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Evaluation of All-Sky Assimilation of FY-3C/MWHS-2 on mei-yu Precipitation Forecasts over the Yangtze-Huaihe River Basin

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Advances in Atmospheric Sciences 2021年第8期38卷 1397-1414页

作者： yu LI Keyi CHEN Zhipeng XIAN School of Atmospheric Sciences Chengdu University of Information TechnologyChengdu 610025China International Center for Climate and Environment Sciences Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029China University of Chinese Academy of Sciences Beijing 100049China

All-sky (i.e., clear, cloudy, and precipitating conditions) assimilation of microwave observations shows potentially positive impacts on the improvement of the forecasts of cloud-associated weather processes. In this study, a typical mei-yu heavy precipitation event that occurred in 2017 was investigated, and the Weather Research and Forecasting data assimilation (WRFDA) as well as its 3D-Var assimilation scheme (excluding cloud and precipitation control variables) were applied to assimilate the Fengyun-3C (FY-3C) Microwave Humidity Sounder-2 (MWHS-2) observations under clear- sky (excluding the observations that are strongly affected by ice clouds and precipitation) and all-sky conditions. Three experiments including a control experiment without assimilating any observations, clear-sky, and all-sky experiments with only FY-3C/MWHS-2 observations assimilated were carried out. The results show that the all-sky assimilation approach that provides more cloud and precipitation information and increased more than 10% of the satellite data usage than the clear-sky experiment. Meanwhile, as compared with the control experiment, the all-sky assimilation reduced nearly 0.5% of the root mean square errors in the humidity fields, leading to more accurate forecast performances regarding the distribution and intensity of heavy rainfall;but it exhibited a neutral to negative impacts on the wind and temperature. Although the system used to conduct all-sky assimilation is only able to adjust control variables for moisture-, wind-, and temperature- related variables in the presence of cloud and does not benefit directly from cloud or precipitation information, the positive effects on heavy rainfall forecasts achieved in this study indicate a potential future benefit regarding disaster prevention and mitigation.

关键词： all-sky assimilation FY-3C MWHS-2 mei-yu rainfall

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Formation of Low-Level Jets over Southern China in the mei-yu Season

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Advances in Atmospheric Sciences 2023年第10期40卷 1731-1748页

作者： Xuanyu LIU Guixing CHEN Sijia ZHANG yu DU School of Atmospheric Sciences Sun Yat-sen Universityand Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai)Zhuhai 519082China Guangdong Province Key Laboratory for Climate Change and Natural Disaster Studies Sun Yat-sen UniversityZhuhai 519082China Key Laboratory of Tropical Atmosphere-Ocean System(Sun Yat-sen University) Ministry of EducationZhuhai 519082China

This study examines the diversity of low-level jet(LLJ)formation and related physical processes over southern China.A total of 171 LLJ formation events with enhanced daily southwesterlies and early-morning maximum wind speeds were observed during the mei-yu seasons of 1989–*** LLJs can be further categorized into four types based on the increases in the daily mean and diurnal amplitude of the low-level *** of the synoptic-scale disturbances shows that the two types of LLJ formation(Q1 and Q4),which feature large increases of daily southerly wind components,are mainly induced by west-east dipole patterns of pressure change,in association with the enhanced southwest vortex and/or the western Pacific subtropical high(WPSH).In contrast,the other two types(Q2 and Q3),which feature relatively large increases in their daily westerly components,are related to a northwest-southeast dipole pattern of pressure change due to the mid-latitude trough and the *** further analyze the considerable variations in the diurnal thermal forcing among the LLJ formation *** strong(weak)daytime heating of solar radiation leads to relatively large(small)increases in the diurnal amplitude of low-level winds in Q1 and Q2(Q3 and Q4)***,different combinations of synopticscale disturbances and diurnal thermal forcings are found to account for the diversity in LLJ formation and associated differences in downstream rainfall *** results help to improve our understanding and prediction of the formation of LLJs.

关键词： low-level jets formation processes diurnal variations synoptic-scale disturbances

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A comparison of two kinds of eastward-moving mesoscale vortices during the mei-yu period of 2010

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Science China Earth Sciences 2013年第2期56卷 282-300页

作者： FU ShenMing yu Fei WANG DongHai XIA RuDi State Key Laboratory of Severe Weather Chinese Academy of Meteorological Sciences International Center for Climate and Environment Sciences Institute of Atmospheric PhysicsChinese Academy of Sciences Graduate University of Chinese Academy of Sciences

During the mei-yu period,the east edge of the Tibetan Plateau and the Dabie Mountain are two main sources of eastward-moving mesoscale vortices along the mei-yu front(MYF).In this study,an eastward-moving southwest vortex(SWV) and an eastward-moving Dabie vortex(DBV) during the mei-yu period of 2010 have been investigated to clarify the main similarities and differences between *** synoptic analyses reveal that the SWV and DBV were both located at the lower troposphere;however,the SWV developed in a "from top down" trend,whereas the DBV developed in an opposite *** were obvious surface closed low centers corresponding to the DBV during its life span,whereas for the SWV,the closed low center only appeared at the mature *** and warm air intersected intensely after the formation of both the vortices,and the cold advection in the SWV case was stronger than that in the DBV case,whereas the warm advection in the DBV case was more intense than that in the SWV *** Bay of Bengal and the South China Sea were main moisture sources for the SWV,whereas for the DBV,in addition to the above two moisture sources,the East China Sea was also an important moisture *** vorticity budget indicates that the convergence was the most important common factor conducive to the formation,development,and maintenance of the SWV and DBV,whereas the conversion from the vertical vorticity to the horizontal one(tilting) was the most important common factor caused the dissipation of both of the *** kinetic energy(KE) budget reveals that the KE generation by the rotational wind was the dominant factor for the enhancement of KE associated with the SWV,whereas for the DBV,the KE transport by the rotational wind was more important than the KE *** KE associated with the SWV and the DBV weakened with different mechanisms during the decaying ***,the characteristics of baroclinic and barotropic energy conversions during the life spans of both vor

关键词： southwest vortex mei-yu vorticity kinetic energy baroclinic energy conversion barotropic energy conversion

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Ground-Based Radar Reflectivity Mosaic of mei-yu Precipitation Systems over the Yangtze River–Huaihe River Basins

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Advances in Atmospheric Sciences 2016年第11期33卷 1285-1296页

作者： Yali LUO Weimiao QIAN yu GONG Hongyan WANG Da-Lin ZHANG State Key Laboratory of Severe Weather Chinese Academy of Meteorological Sciences Beijing 100081 China Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters Nanjing University of Information Science & Technology Nanjing 210044 China Shijiazhuang Meteorological Bureau Shijiazhuang 050081 China National Meteorological Center of China Beijing 100081 China Department of Atmospheric and Oceanic Science University of Maryland College Park Collage Park Maryland 20742 USA

The 3D radar reflectivity produced by a mosaic software system, with measurements from 29 operational weather radars in the Yangtze River–Huaihe River Basins（YRHRB） during the mei-yu season of 2007, is compared to coincident TRMM PR observations in order to evaluate the value of the ground-based radar reflectivity mosaic in characterizing the 3D structures of mei-yu precipitation. Results show reasonable agreement in the composite radar reflectivity between the two datasets,with a correlation coefficient of 0.8 and a mean bias of -1 dB. The radar mosaic data at constant altitudes are reasonably consistent with the TRMM PR observations in the height range of 2–5 km, revealing essentially the same spatial distribution of radar echo and nearly identical histograms of reflectivity. However, at altitudes above 5 km, the mosaic data overestimate reflectivity and have slower decreasing rates with height compared to the TRMM PR observations. The areas of convective and stratiform precipitation, based on the mosaic reflectivity distribution at 3-km altitude, are highly correlated with the corresponding regions in the TRMM products, with correlation coefficients of 0.92 and 0.97 and mean relative differences of -7.9% and -2.5%, respectively. Finally, the usefulness of the mosaic reflectivity at 3-km altitude at 6-min intervals is illustrated using a mesoscale convective system that occurred over the YRHRB.

关键词： reflectivity Yangtze TRMM convective reasonably altitude mesoscale season Precipitation mosaic

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Anomaly of the Moist Potential Vorticity Substance with Mass Forcing and Its Application in Diagnosing mei-yu Front Rainfall

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Atmospheric and Oceanic Science Letters 2015年第1期8卷 39-44页

作者： ZHOU yu-Shu ZHU Ke-Feng ZHANG Zhe Laboratory for Cloud-Precipitation Physics and Severe Storms (LACS) Institute of Atmospheric Physics Chinese Academy of Sciences School of Atmospheric Sciences Nanjing University University of Chinese Academy of Sciences

The effects of precipitation on the moist potential vorticity substance(MPVS) are investigated by analyzing the MPVS with precipitation mass forcing and its impermeability in daily 1°× 1° data of the National Centers for Environmental Prediction/National Center for Atmospheric Research(NCEP/NCAR) over the Yangtze River Basin from 21 June to 2 July 1999. The results show that the positive MPVS anomalies appear mainly along the mei-yu front, where the maximum MPVS collocates with the maximum surface rainfall. Rain case diagnoses indicate that the MPVS anomaly may be used as a dynamical signal to detect the location and shift of the rain band when its impermeability is considered.

关键词： moist potential vorticity substance mass forcing i

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Palladium installed copper-organic framework for C–C coupling reactions

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Science China Chemistry 2025年

作者： yu-mei Wang mei-Xia Tao Kai-Ming Mo Xu Chen Shu-Hua Zhong Elena S Shubina Guo-Hong Ning Dan Li College of Chemistry and Materials Science Guangdong Provincial Key Laboratory of Supramolecular Coordination ChemistryJinan University A.N.Nesmeyanov Institute of Organoelement Compounds Russian Academy of Sciences

The formation of C–C bonds is a crucial aspect of organic synthesis. Synthesists' long-term objective is to identify novel catalysts to optimize reaction systems based on traditional transition metal catalysis. This study explores the synthesis and catalytic potential of palladium-installed covalent metal-organic frameworks(CMOFs) based on copper cyclic trinuclear units(Cu-CTUs). By incorporating palladium ions into the imine-based framework JNM-7 through a straightforward immersion method, we achieved a notable enhancement in catalytic activity for critical C–C coupling reactions, including C–H arylation and Sonogashira cross-coupling. The resulting JNM-7-Pd demonstrated remarkable stability and recyclability, maintaining its efficiency over at least three cycles without any decline in efficiency.

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Efficient photocatalytic reduction of chromium(Ⅵ) using photoreduced graphene oxide as photocatalyst under visible light irradiation

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Journal of Materials Science & Technology 2021年第32期91卷 17-27页

作者： mei yu Jing Shang yu Kuang Department of Environment and Health State Key Joint Laboratory of Environmental Simulation and Pollution ControlCollege of Environmental Sciences and EngineeringPeking UniversityBeijing 100871China

Graphene oxide(GO),a new and promising material,has been widely used as a co-catalyst in photocatalytic reactions;however,its capacity as a sole photocatalyst has rarely been *** this study,ultraviolet(UV) light irradiation was used as a modification method to obtain reduced GO(rGO) *** samples were used as photocatalysts to examine their visible light photocatalytic activity toward hexavalent chromium(Cr(Ⅵ)) *** force microscopy(AFM),X-ray diffraction(XRD),UV-vis spectrophotometry,Raman spectroscopy,X-ray photoelectron spectroscopy(XPS),and electron spin resonance(ESR) spectroscopy were applied to interpret the surface and structure changes with UV *** oxygen-containing functional groups(OFGs) on the GO surface were reduced to defective carbons andπ-conjugated C=C(sp^(2) domains) under UV light;this led to a decrease in the interlayer distance between GO sheets,GO fragmentation,and increased disorder on the GO *** restoration of sp^(2) domains led to a narrower band gap of GO,which favored the rGO excitation by visible light to generate electron-hole *** rGO pre-irradiated with UV for 1 h(rGO-1),possessing the highest defect density and electron generation efficiency,exhibited the best Cr(Ⅵ) reduction efficiency,which was about three times that of the GO sample;moreover,it outperformed most of the reported GO-based *** addition,low pH and the addition of citric acid as a hole scavenger could further improve the photocatalytic *** study proves that GO or rGO can be used as a sole photocatalyst under visible light to remove environmental pollutants such as heavy-metal ions,and it paves the way for the development of this kind of material and its UV-irradiation modification for further applications.

关键词： Graphene oxide Chromium(Ⅵ) Defect density UV-irradiation modification Photocatalytic reduction

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Ordering Trees by Their Spectral Radii

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Acta Mathematicae Applicatae Sinica 2014年第4期30卷 1107-1112页

作者： Ai-mei yu Department of Mathematics Beijing Jiaotong University

Let T be a tree with n vertices and let A（T） be the adjacency matrix of T. Spectral radius of T is the largest eigenvalue of A（T）. Wu et al. [Wu, B.F., yuan, X.Y, and Xiao, E.L. On the spectral radii of trees, Journal of East China Normal University （Natural Science）, 3：22-28 （2004）] determined the first seven trees of order n with the smallest spectral radius. In this paper, we extend this ordering by determining the trees with the eighth to the tenth smallest spectral radius among all trees with n vertices.

关键词： tree spectral radius ordering

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An Analytical Solution for Nearshore Circulation Driven by Focused/Defocused Waves

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China Ocean Engineering 2019年第5期33卷 544-553页

作者： DING yu-mei SHI Fengyan School of Science Tianjin University of Science and Technology Tianjin 300475 China Center for Applied Coastal Research Department of Civil and Environmental Engineering University of Delaware Newark 19716 USA

An offshore shoal or bar refracts ocean surface waves and causes wave focusing/defocusing on the adjacent beach. Wave focal patterns characterized by alongshore variations in wave height, wave angle, and breaking location induce alongshore non-uniformities of wave setup and nearshore circulation, e.g., rip currents and alongshore currents, in the surfzone. A simplified analytic model for nearshore circulation generated by focused/defocused waves on a planar beach is developed and theoretical solutions are obtained using transport stream function and perturbations in alongshore distributions of wave height and wave angle at the breaker line. The analytic model suggests that alongshore currents are strongly affected by a pair of counter-rotating vortices generated shoreward of the wave focal zone. The vortices are persistent, and their strengths depend on the amplitudes of alongshore variations in wave height and wave angle. The alongshore gradient in wave height tends to intensify the vortices while the convergence of wave angle tends to weaken the vortices. Divergent flows associated with the vortices in the surfzone are intense, strengthening alongshore currents in the downstream of the wave focal zone and weakening alongshore currents or causing flows reversal in the upstream. Alongshore currents are modulated by rip currents associated with the wave focusing/defocusing patterns.

关键词： wave focusing and defocusing nearshore circulation rip current alongshore current analytical solution

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Vanishing viscosity limits for the free boundary problem of compressible viscoelastic fluids with surface tension

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Science China Mathematics 2023年第6期66卷 1263-1300页

作者： Xumin Gu yu mei School of Mathematics Shanghai University of Finance and EconomicsShanghai 200433China School of Mathematics and Statistics Northwestern Polytechnical UniversityXi'an 710129China

We consider the free boundary problem of compressible isentropic neo-Hookean viscoelastic fluid equations with surface *** the physical kinetic and dynamic conditions proposed on the free boundary,we investigate the regularity of classical solutions to viscoelastic fluid equations in Sobolev spaces which are uniform in viscosity and justify the corresponding vanishing viscosity *** key ingredient of our proof is that the deformation gradient tensor in Lagrangian coordinates can be represented as a parameter in terms of the flow map so that the inherent structure of the elastic term improves the uniform regularity of normal derivatives in the limit of vanishing *** result indicates that the boundary layer does not appear in the free boundary problem of compressible viscoelastic fluids,which is different from the case studied by mei et al.(2018)for the free boundary compressible Navier-Stokes system.

关键词： free boundary viscoelastic fuid vanishing viscosity compressible fuid elastodynamics

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