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Variational Reconstruction and Simulation Experiments of Sea Surface Wind Field for Ocean Data Buoy

Journal of Ocean University of China 2024年第3期23卷 577-582页

作者： LI Yunzhou huang sixun YAN Shen SUN Xuejin QI Suiping WANG Zhongqiu TANG Xiaoyu College of Meteorology and Oceanography National University of Defense TechnologyChangsha 410073China Institute of Oceanographic Instrumentation Qilu University of Technology(Shandong Academy of Sciences)Qingdao 266061China State Key Laboratory of Industrial Control Technology College of Control Science and EngineeringZhejiang UniversityHangzhou 310027China Laoshan Laboratory Qingdao 266237China

The sea surface wind field is an important physical parameter in oceanography and meteorology.With the continuous refinement of numerical weather prediction,air-sea interface materials,energy exchange,and other studies,three-dimensional(3D)wind field distribution at local locations on the sea surface must be measured accurately.The current in-situ observation of sea surface wind parameters is mainly achieved through the installation of wind sensors on ocean data buoys.However,the results obtained from this single-point measurement method cannot reflect wind field distribution in a vertical direction above the sea surface.Thus,the present paper proposes a theoretical framework for the optimal inversion of the 3D wind field structure variation in the area where the buoy is located.The variation analysis method is first used to reconstruct the wind field distribution at different heights of the buoy,after which theoretical analysis verification and numerical simulation experiments are conducted.The results indicate that the use of variational methods to reconstruct 3D wind fields is significantly effective in eliminating disturbance errors in observations,which also verifies the correctness of the theoretical analysis of this method.The findings of this article can provide a reference for the layout optimization design of wind measuring instruments in buoy observation systems and also provide theoretical guidance for the design of new observation buoys in the future.

关键词： moored buoy three-dimensional wind field distribution variational analysis wind field reconstruction

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Sufficient conditions of Rayleigh-Taylor stability and instability in equatorial ionosphere

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Applied Mathematics and Mechanics(English Edition) 2016年第2期37卷 181-192页

作者： Sicheng WANG sixun huang Institute of Meteorology and Oceanography PLA University of Science and Technology State Key Laboratory of Satellite Ocean Environment Dynamics Second Institute of OceanographyState Oceanic Administration

Rayleigh-Taylor （R-T） instability is known as the fundamental mechanism of equatorial plasma bubbles （EPBs）. However, the sufficient conditions of R-T instability and stability have not yet been derived. In the present paper, the sufficient conditions of R-T stability and instability are preliminarily^derived. Linear equations for small perturbation are first obtained from the electron/ion continuity equations, momentum equations, and the current continuity equation in the equatorial ionosphere. The linear equations can be casted as an eigenvalue equation using a normal mode method. The eigenvalue equation is a variable coefficient linear equation that can be solved using a variational approach. With this approach, the sufficient conditions can be obtained as follows： if the minimum systematic eigenvalue is greater than one, the ionosphere is R-T unstable; while if the maximum systematic eigenvalue is less than one, the ionosphere is R-T stable. An approximate numerical method for obtaining the systematic eigenvalues is introduced, and the R-T stable/unstable areas are calculated. Numerical experiments axe designed to validate the sufficient conditions. The results agree with the derived suf- ficient conditions.

关键词： Rayleigh-Taylor （R-T） instability sufficient condition equatorial iono-sphere variational approach

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Retrieval of Eddy Thermal Conductivity in the Weakly Nonlinear Prandtl Model for Katabatic Flows

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Journal of Meteorological Research 2017年第5期31卷 965-975页

作者： Bing YAN sixun huang Jing FENG Institute of Meteorology and Oceanography National University of Defense Technology State Key Laboratory of Satellite Ocean Environment Dynamics Second Institute of OceanographyState Oceanic Administration

Because the nonlinearity of actual physical processes can be expressed more precisely by the introduction of a non- linear term, the weakly nonlinear Prandtl model is one of the most effective ways to describe the pure katabatic flow （no backgrotmd flow）. Features of the weak nonlinearity are reflected by two factors： the small parameter c and the gradually varying eddy thermal conductivity. This paper first shows how to apply the Wentzel-Kramers-Brillouin （WKB） method for the approximate solution of the weakly nonlinear Prandtl model, and then describes the retrieval of gradually varying eddy thermal conductivity from observed wind speed and perturbed potential temperature. Gradually varying eddy thermal conductivity is generally derived from an empirical parameterization scheme. We utilize wind speed and potential temperature measurements, along with the variational assimilation technique, to de- rive this parameter. The objective function is constructed by the square of the differences between the observation and model value. The new method is validated by numerical experiments with simulated measurements, revealing that the order of the root mean squre error is 10-2 and thus confirming the method＇s robustness. In addition, this me- thod is caoable of anti-interference, as it effectivelv reduces the influence of observation error.

关键词： weakly nonlinear Prandtl model parameter retrieval variational method Wentzel-Kramers-Brillouin（WKB） method

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The Distribution and Uncertainty Quantification of Wind Profile in the Stochastic General Ekman Momentum Approximation Model

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Journal of Meteorological Research 2019年第2期33卷 336-348页

作者： Bing YAN sixun huang Jing FENG Yu WANG College of Meteorology and Oceanography National University of Defense Technology Center for Computational Science and Finance Shanghai University of Finance and Economics

The general Ekman momentum approximation boundary-layer model(GEM) can be effectively used to describe the physical processes of the boundary layer. However, eddy viscosity, which is an approximated value, can lead to uncertainty in the solutions. In this paper, stochastic eddy viscosity is taken into consideration in the GEM, and generalized polynomial chaos is used to quantify the uncertainty. The goal of uncertainty quantification is to investigate the effects of uncertainty in the eddy viscosity on the model and to subsequently provide reliable distribution of simulation results. The performances of the stochastic eddy viscosity and generalized polynomial chaos method are validated based on three different types of eddy viscosities, and the results are compared based on the Monte Carlo method. The results indicate that the generalized polynomial chaos method can be accurately and efficiently used in uncertainty quantification for the GEM with stochastic eddy viscosity.

关键词： generalized polynomial chaos Monte Carlo method general Ekman momentum approximation model Ekman spiral

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Atmospheric duct estimation from multi-source radar sea clutter returns: theoretical framework and preliminary numerical results

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Chinese Science Bulletin 2014年第34期59卷 4899-4906页

作者： Xiaofeng Zhao Dongxiao Wang sixun huang College of Meteorology and Oceanography PLA University of Science and Technology State Key Laboratory of Tropical Oceanography South China Sea Institute of Oceanology Chinese Academy of Sciences

Refractivity from clutter(RFC) technique estimates lower atmospheric refractivity from radar sea clutter returns. An important issue of RFC is how to make the estimate more robust. Rather than using only single beam radar sea clutter returns, this paper puts forward a theoretical framework of combining multi-source clutter power to improve the retrieved results by the variational adjoint approach. The derivation of the adjoint is accomplished by an analytical transformation of the parabolic equation model in a continuous domain. To test the theoretical algorithm, numerical simulations using multi-elevation clutter observations are carried. The results demonstrate that combining two elevation beams gives more stable estimate than using only single beam.

关键词：海杂波估计计算结果雷达大气波导框架大气折射率伴随方法

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Study and application of an improved four-dimensional variational assimilation system based on the physical-space statistical analysis for the South China Sea

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Acta Oceanologica Sinica 2021年第1期40卷 135-146页

作者： Yumin Chen Jie Xiang Huadong Du sixun huang Qingtao Song College of Meteorology and Oceanology National University of Defense TechnologyNanjing 211101China The 93056 Army of People’s Liberation Army Anshan 114000China State Key Laboratory of Satellite Ocean Environment Dynamics Second Institute of OceanographyMinistry of Natural ResourcesHangzhou 310012China National Satellite Ocean Application Service Beijing 100081China

The four-dimensional variational assimilation(4D-Var)has been widely used in meteorological and oceanographic data assimilation.This method is usually implemented in the model space,known as primal approach(P4D-Var).Alternatively,physical space analysis system(4D-PSAS)is proposed to reduce the computation cost,in which the 4D-Var problem is solved in physical space(i.e.,observation space).In this study,the conjugate gradient(CG)algorithm,implemented in the 4D-PSAS system is evaluated and it is found that the non-monotonic change of the gradient norm of 4D-PSAS cost function causes artificial oscillations of cost function in the iteration process.The reason of non-monotonic variation of gradient norm in 4D-PSAS is then analyzed.In order to overcome the non-monotonic variation of gradient norm,a new algorithm,Minimum Residual(MINRES)algorithm,is implemented in the process of assimilation iteration in this study.Our experimental results show that the improved 4D-PSAS with the MINRES algorithm guarantees the monotonic reduction of gradient norm of cost function,greatly improves the convergence properties of 4D-PSAS as well,and significantly restrains the numerical noises associated with the traditional 4D-PSAS system.

关键词： four-dimensional variational data assimilation(4D-Var) physical space analysis system(PSAS) conjugate gradient algorithm(CG) minimal residual algorithm(MINRES) South China Sea

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情绪调节与注意缺陷多动障碍患儿焦虑/抑郁症状:社交问题的中介效应和家庭功能的调节

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四川大学学报（医学版） 2024年第2期55卷 346-352页

作者：李思迅王美雯杨燕平王卓刘沛罗婷婷陶煜杰黄颐四川大学华西医院精神科成都610041

目的探讨社交问题在情绪失调对注意缺陷多动障碍(attention-deficit/hyperactivity disorder, ADHD)患儿焦虑/抑郁情绪的影响路径中的中介效应,以及家庭功能可能的调节效应。方法纳入确诊的6~12岁ADHD患儿235名,分别使用情绪调节核验... 详细信息

目的探讨社交问题在情绪失调对注意缺陷多动障碍(attention-deficit/hyperactivity disorder, ADHD)患儿焦虑/抑郁情绪的影响路径中的中介效应,以及家庭功能可能的调节效应。方法纳入确诊的6~12岁ADHD患儿235名,分别使用情绪调节核验表、Achenbach儿童行为量表社交问题子量表和焦虑/抑郁子量表及家庭功能评定量表评估其情绪调节、社交问题、焦虑/抑郁情绪及家庭功能,使用有调节的中介模型分析社交问题、家庭功能在情绪调节与焦虑/抑郁情绪之间是否存在中介及调节作用。结果社交问题在ADHD患儿情绪调节对其焦虑/抑郁情绪的影响中起部分中介作用,直接效应值为0.26[95%置信区间(confidence interval, CI):(0.17, 0.36), P<0.001],间接效应值为0.13[95%CI:(0.07,0.19), P<0.001],中介效应值占总效应值的33%。家庭功能在社交问题与焦虑/抑郁情绪当中起正向调节作用。结论本研究结果有助于了解ADHD患儿焦虑/抑郁的复杂影响因素,为进一步制定ADHD患儿针对性干预手段和改善预后提供依据。

关键词：注意缺陷多动障碍焦虑抑郁情绪调节社交问题家庭功能

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Atomic Spin Polarization Controllability Analysis:A Novel Controllability Determination Method for Spin-Exchange Relaxation-Free Co-Magnetometers

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IEEE/CAA Journal of Automatica Sinica 2022年第4期9卷 699-708页

作者： Zhuo Wang sixun Liu Ruigang Wang Linlin Yuan Jiong huang Yueyang Zhai Sheng Zou IEEE the Research Institute for Frontier Science the Beijing Advanced Innovation Center for Big Data-Based Precision Medicine Beihang University the School of Instrumentation and Optoelectronic Engineering Beihang University the Research Institute of Frontier Science Beihang University

This paper investigates the atomic spin polarization controllability of spin-exchange relaxation-free co-magnetometers(SERFCMs).This is the first work in the field of controllability analysis for the atomic spin ensembles systems,whose dynamic behaviors of spin polarization are described by the Bloch equations.Based on the Bloch equations,a state-space model of the atomic spin polarization for SERFCM is first established,which belongs to a particular class of nonlinear systems.For this class of nonlinear systems,a novel determination method for the global state controllability is proposed and proved.Then,this method is implemented in the process of controllability analysis on the atomic spin polarization of an actual SERFCM.Moreover,a theoretically feasible and reasonable solution of the control input is proposed under some physical constraints,with whose limitation of realistic conditions,the controller design can be accomplished more practically and more exactly.Finally,the simulation results demonstrate the feasibility and validation of the proposed controllability determination method.

关键词： Atomic spin polarization Bloch equations controllability determination nonlinear state-space model spin-exchange relaxation-free co-magnetometer(SERFCM)

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An improved QuikSCAT wind retrieval algorithm and eye locating for typhoon

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Acta Oceanologica Sinica 2012年第1期31卷 41-50页

作者： ZHONG Jian FEI Jianfang huang sixun DU Huadong ZHANG Liang Institute of Meteorology University of Science and Technology of People's Liberation ArmyNanjing 211101China

This paper proposes a rain considered geophysical model function （GMF）, to be noted as GMF plus Rain. GMF plus Rain is based on the basic raidative transfer model with attenuation and scattering effects of rain on radar signal considered. Combined with the NSCAT2 GMF and the rain correction model, the GMF plus Rain model is used to retrieve the ocean wind vectors from the collocated QuikSCAT and SSM/I rain rate data for typhoon Melor. The resulting wind speed estimates of typhoon Melor show improved agreement with the wind fields derived from the best track analysis of Japan Meteorological Agency （JMA）. The results imply that compared with the GMF model, the GMF plus Rain model can improve the precision of wind retrieval under the rain condition. Then, a new general algorithm of locating the eye of typhoon through the normalized radar cross section （NRCS） is proposed. The implementation of this algorithm in the ten QuikSCAT observations of typhoon Melor suggests that this algorithm is effective.

关键词： scatterometer radiative transfer model typhoon wind field locating the eye of typhoon

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Theoretical analyses and numerical experiments of variational assimilation for one-dimensional ocean temperature model with techniques in inverse problems

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Science China Earth Sciences 2004年第7期47卷 630-638页

作者： huang sixun1,2, HAN Wei1 & WU Rongsheng2 1. P. O. Box 003, Nanjing 211101,China 2. Key Laboratory of Meso-Scale Severe Weather /MOE, Department of Atmospheric Sciences, Nanjing University, Nanjing 210093, China Correspondence should be addressed to huang sixun Nanjing China Key Laboratory of Meso-Scale Severe Weather /MOE Department of Atmospheric Sciences Nanjing University Nanjing China

In the present work, the data assimilation problem in meteorology and physical oceanography is re-examined using the variational optimal control approaches in combination with regularization techniques in inverse problem. Here the estimations of the initial condition, boundary condition and model parameters are performed simultaneously in the framework of variational data assimilation. To overcome the difficulty of ill-posedness, especially for the model parameters distributed in space and time, an additional term is added into the cost functional as a stabilized functional. Numerical experiments show that even with noisy observations the initial conditions and model parameters are recovered to an acceptable degree of accuracy.

关键词： ocean temperature model, variational data assimilation, regularization.

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