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Seasonal variation of mesoscale eddy intensity in the global ocean

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Acta Oceanologica Sinica 2024年第1期43卷 48-58页

作者： Yongcan Zu Yue Fang Shuangwen Sun Libao Gao Yang Yang Guijun Guo First institute of Oceanography/Key Laboratory of Marine Science and numerical Modeling Ministry of Natural ResourcesQingdao 266061China Laboratory for Regional Oceanography and numerical Modeling Laoshan LaboratoryQingdao 266237China Shandong Key Laboratory of Marine Science and numerical Modeling Qingdao 266061China

Mesoscale eddies are a prominent oceanic phenomenon that plays an important role in oceanic mass transport and energy *** by rotational speed,the eddy intensity is one of the most fundamental properties of an ***,the seasonal spatiotemporal variation in eddy intensity has not been examined from a global ocean *** this study,we unveil the seasonal spatiotemporal characteristics of eddy intensity in the global ocean by using the latest satellite-altimetry-derived eddy trajectory data *** results suggest that the eddy intensity has a distinct seasonal variation,reaching a peak in spring while attaining a minimum in autumn in the Northern Hemisphere and the opposite in the Southern *** seasonal variation of eddy intensity is more intense in the tropical-subtropical transition zones within latitudinal bands between 15°and 30°in the western Pacific Ocean,the northwestern Atlantic Ocean,and the eastern Indian Ocean because baroclinic instability in these areas changes *** analysis found that the seasonal variation of baroclinic instability precedes the eddy intensity by a phase of 2–3 months due to the initial perturbations needing time to grow into mesoscale eddies.

关键词： seasonal variation mesoscale eddy intensity baroclinic instability global ocean

Characteristics and triggering mechanisms of early negative Indian Ocean Dipole

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Acta Oceanologica Sinica 2024年第3期43卷 59-65页

作者： Yue Fang Shuangwen Sun Yongcan Zu Jianhu Wang Lin Feng First institute of Oceanography and Key Laboratory of Marine Science and Numerical ModelingMinistry of Natural ResourcesQingdao 266061China Laboratory for Regional Oceanography and numerical Modeling Qingdao Marine Science and Technology CenterQingdao 266237China Shandong Key Laboratory of Marine Science and numerical Modeling Qingdao 266061China

Negative Indian Ocean Dipole(nIOD)can exert great impacts on global climate and can also strongly influence the climate in *** nIOD is a major type of nIOD,which can induce more pronounced climate anomalies in summer than La Niña-related ***,the characteristics and triggering mechanisms of early nIOD are *** results based on reanalysis datasets indicate that the early nIOD and La Niña-related nIOD are the two major types of nIOD,and the former accounts for over one third of all the nIOD events in the past six *** two types of nIODs are similar in their intensities,but are different in their spatial patterns and seasonal *** early nIOD,which develops in spring and peaks in summer,is one season earlier than the La Niña-related *** spatial pattern of the wind anomaly associated with early nIOD exhibits a winter monsoon-like pattern,with strong westerly anomalies in the equatorial Indian Ocean and eastly anomalies in the northern Indian *** to the triggering mechanism of early positve IOD,the early nIOD is induced by delayed Indian summer monsoon *** results of this study are helpful for improving the prediction skill of IOD and its climate impacts.

关键词： Indian Ocean Dipole(IOD) triggering mechanism Indian summer monsoon seasonal cycle negative IOD

Multiple model PHD filter for tracking sharply maneuvering targets using recursive RANSAC based adaptive birth estimation

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Journal of Systems Engineering and Electronics 2024年第3期35卷 780-792页

作者： DING Changwen ZHOU Di ZOU Xinguang DU Runle LIU Jiaqi School of Astronautics Harbin Institute of TechnologyHarbin 150001China School of Electronics and Information Engineering Harbin Institute of TechnologyHarbin 150001China National Key Laboratory of Science and Technology on Test Physics and numerical mathematics Beijing 100076China

An algorithm to track multiple sharply maneuvering targets without prior knowledge about new target birth is proposed. These targets are capable of achieving sharp maneuvers within a short period of time, such as drones and agile *** probability hypothesis density (PHD) filter, which propagates only the first-order statistical moment of the full target posterior, has been shown to be a computationally efficient solution to multitarget tracking problems. However, the standard PHD filter operates on the single dynamic model and requires prior information about target birth distribution, which leads to many limitations in terms of practical applications. In this paper,we introduce a nonzero mean, white noise turn rate dynamic model and generalize jump Markov systems to multitarget case to accommodate sharply maneuvering dynamics. Moreover, to adaptively estimate newborn targets’information, a measurement-driven method based on the recursive random sampling consensus (RANSAC) algorithm is proposed. Simulation results demonstrate that the proposed method achieves significant improvement in tracking multiple sharply maneuvering targets with adaptive birth estimation.

关键词： multitarget tracking probability hypothesis density(PHD)filter sharply maneuvering targets multiple model adaptive birth intensity estimation

Evaluation of Nonbreaking Wave-Induced Mixing Parameterization Schemes Based on a One-Dimensional Ocean Model

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Journal of Ocean University of China 2024年第3期23卷 567-576页

作者： TANG Ran HUANG Chuanjiang DAI Dejun WANG Gang The First institute of Oceanography Ministry of Natural ResourcesQingdao 266061China Laboratory for Regional Oceanography and numerical Modeling Laoshan LaboratoryQingdao 266237China Shandong Key Laboratory of Marine Science and numerical Modeling Qingdao 266061China

Surface waves have a considerable effect on vertical mixing in the upper *** the past two decades,the vertical mixing induced through nonbreaking surface waves has been used in ocean and climate models to improve the simulation of the upper *** far,several nonbreaking wave-induced mixing parameterization schemes have been proposed;however,no quantitative comparison has been performed among *** this paper,a one-dimensional ocean model was used to compare the performances of five schemes,including those of Qiao et al.(Q),Hu and Wang(HW),Huang and Qiao(HQ),Pleskachevsky et al.(P),and Ghantous and Babanin(GB).Similar to previous studies,all of these schemes can decrease the simulated sea surface temperature(SST),increase the subsurface temperature,and deepen the mixed layer,thereby alleviating the common thermal deviation problem of the ocean model for upper ocean *** these schemes,the HQ scheme exhibited the weakest wave-induced mixing effect,and the HW scheme exhibited the strongest effect;the other three schemes exhibited roughly the same *** particular,the Q and P schemes exhibited nearly the same *** the simulation based on observations from the Ocean Weather Station Papa,the HQ scheme exhibited the best performance,followed by the Q *** the experiment with the HQ scheme,the root-mean-square deviation of the simulated SST from the observations was 0.43℃,and the mixed layer depth(MLD)was 2.0 *** a contrast,the deviations of the SST and MLD reached 1.25℃ and 8.4 m,respectively,in the experiment without wave-induced mixing.

关键词： wave-induced mixing surface waves sea surface temperature mixed layer depth General Ocean Turbulence Model

Long-term ocean temperature trend and marine heatwaves

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Journal of Oceanology and Limnology 2024年第4期42卷 1037-1047页

作者： Min ZHANG Yangyan CHENG Gang WANG Qi SHU Chang ZHAO Yuanling ZHANG Fangli QIAO First institute of Oceanography Ministry of Natural ResourcesQingdao 266061China Key Laboratory of Marine Sciences and numerical Modelling Ministry of Natural ResourcesQingdao 266061China Shandong Key Laboratory of Marine Science and numerical Modeling Qingdao 266061China

Marine heatwaves(MHWs)can cause irreversible damage to marine ecosystems and *** MHW characterization remains difficult,because the choice of a sea surface temperature(SST)temporal baseline strongly influences MHW *** a recent work suggesting that there should be a communicating baseline for long-term ocean temperature trends(LTT)and MHWs,we provided an effective and quantitative solution to calculate LTT and MHWs simultaneously by using the ensemble empirical mode decomposition(EEMD)*** long-term nonlinear trend of SST obtained by EEMD shows superiority over the traditional linear trend in that the data extension does not alter prior *** MHWs identified from the detrended SST data exhibited low sensitivity to the baseline choice,demonstrating the robustness of our *** also derived the total heat exposure(THE)by combining LTT and *** THE was sensitive to the fixed-period baseline choice,with a response to increasing SST that depended on the onset time of a perpetual MHW state(identified MHW days equal to the year length).Subtropical areas,the Indian Ocean,and part of the Southern Ocean were most sensitive to the long-term global warming trend.

关键词： marine heatwaves(MHWs) ensemble empirical mode decomposition(EEMD) long-term temperature(LTT)trend total heat exposure(THE)

The dry-hot feedback between soil moisture and atmosphere and the accelerated global warming

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Science China Earth Sciences 2024年第3期67卷 890-891页

作者： Tianjun ZHOU State Key Laboratory of numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics(LASG) Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029China

Greenhouse gas (GHG) emissions have been increasing due to human activities since the Industrial Revolution, resulting in continuous warming of the global climate system and significant drought over a large parts of global land, both have shown a non-linear growth trend in recent decades(Berg et al., 2017;Zhou et al., 2019;IPCC, 2021).

关键词： warming moisture drought

From fundamental theory to realistic modeling of the birth of solar eruptions

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Science China Earth Sciences 2024年

作者： Chaowei JIANG Shenzhen Key Laboratory of numerical Prediction for Space Storm Harbin Institute of Technology

Solar eruptions, primarily manifested as solar flares, filament eruptions and coronal mass ejections, represent explosive releases of magnetic energy stored in the solar corona, with the potential to drive severe space weather. The initiation of solar eruptions remains an open question, leading to various theoretical models that are inferred from observations. However,these models are subjects of debate due to the absence of direct measurements of the three-dimensional(3D) magnetic fields in the corona. numerical simulations, based on solving magnetohydrodynamics(MHD) equations that govern the macroscopic dynamics of solar corona, serve as a touchstone for testing these theoretical models. One early proposed model suggested that eruptions could be triggered by reconnection within a single sheared magnetic arcade, which is known as the tether-cutting reconnection model, but it was never confirmed through 3D MHD simulations until very recently. Consequently, two models have gained more popularity: one involving the eruption of a twisted magnetic flux rope(MFR) due to ideal instability(or loss of equilibrium), and the other known as the breakout eruption, which requires a quadrupolar configuration with a delicately located magnetic null point. Other mixed mechanisms, involving both ideal instability and reconnection, are also proposed in association with localized magnetic flux emergence. Now with the validation of the tether-cutting model, the fundamental mechanisms are boiled down to two types of models, one primarily based on the ideal instability of a pre-existing MFR, and the other based on the reconnection of sheared field lines with or without an MFR. Recently, the modelling of the birth of solar eruption using observed data-based MHD simulations has advanced rapidly, becoming a crucial research tool in the study of the initiation mechanisms. These realistic modellings reveal a higher level of complexity compared to all currently available theories and idealized

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Current observation and analysis based on mooring systems in the Andaman Sea

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Journal of Oceanology and Limnology 2024年第2期42卷 484-491页

作者： Yimeng WANG Jingsong GUO Dapeng QU Zhixin ZHANG Chalermrat SANGMANEE Varintha VASINAMEKHIN Binghuo GUO 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 Phuket Marine Biological Center Department of Marine and Coastal ResourcesPhuket 83000Thailand Marine and Coastal Resources Research&Development institute Department of Marine and Coastal ResourcesBangkok 10210Thailand

The basic structure and intraseasonal evolution of currents in the southeastern Andaman Sea was analyzed based on data collected in 2017 from two subsurface moorings(C1 and C5).Periodic variation in the upper ocean currents of the Andaman Sea was investigated by combining observational and satellite *** observations show that rapid changes of current speed and direction occurred in May and June,with a significant increase in current velocity at the C1 *** the second half of the year,southward flow dominated at the C1 mooring,and alternating northward and southward flows were evident at the C5 mooring during the same period but the northward flow prevailed in boreal *** addition,analysis of the power spectra of the upper currents revealed that the tidal period at both moorings is primarily semidiurnal with weaker energy than that of the low-frequency *** upper ocean currents at the C1 and C5 moorings exhibited intraseasonal variation of 30-60 d and 120 d,while the zonal current at the C1 mooring exhibited a notable period of approximately 180 *** analysis indicated that the variability of currents in the Andaman Sea is influenced primarily by equatorial Kelvin waves and Rossby wave ***,our results suggest that equatorial Kelvin waves from the eastern Indian Ocean entered the Andaman Sea in the form of Wyrtki Jets and propagated primarily along two distinct pathways during the observation *** addition to coastal boundary Kelvin waves,it was found that a branch of the Wyrtki Jet that directly enters the Andaman Sea and flows northward along the slope of the continental shelf,and reflected Rossby wave packets by topography.

关键词： mooring observation Wyrtki Jet Rossby waves intraseasonal variation

The Persistence and Zonal Scale of Atmospheric Dipolar Modes

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Advances in Atmospheric Sciences 2024年第3期41卷 478-492页

作者： Jie SONG State Key Laboratory of numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics(LASG) Institute of Atmospheric Physics(IAP)Chinese Academy of SciencesBeijing 100029China

This study investigates the relationship between the persistence and the zonal scale of atmospheric dipolar modes(DMs). Results from the daily data of ERA5 and the long-term output of an idealized atmospheric model show that the atmospheric DMs with a broader(narrower) zonal scale dipolar structure possess a longer(shorter) persistence. A detailed vorticity budget analysis indicates that the persistence of a hemispheric-scale DM(1/1 DM) and a regional or sectoral DM(1/8 DM) in the model both largely rely on the persistence of the nonlinear eddy forcing. Linear terms can indirectly reduce the persistence of the anomalous nonlinear eddy forcing in a 1/8 DM by modifying the baroclinicity via the arousal of anomalous vertical motions. Therefore, the atmospheric DMs with a broader(narrower) zonal scale possess a longer(shorter) persistence because the effects of the linear terms are less(more) pronounced when the atmospheric DMs have better(worse) zonal symmetry. Further analyses show that the positive eddy feedback effect is weak or even absent in a 1/8DM and the high-frequency eddy forcing acts more like a concomitant phenomenon rather than a leading driving factor for a 1/8 DM. Thus, the hemispheric-scale DM and the regional or sectoral DMs are different, not only in their persistence but also in their dynamics.

关键词： NAM NAO eddy feedback persistence linear term