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1.
Ph. Drobinski S. Bastin J. Dusek G. Zängl P. H. Flamant 《Meteorology and Atmospheric Physics》2006,92(3-4):285-306
Summary This paper investigates the characteristics of channelled airflow in the vicinity of a junction of three idealized valleys
(one valley carrying the incoming flow and two tributaries carrying the outflow), using a two-dimensional single-layer shallow
water model. Particular attention is given to the flow splitting occurring at the junction. Nondimensionalized, the model
depends on the valley geometry, the Reynolds number, which is related to the eddy viscosity, and on the difference of the
hydrostatic pressure imposed at the exit of the tributaries. At the spatial scale considered in this study, the Rossby number
relating the inertial and Coriolis forces is always larger than 1, implying that the effect of earth rotation can be neglected
to a first approximation.
The analysis of the flow structure within the three valleys as well as the calculation of the split ratio (fraction of the
air flow diverted into one of the two downstream valleys with respect to the total mass flux in the upstream valley) show
that (i) the flow pattern depends strongly on the Reynolds number while the split ratio is comparatively insensitive; (ii)
the valley geometry and the difference between the upstream and downstream hydrostatic pressures affect the flow pattern,
the location of the split point and the split ratio; (iii) the relative contribution of flow deflection by the sidewalls and
the blocking/splitting mechanism differs between the settings of a “Y-shape” valley and a “T-shape” valley.
Quantitative comparison of the present results with numerical simulations of realistic cases and with observations collected
in the region of the Rhine and Seez valleys (Switzerland) (“Y-shape” valley) and in the region of the Inn and Wipp valleys
(Austria) (“T-shape” valley) during the Mesoscale Alpine Programme (MAP) field experiment shows good agreement provided that
the normalized valley depth NΔH/Uu significantly exceeds 1, i.e., when “flow around” is expected. A structural disagreement between the idealized simulations
and the observed wind field is found only when NΔH/Uu ≃ 1, that is, in the “flow over” regime. This shows that the dimensionless valley depth
is indeed a good indicator for flow splitting, implying that the stratification is a key player in reality. 相似文献
2.
Using a set of synthetic P‐ and S‐wave onsets, computed in a 1D medium model from sources that mimic a distribution of microseismic events induced by hydrofrac treatment to a monitoring geophone array(s), we test the possibility to invert back jointly the model and events location. We use the Neighbourhood algorithm for data inversion to account for non‐linear effects of velocity model and grid search for event location. The velocity model used is composed of homogeneous layers, derived from sonic logging. Results for the case of one and two monitoring wells are compared. These results show that the velocity model can be obtained in the case of two monitoring wells, if they have optimal relative position. The use of one monitoring well fails due to the trade‐off between the velocity model and event locations. 相似文献
3.
基于P波和S波的谱震级特征对汶川地震进行了定量研究,可以看出P波和S波的最大谱震级出现在不同的周期上。对这一现象的构造物理意义进行了讨论,推测相对于P波而言,地震发生期间辐射的S波能量来自异常大的震源体积。选择部分全球地震的谱特征为背景,对汶川地震的体波谱震级特征进行了分析,结论是汶川地震的特征与其所处的周边环境是一致的。 相似文献
4.
Jaromir Demek 《Geoforum》1978,9(1):29-34
The main object of study of geography is the landscape sphere that includes the surface of our planet. The landscape sphere differs from the other geospheres by displaying unusual complexity and consists of structured sets of components which exhibit discernible relationships with one another and operate as a system. The functioning of the landscape sphere is conditioned by the interrelationships of components, as well as by the transfer of mass and energy from one part of the landscape sphere to another in the form of streams of mobile elements. The author is using the name geosystem for determination of this system of planetary dimensions. The landscape sphere may be further divided into subsystems exhibiting characteristic features which facilitate their identification and delimitation.Territorial differentiation of the landscape sphere, on the basis of the law of zonality, produces horizontal, latitudinal and vertical zones called by author geoms. These geoms may be further subdivided into geosystems of smaller dimensions called geochoras. The basic geochora is the landscape. In most landscapes the key elements in these geosystems are controlled by Man and so-called cultural landscapes are developed. The cultural landscapes are parts of the landscape sphere within which natural and socioeconomic geosystems co-exist. The author further distinguishes cultured, disturbed and devastated landscapes. The study of cultural landscape is amongst the most difficult fields of investigation, but such studies are of great significance in terms of predicting future environmental developments. 相似文献
5.
Ocean Dynamics - A three-dimensional, regional coupled ice-ocean model based on the open-source Community Earth System Model has been developed and implemented for the Baltic Sea. The model... 相似文献
6.
Wolfgang Seifert Dieter Rhede Hans-Jürgen Förster Rudolf Naumann Rainer Thomas Jaromir Ulrych 《Mineralogy and Petrology》2014,108(5):645-662
Macrocrysts of corundum, ilmenite, and spinel-group minerals from alluvial deposits of the Eger Rift were studied for composition, texture, and mineral inclusions. All macrocrysts show usually magmatic corrosion textures indicating disequilibrium with the transporting alkali-basalt magma. Corundum grains, exclusively sapphires, were classified by trace-element signatures as magmatic and metamorphic types. Some sapphire grains show erratic compositions that may have resulted from a metasomatic overprint. The inclusion inventory of magmatic corundum suggests crystallization from a differentiated alkaline silicate melt. Corundum itself was never observed as an inclusion mineral. Magnesium- and Fe3+-rich ilmenite, described as typical mantle-derived species, is the dominant heavy mineral in almost all alluvial deposits of the Eger Rift. Most discrete macrocrysts are similar in appearance and composition to kimberlite- and basanite-related ilmenite. Ilmenite included in alluvial corundum and zircon grains differ from the bulk of discrete ilmenite grains by larger concentrations of Nb and Mn. The mantle origin of the Mg–Fe3+-rich ilmenite is confirmed by compositional and thermo-barometric comparison with ilmenite from clinoproxenitic and hornblenditic xenoliths, which probably originated in the Moho region. The Fe–Ti two-oxide geothermometry and oxygen-barometry of coexisting ilmenite–magnetite pairs yield equilibrium temperatures between 900 and 1,080 °C and oxygen fugacities log10fO2 between ?0.1 and 1.1 (relative to the NNO buffer), which indicate that the upper mantle as well as the mantle/crust transition zone below the rift is at least partially oxidized. The ilmenite macrocrysts were transported from the source region to the surface by explosive alkali-basalt magmas, as implied by the presence of basaltic-pipe breccias in close vicinity to some placer deposits. 相似文献
7.
A criterion, allowing one to assess conditions likely togenerate gap flows and/or hydraulicjumps in stratified flows over a mountain ridge or a mountain pass,is derived. It is based on the one-dimensional reduced-gravity shallow-watertheory generalized to a three-dimensional orography with moderate streamwisevariations by introducing a variable effective flow cross-section. In this way,the hydraulic jump and gap flow are accommodated within the same model. Theresulting steady hyperbolic problem is shown to require the boundaryconditions to be expressed in terms of Riemann invariants. The latter yield the flow betweentwo given sites in a unique way. In particular, it is possible to relateunambiguously the existence of a hydraulic jump/gap flow and its energydiscontinuity to the boundary conditions. A simple method of flow interpolationand energy discontinuity calculation between two sites is presented. 相似文献
8.
在地球内部的大部分区域地震体波的传播是线弹性过程,仅在震源周围区域由于波的辐射和传播效应可能导致非线性。本研究主要涉及对非线性过程占优势区域的尺度估计。 相似文献
9.
Erik Swietlicki Jingchuan Zhou Olle H. Berg Bengt G. Martinsson Gran Frank Sven-Inge Cederfelt Ulrike Dusek Axel Berner Wolfram Birmili Alfred Wiedensohler Brett Yuskiewicz Keith N. Bower 《Atmospheric Research》1999,50(3-4)
The hygroscopic properties of sub-micrometer aerosol particles were studied in connection with a ground-based cloud experiment at Great Dun Fell, in northern England in 1995. Hygroscopic diameter growth factors were measured with a Tandem Differential Mobility Analyser (TDMA) for dry particle diameters between 35 and 265 nm at one of the sites upwind of the orographic cloud. An external mixture consisting of three groups of particles, each with different hygroscopic properties, was observed. These particle groups were denoted less-hygroscopic, more-hygroscopic and sea spray particles and had average diameter growth factors of 1.11–1.15, 1.38–1.69 and 2.08–2.21 respectively when taken from a dry state to a relative humidity of 90%. Average growth factors increased with dry particle size. A bimodal hygroscopic behaviour was observed for 74–87% of the cases depending on particle size. Parallel measurements of dry sub-micrometer particle number size distributions were performed with a Differential Mobility Particle Sizer (DMPS). The inorganic ion aerosol composition was determined by means of ion chromatography analysis of samples collected with Berner-type low pressure cascade impactors at ambient conditions. The number of ions collected on each impactor stage was predicted from the size distribution and hygroscopic growth data by means of a model of hygroscopic behaviour assuming that only the inorganic substances interacted with the ambient water vapour. The predicted ion number concentration was compared with the actual number of all positive and negative ions collected on the various impactor stages. For the impactor stage which collected particles with aerodynamic diameters between 0.17–0.53 μm at ambient relative humidity, and for which all pertinent data was available for the hygroscopic closure study, the predicted ion concentrations agreed with the measured values within the combined measurement and model uncertainties for all cases but one. For this impactor sampling occasion, the predicted ion concentration was significantly higher than the measured. The air mass in which this sample was taken had undergone extensive photochemical activity which had probably produced hygroscopically active material other than inorganic ions, such as organic oxygenated substances. 相似文献
10.