Progress over the past decade in understanding moisture-driven dynamics and torrential rain storms in China is reviewed in this paper. First, advances in incorporating moisture effects more realistically into theory a...Progress over the past decade in understanding moisture-driven dynamics and torrential rain storms in China is reviewed in this paper. First, advances in incorporating moisture effects more realistically into theory are described, including the development of a new parameter, generalized moist potential vorticity（GMPV） and an improved moist ageostrophic Q vector（Qum）. Advances in vorticity dynamics are also described, including the adoption of a ＂parcel dynamic＂ approach to investigate the development of the vertical vorticity of an air parcel; a novel theory of slantwise vorticity development, proposed because vorticity develops easily near steep isentropic surfaces; and the development of the convective vorticity vector（CVV）as an effective new tool. The significant progress in both frontal dynamics and wave dynamics is also summarized, including the geostrophic adjustment of initial unbalanced flow and the dual role of boundary layer friction in frontogenesis, as well as the interaction between topography and fronts, which indicate that topographic perturbations alter both frontogenesis and frontal structure. For atmospheric vortices, mixed wave/vortex dynamics has been extended to explain the propagation of spiral rainbands and the development of dynamical instability in tropical cyclones. Finally, we review wave and basic flow interaction in torrential rainfall, for which it was necessary to extend existing theory from large-scale flows to mesoscale fields, enriching our knowledge of mesoscale atmospheric dynamics.展开更多
This paper reviews the main theoretical progress of mesoscale weather dynamics since 2003, including： （1） The dynamic mechanisms of balanced and unbalanced flow are applied to study the genesis and development prob...This paper reviews the main theoretical progress of mesoscale weather dynamics since 2003, including： （1） The dynamic mechanisms of balanced and unbalanced flow are applied to study the genesis and development problems of mesoscale circulation. The symmetric instability and transverse-wave instability are analyzed in line and vortex atmosphere convection, and further research has been done on nonlinear convective symmetric instability. The interaction between forced convection and unstable convection and the wave characteristics of mesoscale motion are also discussed. （2） Intermediate atmosphere dynamic boundary layer models are developed. The complicated nonlinear interaction is analyzed theoretically between the atmospheric boundary layer and the free atmosphere. The structure of the topography boundary layer, atmospheric frontogenesis, the structure and circulation of the low-level front and other boundary layer dynamic problems are discussed. （3） The formation and development of meso-β-scale rainstorms under the background of the East-Asia atmosphere circulation are diagnosed with the variation of MPV （moist potential vorticity） anomalies. And some physical vectors are modified and applied in the moist atmosphere.展开更多
Mesoscale research conducted by Chinese meteorologists during the past four years is reviewed. Advances in theoretical studies include (a) mesoscale quasi-balanced and semi-balanced dynamics, derived through scale ana...Mesoscale research conducted by Chinese meteorologists during the past four years is reviewed. Advances in theoretical studies include (a) mesoscale quasi-balanced and semi-balanced dynamics, derived through scale analysis and the perturbation method which are suitable for describing mesoscale vortices; (b) subcritical instability and vortex-sheet instability; (c) frontal adjustment mechanism and the effect of topography on frontgenesis; and (d) slantwise vorticity development theories, the slantwise vortex equation, and moist potential vorticity (MPV) anomalies with precipitation-related heat and mass sinks and MPV impermeability theorem. Prom the MPV conservation viewpoint, the transformation mechanism between different scale weather systems is analyzed. Based on the data analysis, a new dew-point front near the periphery of the West Pacific subtropical high is identified. In the light of MPV theory and Q-vector theory, some events associated with torrential rain systems and severe storms are analyzed and diagnosed. Progress in mesoscale numerical simulation has been made in the development of meso-α, meso-β vortices, meso-γ-scale downbursts and precipitation produced by deep convective systems with MM5 and other mesoscale models.展开更多
X-ray free-electron lasers(XFELs)can generate bright X-ray pulses with short durations and narrow bandwidths,leading to extensive applica-tions in many disciplines such as biology,materials science,and ultrafast scien...X-ray free-electron lasers(XFELs)can generate bright X-ray pulses with short durations and narrow bandwidths,leading to extensive applica-tions in many disciplines such as biology,materials science,and ultrafast science.Recently,there has been a growing demand for X-ray pulses with high photon energy,especially from developments in“diffraction-before-destruction”applications and in dynamic mesoscale materials science.Here,we propose utilizing the electron beams at XFELs to drive a meter-scale two-bunch plasma wakefield accelerator and double the energy of the accelerated beam in a compact and inexpensive way.Particle-in-cell simulations are performed to study the beam quality degradation under different beam loading scenarios and nonideal issues,and the results show that more than half of the accelerated beam can meet the requirements of XFELs.After its transport to the undulator,the accelerated beam can improve the photon energy to 22 keV by a factor of around four while maintaining the peak power,thus offering a promising pathway toward high-photon-energy XFELs.展开更多
Based on the latest oceanic surface drifter dataset from the global drifter program during 2000–2019,this study investigated the global variation of relative frequency shift(RFS),near-inertial energy(NIE)and inverse ...Based on the latest oceanic surface drifter dataset from the global drifter program during 2000–2019,this study investigated the global variation of relative frequency shift(RFS),near-inertial energy(NIE)and inverse excess bandwidth(IEB)of near-inertial motions,and analyzed their relations with oceanic mesoscale dynamics,relative vorticity and strain.Compared with previous works,we have some new findings in this study:(1)the RFS was high with negative values in some regions in which we found a significant blue shift of the RFS in the equatorward of 30°N(S)and from 50°N to 60°N in the Pacific,and a red shift in the western boundary currents and their extension regions,the North Atlantic and the Antarctic Circumpolar Current regions;(2)more peak values of the NIE were found in global regions like the South Indian Ocean,the Luzon Strait and some areas of the South Ocean;(3)the global distribution of the IEB were characterized by clear zonal bands and affected by vorticity and wind field;(4)the RFS was elevated as the absolute value of the gradient of vorticity increased,the IEB did not depend on the gradient of vorticity,and the eddy kinetic energy(EKE)weakened with the decrease of the absolute value of RFS;(5)the NIE decreased with increasing absolute value of the relative vorticity and the gradient of vorticity,but it increased with increasing strain and EKE when EKE was larger than 0.0032 m2/s2.展开更多
Among 33 cold frontal systems passed over the Beijing-Tianjin-Tangshan area from May to August during 1963—1979,there existed mesoscale rainbands in the warm sectors ahead of 31 cold fronts.These rainbands, according...Among 33 cold frontal systems passed over the Beijing-Tianjin-Tangshan area from May to August during 1963—1979,there existed mesoscale rainbands in the warm sectors ahead of 31 cold fronts.These rainbands, according to their orientation,movement,formation and development,can be divided into three types:parallel, angulate and perpendicular type.The basic characteristics,sources and propagation of the three types of rainbands and the severe convective weather associated with the bands are presented.The possible mechanis- ms responsible for the formation and development of the bands are also briefly discussed.展开更多
Prediction of solute clustering kinetics in aged multicomponent alloys requires a quantitative understanding of complex vacancy-cluster interactions across multiple scales.Here,we develop an integrated computational f...Prediction of solute clustering kinetics in aged multicomponent alloys requires a quantitative understanding of complex vacancy-cluster interactions across multiple scales.Here,we develop an integrated computational framework combining on-lattice kinetic Monte Carlo(KMC)simulations,absorbing Markov chain models,and mesoscale cluster dynamics(CD)to investigate these interactions in Al-Mg-Zn alloys.The Markov chain model yields vacancy escape times from solute clusters and identifies a two-stage behavior of the vacancy-cluster binding energy.These binding energies are used to estimate residual vacancy concentrations in the Al matrix after quenching,which serve as critical inputs to CD simulations to predict long-term cluster evolution kinetics during natural aging.Our results quantitatively demonstrate the significant impact of quench rate on natural aging kinetics.Results provide insights to guide alloy chemistry,quench rates,and aging time at finite temperatures to control the evolution of solute clusters and eventual precipitates in aged multicomponent alloys.展开更多
基金supported by the National Natural Science Foundation of China (Grant Nos. 91437215 and 41375052)State Key Laboratory of Severe Weather Open Project (Grant No. 2013LASW-A06)the Key Research Program of the Chinese Academy of Sciences (Grant No. KZZD-EW05-01)
文摘Progress over the past decade in understanding moisture-driven dynamics and torrential rain storms in China is reviewed in this paper. First, advances in incorporating moisture effects more realistically into theory are described, including the development of a new parameter, generalized moist potential vorticity（GMPV） and an improved moist ageostrophic Q vector（Qum）. Advances in vorticity dynamics are also described, including the adoption of a ＂parcel dynamic＂ approach to investigate the development of the vertical vorticity of an air parcel; a novel theory of slantwise vorticity development, proposed because vorticity develops easily near steep isentropic surfaces; and the development of the convective vorticity vector（CVV）as an effective new tool. The significant progress in both frontal dynamics and wave dynamics is also summarized, including the geostrophic adjustment of initial unbalanced flow and the dual role of boundary layer friction in frontogenesis, as well as the interaction between topography and fronts, which indicate that topographic perturbations alter both frontogenesis and frontal structure. For atmospheric vortices, mixed wave/vortex dynamics has been extended to explain the propagation of spiral rainbands and the development of dynamical instability in tropical cyclones. Finally, we review wave and basic flow interaction in torrential rainfall, for which it was necessary to extend existing theory from large-scale flows to mesoscale fields, enriching our knowledge of mesoscale atmospheric dynamics.
基金This work was supported by the National Nature Science Foundation of China （Grant Nos. 40575022, 40575025, 40333025, 40325014, and 40333031）the National Key Basic Research and Development Project of China （Grant No. 2004CB418301）.
文摘This paper reviews the main theoretical progress of mesoscale weather dynamics since 2003, including： （1） The dynamic mechanisms of balanced and unbalanced flow are applied to study the genesis and development problems of mesoscale circulation. The symmetric instability and transverse-wave instability are analyzed in line and vortex atmosphere convection, and further research has been done on nonlinear convective symmetric instability. The interaction between forced convection and unstable convection and the wave characteristics of mesoscale motion are also discussed. （2） Intermediate atmosphere dynamic boundary layer models are developed. The complicated nonlinear interaction is analyzed theoretically between the atmospheric boundary layer and the free atmosphere. The structure of the topography boundary layer, atmospheric frontogenesis, the structure and circulation of the low-level front and other boundary layer dynamic problems are discussed. （3） The formation and development of meso-β-scale rainstorms under the background of the East-Asia atmosphere circulation are diagnosed with the variation of MPV （moist potential vorticity） anomalies. And some physical vectors are modified and applied in the moist atmosphere.
文摘Mesoscale research conducted by Chinese meteorologists during the past four years is reviewed. Advances in theoretical studies include (a) mesoscale quasi-balanced and semi-balanced dynamics, derived through scale analysis and the perturbation method which are suitable for describing mesoscale vortices; (b) subcritical instability and vortex-sheet instability; (c) frontal adjustment mechanism and the effect of topography on frontgenesis; and (d) slantwise vorticity development theories, the slantwise vortex equation, and moist potential vorticity (MPV) anomalies with precipitation-related heat and mass sinks and MPV impermeability theorem. Prom the MPV conservation viewpoint, the transformation mechanism between different scale weather systems is analyzed. Based on the data analysis, a new dew-point front near the periphery of the West Pacific subtropical high is identified. In the light of MPV theory and Q-vector theory, some events associated with torrential rain systems and severe storms are analyzed and diagnosed. Progress in mesoscale numerical simulation has been made in the development of meso-α, meso-β vortices, meso-γ-scale downbursts and precipitation produced by deep convective systems with MM5 and other mesoscale models.
基金supported by the National Grand Instrument Project No. SQ2019YFF01014400the Natural Science Foundation of China (Grant Nos. 12375147, 12435011, 12075030)+2 种基金the Beijing Outstanding Young Scientist Project, Project for Young Scientists in Basic Research of Chinese Academy of Sciences (YSBR-115)the Beijing Normal University Scientific Research Initiation Fund for Introducing Talents No. 310432104the Fundamental Research Funds for the Central Universities, Peking University
文摘X-ray free-electron lasers(XFELs)can generate bright X-ray pulses with short durations and narrow bandwidths,leading to extensive applica-tions in many disciplines such as biology,materials science,and ultrafast science.Recently,there has been a growing demand for X-ray pulses with high photon energy,especially from developments in“diffraction-before-destruction”applications and in dynamic mesoscale materials science.Here,we propose utilizing the electron beams at XFELs to drive a meter-scale two-bunch plasma wakefield accelerator and double the energy of the accelerated beam in a compact and inexpensive way.Particle-in-cell simulations are performed to study the beam quality degradation under different beam loading scenarios and nonideal issues,and the results show that more than half of the accelerated beam can meet the requirements of XFELs.After its transport to the undulator,the accelerated beam can improve the photon energy to 22 keV by a factor of around four while maintaining the peak power,thus offering a promising pathway toward high-photon-energy XFELs.
基金The Global Change and Air-Sea Interaction Project under contract No.GASI-IPOVAI-01-03the National Key Research and Development Program under contract Nos 2016YFC1401403 and 2018YFC0309800+2 种基金the National Natural Science Foundation of China under contract Nos 41576009 and 41576006the Strategic Priority Research Program of the CAS under contract No.XDA13030302the Chinese Academy of Sciences Frontier Basic Research Project under contract No.QYJC201910
文摘Based on the latest oceanic surface drifter dataset from the global drifter program during 2000–2019,this study investigated the global variation of relative frequency shift(RFS),near-inertial energy(NIE)and inverse excess bandwidth(IEB)of near-inertial motions,and analyzed their relations with oceanic mesoscale dynamics,relative vorticity and strain.Compared with previous works,we have some new findings in this study:(1)the RFS was high with negative values in some regions in which we found a significant blue shift of the RFS in the equatorward of 30°N(S)and from 50°N to 60°N in the Pacific,and a red shift in the western boundary currents and their extension regions,the North Atlantic and the Antarctic Circumpolar Current regions;(2)more peak values of the NIE were found in global regions like the South Indian Ocean,the Luzon Strait and some areas of the South Ocean;(3)the global distribution of the IEB were characterized by clear zonal bands and affected by vorticity and wind field;(4)the RFS was elevated as the absolute value of the gradient of vorticity increased,the IEB did not depend on the gradient of vorticity,and the eddy kinetic energy(EKE)weakened with the decrease of the absolute value of RFS;(5)the NIE decreased with increasing absolute value of the relative vorticity and the gradient of vorticity,but it increased with increasing strain and EKE when EKE was larger than 0.0032 m2/s2.
文摘Among 33 cold frontal systems passed over the Beijing-Tianjin-Tangshan area from May to August during 1963—1979,there existed mesoscale rainbands in the warm sectors ahead of 31 cold fronts.These rainbands, according to their orientation,movement,formation and development,can be divided into three types:parallel, angulate and perpendicular type.The basic characteristics,sources and propagation of the three types of rainbands and the severe convective weather associated with the bands are presented.The possible mechanis- ms responsible for the formation and development of the bands are also briefly discussed.
基金supported by NSF grant#1905421with computing resources provided by GM Global Technical Center and Stampede3 at TACC(ACCESS allocation DMR190035,NSF grants#2138259,#2138286,#2138307,#2137603,#2138296).The authors thank Prof.Dane Morgan from the University of Wisconsin-Madison for insightful discussions.
文摘Prediction of solute clustering kinetics in aged multicomponent alloys requires a quantitative understanding of complex vacancy-cluster interactions across multiple scales.Here,we develop an integrated computational framework combining on-lattice kinetic Monte Carlo(KMC)simulations,absorbing Markov chain models,and mesoscale cluster dynamics(CD)to investigate these interactions in Al-Mg-Zn alloys.The Markov chain model yields vacancy escape times from solute clusters and identifies a two-stage behavior of the vacancy-cluster binding energy.These binding energies are used to estimate residual vacancy concentrations in the Al matrix after quenching,which serve as critical inputs to CD simulations to predict long-term cluster evolution kinetics during natural aging.Our results quantitatively demonstrate the significant impact of quench rate on natural aging kinetics.Results provide insights to guide alloy chemistry,quench rates,and aging time at finite temperatures to control the evolution of solute clusters and eventual precipitates in aged multicomponent alloys.
