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Assimilating the LAI Data to the VEGAS Model Using the Local Ensemble Transform Kalman Filter: An Observing system simulation Experiment

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Atmospheric and Oceanic science Letters 2014年第4期7卷 314-319页

作者： JIA Bing-Hao Ning ZENG XIE Zheng-Hui State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics (LASG) Institute of Atmospheric Physics Chinese Academy of Sciences Department of Atmospheric and Oceanic Science & Earth System Science Interdisciplinary Center University of Maryland College Park

Information on the spatial and temporal patterns of surface carbon flux is crucial to understanding of source/sink mechanisms and projection of future atmospheric CO2 concentrations and climate. This study presents the construction and implementation of a terrestrial carbon cycle data assimilation system based on a dynamic vegetation and terrestrial carbon model Vegetation-Global-Atmosphere-Soil(VEGAS) with an advanced assimilation algorithm, the local ensemble transform Kalman filter(LETKF, hereafter LETKF-VEGAS). An observing system simulation experiment(OSSE) framework was designed to evaluate the reliability of this system, and numerical experiments conducted by the OSSE using leaf area index(LAI) observations suggest that the LETKF-VEGAS can improve the estimations of leaf carbon pool and LAI significantly, with reduced root mean square errors and increased correlation coefficients with true values, as compared to a control run without assimilation. Furthermore, the LETKF-VEGAS has the potential to provide more accurate estimations of the net primary productivity(NPP) and carbon flux to atmosphere(CFta).

关键词： carbon cycle data assimilation VEGAS,land-atmosphere CO2 flux LETKF OSSE

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The 5.5 cal ka BP climate event, population growth, circumscription and the emergence of the earliest complex societies in China

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science China earth sciences 2018年第2期61卷 134-148页

作者： WU WenXiang ZHENG HongBo HOU Mei GE QuanSheng Key Laboratory of Land Surface Pattern and Simulation Institute of Geographic Sciences and Natural Resources Research Chinese Academy of Sciences Beijing 100101 China Research Center for Earth System Science Yunnan University Kunming 650091 China University of Chinese Academy of Sciences Beijing 100049 China

The emergence of complex society is a milestone in the history of human society evolution. China is one of the few regions in the world where the earliest complex society appeared; however, its driving mechanisms remain unresolved. On the base of available evidence from both archaeology and Holocene climate, in combination with agency theory, this study attempts to address the driving mechanisms for the simultaneous emergence of complex societies in multiple areas of China around 5.5 cal ka BP. It is hypothesized that three factors, including climate change, population growth, and circumscription, jointly act and cause regional population-resource imbalance and trigger inter-group conflicts and wars. Such competitions provide the opportunity for some power-pursuing agents to break the restriction of social leveling mechanism and to become the centralized decision-making leaders, which further lead to the emergence of incipient large-scale complex societies. Increase in extreme climate events during 6.0–5.0 cal ka BP cooling period causes frequent occurrence of resource stress and increase in the frequency of inter-group competitions, which creates conditions for the legitimation, institutionalization, and persistence of centralized leadership, and finally leads to the formation of persistent institutionalized inequity. Our research result can explain not only the process and mechanism of complex society formation, but also two phenomena which cannot be reasonably explained by previous theories, that are, why the earliest complex societies in China emerge around 5.5 cal ka BP, and why they appear simultaneously in multiple regions.

关键词： 5.5 cal ka BP climate event Population growth Circumscription Complex society Driving mechanisms

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Satellite observed shape-based overall rotation—A new aspect in eddy kinematics

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Acta Oceanologica Sinica 2022年第5期41卷 183-194页

作者： Xueqing Yang Guiyan Han Chunyong Ma Chuanchuan Cao Jie Yang Ge Chen School of Marine Technology Ocean University of ChinaQingdao266100China Laboratory for Regional Oceanography and Numerical Modeling Pilot National Laboratory for Marine Science and Technology(Qingdao)Qingdao266237China Frontiers Science Center for Deep Ocean Multispheres and Earth System Ocean University of ChinaQingdao266100China

With the development of satellite altimetry technology,the resolution of sea-level anomaly(SLA)datasets is constantly *** spatial resolution levels can reach a grid size of(1/4)°×(1/4)°,with daily measurements that span from 1993 to 2018,allowing for the precise identification and tracking of individual *** the current study,in addition to the internal circulation and migration of eddies,a new aspect in eddy kinematics is revealed and investigated for the first time:shape-based overall eddy rotation(SOER),based on the intrinsic elliptical shape of eddies identified from a high-resolution SLA *** found that eddies can maintain an elliptical shape and a slow and stable SOER during their migration *** SOER speed was observed to be negatively correlated to eddy lifetime,and exhibited a dependence on latitude,decreasing from low-and high-to *** SOER direction tended to be consistent with the direction of internal circulation,particularly for long-lived *** addition,we identified a negative relationship between internal circulation speed and SOER speed while the migration speed was positively related to SOER *** findings further expand and improve eddy kinematics,which is of great significance for the future study of eddy dynamics.

关键词： mesoscale eddies shape-based overall eddy rotation(SOER) internal circulation eddy migration

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A New Approach to Implement Sigma Coordinate in a numerical Model

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Communications in Computational Physics 2012年第9期12卷 1033-1050页

作者： Yiyuan Li Donghai Wang Bin Wang State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics Institute of Atmospheric PhysicsChinese Academy of SciencesBeijingChina State Key Laboratory of Severe Weather Chinese Academy of Meteorological SciencesBeijingChina Ministry of Education Key Laboratory for Earth System Modeling and Center for Earth System ScienceTsinghua UniversityBeijingChina

This study shows a new way to implement terrain-following s-coordinate in a numerical model,which does not lead to the well-known"pressure gradient force(PGF)"***,the causes of the PGF problemare analyzedwith existing methods that are categorized into two different types based on the ***,the new method that bypasses the PGF problem all together is *** comparing these threemethods and analyzing the expression of the scalar gradient in a curvilinear coordinate system,this study finds out that only when using the covariant scalar equations of s-coordinate will the PGF computational form have one term in each momentum component equation,thereby avoiding the PGF problem completely.A convenient way of implementing the covariant scalar equations of s-coordinate in a numerical atmospheric model is illustrated,which is to set corresponding parameters in the scalar equations of the Cartesian ***,two idealized experimentsmanifest that the PGF calculated with the new method is more accurate than using the classic *** method can be used for oceanic models as well,and needs to be tested in both the atmospheric and oceanic models.

关键词： Pressure gradient force(PGF) terrain-following sigma coordinate non-orthogonal basis vectors numerical modeling computational errors

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Autumn Snow Cover Variability over Northern Eurasia and Roles of Atmospheric Circulation

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Advances in Atmospheric sciences 2017年第7期34卷 847-858页

作者： Kunhui YE Renguang WU Institute of Space and Earth Information Science The Chinese University of Hong Kong Hong Kong China Center for Monsoon System Research/State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics Institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100029 China

This study analyzes the variability of northern Eurasian snow cover（SC） in autumn and the impacts of atmospheric circulation changes. The region of large SC variability displays a southward shift from September to November, following the seasonal progression of the transition zones of surface air temperature（SAT）. The dominant pattern of SC variability in September and October features a zonal distribution, and that in November displays an obvious west-east contrast. Surface air cooling and snowfall increase are two factors for larger SC. The relative contribution of SAT and snowfall changes to SC, however, varies with the region and depends upon the season. The downward longwave radiation and atmospheric heat advection play important roles in SAT changes. Anomalous convergence of water vapor flux contributes to enhanced *** changes in downward longwave radiation are associated with those in atmospheric water content and column *** in snowfall and the transport of atmospheric moisture determine the atmospheric moisture content in September and October, and the snowfall appears to be a main factor for atmospheric moisture change in November. These results indicate that atmospheric circulation changes play an important role in snow variability over northern Eurasia in autumn. Overall, the coupling between autumn Eurasian snow and atmospheric circulation may not be driven by external forcing.

关键词： Autumn Eurasian snow cover surface air temperature surface heat fluxes atmospheric circulation water vaportransport

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Assessment of Interannual Sea Surface Salinity Variability and Its Effects on the Barrier Layer in the Equatorial Pacific Using BNU-ESM

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Advances in Atmospheric sciences 2016年第3期33卷 339-351页

作者： Hai ZHI Rong-Hua ZHANG Fei ZHENG Pengfei LIN Lanning WANG Peng YU Earth System Modeling Center and College of Atmospheric Sciences Nanjing University of Information Science and Technology Key Laboratory of Ocean Circulation and Waves Institute of OceanologyChinese Academy of Sciences International Center for Climate and Environment Science Institute of Atmospheric PhysicsChinese Academy of Sciences State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics Institute of Atmospheric PhysicsChinese Academy of Sciences College of Global Change and Earth System Science Beijing Normal University Cooperative Institute for Climate and Satellites University of MarylandCollege Park

As salinity stratification is necessary to form the barrier layer （BL）, the quantification of its role in BL interannual variability is crucial. This study assessed salinity variability and its effect on the BL in the equatorial Pacific using outputs from Beijing Normal University earth system Model （BNU-ESM） simulations. A comparison between observations and the BNU-ESM simulations demonstrated that BNU-ESM has good capability in reproducing most of the interannual features observed in nature. Despite some discrepancies in both magnitude and location of the interannual variability centers, the displacements of sea surface salinity （SSS）, barrier layer thickness （BLT）, and SST simulated by BNU-ESM in the equatorial Pacific are realistic. During E1 Nifio, for example, the modeled interannual anomalies of BLT, mixed layer depth, and isothermal layer depth, exhibit good correspondence with observations, including the development and decay of E1 Nifio in the central Pacific, whereas the intensity of the interannual variabilities is weaker relative to observations. Due to the bias in salinity simulations, the SSS front extends farther west along the equator, whereas BLT variability is weaker in the central Pacific than in observations. Further, the BNU-ESM simulations were examined to assess the relative effects of salinity and temperature variability on BLT. Consistent with previous observation-based analyses, the interannual salinity variability can make a significant contribution to BLT relative to temperature in the western-central equatorial Pacific.

关键词： feedback interannual variability sea surface salinity barrier layer thickness

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Impacts of uncertain cloud-related parameters on Pacific Walker circulation simulation in GAMIL2

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Atmospheric and Oceanic science Letters 2018年第1期11卷 7-14页

作者： XIE Feng LI Li-Juan WANG Bin XUE Wei State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics （LASG） Institute of Atmospheric Physics Chinese Academy of Sciences Beijing China College of Earth Science University of Chinese Academy of Sciences Beijing China Ministry of Education Key Laboratory for Earth System Modeling Center of Earth System Science （CESS） Tsinghua University Beijing China Department of Computer Science and Technology Tsinghua University Beijing China

To investigate the impacts of uncertain parameters on simulated Pacific Walker circulation （PWC）, a large number of perturbed parameter simulations are conducted using GAMIL2 （the Grid-point Atmospheric Model of IAP/LASG, version 2）, and three different PWC indices are *** results show that the influences of some parameters on PWC are dependent on the selected index - a finding supported by the inconsistent responses of different indexes to these parameters. Among the nine parameters, the RH threshold for deep convection （RHCRIT） is the most sensitive in simulating PWC. Increased RHCRIT weakens deep convective heating and stratiform cooling, and strengthens shallow convective heating. Further analysis reveals that uncertain parameters affect the simulated PWC through changing the diabatic heating and vertical motion.

关键词： Walker circulation Pacific uncertainty cloud-relatedparameters GAMIL2 diabaticheating

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Trends of Extreme Precipitation in Eastern China and Their Possible Causes

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Advances in Atmospheric sciences 2015年第8期32卷 1027-1037页

作者： LIU Run LIU Shaw Chen Ralph J.CICERONE SHIU Chein-Jung LI Jun WANG Jingli ZHANG Yuanhang State Key Joint Laboratory of Environmental Simulation and Pollution Control College of Environmental Sciences and Engineering Peking University Research Center for Environmental Changes Academia Sinica Department of Atmospheric Science NCU National Academy of Sciences Earth System Science University of California Institute of Urban Meteorology of China Meteorological Administration

Significant increases of heavy precipitation and decreases of light precipitation have been reported over widespread regions of the globe. Global warming and effects of anthropogenic aerosols have both been proposed as possible causes of these changes. We examine data from urban and rural meteorological stations in eastern China （1955-2011） and compare them with Global Precipitation Climatology Project （GPCP） data （1979-2007） and reanalysis data in various latitude zones to study changes in precipitation extremes. Significant decreases in light precipitation and increases in heavy precipitation are found at both rural and urban stations, as well as low latitudes over the ocean, while total precipitation shows little change. Characteristics of these changes and changes in the equatorial zone and other latitudes suggest that global warming rather than aerosol effects is the primary cause of the changes. In eastern China, increases of annual total dry days （28 days） and ） 10 consecutive dry days （36%） are due to the decrease in light precipitation days, thereby establishing a causal link among global warming, changes in precipitation extremes, and higher meteorological risk of floods and droughts. Further, results derived from the GPCP data and reanalysis data suggest that the causal link exists over widespread regions of the globe.

关键词： extreme precipitation global warming aerosols meteorological risk of floods and droughts

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Cross-sectional rainfall observation on the central-western Tibetan Plateau in the warm season:system design and preliminary results

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science China earth sciences 2023年第5期66卷 1015-1030页

作者： Kun YANG Yingying CHEN Lazhu Changhui ZHAN Xiaoyan LING Xu ZHOU Yaozhi JIANG Xiangnan YAO Hui LU Xiaogang MA Lin OUYANG Weihao PAN Yanghang REN Changkun SHAO Jiaxin TIAN Yan WANG Hua YANG Siyu YUE Ke ZHANG Dingchi ZHAO Long ZHAO Jianhong ZHOU Mijun ZOU Ministry of Education Key Laboratory for Earth System Modeling Department of Earth System ScienceInstitute for Global Change StudiesTsinghua UniversityBeijing100084China National Tibetan Plateau Data Center State Key Laboratory of Tibetan Plateau Earth System and Resource EnvironmentInstitute of Tibetan Plateau ResearchChinese Academy of SciencesBeijing100101China Research Center for Ecology College of ScienceTibet UniversityLhasa850011China Key Laboratory of Land Surface Pattern and Simulation Institute of Geographic Science and Natural Resources ResearchChinese Academy of SciencesBeijing100101China Chongqing Jinfo Mountain Karst Ecosystem National Observation and Research Station School of Geographical SciencesSouthwest UniversityChongqing400715China

The central and western Tibetan Plateau(CWTP)is characterized by harsh environment and strong interactions among the spheres of earth as well as significant changes in climate and water cycles over the past four *** lack of precipitation observations is a bottleneck for the study of land surface processes in this *** the past six years,we have designed and established two observation transects across the south-north and the west-east in this region to obtain hourly rainfall data during the warm season(May-September).The south-north transect extends from Yadong Valley on the southern slope of the Himalayas to Shuanghu County in the hinterland of the plateau,with a total of 31stations;the west-east transect extends from Shiquanhe in the west to Naqu in the central TP,with a total of 22 *** observation dataset has been applied to clarify the spatiotemporal characteristics of precipitation in the CWTP,to evaluate the quality of typical gridded precipitation products,to support the development of regional climate models,and to reveal the processes of summertime lake-air *** observation dataset has been released in the National Tibetan Plateau Data center.

关键词： Central and western Tibetan Plateau Rainfall observation transects Observation uncertainty Spatiotemporal characteristics of precipitation Precipitation data evaluation

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Strengthening of the annual temperature cycle in the mid-latitudes of Northern Hemisphere

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Discover Geoscience 2024年第1期2卷 1-6页

作者： Tang, Tao Lee, Xuhui Cao, Junji Science Center for Earth System Numerical Simulation Institute of Atmospheric Physics Chinese Academy of Sciences Beijing China Key Laboratory of Earth System Numerical Modeling and Application Institute of Atmospheric Physics Chinese Academy of Sciences Beijing China School of the Environment Yale University New Haven USA

The annual temperature cycle (ATC), defined as the surface temperature difference between summer and winter, plays a crucial role in controlling the phenology of biological systems (Sparks and Menzel in Int J Climatol 22(14):1715–25, 2002) and in global and regional circulation patterns (Schott and McCreary in Prog Oceanogr 51(1):1–123, 2001), (Adam et al. in J Clim 29(9): 3219–3230, 2016). Contrary to previous studies which report a decreasing trend in the ATC worldwide (Mann and Park in Geophys Res Lett 23(10):1111–4, 1996), (Wallace and Osborn in Climate Res 22(1):1–11, 2002), recent studies suggest an increasing ATC trend in the mid-latitude regions (Wang and Dillon in Nat Clim Chang 4(11):988–92, 2014). Although the trend may bear anthropogenic fingerprints, the underlying mechanism remains elusive. Using atmospheric reanalysis data and observational records, we confirm that the increasing trend in the ATC occurred during 1980–2020, mainly in the West North America, Mediterranean region and part of North Asia. The main driver of this ATC change is the faster increase in the incoming radiation on the land surface in the summer as a result of the buildup of water vapor and reduction in cloudiness. This increase was further amplified by continental dryness in the summer.

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