近共振地形强迫Rossby孤立波   总被引：1，自引：1，他引：1  

吕克利  蒋后硕 《气象学报》1996,54(2):142-153

利用扰动展开和时空伸长变换导得了包括地形强迫的非齐次ＫｄＶ方程，讨论了近共振地形强迫Ｒｏｓｓｂｙｙ孤立波的产生，及其与自由孤立波的相互作用，得到了一些有意义的结果，显示出地形对扰动具有明显的增幅作用，在某种程度上可以解释局地地形在阻塞高压形成中的作用。  相似文献   

有地形坡度的非线性Kelvin行波     

朱红伟  蔡其发  张铭 《高原气象》2003,22(4):361-364

提出了一个考虑地形坡度的非线性Kelvin行波解的模型，在假定了地形坡度沿山脉走向不变而仅在垂直于山脉走向的方向有改变的情况下，求得了该模型的解析解，这有助于加深对沿海山地捕获波的认识。文中还将该解与经典情形(即侧边界取为垂直刚壁而底面为水平)的解作了比较，发现前者的波速与扰动振幅均较后者要小，这与我国东南沿海武夷山区的沿海山地捕获波的情况相一致。  相似文献   

National height datum,the Gauss–Listing geoid level value w0 and its time variation 0 (Baltic Sea Level Project: epochs 1990.8, 1993.8, 1997.4)     

A. Ardalan  E. Grafarend  J. Kakkuri 《Journal of Geodesy》2002,76(1):1-28

 A methodology for precise determination of the fundamental geodetic parameter w ₀, the potential value of the Gauss–Listing geoid, as well as its time derivative ₀, is presented. The method is based on: (1) ellipsoidal harmonic expansion of the external gravitational field of the Earth to degree/order 360/360 (130 321 coefficients; http://www.uni-stuttgard.de/gi/research/ index.html projects) with respect to the International Reference Ellipsoid WGD2000, at the GPS positioned stations; and (2) ellipsoidal free-air gravity reduction of degree/order 360/360, based on orthometric heights of the GPS-positioned stations. The method has been numerically tested for the data of three GPS campaigns of the Baltic Sea Level project (epochs 1990.8,1993.4 and 1997.4). New w ₀ and ₀ values (w ₀=62 636 855.75 ± 0.21 m²/s², ₀=−0.0099±0.00079 m²/s² per year, w ₀/&γmacr;=6 379 781.502 m,₀/&γmacr;=1.0 mm/year, and &γmacr;= −9.81802523 m²/s²) for the test region (Baltic Sea) were obtained. As by-products of the main study, the following were also determined: (1) the high-resolution sea surface topography map for the Baltic Sea; (2) the most accurate regional geoid amongst four different regional Gauss–Listing geoids currently proposed for the Baltic Sea; and (3) the difference between the national height datums of countries around the Baltic Sea. Received: 14 August 2000 / Accepted: 19 June 2001  相似文献   

Vortex–ridge interaction in a rotating fluid     

L. Zavala Sansn 《Dynamics of Atmospheres and Oceans》2002,35(4)

The evolution of barotropic vortices interacting with a topographic ridge on a f-plane is studied by means of laboratory experiments in a rotating tank and numerical simulations. The initial condition in all experiments is a cyclonic vortex created at a certain distance from the ridge. The results are presented in two main scenarios: (a) weak interactions, which occur at early stages of the experiments, when the vortex is far from the ridge, and thus weakly experiences the influence of the topography. In these situations, the vortex slowly drifts towards the ridge with a leftward inclination due to the ascending slope of the topography. Such a behaviour is similar to the “northwestern” motion of cyclones over a weak sloping bottom. The circular shape of the monopolar vortex is preserved. (b) Strong interactions, in which the vortex core reaches the ridge and presents a more complicated evolution. The cyclone “climbs” to the top of the topography and crosses to the other side. Once the vortex experiences the opposite slope, it moves backwards trying to return to the original side of the ridge. For strong enough vortices, this process may be repeated a number of times until the vortex is dissipated by viscous effects. During these interactions the shape of the vortex is strongly deformed and several filaments are produced. In some cases the vortex is cleaved in two parts when crossing the ridge, one at each side of it and moving in opposite directions.Weak and strong interactions are numerically simulated by using a quasi-two-dimensional model. The results confirm that the vortex behaviour is governed by stretching and squeezing effects associated with changes in depth over the ridge and, at latter stages, by Ekman damping due to the solid bottom. The main results observed during strong interactions on a f-plane are also found on preliminar topographic β-plane experiments.  相似文献   

Comparison of USGS and DLR topographic models of Comet Borrelly and photometric applications     

Randolph L Kirk  Elpitha Howington-Kraus  Bernd Giese 《Icarus》2004,167(1):54-69

Stereo analysis of images obtained during the 2001 flyby of Comet Borrelly by NASA's Deep Space 1 (DS1) probe allows us to quantify the shape and photometric behavior of the nucleus. The shape is complex, with planar facets corresponding to the dark, mottled regions of the surface whereas the bright, smooth regions are convexly curved. The photometric as well as textural differences between these regions can be explained in terms of topography (roughness) at and below the image resolution, without invoking significant variations in single-particle properties; the material on Borrelly's surface could be quite uniform. A statistical comparison of the digital elevation models (DEMs) produced from the three highest-resolution images independently at the USGS and DLR shows that their difference standard deviation is 120 m, consistent with a matching error of 0.20 pixel (similar to reported matching accuracies for many other stereo datasets). The DEMs also show some systematic differences attributable to manual versus automatic matching. Disk-resolved photometric modeling of the nucleus using the DEM shows that bright, smooth terrains on Borrelly are similar in roughness (Hapke roughness θ=20°) to C-type asteroid Mathilde but slightly brighter and more backscattering (single-scattering albedo w=0.056, Henyey-Greenstein phase parameter g=−0.32). The dark, mottled terrain is photometrically consistent with the same particles but with roughnesses as large as 60°. Intrinsically darker material is inconsistent with the phase behavior of these regions. Many local radiance variations are clearly related to topography, and others are consistent with a topographic explanation; one need not invoke albedo variations greater than a few tens of percent to explain the appearance of Borrelly.  相似文献   

Recent changes in flood risk in the Gran La Plata,Buenos Aires province,Argentina: causes and management strategy     

María Isabel Andrade  Olga Eugenia Scarpati 《GeoJournal》2007,70(4):245-250

The paper analyses the causes of flood occurrence in the Gran La Plata, Buenos Aires Province, Argentina, and the changes that have occurred since the 1970s. The area is characterized by serious deficiencies in the use and management of water resources. The main factors are: (1) flood risk information is not updated; (2) urban building organization does not consider the flood risk; (3) the topography and other physical features are not taken into account in urban development. This research considers some specific problems, especially in data availability, and suggests ways to solve them, including improved analytical methodology. One of the main objectives is to analyse flood risk in social terms, producing a map of flood risk from the “human social vulnerability” point of view. The results suggest that flood risk has increased since the 1980s and that this is associated with changes in precipitation patterns that have also been aggravated by lack of controls on urban development. The poorer areas with the lowest level of infrastructure and public services, many of them developed over the last quarter-century, are especially vulnerable.  相似文献   

局部地形对出平面运动谱特性的影响分析   总被引：3，自引：0，他引：3  

荣棉水  李小军 《中国地震》2007,23(2):147-156

本文利用显式有限元有限差分方法进行了脉冲和实际地震动输入下的粘弹性场地地形影响的分析计算,研究了坡地地形在高宽比不同、体波入射角度不同时出平面运动谱特性的差异。结果显示:地形的特征尺寸和入射角度不仅对地震动的峰值有影响,而且对地震动的谱特性有较大的影响,其中入射角度的影响尤为显著。另外,研究还表明,基于脉冲输入研究粘弹性地形谱特性的影响仍不失为一种有效的方法。  相似文献   

Resolution issues in numerical models of oceanic and coastal circulation     

David A. Greenberg  Frédéric Dupont  Florent H. Lyard  Daniel R. Lynch  Francisco E. Werner 《Continental Shelf Research》2007

The baroclinic and barotropic properties of ocean processes vary on many scales. These scales are determined by various factors such as the variations in coastline and bottom topography, the forcing meteorology, the latitudinal dependence of the Coriolis force, and the Rossby radius of deformation among others. In this paper we attempt to qualify and quantify scales of these processes, with particular attention to the horizontal resolution necessary to accurately reproduce physical processes in numerical ocean models. We also discuss approaches taken in nesting or down-scaling from global/basin-scale models to regional-scale or shelf-scale models. Finally we offer comments on how vertical resolution affects the representation of stratification in these numerical models.  相似文献   

地形对沙尘暴的影响及敏感试验研究   总被引：2，自引：3，他引：2  

沈建国  姜学恭  孙照渤 《高原气象》2007,26(5):1013-1022

在初步探讨地形影响沙尘扬升、传输、沉降等动力过程可能机制的基础上,利用沙尘数值预报模式对一次强沙尘暴过程进行了模拟研究,结果表明:沙尘暴形成阶段沙尘主要来源于阿尔泰—萨彦岭及以东地区,这部分沙尘主要向东扩展,该区域地形对其强度具有重要影响;内蒙古中西部、甘肃、宁夏等地的起沙主要在沙尘暴持续阶段产生影响,之后主要向南输送,青藏高原东侧地形绕流对其强度具有影响。地形影响可以使沙尘的扩展分为两种不同的方式,当上下游地形落差较小时形成整体推进式传输,此时沙尘位于对流层低层,没有上下沙尘层的分离;当上下游地形落差较大时形成分离式传输,沙尘位于对流层中层且在传输过程中沉降很弱,同时与地面附近的沙尘层分离。源于蒙古国、内蒙古等地的沙尘往往产生整体推进式传输;而产生于青藏高原的沙尘常形成分离式传输。  相似文献   

Algorithms to Account for Topographic Shading Effects and Surface Temperature Dependence on Terrain Elevation in Diagnostic Meteorological Models     

R.?BellasioEmail author  G.?Maffeis  J.?S.?Scire  M.?G.?Longoni  R.?Bianconi  N.?Quaranta 《Boundary-Layer Meteorology》2005,114(3):595-614

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