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

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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Determining the Spectrum of the Nonlinear Local Lyapunov Exponents in a Multidimensional Chaotic system

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Advances in Atmospheric Sciences 2017年第9期34卷 1027-1034页

作者： Ruiqiang DING Jianping LI Baosheng LI State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics Institute of Atmospheric PhysicsChinese Academy of Sciences Plateau Atmosphere and Environment Key Laboratory of Sichuan Province Chengdu University of Information Technology College of Global Change and Earth System Sciences Beijing Normal University University of Chinese Academy of Sciences

For an n-dimensional chaotic system, we extend the definition of the nonlinear local Lyapunov exponent （NLLE） from one- to n-dimensional spectra, and present a method for computing the NLLE spectrum. The method is tested on three chaotic systems with different complexity. The results indicate that the NLLE spectrum realistically characterizes the growth rates of initial error vectors along different directions from the linear to nonlinear phases of error growth. This represents an improvement over the traditional Lyapunov exponent spectrum, which only characterizes the error growth rates during the linear phase of error growth. In addition, because the NLLE spectrum can effectively separate the slowly and rapidly growing perturbations, it is shown to be more suitable for estimating the predictability of chaotic systems, as compared to the traditional Lyapunov exponent spectrum.

关键词： Lyapunov exponent nonlinear local Lyapunov exponent predictability

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Revisiting Unstable ENSO Teleconnections From a Global Perspective

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Journal of Geophysical Research: Atmospheres 2025年第10期130卷

作者： Jiapeng Miao Xian Wu Dabang Jiang Xiangzhou Song Tao Wang Xinping Xu Observation and Research Station of Air-Sea Interface Ministry of Natural Resources Hohai University Nanjing China Key Laboratory of Meteorological Disaster (KLME) Ministry of Education & Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters (CIC–FEMD) Nanjing University of Information Science & Technology Nanjing China Department of Sustainable Earth Systems Sciences The University of Texas at Dallas Richardson Texas USA State Key Laboratory of Earth System Numerical Modeling and Application Institute of Atmospheric Physics Chinese Academy of Sciences Beijing China School of Atmospheric Sciences Nanjing University Nanjing China

The impacts of El Niño-Southern Oscillation (ENSO) on regional climate may vary from decade to decade. Here, we quantify these unstable ENSO impacts on a global scale by calculating the range of possible correlation coefficients (CCs) between the Niño-3.4 index and climate anomalies in boreal winter at each ∼1° grid point of the globe over any 31-year running time windows during 1880–2014. In observations, the CCs between the Niño-3.4 index and surface air temperature (SAT)/precipitation are significantly unstable at a 95% confidence level over 74.7%/73.6% of the globe, respectively, mainly over tropical Indian and Atlantic Oceans, Africa, Australia, North America, and Eurasia. Further Analyses on Community earth system Model version 2 pacemaker simulations suggest that after the non-ENSO-related internal variability is largely removed, the simulated CCs are always significant over most of the tropics and North America. This suggests that internal variability is essential for driving unstable ENSO teleconnections over these regions mainly by modulating the Southern Oscillation and Pacific-North American teleconnections. Our findings on the nonstationary impacts of ENSO have important implications for understanding and enhancing global seasonal forecast skill. Approximately 74% of the world experiences unstable El Niño-Southern Oscillation (ENSO) impacts on surface air temperature (SAT) and precipitation in boreal winter on multidecadal timescales Internal variability plays an essential role in the unstable ENSO teleconnections over a broad region in the tropics and North America Internal variability affects linkages between ENSO and remote SAT/precipitation by modulating Southern Oscillation and Pacific-North American teleconnections The El Niño-Southern Oscillation (ENSO) phenomenon is the leading mode of interannual climate variability strongly influencing global climate. Skillful ENSO predictions are crucial for predicting global climate on seasonal timescales. H

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Simulation and Causes of Eastern Antarctica Surface Cooling Related to Ozone Depletion during Austral Summer in FGOALS-s2

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Advances in Atmospheric Sciences 2014年第5期31卷 1147-1156页

作者： YANG Jing BAO Qing JI Duoying GONG Daoyi MAO Rui ZHANG Ziyin Seong-Joong KIM State Key Laboratory of Earth Surface Processes and Resource Ecology Beijing Normal University State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics Institute of Atmospheric Physics Chinese Academy of Sciences College of Global Change and Earth System Science Beijing Normal University Beijing Meteorological Bureau Korea Polar Research Institute Incheon 406-130 Korea

Two parallel sets of numerical experiments （an ozone-hole simulation and a non-ozone-hole simulation） were performed to investigate the effect of ozone depletion on surface temperature change using the second spectral version of the Flexible Global Ocean-Atmosphere-Land system model （FGOALS-s2）, focusing on the eastern Antarctica （EA） continent in austral summer. First, we evaluated the ability of the model to simulate the EA surface cooling, and found the model can successfully reproduce the cooling trend of the EA surface, as well as the circulation change circling the South Pole in the past 30 years. Second, we compared the two experiments and discovered that the ozone depletion causes the cooling trend and strengthens the circumpolar westerly flow. We further investigated the causes of the EA surface cooling associated with the ozone hole and found two major contributors. The first is the ozone-hole direct radiation effect （DRE） upon the surface that happens because the decrease of the downward longwave （LW） radiation overcomes the increase of the downward shortwave （SW） radiation under clear sky. The second is the cloud radiation effect （CRE） induced by ozone depletion, which happens because the decreased downward SW radiation overcomes the increased downward LW radiation in the case of increased cloud. Although the CRE is theoretically opposite to the DRE, their final net effect makes comparable contributions to the EA surface cooling. Compared with the surface radiation budget, the surface heat flux budgets have a much smaller contribution. We additionally note that the CRE is basically ascribed to the circulation change.

关键词： ozone depletion eastern Antarctica surface cooling numerical simulation

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The Relationship between Deterministic and Ensemble Mean Forecast Errors Revealed by Global and Local Attractor Radii

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Advances in Atmospheric Sciences 2019年第3期36卷 271-278,339页

作者： Jie FENG Jianping LI Jing ZHANG Deqiang LIU Ruiqiang DING School of Meteorology University of Oklahoma College of Global Change and Earth System Science (GCESS) Beijing Normal University Laboratory for Regional Oceanography and Numerical Modeling Qingdao National Laboratory for Marine Science and Technology Cooperative Institute for Research in the Atmosphere GSD/ESRL/OAR/NOAA Fujian Meteorological Observatory Wuyishan National Park Meteorological Observatory State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics Institute of Atmospheric Physics Chinese Academy of Sciences Plateau Atmosphere and Environment Key Laboratory of Sichuan Province Chengdu University of Information Technology

It has been demonstrated that ensemble mean forecasts, in the context of the sample mean, have higher forecasting skill than deterministic(or single) forecasts. However, few studies have focused on quantifying the relationship between their forecast errors, especially in individual prediction cases. Clarification of the characteristics of deterministic and ensemble mean forecasts from the perspective of attractors of dynamical systems has also rarely been involved. In this paper, two attractor statistics—namely, the global and local attractor radii(GAR and LAR, respectively)—are applied to reveal the relationship between deterministic and ensemble mean forecast errors. The practical forecast experiments are implemented in a perfect model scenario with the Lorenz96 model as the numerical results for verification. The sample mean errors of deterministic and ensemble mean forecasts can be expressed by GAR and LAR, respectively, and their ratio is found to approach2^(1/2) with lead time. Meanwhile, the LAR can provide the expected ratio of the ensemble mean and deterministic forecast errors in individual cases.

关键词： attractor radius ensemble forecasting ensemble mean forecast error saturation

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A Theoretical Explanation of Anomalous Atmospheric Circulation Associated with ENSO Modoki during Boreal Winter

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Atmospheric and Oceanic Science Letters 2014年第4期7卷 352-357页

作者： XING Nan LI Jian-Ping LI Yao-Kun State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics Institute of Atmospheric Physics Chinese Academy of Sciences University of the Chinese Academy of Sciences College of Global Change and Earth System Science Beijing Normal University

Based on a linear model, the present study provides analytical solutions for ideal triple forcing sources similar to sea surface temperature anomaly （SSTA） pat- terns associated with El Nino-Southern Oscillation （ENSO） Modoki in winter. The ideal triple pattern is composed of an equatorially symmetric heat source in the middle and equatoriaUy asymmetric cold forcing in the southeast and northwest. The equatorially symmetric heat source excites low-level cyclonic circulation anomalies associated with Rossby waves in both hemispheres, while the northwest- ern and southeastern equatorially asymmetric cold sources induce low-level anomalous anticyclones associated with Rossby waves in the hemisphere where the forcing source is located. Low-level zonal winds converge toward the heat sources associated with Kelvin and Rossby waves. Due to unequal forcing intensity in the northwest and southeast, atmospheric responses around the equatorially symmetric forcing become asymmetric, and low-level cyclonic circulation anomalies in the Southern Hemisphere become greater than those in the Northern Hemisphere. Ascending （descending） flows coincide with heat （cold） sources, resulting in a double-cell structure over the regions of forcing sources. Ideal triple patterns similar to SSTA patterns associated with La Nina Modoki produce opposite atmospheric responses. The theoretical atmospheric responses are consistent with observed circulation anomalies associated with ENSO Modoki. Therefore, the theoretical solutions can explain the dynamics responsible for atmospheric circulation anomalies associated with ENSO Modoki events.

关键词： external forcing sources atmospheric responses ENSO Modoki

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A Long-Time-Step-Permitting Tracer Transport Model on the Regular Latitude–Longitude Grid

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Advances in Atmospheric Sciences 2024年第3期41卷 493-508页

作者： Jianghao LI Li DONG Key Laboratory of Earth System Modeling and Prediction China Meteorological AdministrationBeijing 100081China State key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics(LASG) Institute of Atmospheric Physics(IAP)Chinese Academy of SciencesBeijing 100029China State Key Laboratory of Severe Weather(LaSW) Chinese Academy of Meteorological SciencesChina Meteorological AdministrationBeijing 100081China College of Earth and Planetary Sciences University of Chinese Academy of SciencesBeijing 100049China

If an explicit time scheme is used in a numerical model, the size of the integration time step is typically limited by the spatial resolution. This study develops a regular latitude–longitude grid-based global three-dimensional tracer transport model that is computationally stable at large time-step sizes. The tracer model employs a finite-volume flux-form semiLagrangian transport scheme in the horizontal and an adaptively implicit algorithm in the vertical. The horizontal and vertical solvers are coupled via a straightforward operator-splitting technique. Both the finite-volume scheme's onedimensional slope-limiter and the adaptively implicit vertical solver's first-order upwind scheme enforce monotonicity. The tracer model permits a large time-step size and is inherently conservative and monotonic. Idealized advection test cases demonstrate that the three-dimensional transport model performs very well in terms of accuracy, stability, and efficiency. It is possible to use this robust transport model in a global atmospheric dynamical core.

关键词： tracer transport numerical stability latitude–longitude grid

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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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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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Relationships among the Monsoon-like Southwest Australian Circulation,the Southern Annular Mode, and Winter Rainfall over Southwest Western Australia

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Advances in Atmospheric Sciences 2015年第8期32卷 1063-1076页

作者： FENG Juan LI Jianping Yun LI ZHU Jianlei XIE Fei College of Global Change and Earth System Science Beijing Normal University State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics Institute of Atmospheric Physics Chinese Academy of Sciences Joint Center for Global Change Studies Data Analytics CSIRO Digital Productivity Flagship Floreat6083 Western Australia Australia

This study examines the relationships among the monsoon-like southwest Australian circulation （SWAC）, the South- ern Annular Mode （SAM）, and southwest Western Australia winter rainfall （SWR）, based on observed rainfall, reanalysis datasets, and the results of numerical modeling. By decomposing the SWAC into two components using a linear model, i.e. the component related to SAM （RSAM） and the component unrelated to SAM （SWACI＊）, we find it is the SWACI＊ that shows a significant influence on SWR. Similarly, it is the component of SAM associated with SWAC that exhibits an impact on SWR, whereas the component unrelated to SAM. A similar result is obtained in terms of the circulation associated with SWAC and the SAM. These facts suggest the SAM plays an indirect role in influencing SWR, and raise the possibility that SWAC acts as a bridge between the SAM and SWR, by which the SAM passes its influences onto SWR. This is due to the fact that the variations of SWAC are closely linked to the thermal contrast between land and sea across the southern Indian Ocean and southwest Australia. By contrast, the SAM does not significantly relate to this thermal structure, particularly for the component unrelated to SWAC. The variations of surface sea temperature over the southern Indian Ocean contribute to the favored rainfall circulation patterns. This finding is supported by the numerical modeling results. The strong coupling between SWAC and SWR may be instrumental for understanding the interactions between SWR and the southern Indian Ocean, and provides another perspective in examining the variations in SWR.

关键词： monsoon-like Southwest Australian Circulation Southern Annular Mode southwest Western Australian winterrainfall

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