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41.
科氏力作用下涡旋运动的等值线动力学   总被引:2,自引:1,他引:1       下载免费PDF全文
罗哲贤 《气象学报》1993,51(4):394-404
本文提出了在科氏力作用下,单圈常值涡旋运动等值线动力学的计算公式。用这些公式实施了四组计算,结果与以往动力学分析和数值试验的结论定性一致,数值也较为合理。  相似文献   
42.
    
The research of deep-water combined-flow deposits is still in its infancy at present, which has great significance for discovering new case study and discussing the indication effects of combined-flow sedimentary structures on depositional environment. The Upper Ordovician Lashenzhong Formation in Zhuozishan area, Inner Mongolia, in the north of western Ordos Basin, is mainly deposited by turbidity currents concomitant with contour currents as well as internal-waves and internal-tides in deep-water slope and basin floor environment which display typical complex hydrodynamic conditions. Here we studied the deep-water combined-flow sedimentary structures of Lashenzhong Formation in detail based on careful field work, combined with the results of flume experiments and other related case studies in literatures. Several combined-flow sedimentary structures were found in deep-water environment, which include combined-flow-ripple lamination, quasi-planar lamination and small-scale hummocky cross-stratification-like structures. These sedimentary structures can be summarized vertically as 6 sedimentary structure successions: normal graded layer through wave-ripple lamination to combined-flow-ripple lamination (a), quasi-planar lamination through normal graded layer to combined- flow-ripple lamination (b), amphibolous normal graded layer overlaying by quasi-planar lamination (c), quasi-planar lamination through bi-directional cross-lamination to small-scale hummocky cross-stratification-like structures (d), amalgamated small-scale hummocky cross-stratification-like structures enveloped claystone (e) and combined- flow-ripple lamination enveloped claystone (f). The origin of deep-water combined-flow deposits perhaps is the interactions of turbidity currents, contour currents and internal-wave currents according to the sedimentary types and environment in Lashenzhong Formation. Based on the interactions between sedimentary currents and sea floor topography, four sedimentation zones were suggested: turbidity currents restrained zone (succession a and b), strong interaction zone (succession c), internal-wave action zone (succession d) and weak interaction zone (succession e and f). This study will be helpful for the study of interactions of internal-waves and internal-tides with sea floor topography, and related sedimentation zone division in geological records.  相似文献   
43.
    
This work explores the effect of a cyclonic mesoscale feature of the Brazil Current (BC) moving northward off SE Brazil (20° S–23° S) in the Nutrients-Phytoplankton-Zooplankton (NPZ) dynamics. We employ the contour dynamics technique in a quasi-geostrophic, inviscid, 1½-layer model set as a meridional jet flowing southward along a rigid western boundary. This hydrodynamical model is coupled to a conventional NPZ model. We evaluate two distinct scenarios: (1) Plankton in a mixed layer (ML) with time-variable depth and no entrainment and; (2) Plankton in an ML held at a fixed depth, which allows entrainment. We perform simulations with different ML depths representing summer (42 m) and winter (86 m) for the region of interest. The presence of the western boundary allows the cyclonic ring to propagate northward due to image effect. The eddy motion produces upwelling (downwelling) in the leading (trailing) edge resulting in different responses in the two scenarios examined. In the variable ML depth simulations, Z is favored relative to P because there is no injection of N. On the other hand, in the fixed ML depth simulations, P is favored relative to Z due to dilution. All simulations show P enrichment within the eddy, but winter simulations show a greater response to the physical forcing. We conclude that the cyclonic eddy shed from BC provides favorable conditions for planktonic growth. Winter-like conditions seem to be more favorable than summer-like ones and, therefore, present more intense blooms associated with the ring.  相似文献   
44.
流域面雨量的计算方法   总被引:3,自引:0,他引:3  
经对面雨量的几种计算方法对比分析,确定了以等雨量线法为计算流域面雨量的方法,同时对于计算方法进行了部分优化,并应用于业务中。  相似文献   
45.
通过对国家1︰5万DLG更新数据的生产实践,提出在ArcMAP中利用TIN检查1︰5万DLG数据等高线点线矛盾的方法,文中详细探讨了检查的基本原理、思路以及在VB.NET中代码实现的过程。  相似文献   
46.
应用国家地震局 85 - 0 4 - 0 1课题提供的部分地震学预报地震方法对 1 980年和 1 981年博克图地震进行了研究。结果表明 ,该地震前后某些地震学预报项目出现了明显的异常变化。这些可作为监视该区地震活动的判定指标  相似文献   
47.
等值线(ICCP)匹配算法是辅助导航中的一个重要匹配算法,但目前缺乏本算法的系统仿真试验。本文对ICCP算法在地形辅助导航中的应用进行了正交实验设计,按照设计方案进行大量仿真研究。通过对仿真结果的分析,得出等值线匹配精度的主要因素。  相似文献   
48.
The main goal of this study was to research the answer to two important questions in flow modeling; i) how to optimally design the cross‐section of an open channel for a given flow, and ii) in the case of selecting the fuzzy method for modeling, how to construct the membership functions (MFs) and fuzzy rules (FRs) such that the system yields the best results. The first question is answered in order to minimize difficulties in excavation and related costs by using the appropriate flow velocity. To provide the best answer researchers use several methods. The second question is answered in order to minimize model error. For this aim, there are many algorithms proposed by researchers in the literature. In this paper, the fuzzy logic method was used for open canal flow modeling. Furthermore, a simple membership function and fuzzy rule generation technique (SMRGT) is introduced, and used for fuzzy modeling. Two fuzzy models, each for different cross‐sectional shape, are presented in this study as an application of SMRGT. The comparison depends on various statistics, mean absolute relative error, and contour maps showed that the fuzzy models were successful in open channel flow modeling and SMRGT is useful for MF (membership function) and FR (fuzzy rule) generation.  相似文献   
49.
The geometry of impounded surfaces is a key tool to reservoir storage management and projection. Yet topographic data and bathymetric surveys of average-aged reservoirs may be absent for many regions worldwide. This paper examines the potential of contour line interpolation (TOPO) and Structure from Motion (SfM) photogrammetry to reconstruct the topography of existing reservoirs prior to dam closure. The study centres on the Paso de las Piedras reservoir, Argentina, and assesses the accuracy and reliability of TOPO- and SfM- derived digital elevation models (DEMs) using different grid resolutions. All DEMs were of acceptable quality. However, different interpolation techniques produced different types of error, which increased (or decreased) with increasing (or decreasing) grid resolution as a function of their nature, and relative to the terrain complexity. In terms of DEM reliability to reproduce area–elevation relationships, processing-related disagreements between DEMs were markedly influenced by topography. Even though they produce intrinsic errors, it is concluded that both TOPO and SfM techniques hold great potential to reconstruct the bathymetry of existing reservoirs. For areas exhibiting similar terrain complexity, the implementation of one or another technique will depend ultimately on the need for preserving accurate elevation (TOPO) or topographic detail (SfM).  相似文献   
50.
Abstract

In this paper we use the CASL method to explore the role of boundary conditions in determining the long-time behaviour of rotating, stratified, quasi-geostrophic turbulence. We find that initially two-dimensional (sufficiently tall) columns of potential vorticity (PV) break down through three-dimensional instability to give a fully three-dimensional flow consisting of ellipsoidal structures. This is the case both for rigid-lid (isothermal) vertical boundary conditions and for vertically periodic boundaries. However, the rigid boundary case gives rise to semi-ellipsoids at both the top and bottom boundaries, and, for sufficient domain depths, preferred depths for the formation of ellipsoids in the interior. By contrast, in the vertically periodic case, the distribution of ellipsoids is homogeneous in depth.

The role of the horizontal boundaries is indirect, but still significant. In all cases doubly periodic horizontal boundary conditions are imposed. We consider a range of initial conditions where in each case equal numbers of two-dimensional columns of positive and negative vorticity are used, taking up a fixed, but relatively small fraction of the domain (approximately 5%). Thus when there is only a small number of vortices, they have larger radius. When the initial number of vortices is small enough (i.e., when the radius is not small compared with the horizontal domain width), at long time there is a two-dimensionalisation giving rise to a single column of positive PV and a single column of negative PV, as has been observed in some previous simulations. We find the same phenomenon for both vertically periodic and rigid lid boundary conditions, but it occurs over a broader range of initial conditions in the vertically periodic case. However, in all cases fully three-dimensional final states are regained when the number of vortices is increased while keeping the fraction of the domain occupied by vortices fixed, i.e., when the vortex radius/domain width ratio is sufficiently small.  相似文献   
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