The bimodal structure of the Meiyu front system is readdressed after Zhou et al.（2005）. The physical mechanism of the formation of the bimodal distribution is discussed. The bimodal structure of the Melyu front syst...The bimodal structure of the Meiyu front system is readdressed after Zhou et al.（2005）. The physical mechanism of the formation of the bimodal distribution is discussed. The bimodal structure of the Melyu front system considerably results from atmospheric moisture gradients, though atmospheric temperature gradients are also not negligible. According to the definition of equivalent potential temperature, and by scale analysis, we find that atmospheric equivalent potential temperature gradients, which could be regarded as an indicator of the Meiyu front system, could be mainly attributed to the variations of atmospheric potential temperature gradients with a scaling factor of 1 and moisture gradients multiplied by a scaling factor of an order of about 2.5 × 10^3, which means that small variations of atmospheric moisture gradients could lead to large variations of equivalent potential temperature gradients, and thus large variations of the Meiyu front system. Quantitative diagnostics with a mesoscale simulation data in the vicinity of the Meiyu front system show that moisture gradients contribute to equivalent potential temperature gradients more than potential temperature gradients.展开更多
In this paper, we consider a class of reaction hyperbolic systems for axonal trans- port arising in neuroscience which can be regarded as hyperbolic systems with relaxation. We prove the BV entropy solutions of the hy...In this paper, we consider a class of reaction hyperbolic systems for axonal trans- port arising in neuroscience which can be regarded as hyperbolic systems with relaxation. We prove the BV entropy solutions of the hyperbolic systems converge toward to the unique entropy solution of the equilibrium equation at the optimal rate O（√δ） in L1 norm as the relaxation time δ tends to zero.展开更多
A uniformly first-order convergent numerical method for the discrete-ordinate transport equation in the rectangle geometry is proposed in this paper. Firstly we approximate the scattering coefficients and source terms...A uniformly first-order convergent numerical method for the discrete-ordinate transport equation in the rectangle geometry is proposed in this paper. Firstly we approximate the scattering coefficients and source terms by piecewise constants determined by their cell averages. Then for each cell, following the work of De Barros and Larsen [1, 19], the solution at the cell edge is approximated by its average along the edge. As a result, the solution of the system of equations for the cell edge averages in each cell can be obtained analytically. Finally, we piece together the numerical solution with the neighboring cells using the interface conditions. When there is no interface or boundary layer, this method is asymptotic-preserving, which implies that coarse meshes （meshes that do not resolve the mean free path） can be used to obtain good numerical approximations. Moreover, the uniform first-order convergence with respect to the mean free path is shown numerically and the rigorous proof is provided.展开更多
The zonal-mean position of the intertropical convergence zone(ITCZ)and its shift in the meridional direction significantly influence both the tropical and even global climate.This work reviews three aspects of the pro...The zonal-mean position of the intertropical convergence zone(ITCZ)and its shift in the meridional direction significantly influence both the tropical and even global climate.This work reviews three aspects of the progress in ITCZ-relevant research:1)the mechanism behind the asymmetry of the ITCZ annual-and zonal-mean positions relative to the equator;2)causes of the double-ITCZ problem(pervasive in climate models)and the efforts to solve it;and 3)the physical mechanisms by which anthropogenic aerosols affect the location of the zonal-mean ITCZ.According to recent studies,the north-of-the-equator location of the annual-and zonal-mean ITCZ is mainly driven by the cross-equatorial energy transports in the ocean,induced by the Atlantic overturning circulation.A quantitative relationship between the ITCZ shift and the anomalous cross-equatorial energy transport in the atmosphere has been found.Presently,the double-ITCZ problem is still the most common and pronounced bias in tropical precipitation simulations with climate models.Recently,some studies have found that simply correcting the biases in hemispheric energy contrast does not improve the simulation of the ITCZ with climate models;whereas others have found that improving model resolutions and convective parameterizations in climate models,such as entrainment rate,raindroplet re-evaporation,and convection triggering function,can alleviate the double-ITCZ bias.Therefore,it seems that the double-ITCZ problem in climate models is rooted in the complex physics of the models,which is not yet well-understood.In addition,anthropogenic aerosols are suggested to be able to induce meridional shifts of the ITCZ,but through various physical mechanisms.Absorbing aerosols like black carbon influence the ITCZ position basically via instantaneous absorption of shortwave radiation in the atmosphere,whereas scattering aerosols like sulfate affect the location of the ITCZ through the cloud lifetime effect and the subsequent response of surface evaporation.展开更多
This article is concerned with the pointwise error estimates for vanishing vis- cosity approximations to scalar convex conservation laws with boundary.By the weighted error function and a bootstrap extrapolation techn...This article is concerned with the pointwise error estimates for vanishing vis- cosity approximations to scalar convex conservation laws with boundary.By the weighted error function and a bootstrap extrapolation technique introduced by Tadmor-Tang,an optimal pointwise convergence rate is derived for the vanishing viscosity approximations to the initial-boundary value problem for scalar convex conservation laws,whose weak entropy solution is piecewise C 2 -smooth with interaction of elementary waves and the ...展开更多
目前,从“三网”融合的角度看,我国的电信网、计算机网和有线电视网都具有各自的优势和问题。几年前,只有电信网形成了宽带基础传输网;如今,有线电视网建成了SDH传送系统;计算机网也正在建设独立的宽带基础网。“三网”的基础网以不同...目前,从“三网”融合的角度看,我国的电信网、计算机网和有线电视网都具有各自的优势和问题。几年前,只有电信网形成了宽带基础传输网;如今,有线电视网建成了SDH传送系统;计算机网也正在建设独立的宽带基础网。“三网”的基础网以不同的形式支持IP宽带网络。电信网多数选用IP over ATM;有线电视网最方便的选择是IP over SDH;而计算机网往往选用IP over optics。因此,近期“三网”融合将限于在各自基于IP的数据应用平台上提供多媒体信息服务,短期内不可能由任何单一的网络所代替。展开更多
Criticality problem of nuclear tractors generMly refers to an eigenvalue problem for the transport equations. In this paper, we deal with the eigenvalue of the anisotropic scattering transport equation in slab geometr...Criticality problem of nuclear tractors generMly refers to an eigenvalue problem for the transport equations. In this paper, we deal with the eigenvalue of the anisotropic scattering transport equation in slab geometry. We propose a new discrete method which was called modified discrete ordinates method. It is constructed by redeveloping and improving discrete ordinates method in the space of L1（X）. Different from traditional methods, norm convergence of operator approximation is proved theoretically. Furthermore, convergence of eigenvalue approximation and the corresponding error estimation are obtained by analytical tools.展开更多
基于第五次国际间耦合模式比较计划(The phase 5 of the Coupled Model Intercomparison Project,CMIP5)中在4.5 W/m^2的典型浓度路径(Representative Concentration Pathway,RCP4.5)试验结果,本文通过能量框架分析方法研究了全球变暖...基于第五次国际间耦合模式比较计划(The phase 5 of the Coupled Model Intercomparison Project,CMIP5)中在4.5 W/m^2的典型浓度路径(Representative Concentration Pathway,RCP4.5)试验结果,本文通过能量框架分析方法研究了全球变暖不同阶段热带辐合带(Intertropical Convergence Zone,ITCZ)的南北移动及其主要机制,发现在温室气体持续增加的海洋快响应和温室气体达到稳定后的海洋慢响应两个阶段,ITCZ的移动都和跨赤道的大气能量输送(Atmosphere Heat Transport,AHT)变化显著相关,但两者变化的原因在两个阶段中是不同的。在快响应阶段,ITCZ位置的移动以及跨赤道AHT受大气层顶(Top of the Atmosphere,TOA)的能量变化驱动,主要与南大洋云短波辐射响应、北半球中高纬度云和地表的短波辐射响应有关,气溶胶减少引起的辐射响应变化使得ITCZ在大多数模式中表现出向北移动的特征。在慢响应下辐射强迫保持稳定,ITCZ在大多数模式中表现出向南移动的特征。这一时期ITCZ的移动由大气表面能量通量变化驱动,主要与潜热通量变化的南北半球差异有关。全球变暖不同阶段ITCZ移动与大气能量输送变化的关系差异反映了海洋对于气候变化的重要调控作用。展开更多
文摘The bimodal structure of the Meiyu front system is readdressed after Zhou et al.（2005）. The physical mechanism of the formation of the bimodal distribution is discussed. The bimodal structure of the Melyu front system considerably results from atmospheric moisture gradients, though atmospheric temperature gradients are also not negligible. According to the definition of equivalent potential temperature, and by scale analysis, we find that atmospheric equivalent potential temperature gradients, which could be regarded as an indicator of the Meiyu front system, could be mainly attributed to the variations of atmospheric potential temperature gradients with a scaling factor of 1 and moisture gradients multiplied by a scaling factor of an order of about 2.5 × 10^3, which means that small variations of atmospheric moisture gradients could lead to large variations of equivalent potential temperature gradients, and thus large variations of the Meiyu front system. Quantitative diagnostics with a mesoscale simulation data in the vicinity of the Meiyu front system show that moisture gradients contribute to equivalent potential temperature gradients more than potential temperature gradients.
基金partially supported by the NSFC(11371349)National Basic Research Program of China(973 Program)(2011CB808002)
文摘In this paper, we consider a class of reaction hyperbolic systems for axonal trans- port arising in neuroscience which can be regarded as hyperbolic systems with relaxation. We prove the BV entropy solutions of the hyperbolic systems converge toward to the unique entropy solution of the equilibrium equation at the optimal rate O（√δ） in L1 norm as the relaxation time δ tends to zero.
文摘A uniformly first-order convergent numerical method for the discrete-ordinate transport equation in the rectangle geometry is proposed in this paper. Firstly we approximate the scattering coefficients and source terms by piecewise constants determined by their cell averages. Then for each cell, following the work of De Barros and Larsen [1, 19], the solution at the cell edge is approximated by its average along the edge. As a result, the solution of the system of equations for the cell edge averages in each cell can be obtained analytically. Finally, we piece together the numerical solution with the neighboring cells using the interface conditions. When there is no interface or boundary layer, this method is asymptotic-preserving, which implies that coarse meshes （meshes that do not resolve the mean free path） can be used to obtain good numerical approximations. Moreover, the uniform first-order convergence with respect to the mean free path is shown numerically and the rigorous proof is provided.
基金Supported by the National Natural Science Foundation of China(42005128)National Key Research and Development Program of China(2017YFA0603502)。
文摘The zonal-mean position of the intertropical convergence zone(ITCZ)and its shift in the meridional direction significantly influence both the tropical and even global climate.This work reviews three aspects of the progress in ITCZ-relevant research:1)the mechanism behind the asymmetry of the ITCZ annual-and zonal-mean positions relative to the equator;2)causes of the double-ITCZ problem(pervasive in climate models)and the efforts to solve it;and 3)the physical mechanisms by which anthropogenic aerosols affect the location of the zonal-mean ITCZ.According to recent studies,the north-of-the-equator location of the annual-and zonal-mean ITCZ is mainly driven by the cross-equatorial energy transports in the ocean,induced by the Atlantic overturning circulation.A quantitative relationship between the ITCZ shift and the anomalous cross-equatorial energy transport in the atmosphere has been found.Presently,the double-ITCZ problem is still the most common and pronounced bias in tropical precipitation simulations with climate models.Recently,some studies have found that simply correcting the biases in hemispheric energy contrast does not improve the simulation of the ITCZ with climate models;whereas others have found that improving model resolutions and convective parameterizations in climate models,such as entrainment rate,raindroplet re-evaporation,and convection triggering function,can alleviate the double-ITCZ bias.Therefore,it seems that the double-ITCZ problem in climate models is rooted in the complex physics of the models,which is not yet well-understood.In addition,anthropogenic aerosols are suggested to be able to induce meridional shifts of the ITCZ,but through various physical mechanisms.Absorbing aerosols like black carbon influence the ITCZ position basically via instantaneous absorption of shortwave radiation in the atmosphere,whereas scattering aerosols like sulfate affect the location of the ITCZ through the cloud lifetime effect and the subsequent response of surface evaporation.
基金supported by the NSF China#10571075NSF-Guangdong China#04010473+1 种基金The research of the second author was supported by Jinan University Foundation#51204033the Scientific Research Foundation for the Returned Overseas Chinese Scholars,State education Ministry#2005-383
文摘This article is concerned with the pointwise error estimates for vanishing vis- cosity approximations to scalar convex conservation laws with boundary.By the weighted error function and a bootstrap extrapolation technique introduced by Tadmor-Tang,an optimal pointwise convergence rate is derived for the vanishing viscosity approximations to the initial-boundary value problem for scalar convex conservation laws,whose weak entropy solution is piecewise C 2 -smooth with interaction of elementary waves and the ...
文摘目前,从“三网”融合的角度看,我国的电信网、计算机网和有线电视网都具有各自的优势和问题。几年前,只有电信网形成了宽带基础传输网;如今,有线电视网建成了SDH传送系统;计算机网也正在建设独立的宽带基础网。“三网”的基础网以不同的形式支持IP宽带网络。电信网多数选用IP over ATM;有线电视网最方便的选择是IP over SDH;而计算机网往往选用IP over optics。因此,近期“三网”融合将限于在各自基于IP的数据应用平台上提供多媒体信息服务,短期内不可能由任何单一的网络所代替。
基金Supported by National Natural Science Foundation of China(Grant No.11201007)
文摘Criticality problem of nuclear tractors generMly refers to an eigenvalue problem for the transport equations. In this paper, we deal with the eigenvalue of the anisotropic scattering transport equation in slab geometry. We propose a new discrete method which was called modified discrete ordinates method. It is constructed by redeveloping and improving discrete ordinates method in the space of L1（X）. Different from traditional methods, norm convergence of operator approximation is proved theoretically. Furthermore, convergence of eigenvalue approximation and the corresponding error estimation are obtained by analytical tools.
文摘基于第五次国际间耦合模式比较计划(The phase 5 of the Coupled Model Intercomparison Project,CMIP5)中在4.5 W/m^2的典型浓度路径(Representative Concentration Pathway,RCP4.5)试验结果,本文通过能量框架分析方法研究了全球变暖不同阶段热带辐合带(Intertropical Convergence Zone,ITCZ)的南北移动及其主要机制,发现在温室气体持续增加的海洋快响应和温室气体达到稳定后的海洋慢响应两个阶段,ITCZ的移动都和跨赤道的大气能量输送(Atmosphere Heat Transport,AHT)变化显著相关,但两者变化的原因在两个阶段中是不同的。在快响应阶段,ITCZ位置的移动以及跨赤道AHT受大气层顶(Top of the Atmosphere,TOA)的能量变化驱动,主要与南大洋云短波辐射响应、北半球中高纬度云和地表的短波辐射响应有关,气溶胶减少引起的辐射响应变化使得ITCZ在大多数模式中表现出向北移动的特征。在慢响应下辐射强迫保持稳定,ITCZ在大多数模式中表现出向南移动的特征。这一时期ITCZ的移动由大气表面能量通量变化驱动,主要与潜热通量变化的南北半球差异有关。全球变暖不同阶段ITCZ移动与大气能量输送变化的关系差异反映了海洋对于气候变化的重要调控作用。
