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Incremental 4D-VAR assimilation scheme based on Lorenz model

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Acta Oceanologica Sinica 2008年第Z1期27卷 93-100页

作者： wang xidong XU Dongfeng XU Xiaohua State Key Laboratory of Satellite Ocean Environment Dynamics Second Institute of Oceanography State Oceanic Administra-tion Hangzhou 310012China State Key Laboratory of Satellite Ocean Environment Dynamics Second Institute of Oceanography State Oceanic Administra-tion Hangzhou 310012China State Key Laboratory of Satellite Ocean Environment Dynamics Second Institute of Oceanography State Oceanic Administra-tion Hangzhou 310012China

Four-dimensional variational(4D-VAR) data assimilation method is a perfect data assimilation solution in theory, but the computational issue is quite difficult in operational *** incremental 4D-VAR assimilation scheme is set up in order to reduce the computational cost. It is shown that the accuracy of the observations, the length of the assimilation window and the choice of the first guess have an important influence on the assimilation outcome through the contrast experiment. Compared with the standard 4D-VAR assimilation scheme, the incremental 4D-VAR assimilation scheme shows its advantage in the computation speed through an assimilation experiment.

关键词： 4D-VAR assimilation,incremental 4D-VAR assimilation Lorenz model

Tropical Cyclone Genesis Potential Index over the Western North Pacific Simulated by CMIP5 Models

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Advances in Atmospheric Sciences 2015年第11期32卷 1539-1550页

作者： SONG Yajuan wang Lei LEI Xiaoyan wang xidong College of Physical and Environmental Oceanography Ocean University of China First Institute of Oceanography State Oceanic Administration State Key Laboratory of Tropical Oceanography South China Sea Institute of OceanologyChinese Academy of Sciences Key Laboratory of Marine Environment Information Technology State Oceanic Administration

Tropical cyclone （TC） genesis over the western North Pacific （WNP） is analyzed using 23 CMIP5 （Coupled Model Intercomparison Project Phase 5） models and reanalysis datasets. The models are evaluated according to TC genesis potential index （GPI）. The spatial and temporal variations of the GPI are first calculated using three atmospheric reanalysis datasets （ERA-Interim, NCEP/NCAR Reanalysis- 1, and NCEP/DOE Reanalysis-2）. Spatial distributions of July-October-mean TC frequency based on the GPI from ERA-interim are more consistent with observed ones derived from IBTrACS global TC data. So, the ERA-interim reanalysis dataset is used to examine the CMIP5 models in terms of reproducing GPI during the period 1982-2005. Although most models possess deficiencies in reproducing the spatial distribution of the GPI, their multi- model ensemble （MME） mean shows a reasonable climatological GPI pattern characterized by a high GPI zone along 20°N in the WNP. There was an upward trend of TC genesis frequency during 1982 to 1998, followed by a downward trend. Both MME results and reanalysis data can represent a robust increasing trend during 1982-1998, but the models cannot simulate the downward trend after 2000. Analysis based on future projection experiments shows that the GPI exhibits no significant change in the first half of the 21st century, and then starts to decrease at the end of the 21st century under the representative concentration pathway （RCP） 2.6 scenario. Under the RCP8.5 scenario, the GPI shows an increasing trend in the vicinity of 20°N, indicating more TCs could possibly be expected over the WNP under future global warming.

关键词： tropical cyclone genesis potential index CMIP5 western North Pacific global warming.

Hydrothermal growth of well-aligned TiO_2 nanorod arrays: Dependence of morphology upon hydrothermal reaction conditions

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Rare Metals 2010年第3期29卷 286-291页

作者： LI Yuxiang ZHANG Mei GUO Min wang xidong Department of Physical Chemistry University of Science and Technology Beijing Beijing 100083 China College of Engineering Peking University Beijing 100871 China

Well-aligned TiO2 nanorod arrays （TNAs） were prepared on pretreated quartz substrates via hydrothermal *** effect of the different preparation conditions on the growth morphologies of TNAs was systematically investigated by X-ray diffraction （XRD） and field-emission scanning electron microscopy （FE-SEM）.The photocatalytic properties were tested by photodegradation of a methyl blue *** is demonstrated that the hydrothermal reaction conditions,such as precursor concentration,hydrothermal reaction temperature,and hydrothermal reaction times,can greatly affect the growth of *** the preparation process,TNAs with 2 μm in length and 140-170 nm in diameter and well-aligned orientation have been successfully *** photocatalytic experiment results indicate that TNAs have much better photocatalytic activity than TiO2 nanoparticles.

关键词： titanium dioxide nanorod arrays hydrothermal method photocatalyst

Effects of Stokes production on summer ocean shelf dynamics

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Acta Oceanologica Sinica 2014年第1期33卷 24-34页

作者： ZHANG Xuefeng HANGuijun wang xidong ZHANG Lianxin Key Laboratory of Marine Environmental Information Technology State Oceanic Administration National Marine Data and Information Service State Oceanic Administration

A two-dimensional numerical model,which is configured on the basis of Princeton ocean model（POM）,is used to study the effect of Stokes production（SP） of the turbulent kinetic energy on a density profile and Ekman transport in an idealized shelf region in *** energy input from SP is parameterized and included into the Mellor-Yamada turbulence closure *** reveal that the intensity of wind-driven upwelling fronts near the sea surface is weakened by the SP-associated turbulent kinetic energy *** vertical eddy viscosity coefficient in the surface boundary layer is enhanced greatly owing to the impact of SP,which decreases the alongshore velocity and changes the distribution of *** addition,the SP-induced mixing easily suppresses the strong stratification and significantly increases the depth of the upper mixed layer（ML） under strong winds.

关键词： Stokes production POM upper mixed layer upwelling

Responses of the Southern Ocean mixed layer depth to the eastern and central Pacific El Niño events during austral winter

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Acta Oceanologica Sinica 2024年第7期43卷 1-14页

作者： Yuxin Shi Hailong Liu xidong wang Quanan Zheng School of Oceanography Shanghai Jiao Tong UniversityShanghai 200240China Yunnan Key Laboratory of Meteorological Disasters and Climate Resources in the Greater Mekong Subregion Yunnan UniversityKunming 600650China College of Oceanography Hohai UniversityNanjing 210098China Department of Atmospheric and Oceanic Science University of Maryland at College ParkCollege Park 20742USA

Based on the Ocean Reanalysis System version 5(ORAS5)and the fifth-generation reanalysis datasets derived from European Centre for Medium-Range Weather Forecasts(ERA5),we investigate the different impacts of the central Pacific(CP)El Niño and the eastern Pacific(EP)El Niño on the Southern Ocean(SO)mixed layer depth(MLD)during austral *** MLD response to the EP El Niño shows a dipole pattern in the South Pacific,namely the MLD dipole,which is the leading El Niño-induced MLD variability in the *** tropical Pacific warm sea surface temperature anomaly(SSTA)signal associated with the EP El Niño excites a Rossby wave train propagating southeastward and then enhances the Amundsen Sea low(ASL).This results in an anomalous cyclone over the Amundsen *** a result,the anomalous southerly wind to the west of this anomalous cyclone advects colder and drier air into the southeast of New Zealand,leading to surface cooling through less total surface heat flux,especially surface sensible heat(SH)flux and latent heat(LH)flux,and thus contributing to the mix layer(ML)*** east of the anomalous cyclone brings warmer and wetter air to the southwest of Chile,but the total heat flux anomaly shows no significant *** warm air promotes the sea ice melting and maintains fresh water,which strengthens *** results in a shallower *** the CP El Niño,the response of MLD shows a separate negative MLD anomaly center in the central South *** Rossby wave train triggered by the warm SSTA in the central Pacific Ocean spreads to the Amundsen Sea,which weakens the ***,the anomalous anticyclone dominates the Amundsen ***,the anomalous northerly wind to the west of anomalous anticyclone advects warmer and wetter air into the central and southern Pacific,causing surface warming through increased SH,LH,and longwave radiation flux,and thus contributing to the ML ***,to the east of the anomalous anticyclone,there is n

关键词： Southern Ocean mixed layer depth Central Pacific El Niño Eastern Pacific El Niño Rossby wave train

Novel titanium particles reinforced Zr-based bulk metallic glass composites prepared by infiltration casting

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Journal of University of Science and Technology Beijing 2008年第4期15卷 505-508页

作者： Cuimei Zhang xidong Hui Meiling wang Guoliang Chen State Key Laboratory for Advanced Metals and Materials University of Science and Technology Beijing Beijing 100083 China

A novel Ti/Zr41.2Ti13.8Cu12.5Ni10.0Be22.5 composite was successfully prepared by infiltrating the melt into sintered Ti preform. It shows that the introduction of Ti particles into the composite results in an increase in elastic strain to 3% and an enhancement of the strength up to 2.1 GPa. High specific strength has been obtained because of the decrease in density of the composite. It is suggested that an improvement in the mechanical properties of the composite may be attributed to the generation of multiple shear bands and some deformation in the Ti particles.

关键词： melt infiltration bulk metallic-glass Ti particles mechanical properties

Conductivity properties of β-SiAlON ceramics

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Science China(Technological Sciences) 2012年第9期55卷 2409-2415页

作者： DONG PengLi wang xidong ZHANG Mei SESHADRI Seetharaman The Chinese Society for Metals Beijing 100711China College of Engineering Peking UniversityBeijing 100871China Department of Physical Chemistry University of Science and Technology BeijingBeijing 100083China Department of Materials Science Engineering Royal Institute of TechnologyStockholm SE 100-44Sweden

The thermal diffusivity and heat capacity of β-SiAION ceramics with different Z values （0.6, 1.5, 3.0） were measured by laser flash technique and differential scanning calorimetry （DSC）, respectively. The thermal conductivity of β-SiAION was calculated from thermal diffusivity, heat capacity and density and it decreased and then kept almost constant with increasing of temperature. Two different models representing effective thermal conductivity were established and the various parameters of these models were simulated based on the results from the present work. The fitted regression lines were in good agreement with the experimental values.

关键词： β-SiAION thermal diffusivity heat capacity effective thermal conductivity

Effect of Substrate Pretreatment on Controllable Growth of TiO_2 Nanorod Arrays

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Journal of Materials Science & Technology 2012年第7期28卷 577-586页

作者： Minjiang Cao Yuxiang Li Min Guo Mei Zhang xidong wang College of Engineering Peking University Beijing 100871 China Institute of Powder Engineering School of Material Science and Engineering Xi'an University of Architecture andTechnology Xi~an 710055 China Department of Physical Chemistry University of Science and Technology Beijing Beijing 100083 China

Well-aligned TiO2 nanorod arrays （TNAs） were prepared on the pretreated quartz substrates. The effect of the pretreatment conditions on the growth of TNAs was systematically investigated by X-ray diffraction （XRD）, field-emission scanning electron microscopy （FE-SEM） and high-resolution transmission electron microscopy （HRTEM）. It is demonstrated that the pre-coating TiO2 crystal seeds on the substrates can greatly improve the growth orientation of TNAs. Rutile Ti02 crystal seeds induce the nucleation and growth of TNAs more preferably than the anatase TiO2 seeds. The growth density and diameter distribution of TNAs strongly depend on the TiO2 crystal seeds density. It is proved that TNAs with different morphologies can be controllably synthesized by using hydrothermal approach by pretreating substrates. The photocatalytic activity of TNAs was investigated by measuring the photodegradation rate of methyl blue aqueous solution under UV irradiation （254 nm）. And the results show that TNAs with large growth density and small diameter size exhibit relatively higher photocatalytic activity.

关键词： Titanium dioxide Nanorod arrays Hydrothermal synthesis Photocatalytic properties

Evaluation on monthly sea surface wind speed of four reanalysis data sets over the China seas after 1988

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Acta Oceanologica Sinica 2020年第1期39卷 83-90页

作者： Guosong wang xidong wang Hui wang Min Hou Yan Li Wenjing Fan Yulong Liu College of Oceanography Hohai University Nanjing 210098China National Marine Data and Information Service Tianjin 300171China Tianjin Binhai New Area Meteorology Administration Tianjin 300457China

This study investigates the long-term changes of monthly sea surface wind speeds over the China seas from 1988 to 2015. The 10-meter wind speeds products from four major global reanalysis datasets with high resolution are used: Cross-Calibrated Multi-Platform data set(CCMP), NCEP climate forecast system reanalysis data set(CFSR),ERA-interim reanalysis data set(ERA-int) and Japanese 55-year reanalysis data set(JRA55). The monthly sea surface wind speeds of four major reanalysis data sets have been investigated through comparisons with the longterm and homogeneous observation wind speeds data recorded at ten stations. The results reveal that(1) the wind speeds bias of CCMP, CFSR, ERA-int and JRA55 are 0.91 m/s, 1.22 m/s, 0.62 m/s and 0.22 m/s, *** wind speeds RMSE of CCMP, CFSR, ERA-int and JRA55 are 1.38 m/s, 1.59 m/s, 1.01 m/s and 0.96 m/s,respectively;(2) JRA55 and ERA-int provides a realistic representation of monthly wind speeds, while CCMP and CFSR tend to overestimate observed wind speeds. And all the four data sets tend to underestimate observed wind speeds in Bohai Sea and Yellow Sea;(3) Comparing the annual wind speeds trends between observation and the four data sets at ten stations for 1988-1997, 1988–2007 and 1988–2015, the result show that ERA-int is superior to represent homogeneity monthly wind speeds over the China seaes.

关键词： monthly sea surface wind speeds China Sea reanalysis data inhomogeneity evaluation trend analysis