Global trends of tropopause folds in recent decades

对流层顶折卷是平流层-对流层物质交换的主要机制.本研究采用三维标记方法,利用1979-2020年间的ERA5再分析数据,分析了对流层顶折卷的时空变化特征及机理.研究结果表明,全球对流层顶折卷的多年变化趋势存在明显的季节性和区域性差异.总体上,对流层顶折卷呈增加趋势,其中北半球的春季,夏季和冬季,对流层顶折卷主要沿副热带急流区呈现明显增加的趋势.进一步分析表明,对流层顶折卷发生频率的增加与大气斜压性增大导致的锋生增强有关,而经向位温梯度的增大使得次级环流增强,也可能促进了对流层顶折卷活动的增多.

Dynamic mode decomposition of the geomagnetic field over the last two decades

Earth’s magnetic field,which is generated in the liquid outer core through the dynamo action,undergoes changes on timescales of a few years to several million years,yet the underlying mechanisms responsible for the field variations remain to be elucidated.In this study,we apply a novel data analysis technique developed in fluid dynamics,namely the dynamic mode decomposition,to analyze the geomagnetic variations over the last two decades when continuous satellite observations are available.The dominant dynamic modes are extracted by solving an eigen-value problem,so one can identify modes with periods longer than the time span of data.Our analysis show that similar dynamic modes are extracted from the geomagnetic secular variation and secular acceleration,justifying the validity of applying the dynamic mode decomposition method to geomagnetic field.We reveal that the geomagnetic field variations are characterized by a global mode with period of 58 years,a localized mode with period of 16 years and an equatorially trapped mode with period of 8.5 years.These modes are possibly related to magnetohydrodynamic waves in the Earth’s outer core.

The effect of model errors in ensemble sequential assimilation of geomagnetic field

Earth’s magnetic field is generated in the fluid outer core through the dynamo process.Over the last decade,data assimilation has been used to retrieve the core dynamics and predict the evolution of the geomagnetic field.The presence of model errors in the geomagnetic data assimilation is inevitable because current numerical geodynamo models are still far from realistic core dynamics.In this paper,we investigate the effect of model errors in geomagnetic data assimilation based on ensemble Kalman filter(EnKF).We construct two dynamo models with different control parameters but exhibiting similar force balance and magnetic morphology at the core surface.We then use one dynamo model to generate synthetic observations and the other as the forward model in EnKF.Our test experiments show that the EnKF approach with the pre-setting model errors can nevertheless recover large-scale core surface flow and make a rough short-term(5-year)prediction.However,the data assimilation in the presence of model errors cannot keep improving the core state even though new observations are available.Motivated by the planned Macao Science Satellite-1,which is expected to provide improved internal geomagnetic field model,we also perform a test experiment using synthetic observations up to spherical harmonic degree l=18.Our results indicate that high-resolution observations are crucial in reconstructing small scale flow.

Effects of leukemia inhibitory factor and basic fibroblast growth factor on free radicals and endogenous stem cell proliferation in a mouse model of cerebral infarction

The present study established a mouse model of cerebral infarction by middle cerebral artery occlusion, and monitored the effect of 25 tJg/kg leukemia inhibitory factor and （or） basic fibroblast growth factor administration 2 hours after model establishment. Results showed that following administration, the number of endogenous neural stem cells in the infarct area significantly increased, malondialdehyde content in brain tissue homogenates significantly decreased, nitric oxide content, glutathione peroxidase and superoxide dismutase activity significantly elevated, and mouse motor function significantly improved as confirmed by the rotarod and bar grab tests. In particular, the effect of leukemia inhibitory factor in combination with basic fibroblast growth factor was the most significant. Results indicate that leukemia inhibitory factor and basic fibroblast growth factor can improve the microenvironment after cerebral infarction by altering free radical levels, improving the quantity of endogenous neural stem cells, and promoting neurological function of mice with cerebral infarction.

Effects of leukemia inhibitory factor on endogenous neural stem cell proliferation and glycoprotein-130 expression in a mouse model of cerebral infarction

Leukemia inhibitory factor （LIF） has been shown to promote proliferation of endogenous neural stem cells. In this study, we treated mice with cerebral infarction using LIF to investigate whether the LIF receptor subunit glycoprotein （gp）130 is involved in neuroprotection. After LIF treatment, the motor function of model mice was significantly improved. Immunofluorescence histochemistry showed increased numbers of endogenous neural stem cells surrounding the infarct foci. Western blot analysis revealed that gp130 expression was significantly decreased surrounding the infarcted foci. Results demonstrated that LIF promoted the proliferation of endogenous neural stem cells by inhibiting gp130 protein expression.

Influence of reference states on Jupiter’s dynamo simulations

Jupiter’s magnetic field is thought to be generated in its deep metallic hydrogen region through dynamo action,yet the detailed dynamic process remains poorly understood.Numerical simulations have produced Jupiter-like magnetic fields,albeit using different control parameters and reference state models.In this study,we investigate the influence of different reference state models,based on ab initio calculations and based on the polytropic equation of state.In doing so,we perform five anelastic convection dynamo simulations that can be divided into two groups.In each group,different reference states are used while other control parameters and conditions are set to be identical.We find the reference state model can be very influential for the simulations in which buoyancy force is dominant over the Lorentz force.In this regime,different dynamical outcomes can be attributed to the effective buoyancy force resulting from different reference states.For simulations in which the Lorentz force is dominant over the buoyancy force,however,dynamo actions tend to be insensitive to different reference state models.If Jupiter’s dynamo is in a strong field regime,i.e.,the Lorentz force plays a dominant role,our numerical results suggest that Jupiter’s internal reference state,which remains poorly constrained,may play a minor role in the dynamo process of the planet.

3D finite-element modeling of Earth induced electromagnetic field and its potential applications for geomagnetic satellites

The accumulated large amount of satellite magnetic data strengthens our capability of resolving the electrical conductivity of Earth’s mantle.To invert these satellite magnetic data,accurate and efficient forward modeling solvers are needed.In this study,a new finite-element based forward modeling solver is developed to accurately and efficiently compute the induced electromagnetic field for a realistic 3D Earth.Firstly,the nodal-based finite element method with linear shape function on tetrahedral grid is used to assemble the final system of linear equations for the magnetic vector potential and electric scalar potential.The FGMRES solver with algebraic multigrid(AMG)preconditioner is used to quickly solve the final system of linear equations.The weighted moving least-square method is employed to accurately recover the electromagnetic field from the numerical solutions of magnetic vector and electric scalar potentials.Furthermore,a local mesh refinement technique is employed to improve the accuracy of the estimated electromagnetic field.At the end,two synthetic models are used to verify the accuracy and efficiency of our newly developed forward modeling solver.A realistic 3D Earth model is used to simulate the induced magnetic field at 450 and 200 km altitudes which are the planned flying altitudes of Macao’s geomagnetic satellites.The simulation indicates that(1)the amplitude of the mantle-induced magnetic field can reach 10–30 nT at 450 km altitude,which is 10–30%of the primary magnetic field.The induced magnetic field at 200 km altitude has larger amplitudes.These mantleinduced magnetic fields can be measured by Macao geomagnetic satellites;(2)the amplitude of the ocean-induced magnetic field can reach 5–30 nT at satellite altitudes,which needs to be carefully considered in the interpretation of satellite magnetic data.We are confident that our newly developed forward modeling solver will become a key tool for interpreting satellite magnetic data.

Load forecasting for diurnal management of community battery systems

This paper compares three methods of load forecasting for the optimum management of community battery storages. These are distributed within the low voltage(LV) distribution network for voltage management,energy arbitrage or peak load reduction. The methods compared include: a neural network(NN) based prediction scheme that utilizes the load history and the current metrological conditions; a wavelet neural network(WNN)model which aims to separate the low and high frequency components of the consumer load and an artificial neural network and fuzzy inference system(ANFIS) approach.The batteries have limited capacity and have a significant operational cost. The load forecasts are used within a receding horizon optimization system that determines the state of charge(SOC) profile for a battery that minimizes a cost function based on energy supply and battery wear costs. Within the optimization system, the SOC daily profile is represented by a compact vector of Fourier series coefficients. The study is based upon data recorded within the Perth Solar City high penetration photovoltaic(PV)field trials. The trial studied 77 consumers with 29 rooftop solar systems that were connected in one LV network. Data were available from consumer smart meters and a data logger connected to the LV network supply transformer.