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NONLINEAR MECHANISM OF ABRUPT CHANGE OF atmospheric CIRCULATION DURING JUNE AND OCTOBER

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Science in china,Ser.B 1983年第7期26卷 746-754页

作者：李麦村罗哲贤 Institute of atmospheric Physics Academic Sinica Beijing department of Meteorology and Physical Oceanography Massachusetts Institute of Technology Meteorological Bureau of Gansu Province lanzhou

By the low-order spectral model, the abrupt change of the circulation in the barotropic atmosphere is studied. In certain parametric combinations, along with the gradual change of the external thermal forcing, the quasi-cusp pattern abrupt changes of both the spectral coefficients and the locations of west jet stream are stimulated, which are similar to the rapid northward jumping and suddenly establishing of the 'South-Branch' jet stream during June and October respectively. Depending on the changes of the parametric combinations, the motional form of the abrupt change can be substituted by that of the gradual change of one stable equilibrium, or by that of the branching phenomena of the multiple equilibria. The abrupt change mechanism of the atmospheric circulation is a nonlinear mechanism which contains the thermal forcing, dissipation, and thermal and dynamic effects.

关键词： NONLINEAR MECHANISM OF ABRUPT CHANGE OF atmospheric CIRCULATION DURING JUNE AND OCTOBER

Large eddy simulation of stably stratified turbulence

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Science china(Physics,Mechanics & Astronomy) 2010年第1期53卷 135-146页

作者： SHEN Zhi, LI YuPeng, CUI GuiXiang & ZHANG ZhaoShun department of Engineering Mechanics, Tsinghua university, Beijing 100084, china 1. department of Engineering Mechanics Tsinghua University Beijing 100084 China

Stable stratification turbulence, as a common phenomenon in atmospheric and oceanic flows, is an important mechanism for numerical prediction of such flows. In this paper the large eddy simulation is utilized for investigating stable stratification turbulence numerically. The paper is expected to provide correct statistical results in agreement with those measured in the atmosphere or ocean. The fully developed turbulence is obtained in the stable stratification fluid by large eddy simulation with different initial velocity field and characteristic parameters, i.e. Reynolds number Re and Froude number Fr. The evolution of turbulent kinetic energy, characteristic length scales and parameters is analyzed for investigating the development of turbulence in stable stratification fluid. The three-dimensional energy spectra, horizontal and vertical energy spectrum, are compared between numerical simulation and real observation in the atmosphere and ocean in order to test the reliability of the numerical simulation. The results of numerical cases show that the large eddy simulation is capable of predicting the properties of stable stratification turbulence in consistence with real measurements at less computational cost. It has been found in this paper that the turbulence can be developed under different initial velocity conditions and the internal wave energy is dominant in the developed stable stratification turbulence. It is also found that the characteristic parameters must satisfy certain conditions in order to have correct statistical property of stable stratification turbulence in the atmosphere and ocean. The Reynolds number and Froude number are unnecessarily equal to those in atmosphere or ocean, but the Reynolds number must be large enough, say, greater than 10 2 , and Froude number must be less than 0.1. The most important parameter is ReFr 2 which must be greater than 10.

关键词： stratified turbulence internal wave potential vortex large eddy simulation

Potential　enstrophical　diagnostic　analyses　on　the　mechanism　of　change　of　tropical　cyclone　intensity

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Acta Oceanologica Sinica 1994年第3期13卷 361-375页

作者： Laing Biqi and He Caifu(This project is supported by the National Natural Science Foundation of china.).(department of atmospheric Science,Zhongshan university, Guangzhou 510275, china)( Jiangxi Meteorological Observatory, Nanchang 330046, china)

It is indicated that the change of mean potential enstrophy within tropical cyclone (TC) corresponds tothe change of TC intensity. A series of factors influencing the intensity change have been discussed by calculating budget of potential enstrophy in tangential wave-number domain in cylindric coordinates. The results indicate thatthe vertical distribution of mean diabatic heating is an important factor that influences the change of TC intensitythrough transformation mechanism of the Coriolis effect and cyclonic vorticity, especially in the sudden intensifyingstage of TC. It is favourable to the intensification when the diabatic heating is largest in upper-middle troposphere,while TC weakens when this kind of role of heating become small or the heating is largest in lower troposphere. Therole of the axisymmetric fields of TC is different from that of the non-axisymmetric fields. In addition,we have analysed some other factors that influence TC intensity.

关键词： Change of TC intensity potential enstrophy diabatic heating beating profile

The eastward subtropical countercurrent on isopycnal surface in the western North Pacific

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Science china Earth sciences 2005年第7期48卷 1065-1073页

作者： LI Rongfeng1, YOU Xiaobao1 & Peter C. Chu2 1. LASG, Institute of atmospheric Physics, Chinese Academy of sciences, Beijing 100029, china 2. department of Oceanography, Naval Postgraduate School, Monterey, CA 93943-5122, USA LASG Institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100029 China department of Oceanography Naval Postgraduate School Monterey CA 93943-5122 United States

The monthly circulations on isopycnal surface in the western North Pacific are calculated based on the Navy’s Generalized Digital Environmental Model climatological tem- perature and salinity data on a 1/2° × 1/2° grid using a P-vector method. The eastward Sub- tropical Countercurrent (STCC) in the central subtropical gyre has been studied with emphasis on its spatial distribution, vertical structure, volume transport and its nearby eddy phenomenon. The results reproduce the observed feature of STCC, and reveal some new phenomena on isopycnal surface, such as: (1) At σθ = 24.6, there is strong seasonal variability in the distribution, origin and flow status of STCC. There is no STCC in January, February and March. (2) From May to October, a branch of the Kuroshio Countercurrent to the south of Japan merges into STCC, which increases the velocity of STCC and widens its width. (3) The velocity vector field shows that STCC and nearby eddies coexist. (4) The eastward volume transport of STCC across 137.5°E is the strongest in summer with the maximum of 6.9 Sv ( 1 Sv ≡ 106 m3 s?1) in August, and weaker in spring and autumn with 1.7 Sv in April and 1.6 Sv in November. Most of the transports of STCC occur between isopycnal surfaces 24.0σθ and 25.0σθ. (5) The distributions of the zonal flow along 137.5°E show that the flow core of STCC is between 24.3σθ and 24.7σθ .

关键词： P-vector method on isopycnal surface eastward subtropical countercurrent eddy phenomenon.

MESOSCALE RAIN BELTS AND RAIN PEAKCLUSTER IN THE MEIYU PERIOD

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Science china Chemistry 1989年第6期32卷 737-748页

作者：余志豪陆汉城 department of atmospheric sciences Nanjing University Meteorological Institute of Air Force PLA

The case of heavy rain on the meiyu front of June 24—27, 1981 is analysed by use of the mesoscale data with 45×45 km×50 hPa grid mesh. It is found that there exist some meso-α scale rain belts embedded in the area of the meiyu front, and a lot of meso-β scale rain peak cluster moving along these rain *** meso-α scale rain belts are corresponding to the mesoscale convergence lines and the tilting rotor circulation cells. Since the isentropic slope is relatively steep there, and even appears in folding, it satisfies the criterion of the conditional asymmetric instability. Thus, it can be recognized that the meso-α scale rain belts are triggered by the developing inertial-gravitational waves. However, the meso-β scale rain peak clusters are corresponding to the inertial-gravitational waves with the mixed vertical structure, which basically satisfies the instable criterion of the transversal waves.

关键词： meso-α and-β scale inertial-gravitational waves, conditional asymmetric instability.

Studies on wind environment around high buildings in urban areas

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Science china Earth sciences 2005年第Z2期48卷 102-115页

作者： LIU Huizhi, JIANG Yujun, LIANG Bin, ZHU Fengrong, ZHANG Boyin & SANG Jianguo LAPC, Institute of atmospheric Physics, Chinese Academy of sciences, Beijing 100029, china department of atmospheric sciences, School of Physics, Peking university, Beijing 1000871, china State Key Laboratory of Turbulence and Complex System, Peking university, Beijing 1000871, china LAPC Institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100029 China department of atmospheric sciences School of Physics Peking University Beijing 1000871 China State Key Laboratory of Turbulence and Complex System Peking University Beijing 1000871 China

High buildings or architectural complex in urban areas remarkably distort the urban surface wind fields. As the air flow approaches,local strong wind may appear around the buildings. The strong wind makes the pedestrians on sidewalks, entrances and terrace very uncomfortable and causes the pedestrian level wind environment problem. In this studies, hot-wire wind measurement, wind scouring in wind tunnel and numerical computation were carried out to evaluate the wind environment of tall buildings in the prevailing flow conditions in Beijing areas. The results obtained by three techniques were compared and mutually verified. The conclusions drawn from three approaches agree with each other. Also the advantages and limitations of each method were analyzed. It is suggested that the combination of different techniques may produce better assessment of wind environment around high buildings.

关键词： high buildings in urban areas, wind environment, wind tunnel, numerical simulation.

Paleoenvironmental records from the northern South china Sea since the Last Glacial Maximum

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Acta Oceanologica Sinica 2010年第3期29卷 46-62页

作者： GE Qian CHU Fengyou XUE Zuo LIU J Paul DU Yuansheng FANG Yinxia Faculty of Earth sciences China University of Geosciences Wuhan 430074 China Key Laboratory of Submarine Geosciences State Ocean Administration Hangzhou 310012 China department of Marine Earth and Atmospheric Sciences North Carolina State University Raleigh NC 27695 USA

Core ZHS-176 contains the paleoenvironmental records from the northern South china Sea （NSCS） since the Last Glacial Maximum （LGM）. A coupled approach based on clay mineral assemblages, planktonic foraminiferal oxygen and carbon isotopes, and calcium carbonate content is used to trace the sources of the fine-grained sediment and to investigate the paleoenviornmental evolution in this area. Clay mineral assemblages are dominated by illite （average about 39%） and chlorite （about 27%）, which comes mainly from Taiwan and the East china Sea. Kaolinite, which accounts for about 13%, comes mainly from the Zhujiang （Pearl） River, and Luzon Island is the main source for smectite （about 21%）. The planktonic foraminiferal oxygen isotopic oscillations during the last glacial period are coeval with climate variations recorded in the Greenland ice core and Western Pacific sediment. These variations include the LGM, Heinrich event 1, Bφlling-Allerφd （B/A）, and Younger Dryas. For the Holocene, three periods of strong precipitation （S1-S3） and three periods of weak precipitation （W1-W3） are identified. The oxygen isotopic record exhibits corre-lation with climate records from distant regions, including the high-latitude Northern Hemisphere, providing evidence for global tele-connection among regional climate. A brief, negative planktonic foraminiferal carbon isotopic excursion during B/A reflects increased methane released from marine gas hydrate due to the rapid warming of the water. By comparing calcium carbonate content curves of the core ZHS-176 with these of other five boreholes lying above the lysocline, a remarkable low calcium carbonate event is found during the early Holocene in NSCS.

关键词： clay mineral oxygen and carbon isotopes calcium carbonate content South china Sea paleoenvironmental evolution

A new method to prepare clean cuticular membrane from fossil leaves with thin and fragile cuticles

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Science china Earth sciences 2011年第2期54卷 223-227页

作者： WANG Li1,2 & LENG Qin1,3 1 State Key Laboratory of Palaeobiology and Stratigraphy,Nanjing Institute of Geology and Palaeontology,Chinese Academy of sciences,Nanjing 210008,china 2 Graduate School of Chinese Academy of sciences,Beijing 100049,china 3 department of Science and Technology,Bryant university,Smithfield RI 02917,USA 1. State Key Laboratory of Palaeobiology and Stratigraphy Nanjing Institute of Geology and Palaeontology Chinese Academy of Sciences Nanjing 210008 China2. Graduate School of Chinese Academy of Sciences Beijing 100049 China3. Department of Science and Technology Bryant University Smithfield RI 02917 USA

Leaf cuticle analysis has long been a powerful tool for fossil plant identification, systematics, and palaeoclimatological recon- struction. In recent decades the application of stomatal frequency data that are relied on precise calculation of stomata on plant fossil cuticles to reconstruct ancient atmospheric CO2 concentration made the preparation of cuticular membrane with sufficient size a critical technique in palaeoclimatological research. However, for plants with originally thin and fragile cuticles, e.g., most deciduous plants, conventional techniques sometimes fail to obtain cuticular membranes with sufficient size, or sometimes unable to recover any. This has largely hampered the usage of fossil cuticle analysis in palaeobotanical and palaeo- climatological research. Here, we describe a new method using clear nail polish as a medium to ＂strengthen＂ the originally thin and fragile cuticles prior to maceration procedures. We demonstrate the method by using middle Eocene Metasequoia fossils that were notorious for the difficulty of recovering large-sized clean cuticular membranes due to their thin and fragile nature. Metasequoia, with well-documented and widely-distributed fossil records since the Late Cretaceous and with a living repre- sentative, 114. glyptostroboides, as a comparative reference, bas been widely used as a model genus for the study of evolution of plants, palaeoclimatological reconstruction, and plant adaptation to climate changes. But its deciduous habit produces thin cuticles and makes the preparation of clean cuticular membranes a tedious process. The new method successfully allows us to recover its delicate cuticular membranes with sufficient sizes for SEM observation and stomatal frequency analysis.

关键词： fossil leaf cuticle Metasequoia new method thin and fragile cuticle SEM observation stomatal frequency CO2

THE LARGE-SCALE TOPOGRAPHY AND THE STABILITY OF ROSSBY WAVE IN THE BAROTROPIC ATMOSPHERE

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Acta Meteorologica Sinica 1988年第1期 10-17页

作者：吕克利 department of atmospheric sciences Nanjing university

The effects of the large-scale topography on the stability of Rossby wave are discussed by usingthe method of the multiple scale analysis. The results show that the influences of the topographywith north-south or west... 详细信息

关键词： THE LARGE-SCALE TOPOGRAPHY AND THE STABILITY OF ROSSBY WAVE IN THE BAROTROPIC ATMOSPHERE