UniversityNanjing 210098China College of Marine Technology Faculty of Information Science and EngineeringOcean University of ChinaQingdao 266100China Department of Atmospheric and Oceanic Science University of MarylandCollege ParkMaryland 20742USA First Institute of Oceanography Ministry of Natural ResourcesQingdao 266061China National Satellite Ocean Application Service State Oceanic AdministrationBeijing 100081China Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou) Guangzhou 511458China PIESAT Information Technology Co. Ltd.Beijing 100195China

This study assesses the accuracy and the applicability of the Korteweg-de Vries(KdV)and the nonlinear Schr?dinger(NLS)equation solutions to derivation of dynamic parameters of internal solitary waves(ISWs)from satellite images.Visible band images taken by five satellite sensors with spatial resolutions from 5 m to 250 m near the Dongsha Atoll of the northern South China Sea(NSCS)are used as a baseline.From the baseline,the amplitudes of ISWs occurring from July 10 to 13,2017 are estimated by the two approaches and compared with concurrent mooring observations for assessments.Using the ratio of the dimensionless dispersive parameter to the square of dimensionless nonlinear parameter as a criterion,the best appliable ranges of the two approaches are clearly separated.The statistics of total 18 cases indicate that in each 50%of cases,the KdV and the NLS approaches give more accurate estimates of ISW amplitudes.It is found that the relative errors of ISW amplitudes derived from two theoretical approaches are closely associated with the logarithmic bottom slopes.This may be attributed to the nonlinear growth of ISW amplitudes as propagating along a shoaling thermocline or topography.The test results using three consecutive satellite images to retrieve the ISW propagation speeds indicate that the use of multiple satellite images(>2)may improve the accuracy of retrieved phase speeds.Meanwhile,repeated multi-satellite images of ISWs can help to determine the types of ISWs if mooring data are available nearby.

关键词： internal solitary waves KdV equation NLS equation South China Sea satellite images

Advances in interscale and interdisciplinary approaches to the South China Sea

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Acta Oceanologica Sinica 2021年第11期40卷 196-199页

作者： Lingling Xie Yi Guan Jianyu Hu quanan zheng Laboratory of Coastal Ocean Variation and Disaster Prediction College of Ocean and MeteorologyGuangdong Ocean UniversityZhanjiang 524088China Key Laboratory of Climate Resources and Environments in Continent Shelf Sea and Deep OceanZhanjiang 524088China Key Laboratory of Space Ocean Remote Sensing and Applications Ministry of Natural ResourcesBeijing 100081China State Key Laboratory of Marine Environmental Science College of Ocean and Earth SciencesXiamen UniversityXiamen 361005China Department of Atmospheric and Oceanic Science University of MarylandCollege Park 20742USA

The South China Sea(SCS)connects the Pacific Ocean and the Indian Ocean,and acts as an important part in regional and global climate systems(e.g.,Qu et al.,2009;Wang et al.,2009).Multi-scale dynamic and biogeochemical processes in the SCS,comprising a hot spot in marginal sea studies,have attracted great attentions from researchers(e.g.,Chen et al.,2020;Hu et al.,2020).The South China Sea Annual Meeting(SCSAM)2021,recently held on October 22–24 in Zhanjiang,China,focused on academic exchanges of the newly research results and progresses in the interdisciplinary multi-scale processes in the SCS.The SCSAM 2021 is the eighth international workshop of the series,which started in April 2013(Zhu,2013)and renamed as SCSAM in 2018.There were 90 oral presentations and 57 posters in the meeting this year,which attracted attentions of more than 2000 audiences both on line and on site.This short article summaries the cutting-edge advances in interscale and interdisciplinary approaches to the SCS from the meeting presentations and the associated research.

关键词： South Indian marginal

Progress in research of submesoscale processes in the South China Sea

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Acta Oceanologica Sinica 2020年第1期39卷 1-13页

作者： quanan zheng Lingling Xie Xuejun Xiong Xiaomin Hu Liang Chen Department of Atmospheric and Oceanic Science University of MarylandCollege Park 27042USA Guangdong Key Laboratory of Coastal Ocean Variability and Disaster Prediction Guangdong Ocean UniversityZhanjiang 524088China Southern Marine Science and Engineering Guangdong Laboratory(Zhanjiang) Zhanjiang 524025China First Institute of Oceanography Ministry of Natural ResourcesQingdao 266061China

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.

关键词： submesoscale processes internal waves fronts and jets submesoscale turbulence South China Sea

A case study of a Kuroshio main path cut-off event and impacts on the South China Sea in fall-winter 2013–2014

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Acta Oceanologica Sinica 2019年第4期38卷 12-19页

作者： quanan zheng Chung-Ru Ho Lingling Xie Mingming Li Department of Atmospheric and Oceanic Science University of Maryland Guangdong Key Laboratory of Coastal Ocean Variability and Disaster Prediction Guangdong Ocean University Department of Marine Environmental Informatics National Taiwan Ocean University

This study examines a Kuroshio main path(KMP) cut-off event east of Taiwan Island occurred in fall-winter2013–2014 and its impacts on the South China Sea(SCS) by analyzing satellite altimetry and mooring observations. Satellite altimeter sea level anomaly(SLA) images reveal a complete process that a huge cyclonic eddy(CE) from the Pacific collided with the Kuroshio and the western boundary from 15 October 2013 to 15 January 2014. Mooring observations evidenced that the Kuroshio upper ocean volume transport was cut off more than 82% from 17×106 m^3/s in September to 3×106 m^3/s in November 2013. The KMP cut-off event caused the Kuroshio branching and intruding into the SCS and strengthened the eddy kinetic energy in the northern SCS west of the Luzon Strait. Using the total momentum as a dynamic criterion to determine the role of eddy collision with the Kuroshio reasonably explains the KMP cut-off event.

关键词： KMP cut-off event eddy kinetic energy dynamic criterion South China Sea

Unusual coastal ocean cooling in the northern South China Sea by a katabatic cold jet associated with Typhoon Mujigea(2015)

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Acta Oceanologica Sinica 2019年第5期38卷 62-75页

作者： Yuxin Shi Lingling Xie quanan zheng Shuwen Zhang Mingming Li Junyi Li Guangdong Key Laboratory of Coastal Ocean Variation and Disaster Prediction Guangdong Ocean University Department of Atmospheric and Oceanic Science University of Maryland

This study deals with a unusual cooling event after Typhoon Mujigea passed over the northern South China Sea(SCS) in October 2015. We analyze the satellite sea surface temperature(SST) time series from October 3 to 18,2015 and find that the cooling process in the coastal ocean had two different stages. The first stage occurred immediately after typhoon passage on October 3, and reached a maximum SST drop of –2℃ on October 7 as the usual cold wake after typhoon. The second stage or the unusual extended cooling event occurred after 7d of the typhoon passage, and lasted for 5d from October 10 to 15. The maximum SST cooling was –4℃ and occurred after 12d of typhoon passage. The mechanism analysis results indicate that after landing and moving northwestward to the Yunnan-Guizhou Plateau(YGP), Typhoon Mujigea(2015) met the westerly wind front on October 5. The lowpressure and positive-vorticity disturbances to the front triggered meridional air flow and low-pressure trough,thus induced a katabatic cold jet downward from the Qinghai-Tibet Plateau(QTP) passing through the YGP to the northwestern SCS. The second cooling reached the maximum SST drop 4d later after the maximum air temperature drop of –9℃ on October 11. The simultaneous air temperature and SST observations at three coastal stations reveal that it is this katabatic cold jet intrusion to lead the unusual SST cooling event.

关键词： Typhoon Mujigea(2015) second-round cooling katabatic cold jet South China Sea westerly wind front

Statistical analysis of mesoscale eddy propagation velocity in the South China Sea deep basin

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Acta Oceanologica Sinica 2020年第11期39卷 91-102页

作者： Runqi Huang Lingling Xie quanan zheng Mingming Li Peng Bai Keyi Tan Laboratory of Coastal Ocean Variation and Disaster Prediction College of Ocean and MeteorologyGuangdong Ocean UniversityZhanjiang 524088China Marine Resources Big Data Center of South China Sea Southern Marine Science and Engineering Guangdong Laboratory(Zhanjiang)Zhanjiang 524025China Department of Atmospheric and Oceanic Science University of MarylandCollege ParkMaryland 20742USA

Using mesoscale eddy trajectory product derived from satellite altimetry data from 1993 to 2017,this study analyzes the statistical characteristics of spatiotemporal distribution of mesoscale eddy propagation velocities(C)in the South China Sea(SCS)deep basin with depths>1000 m.Climatologically,the zonal propagation velocities(cx)are westwards in the whole basin,and the meridional velocities(cy)are southwards in the northwestern basin,and northwards in the southeastern basin.The variation of cy with longitude is consistent with that of the background meridional currents with correlation coefficient R2 of 0.96,while the variation of cx is related both to the background zonal currents andβeffect.The propagation velocities characterize significant seasonality with the minimum magnitude occurring in summer and the maximum in winter for cx and C.Interannually,larger values of cx and cy mostly occurred in La Ni?a years in the negative phase of the Pacific Decadal Oscillation(PDO).Mesoscale eddies move fast at the beginning and end of their life span,i.e.,at their growth and dissipation periods,and slowly during their stable"midlife"period.This trend is negatively correlated with the rotating tangential velocity with R2 of–0.93.Eddies with extreme propagation velocities are defined,which are slower(faster)than 1.5 cm/s(15.4 cm/s)and take 1.5%(1.9%)of the total eddies.The extremely slow-moving(fastmoving)eddies tend to appear in the middle(on the edge)of the basin,and mostly occur in summer(winter).The mechanism analysis reveals that the spatiotemporal distributions of the propagation velocities of mesoscale eddies in the SCS are modulated by the basin-scale background circulation.

关键词： South China Sea mesoscale eddies eddy propagation velocity variation in life span eddies with abnormal speeds

Seasonal and interannual variability of water mass sources of Indonesian throughflow in the Maluku Sea and the Halmahera Sea

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Acta Oceanologica Sinica 2019年第4期38卷 58-71页

作者： Lu Wang Lei Zhou Lingling Xie quanan zheng Qiang Li Mingming Li Guangdong Key Laboratory of Coastal Ocean Variability and Disaster Prediction Guangdong Ocean University Department of Navigation PLA Navy Petty Officer Academy School of Oceanography Shanghai Jiao Tong University Laboratory for Regional Oceanography and Numerical Modeling Pilot National Laboratory for Marine Science and Technology (Qingdao) Department of Atmospheric and Oceanic Science University of Maryland

So far, large uncertainties of the Indonesian throughflow(ITF) reside in the eastern Indonesian seas, such as the Maluku Sea and the Halmahera Sea. In this study, the water sources of the Maluku Sea and the Halmahera Sea are diagnosed at seasonal and interannual timescales and at different vertical layers, using the state-of-the-art simulations of the Ocean General Circulation Model(OGCM) for Earth Simulator(OFES). Asian monsoon leaves clear seasonal footprints on the eastern Indonesian seas. Consequently, the subsurface waters(around 24.5σ_θ and at ～150 m) in both the Maluku Sea and the Halmahera Sea stem from the South Pacific(SP) during winter monsoon, but during summer monsoon the Maluku Sea is from the North Pacific(NP), and the Halmahera Sea is a mixture of waters originating from the NP and the SP. The monsoon impact decreases with depth, so that in the Maluku Sea, the intermediate water(around 26.8σ_θ and at ～480 m) is always from the northern Banda Sea and the Halmahera Sea water is mainly from the SP in winter and the Banda Sea in summer. The deep waters(around27.2σ_θ and at ～1 040 m) in both seas are from the SP, with weak seasonal variability. At the interannual timescale,the subsurface water in the Maluku Sea originates from the NP/SP during El Ni?o/La Ni?a, while the subsurface water in the Halmahera Sea always originates from the SP. Similar to the seasonal variability, the intermediate water in Maluku Sea mainly comes from the Banda Sea and the Halmahera Sea always originates from the SP. The deep waters in both seas are from the SP. Our findings are helpful for drawing a comprehensive picture of the water properties in the Indonesian seas and will contribute to a better understanding of the ocean-atmosphere interaction over the maritime continent.

关键词： water mass Indonesian throughflow monsoon ENSO Maluku Sea Halmahera Sea

Seasonal variability of mesoscale eddies in the Banda Sea inferred from altimeter data

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Acta Oceanologica Sinica 2020年第12期39卷 11-20页

作者： Baiyang Chen Lingling Xie quanan zheng Lei Zhou Lei Wang Baoxin Feng Zipeng Yu Laboratory of Coastal Ocean Variation and Disaster Prediction College of Ocean and MeteorologyGuangdong Ocean UniversityZhanjiang 524088China Key Laboratory of Climate Resourcesand Environment in Continental Shelf Sea and Deep OceanGuangdong Ocean UniversityZhanjiang 524088China Department of Atmospheric and Oceanic Science University of MarylandCollege ParkMaryland 20742USA School of Oceanography Shanghai Jiao Tong UniversityShanghai 200240China Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai) Zhuhai 519000China State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029China

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.

关键词： mesoscale eddies polarity distribution reversal(PDR) meridional shear Banda Sea Indonesian seas