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Comparison of a Very-fine-resolution GCM with RCM Dynamical Downscaling in Simulating Climate in China

Advances in Atmospheric Sciences 2016年第5期33卷 559-570页

作者： donglin guo Huijun WANG Nansen-Zhu International Research Center Institute of Atmospheric Physics Chinese Academy of Sciences Climate Change Research Center Chinese Academy of Sciences Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters Nanjing University of Information Science & Technology

Regional climate simulation can generally be improved by using an RCM nested within a coarser-resolution ***, whether or not it can also be improved by the direct use of a state-of-the-art GCM with very fine resolution, close to that of an RCM, and, if so, which is the better approach, are open questions. These questions are important for understanding and using these two kinds of simulation approaches, but have not yet been investigated. Accordingly, the present reported work compared simulation results over China from a very-fine-resolution GCM（VFRGCM） and from RCM dynamical downscaling. The results showed that：（1） The VFRGCM reproduces the climatologies and trends of both air temperature and precipitation, as well as inter-monthly variations of air temperature in terms of spatial pattern and amount, closer to observations than the coarse-resolution version of the GCM. This is not the case, however, for the inter-monthly variations of precipitation.（2） The VFRGCM captures the climatology, trend, and inter-monthly variation of air temperature, as well as the trend in precipitation, more reasonably than the RCM dynamical downscaling method.（3） The RCM dynamical downscaling method performs better than the VFRGCM in terms of the climatology and inter-monthly variation of precipitation. Overall,the results suggest that VFRGCMs possess great potential with regard to their application in climate simulation in the future,and the RCM dynamical downscaling method is still dominant in terms of regional precipitation simulation.

关键词： climate simulation dynamical downscaling GCM RCM

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The long-term trend of Bohai Sea ice in different emission scenarios

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Acta Oceanologica Sinica 2021年第7期40卷 100-118页

作者： donglin guo Rui Li Peng Zhao College of Oceanic and Atmospheric Sciences Ocean University of ChinaQingdao 266100China North China Sea Marine Forecasting Center Ministry of Natural ResourcesQingdao 266061China

Based on a coupled ocean-sea ice model,this study investigates how changes in the mean state of the atmosphere in different CO2 emission scenarios (RCP 8.5,6.0,4.5 and 2.6) may affect the sea ice in the Bohai Sea,China,especially in the Liaodong Bay,the largest bay in the Bohai Sea. In the RCP 8.5 scenario,an abrupt change of the atmospheric state happens around 2070. Due to the abrupt change,wintertime sea ice of the Liaodong Bay can be divided into 3 periods: a mild decreasing period (2021–2060),in which the sea ice severity weakens at a near-constant rate;a rapid decreasing period (2061–2080),in which the sea ice severity drops dramatically;and a stabilized period (2081–2100). During 2021–2060,the dates of first ice are approximately unchanged,suggesting that the onset of sea ice is probably determined by a cold-air event and is not sensitive to the mean state of the atmosphere. The mean and maximum sea ice thickness in the Liaodong Bay is relatively stable before 2060,and then drops rapidly in the following decade. Different from the RCP 8.5 scenario,atmospheric state changes smoothly in the RCP 6.0,4.5 and 2.6 scenarios. In the RCP 6.0 scenario,the sea ice severity in the Bohai Sea weakens with time to the end of the twenty-first century. In the RCP 4.5 scenario,the sea ice severity weakens with time until reaching a stable state around the 2070s. In the RCP 2.6 scenario,the sea ice severity weakens until the 2040s,stabilizes from then,and starts intensifying after the 2080s. The sea ice condition in the other bays of the Bohai Sea is also discussed under the four CO_(2) emissions scenarios. Among atmospheric factors,air temperature is the leading one for the decline of the sea ice extent. Specific humidity also plays an important role in the four scenarios. The surface downward shortwave/longwave radiation and meridional wind only matter in certain scenarios,while effects from the zonal wind and precipitation are negligible.

关键词： sea ice Liaodong Bay RCP scenarios NEMO LIM2

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Simulated change in the near-surface soil freeze/thaw cycle on the Tibetan Plateau from 1981 to 2010

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Chinese Science Bulletin 2014年第20期59卷 2439-2448页

作者： donglin guo Huijun Wang Nansen-Zhu International Research Center Institute of Atmospheric Physics Chinese Academy of Sciences University of Chinese Academy of Sciences Climate Change Research Center Chinese Academy of Sciences

The near-surface freeze/thaw cycle in cold regions plays a major role in the surface energy budget,hydrological activity,and terrestrial *** this study,the Community Land Model,Version 4 and a suite of high-resolution atmospheric data were used to investigate the changes in the near-surface soil freeze/thaw cycle in response to the warming on the Tibetan Plateau from1981 to *** in situ observations-based validation showed that,considering the cause of scale mismatch in the comparison,the simulated soil temperature,freeze start and end dates,and freeze duration at the near-surface were *** response to the warming of the Tibetan Plateau at a rate of approximately 0.44°C decade-1,the freeze start-date became delayed at an area-mean rate of1.7 days decade-1,while the freeze end-date became advanced at an area-mean rate of 4.7 days *** delaying of the freeze start-date,which was combined with the advancing of the freeze end-date,resulted in a statistically significant shortening trend with respect to the freeze duration,at an area-mean rate of 6.4 days *** changes would strongly affect the surface energy flux,hydrological processes,and vegetation *** also found that the rate of freeze-duration shortening at the near-surface soil layer was approximately 3.0 days decade-1lower than that at a depth of 1 *** implied that the changes in soil freeze/thaw cycles at the near surface cannot be assumed to reflect the situation in deeper soil *** significant correlations between freeze duration and air temperature indicated that the shortening of the near-surface freeze duration was caused by the rise in air temperature,which occurred especially in spring,followed by *** results can be used to reveal the laws governing the response of the near-surface freeze/thaw cycle to climate change and indicate related changes in permafrost.

关键词：土壤冻结青藏高原近地表解冻周期模拟冷冻时间陆地生态系统

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Room-Temperature Magnetism of Ceria Nanocubes by Inductively Transferring Electrons to Ce Atoms from Nearby Oxygen Vacancy

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Nano-Micro Letters 2016年第1期8卷 13-19页

作者： Yue Kang Qiang Leng donglin guo Dezhi Yang Yanping Pu Chenguo Hu Department of Applied Physics Chongqing University School of Public Affairs Chongqing University

Ceria(CeO_2) nanocubes were synthesized by a hydrothermal method and weak ferromagnetism was observed in room temperature. After ultraviolet irradiation, the saturation magnetization was significantly enhanced from*3.18×10^(-3) to *1.89×10^(-2) emug^(-1). This is due to the increase of oxygen vacancies in CeO_2 structure which was confirmed by X-ray photoelectron spectra. The first-principle calculation with Vienna ab-initio simulation package was used to illustrate the enhanced ferromagnetism mechanism after calculating the density of states(DOSs) and partial density of states(PDOSs) of CeO_2 without and with different oxygen vacancies. It was found that the increase of oxygen vacancies will enlarge the PDOSs of Ce 4f orbital and DOSs. Two electrons in one oxygen vacancy are respectively excited to 4f orbital of two Ce atoms neighboring the vacancy, making these electron spin directions on 4f orbitals of these two Ce atoms parallel. This superexchange interaction leads to the formation of ferromagnetism in CeO_2 at room temperature. Our work indicates that ultraviolet irradiation is an effective method to enhance the magnetism of CeO_2 nanocube, and the firstprinciple calculation can understand well the enhanced magnetism.

关键词： UV irradiation Oxygen vacancies Saturation magnetism Spin direction Superexchange interaction

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Permafrost Thaw and Associated Settlement Hazard Onset Timing over the Qinghai-Tibet Engineering Corridor

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International Journal of Disaster Risk Science 2015年第4期6卷 347-358页

作者： donglin guo Jianqi Sun Nansen-Zhu International Research Center Institute of Atmospheric PhysicsChinese Academy of Sciences

In permafrost areas, the timing of thermal surface settlement hazard onset is of great importance for the construction and maintenance of engineering *** permafrost thaw and the associated thermal settlement hazard onset timing in the Qinghai-Tibet engineering corridor(QTEC) were analyzed using high-resolution soil temperature data from the Community Land Model version4 in combination with multiple model and scenario soil temperature data from the fifth phase of the Coupled Model Intercomparison Project(CMIP5). Compared to the standard frozen ground map for the Tibetan Plateau and ERAInterim data, a multimodel ensemble reproduces the extent of permafrost and soil temperature change in the QTEC at a 1 m depth from 1986–2005. Soil temperature and active layer thickness increase markedly during 2006–2099 using CMIP5 scenarios. By 2099, the ensemble mean soil temperature at 15 m depth will increase between 1.0 and 3.6 ℃ in the QTEC. Using crushed-rock revetments can delay the onset of thermal settlement hazard for colder permafrost areas by approximately 17 years in the worst case scenario of RCP8.5. Nearly one-third of the area of the QTEC exhibits settlement hazard as early as 2050, and half of this one-third of the area is traversed by the QinghaiTibet highway/railway, a situation that requires more planning and remedial attention. Simulated onsets of thermal settlement hazard correspond well to the observed soil temperature at 15 m depth for seven grid areas in the QETC, which to some extent indicates that these timingestimates are reasonable. This study suggests that climate model-based timing estimation of thermal settlement hazard onset is a valuable method, and that the results are worthy of consideration in engineering design and evaluation.

关键词： Hazard onset timing Permafrost QinghaiTibet railway Thermal hazard

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Preparation and magnetic properties of anisotropic Nd2Fe14B/Sm2Co17 hybrid-bonded magnets

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Journal of Rare Earths 2019年第10期37卷 1047-1052页

作者： Xueguo Yin Yue Sui Qiqi Yang Qian Shen Yilong Ma Bin Shao Jianchun Sun donglin guo College of Material Science and Engineering Chongqing University of TechnologyChongqing400054China College of Metallurgy and Materials Engineering Chongqing University of Science and TechnologyChongqing401331China College of Chemistry and Chemical Engineering Chongqing University of Science and TechnologyChongqing401331China

In the present work, anisotropic Nd2 Fe14 B/Sm2 Co17 hybrid-bonded magnets were prepared with different Nd-Fe-B contents. It is found that the particle distributions and ratios between the two magnetic phases have important roles in the magnetic properties, microstructures and thermal stability of the magnets. With increase of Nd-Fe-B content, the saturation magnetization of the anisotropic hybrid magnet increases significantly, however, coercivity decreases, and the demagnetization curves show magnetically single-phase behavior. The anisotropic Nd2 Fe14 B/Sm2 Co17 hybrid-bonded magnets exhibit a maximum energy product and remanence of 14.15 MGOe and 99.53 A·m2/kg, respectively, when the NdFe-B content is 70 wt% at room temperature. Furthermore, the hybrid magnets also have better thermal stability at elevated temperatures due to the interaction between the two magnetic particles.

关键词： Magnetic properties Anisotropic Hybrid-bonded magnets Thermal stability Rare earths

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Magnetic properties and microstructure of nanocrystalline bulk Nd-Fe-B with Ce-Co addition

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Journal of Rare Earths 2021年第6期39卷 689-695,I0003页

作者： Yilong Ma Qiqi Yang Xiaoli Chen Ying He Wenbo Xiang Jiaqi Lai Bin Shao donglin guo Dengming Chen Kejian Li College of Metallurgy and Materials Engineering Chongqing University of Science and TechnologyChongqing 401331China The Center of Material Analysis and Testing Chongqing University of Science and TechnologyChongqing 401331China

The influence of Ce-Co alloy addition and sintering holding time on permanent magnetic properties and micro structure of nanocrystalline Nd-Fe-B bulk alloy were *** coercivity of Nd-Fe-B bulk alloy can be enhanced greatly by more than 100% after adding Ce-Co ***,when the concentration of Ce-Co is up to 30 wt%,the density of the magnet can reach the maximum value of 7.58 g/cm^(3),but the coercivity does not increase *** the other hand,with the increase of holding time to 10 min,the density and coercivity of magnets increase gradually,reaching up to 7.55 g/cm^(3) and 1134.3 kA/m,*** the addition of Ce-Co alloy,Ce-Co may easily diffuse into the Nd-Fe-B matrix during hot-pressing and under the high pressure and temperature,thus increasing the content of grain boundary phase and the pinning effect of grain boundary,which leads to the increase of *** extension of the hot-pressing holding time may be more conducive to the diffusion of CeCo into the Nd-Fe-B *** addition,the effect of Ce-Co addition on the magnetic properties of Nd-FeB with different content of rare earth was also *** addition of Ce-Co can effectively increase the coercivity of nanocomposite Nd_(2)Fe_(14)B/α-Fe *** addition of Nb to the parent alloy can further improve the *** Nd_(11)Fe_(81.5)Nb_(1)Ga_(0.5)B_(6) alloy with 10 wt% Ce-Co addition,the coercivity can increase from 740.28 to 1098.48 kA/m.

关键词： Nd-Fe-B magnet Ce-Co addition Coercivity Microstructure Nanocomposite Rare earths

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Simulated effect of soil freeze-thaw process on surface hydrologic and thermal fluxes in frozen ground region of the Northern Hemisphere

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Research in Cold and Arid Regions 2021年第1期13卷 18-29页

作者： Di Ma SiQiong Luo donglin guo ShiHua Lyu XianHong Meng BoLi Chen LiHui Luo Key Laboratory for Land Surface Process and Climate Change in Cold and Arid Regions Northwest Institute of Eco-Environment and ResourcesChinese Academy of ScienceLanzhouGansu 730000China College of Atmospheric Sciences Lanzhou UniversityLanzhouGansu 730000China Nansen-Zhu International Research Center Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029China School of Atmospheric Sciences Plateau Atmosphere and Environment Key Laboratory of Sichuan ProvinceChengdu University of Information TechnologyChengduSichuan 610225China Changzhou Meteorological Bureau ChangzhouJiangsu 213000China State Key Laboratory of Frozen Soils Engineering Northwest Institute of Eco-Environment and ResourcesChinese Academy of SciencesLanzhouGansu 730000China

Soil freeze-thaw process is closely related to surface energy budget,hydrological activity,and terrestrial *** this study,two numerical experiments(including and excluding soil freeze-thaw process)were designed to examine the effect of soil freeze-thaw process on surface hydrologic and thermal fluxes in frozen ground region in the Northern Hemisphere based on the state-of-the-art Community Earth System Model version *** show that in response to soil freeze-thaw process,the area averaged soil temperature in the shallow layer(0.0175−0.0451 m)decreases by 0.35℃in the TP(Tibetan Plateau),0.69℃in CES(Central and Eastern Siberia),and 0.6℃in NA(North America)during summer,and increases by 1.93℃in the TP,2.28℃in CES and 1.61℃in NA during winter,***,in response to soil freeze-thaw process,the area averaged soil liquid water content increases in summer and decrease in *** surface heat flux components,the ground heat flux is most significantly affected by the freeze-thaw process in both summer and winter,followed by sensible heat flux and latent heat flux in *** the TP area,the ground heat flux increases by 2.82 W/m2(28.5%)in summer and decreases by 3.63 W/m2(40%)in ***,in CES,the ground heat flux increases by 1.89 W/m2(11.3%)in summer and decreases by 1.41 W/m2(18.6%)in *** heat fluxes in the Tibetan Plateau are more susceptible to the freeze-thaw process compared with the high-latitude frozen soil *** freeze-thaw process can induce significant warming in the Tibetan Plateau in ***,this process induces significant cooling in high-latitude regions in *** frozen ground can prevent soil liquid water from infiltrating to deep soil layers at the beginning of thawing;however,as the frozen ground thaws continuously,the infiltration of the liquid water increases and the deep soil can store water like a sponge,accompanied by decreasing surface *** influence of the soil freeze-thaw pr

关键词： freeze-thaw effect hydrologic and thermal frozen ground Northern Hemisphere

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CBPS-Based Inference in Nonlinear Regression Models with Missing Data

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Open Journal of Statistics 2016年第4期6卷 675-684页

作者： donglin guo Liugen Xue Haiqing Chen College of Applied Sciences Beijing University of Technology Beijing China School of Mathematics and Information Science Shangqiu Normal University Shangqiu China

In this article, to improve the doubly robust estimator, the nonlinear regression models with missing responses are studied. Based on the covariate balancing propensity score (CBPS), estimators for the regression coefficients and the population mean are obtained. It is proved that the proposed estimators are asymptotically normal. In simulation studies, the proposed estimators show improved performance relative to usual augmented inverse probability weighted estimators.

关键词： Nonlinear Regression Model Missing at Random Covariate Balancing Propensity Score GMM Augmented Inverse Probability Weighted

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Local changes in snow depth dominate the evolving pattern of elevation-dependent warming on the Tibetan Plateau

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Science Bulletin 2021年第11期66卷 1146-1150,M0004页

作者： donglin guo Nick Pepin Kun Yang Jianqi Sun Duo Li Nansen-Zhu International Research Centre Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029China Key Laboratory of Meteorological Disaster Ministry of Education/Collaborative Innovation Center on Forecast and Evaluation of Meteorological DisastersNanjing University of Information Science&TechnologyNanjing 210044China Department of Geography Buckingham BuildingLion TerraceUniversity of PortsmouthPortsmouth PO13HEUK The Ministry of Education Key Laboratory for Earth System Modeling Department of Earth System ScienceTsinghua UniversityBeijing 100084China Center for Excellence in Tibetan Plateau Earth Sciences Chinese Academy of SciencesBeijing 100101China National Climate Center China Meteorological AdministrationBeijing 100081China National Tibetan Plateau Center Institute of Tibetan Plateau ResearchChinese Academy of SciencesBeijing 100101China

Elevation-dependent warming(EDW),whereby warming rates are stratified by elevation,may increase the threat to the life-supporting solid water reservoir on the Tibetan *** studies have debated whether EDW exists and how it is *** temperatures at 133 weather stations on the Tibetan Plateau during 17 different periods generated using a 30-year sliding window over 1973-2018,this study finds that the existence of EDW varies as the period moves forward,and critically it has become more severe over *** the early part of the record with weaker regional warming,there were limited changes in snow depth and no EDW,but as time advances and regional warming intensifies,snow depth declines significantly at higher elevations,causing development of *** conclude that enhanced regional warming has caused decreases in snow depth,largely controlling the pattern of EDW on the Tibetan *** may explain contrasting conclusions on EDW from previous studies which have used data for different periods,and our findings support enhanced EDW and more severe depletion of the Tibetan Plateau solid water reserves in a warmer future.

关键词： Elevation-dependent warming Tibetan Plateau Climate warming Snow depth

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