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91.
AN EVALUATION OF SEVERAL TURBULENCE SCHEMES FOR THE PREDICTION OF MEAN AND TURBULENT FIELDS IN COMPLEX TERRAIN 总被引:2,自引:0,他引:2
PETER J. HURLEY 《Boundary-Layer Meteorology》1997,83(1):43-73
A prognostic three-dimensional mesoscale model has been developed andused in one- and two-dimensional modes to evaluate ten local turbulenceclosure schemes. The schemes ranged from first-order to the two-equationprognostic schemes. Predictions by the models were compared for aone-dimensional convective boundary layer using mixed layer scaling andmeasurements to interpret the results. Two-dimensional simulations were alsoperformed for a sea-breeze flow and for flow over a hill. The results showedthat for all of the models considered, minor differences were produced in themean meteorological fields and in the vertical scalar fluxes, but majordifferences were apparent in the velocity variances and dissipation rate.Predicted tracer concentrations were very sensitive to the turbulence modelformulation for dispersion from a point source in the convective boundarylayer, particularly for the prediction of maximum concentrations. Predictedtracer concentrations from a surface volume source for the two-dimensionalsimulations were similar for all models, although the degree of mixing in themorning growth period produced some differences. Generally, good results forthe mean meteorological fields can be obtained with first-order schemes, evenif they underpredict the magnitude of turbulence in the convective boundarylayer, and reasonable tracer concentrations can also be obtained with thesemodels provided near-source effects are not important. The two-equationprognostic models performed best for the prediction of turbulence in theconvective boundary layer. 相似文献
92.
H. E. Scheel H. Areskoug H. Geiss B. Gomiscek K. Granby L. Haszpra L. Klasinc D. Kley T. Laurila A. Lindskog M. Roemer R. Schmitt P. Simmonds S. Solberg G. Toupance 《Journal of Atmospheric Chemistry》1997,28(1-3):11-28
Surface ozone data from 25 Europeanlow-altitude sites and mountain sites located between79°N and 28°N were studied. The analysiscovered the time period March 1989–February 1993.Average summer and winter O3 concentrations inthe boundary layer over the continent gave rise togradients that were strongest in the north-west tosouth-east direction and west-east direction, respectively. WintertimeO3 ranged from 19 to 27 ppbover the continent, compared to about 32 ppb at thewestern border, while for summer the continentalO3 values ranged between 39 and 56 ppb and theoceanic mixing ratios were around 37 ppb. In the lowerfree troposphere average wintertime O3 mixingratios were around 38 ppb, with only an 8 ppbdifference between 28°N and 79°N. For summerthe average O3 levels decreased from about 55 ppbover Central Europe to 32 ppb at 79°N. Inaddition, O3 and Ox(= O3 + NO2)in polluted and clean air were compared. Theamplitudes of the seasonal ozone variations increasedin the north-west to south-east direction, while thetime of the annual maximum was shifted from spring (atthe northerly sites) to late summer (at sites inAustria and Hungary), which reflected the contributionof photochemical ozone production in the lower partsof the troposphere. 相似文献
93.
Tan Ming Qin Xiaoguang Liu Tungsheng Laboratory of Speleothem Paleoclimatology Institute of Geology CAS Beijing People’s Republic of China 《地理学报(英文版)》1997,(3)
I.IntroductionStalagmiteshavebeenappliedtouseashighresolutionpaleoclimaticindicatorssincetheannualgrowthbandingwasrecognizedinstalagmites[1,2].Annualgrowthbandingcanbemanifestedinseveralmannersdefinedby1)alternatingfluorescentandnon-fluorescentcalcite[3,4];2)… 相似文献
94.
天山地震活动区的深部构造特征 总被引:1,自引:0,他引:1
以地壳介质的P波速度分布和导电性为基础,描述了天山地区几个主要地震活动区域深部构造特征,地震大都发生在地壳内不同速度块体之间的过渡带附近;沿着天山的南缘和毗邻塔里木盆地的西昆仑、阿尔金等山前地带,壳内高导层由北向南、由东向西逐渐加深并增厚,它们与所在地区震源深度的分相相吻合。这种不稳定的地壳结构有长期受力情况下非常容易发生形变甚至破裂而引发地震。 相似文献
95.
大陆层控构造论盆-山系与造山带成因及演化新模式 总被引:1,自引:0,他引:1
大陆构造以受中地壳塑性层控制的盆-山系和冲叠造山带厚皮构造为主要构造类型,而与中生代以来才出现的受软流层控制的大洋岩石圈板块构造截然不同。由上地壳正断层上盘断陷盆地和下盘断隆山所组成的盆-山系,与地球自转速度逐渐变慢派生不同性质水平力和重力的共同作用有关。当地球自转速度突然变化时,将派生强烈的侧压力,使升降幅度较大、具有侧向应变空间的断陷盆地与断隆山之间的上地壳发生冲叠运动,盆-山系由此演变成冲叠造山带。后者对前者存在着严格的继承关系,服从于“升降-冲叠律”。中生代以来的盆-山系和冲叠造山带有的是板块活动产物 相似文献
96.
气相色谱和薄层色谱法在形态分析中的应用 总被引:2,自引:0,他引:2
评述了气相色谱和薄层色谱法用于氯、溴、碘、硫、硒、碲、铬、氮、磷、砷、钒、碳、锡、铅、铁和汞16种元素的不同形态分析的进展。这些形态包括不同价态、有机态、无机态、阳离子和阴离子态等。由于气相色谱和薄层色谱法都具有分离和检测两种功能结合的特点,因此它们是用于元素形态分析的有效和方便的方法。引用1980~1994年文献92篇 相似文献
97.
多波资料综合解释方法研究的若干进展 总被引:9,自引:0,他引:9
本文较系统地总结了多波层位识别的主要原则和方法;提出了利用井中纵、横波速度求取地层密度、孔隙度的改进方法;研制了以小波分解与重建为基础的沿层分频处理法和高分辨剖面重建方法,提高了薄层识别的横向和纵向分辨率;发展了精度高、误差小计算薄层速度的补层加权法;介绍了各向异性介质参数反演的遗传算法,走时法以及P-SV波AVO分析等方法;建立了多波解释系统的总体框架。所提方法的有效性和正确性均经过实际地震记录和数值模拟计算的检验,对丰富多波地震资料的解释理论,形成多波解释系统,扩大应用领域,提高应用效果具有重要参考意义。 相似文献
98.
滇东早寒武世梅树村期浅色粘土岩层的地球化学特征和地质意义 总被引:2,自引:0,他引:2
滇东早寒武世梅树村期含磷岩系中出现的十多层浅色粘土岩层为酸性火山灰蚀变而成的变斑脱岩,它们是火山喷发事件和事件地层对比的标志。这些浅色粘土岩层中稳定微量元素Hf、Nb、Y、Th、Zr含量高于非火山成因的粘土,而Fe、Ni、Co、Cr含量低于筇竹寺组泥岩。TiO2/Al2O3、Zr/Hf、Ti/Th比值属于酸性岩浆范围,球粒标准化稀土元素配分模式和具中至大的Eu负异常类似于花岗岩稀土配分模式。岩浆判别图指示了梅树村期变斑脱岩具板内花岗岩位置的亚碱性流纹岩和粗面岩岩浆亲缘性。变斑脱岩在地层序列上和区域上分布表明扬子地台西缘早寒武世初期火山活动频繁,火山喷发事件与古大陆解体和板内拉张构造运动有关。 相似文献
99.
100.
Screening Effect of the Diffusive Boundary Layer in Sediments of Lake Aha in the Suburbs of Guiyang City,Guizhou Province 总被引:6,自引:0,他引:6
The redox cycle of iron and manganese is a major geochemica process at the boundary layers of lake sediments.Lake Aha,which lies in the suburbs of Guiyang City,Guizhou Province,China,is a medium-sized artificial reservoir with seasonally anoxic hypolimnion,Long-term sedimentary accumulation of iron and manganese resulted in their enrichment in the upper sediments,In the anoxic season,Fe^2 and Mn^2 ,formed by diological oxidation,would diffuse up to overlying waters from sediments.However,the concentration of oxidation,would diffuse up to overlying waters from sediments,However,the concentration of Fe^2 increased later and decreased earlier than that of Mn^2 .Generally,sulfate reduction occurred at 6 cm below the sediment-water interface.Whereas,in the anoxic season.the reduction reached upper sediments,inhibiting the release of Fe^2 ,The Fe concentration of anoxic water is quickly decreased from high to low as a result of reduction of the suplhur system. 相似文献