Propagation of planetary-scale zonal mean wind anomalies and polar oscillations

Global atmospheric variables can be physically decomposed into four components:(1) the zonal time averaged climate symmetric component,(2) the time averaged climate asymmetric,(3) the zonal-mean transient symmetric anomaly,and (4) the transient asymmetric anomaly.This study analyzes the relationships between the intra-seasonal and inter-annual variability of planetary scale decomposed zonal and meridional winds in the tropopause,and oscillations such as those from the El Ni o-Southern Oscillation (ENSO),the Arctic Oscillation (AO) and the Antarctic Oscillation (AAO).The tropical inter-annual zonal mean wind anomalies in the tropopause are linked with the ENSO cycle and can propagate into the subtropics,mid-latitudes,and polar front regions via abnormal meridional vertical cells.Similarly,tropical intra-seasonal (40-60-d) zonal wind anomalies can reach the subtropics and mid-latitudes.The polar intra-seasonal zonal wind anomalies in the tropopause can propagate toward high-latitude areas.Thus,the AO and the AAO are the result of the interaction and propagation of these planetary scale zonal wind anomalies.     

Effect of initial perturbations on the simulation capability of numerical models

The effect of an initial perturbation on simulation is studied in a series of numerical experiments using a one-dimensional nonlinear advection equation model. It is shown that the capability of the model tends to decline with an increase in initial perturbation. The error in the initial perturbation grows in a nonlinear manner, indicating that the simulating results can be improved only to a limited degree by increasing the accuracy of the initial data.     

Nonlinear Transversal Vibration Analysis of an Axially Moving Viscoelastic Yarn in Tufting Process

The nonlinear transversal vibration of axially moving yarn with time-dependent tension is investigated. Yarn material is modeled as Kelvin model. A partial differential equation governing the transversal vibration is derived from the Newton＇s second law. Galerkin method is used to truncate the governing nonlinear differential equation, and thus the first.order ordinary differential equation is obtained. The periodic vibration equation and the natural frequency of moving yarn are received by applying homotopy perturbation method. As a result, the condition which should be avoided during the tufting process for resonance is obtained.     

Reaction diffusion equations for nonlinear boundary conditions

A class of singularly perturbed initial boundary value problems of reaction diffusion equations for nonlinear boundary conditions is considered.Under suitable conditions,by using the theory of differential inequalities,the existence and asymptotic behavior of solution for initial boundary value problem are studied.Moreover,the obtained solution indicates that there are initial and boundary layers,and the thickness of the initial layer is less than that of the boundary layer.     

Analytical Solution to the Density-Gradient Equation for MOS Quantum Tunneling

Engineering-oriented simulations of quantum mechanical tunneling are often based on density-gradient(DG) theory.This paper presents an analytical solution to the DG equation for quantum tunneling through an ultra-thin oxide in a MOS capacitor with an n+ poly-silicon gate obtained using the method of matched asymptotic expansions.Tunneling boundary conditions extend the approximation into the entire region of the poly-silicon gate,oxide barrier,and substrate.An analytical solution in the form of an asymptotic series is obtained in each region by treating each part of the domain as a separate singular perturbation problem.The solutions are then combined through ’matching’ to obtain an approximate solution for the whole domain.Analytical formulae are given for the electrostatic potential and the electron density profiles.The results capture the features of the quantum effects which are quite different from classical physics predictions.The analytical results compare well with exact numerical solutions over a broad range of voltages and different oxide thicknesses.The analytical results predict the enhancement of the quantum tunneling effect as the oxide thickness is reduced.     

A Thermodynamic Model for Calculating the Surface Tension of Pure Liquids and Liquid Mixtures

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副热带圈和赤道太平洋SST的海-气振子模型

研究了一个海-气振子模型的时滞方程的模型.利用变分迭代原理,首先构造了相应的泛函,选取其Lagrange乘子,再采用迭代方法,最后得到了海-气振子模型解的近似式.     

厄尔尼诺-南方涛动影响下月尺度水文模型参数可移植性

以浙江省3个流域作为研究对象,采用两参数月水量平衡模型（XM模型）和四参数月水量平衡模型（ABCD模型）,结合极大似然不确定性估计方法（GLUE）对水文模拟的不确定性区间进行估计,在此基础上,研究不同模型在ENSO（厄尔尼诺-南方涛动）和不同流域地理情况下的参数移植能力。结果表明,厄尔尼诺时期的参数移植至拉尼娜时期,模型模拟效果要略好于拉尼娜时期的参数移植至厄尔尼诺时期;参数少的模型（XM模型）参数移植合格率要优于参数多的模型（ABCD模型）;相邻流域间的参数移植效果要明显优于距离较远的流域;ABCD模型具有更好的空间可参数移植能力。     

A new approach to studying ENSO predictability： Conditional nonlinear optimal perturbation

A new approach, the conditional nonlinear optimal perturbation (CNOP) is introduced to study the predictability of El Nifio-Southern Oscillation (ENSO) using a theoretical coupled ocean-atmosphere model. The differences between CNOP and linear singular vector (LSV) are demonstrated. The results suggest that the nonlinear model and CNOP are superior in determining error growth for studying predictability of the ENSO. In particular, the CNOP approach is used to explore the nature of the ‘spring predictability barrier‘ in ENSO prediction.     

多头时空注意力机制在ENSO长期预测中的应用

厄尔尼诺-南方涛动（ENSO）是全球热带太平洋地区最显著的气候事件之一,能对全球气候系统产生重要影响,引发干旱、洪水和热浪等极端气候事件.准确预测ENSO的发生对于农业生产、水资源管理、灾害防范和经济规划具有重要意义.然而,ENSO具有非线性和复杂特性,准确预测其强度、持续时间和发生时机具有较大挑战性.针对这一问题,提出了一种基于线性注意力机制的时空Transformer(Linformer-ST)模型,引入了线性注意力机制,取代传统的Softmax注意力机制,将时空特征的建模复杂度从O (n2)降至O (nlog(n)),显著提升了计算效率.在CMIP6数据集上进行了预训练,在SODA数据集上进行了迁移学习,并在GODAS数据集上进行了验证.实验结果表明,该模型在Nino 3.4海表温度异常预测中表现优异,在20个月的预测范围内保持较高的相关性和精度.     

厄尔尼诺/拉尼娜事件对陕西气候的影响

通过对陕西50多年来气象资料和历史资料的搜集和整理,从陕南、关中、陕北三个不同的区域研究厄尔尼诺/拉尼娜(El Nino-Southern Oscillation,ENSO)事件对陕西气候的影响.通过对降水量、气温、自然灾害事件等气候因子与ENSO事件的特征进行对比统计分析,揭示了ENSO事件与陕西气候变化的相关关系.结果表明:ENSO事件对陕西气候的影响存在从陕南到关中再到陕北逐渐增强的趋势;ENSO事件的发生对该区不同地域气温和降水的影响显著;ENSO暖事件(厄尔尼诺事件)增温且降水减少,ENSO冷事件(拉尼娜事件)降温且降水增加;ENSO暖事件对陕西气候特别是自然灾害的影响比ENSO冷事件更为显著和强烈.     

基于信号补偿的鲁棒控制方法

对于具有多种类型不确定性的系统 ,研究实现不同类型鲁棒控制性能的鲁棒控制系统设计问题 ,提出基于信号补偿的鲁棒控制方法。该方法与现有的基于系统传递特性或输入输出特性的方法不同 ,它将系统所具有的不确定性对闭环系统控制性能的影响视为等价干扰的影响 ,在对标称受控对象设计的标称控制器的基础上加入一鲁棒补偿器 ,产生鲁棒补偿信号 ,抵消或抑制等价干扰的影响 ,实现鲁棒控制。该方法设计的鲁棒控制器结构意义明确 ,参数易于在线整定     

基于集结模型的精馏塔产品质量非线性鲁棒控制

将奇异摄动方法应用于一个二元精馏塔的模型降阶 ,得到了一个用于控制器设计的集结简化模型。考虑到模型的误差和其他不确定性 ,设计了一个基于状态反馈的非线性鲁棒控制器。由于难以实时测量中间状态 ,又设计了一个非线性Luenberger型的观测器 ,使该控制器基于输出动态反馈。应用结果表明 ,该非线性鲁棒控制器对干扰和模型误差具有鲁棒控制作用