Micrometeorological Measurements in a Street Canyon during the Joint ATREUS-PICADA Experiment     

Marcin Idczak  Patrice Mestayer  Jean-Michel Rosant  Jean-Francois Sini  Michel Violleau 《Boundary-Layer Meteorology》2007,124(1):25-41

In order to investigate the microclimatic conditions in a street canyon, a physical model was used to conduct the Joint ATREUS-PICADA Experiment (JAPEX) in situ experimental campaign. Four lines of buildings simulated by steel containers were installed to form three parallel street canyons at 1:5 scale, with width/height aspect ratio approximately 0.40. The reference wind and atmospheric conditions were measured, as well as the flow velocity and direction in the street. Preliminary results concern street canyon ventilation and thermal effects on in-canyon airflow, and show that vortical motions appear for reference wind directions perpendicular to the street axis. The presence of adjacent rows of buildings did not appear to significantly influence the flow character within the canyon for the case of a low aspect ratio corresponding to a skimming flow regime. The flow structure was not significantly affected by the thermal effects although some slight interference occurred in the lower part of the canyon. An analysis of horizontal temperature gradients indicated that a thin boundary layer develops near the heated facade. These facts imply that the thermal effects are considerable only very close to the wall.  相似文献   

水岩作用对雅鲁藏布大拐弯北段滑坡的影响   总被引：12，自引：1，他引：12  

廖秋林  李晓  尚彦军  杜国栋 《水文地质工程地质》2002,29(5):19-21

通过对川藏公路南线八一至然乌段实地考察及对考察结果，已有资料的分析，本文运用统计学原理探讨了雅鲁藏布大拐弯北段地区滑坡与水岩作用的关系，并结合该地区发育的滑坡灾害具体分析了该地区水岩作用与滑坡的关系。经分析认为，该地区水岩作用条件复杂且利于发育各种典型的水岩作用，但地域性特殊的水岩作用形式更发育，并对雅鲁藏布地区滑坡灾害形成，诱发都有重要影响。  相似文献   

Effects of a covering layer in a circular-arc canyon on incident plane SV waves     

梁建文  严林隽 《地震学报(英文版)》2001,14(6):660-675

Introduction The effect of local topographies on seismic wave propagation is one of the most attractive topics in seismology. It may be resolved by either an analytical method or a numerical method. Here, the analytical method is the wave function expansion method; numerical methods include the finite difference, finite element, boundary integration equation, and discrete wave number method, etc. The advantage of these numerical methods is that they can be applied to local inhomogeneity and ir…  相似文献   

峡谷的自然地理特征与旅游开发研究   总被引：5，自引：0，他引：5  

方起东  祝炜平 《地域研究与开发》2002,21(2):68-71

峡谷可以按照峡谷的自然地理特征，即峡谷所处的河段，形态，形成时的地质营力，两岸岩石性质等进行分类，峡谷有着丰富的资源，包括水力资源，生态环境资源和旅游资源等，峡谷景观具有美学特征，也具有观光和科学文化旅游价值，峡谷旅游资源在中国风景名胜区中占有重要位置，全国国家级风景名胜区中有峡谷的景区占一半以上，峡谷旅游一直以来被人们所重视，而目前在浙江等经济比较发达区域的中低山丘陵地区峡谷旅游开发速度与规模进一步加大，峡谷开发过程中存在一些问题，因此，在开发过程中要强调规划先行，并注意峡谷群开发及分区开发和峡谷生态环境保护。  相似文献   

海底峡谷成因新探     

周家乐 《海洋湖沼通报》1991,(4):53-56

海底峡谷,是由于地壳板块运动而形成的一种地质构造。板块不同形式的运动,造成了不同特征的海底峡谷。河流和浊流等因素对地层岩石的冲刷作用,只能改变海底峡谷的外貌,却不是海底峡谷的成因。  相似文献   

Downward particle fluxes in the Guadiaro submarine canyon depositional system (north-western Alboran Sea), a river flood dominated system     

Albert Palanques  Mohamed El Khatab  Pere Puig  Pere Masqu    Joan Albert S  nchez-Cabeza  Enrique Isla 《Marine Geology》2005,220(1-4):23-40

Three moorings equipped with sediment traps were deployed in the north-western Alboran continental margin to study downward particle fluxes in the Guadiaro submarine canyon depositional system. This area is located close to the Strait of Gibraltar and is influenced by the upwelling induced by the Atlantic Jet and by episodic flood events from the Guadiaro River. Sediment traps were installed in the Guadiaro Canyon, in the Guadiaro Channel and in the adjacent continental slope. The overall duration of the deployment was 12 months (from November 1997 to October 1998). Time-series of downward particle fluxes, major constituents (organic carbon, nitrogen, biogenic opal, calcium carbonate and lithogenics) and ²¹⁰Pb were determined near the surface at mid-depths and near the bottom. Total mass fluxes (TMF) in this area fluctuated more than two orders of magnitude and showed an important seasonal variability with higher fluxes in winter. Increases in TMF and lithogenics together with decreases in ²¹⁰Pb, organic carbon and opal were recorded in all traps coinciding with river floods, indicating a direct response of the system to these events and a rapid offshore transport of suspended matter affecting the entire water column. The channel site received similar particle fluxes to the western open slope site, indicating that this channel did not act as a preferential sediment conduit during the deployment period. In the Guadiaro Canyon, TMF were more than one order of magnitude higher, ²¹⁰Pb concentration was lower (one half) and organic matter was more degraded than at the channel site during spring and summer, as a consequence of receiving particles resuspended by internal waves and occasionally by trawling activities. These particles were mainly retained in the canyon, which works as a trap. Also, during spring and summer, the opal and organic carbon percentages increased in all traps both in magnitude and variability, and peaks seem to be associated with biological blooms.  相似文献   

Contourite drift construction influenced by capture of Mediterranean Outflow Water deep-sea current by the Portimão submarine canyon (Gulf of Cadiz, South Portugal)     

Elodie Marchès  Thierry Mulder  Michel Cremer  Cédric Bonnel  Vincent Hanquiez  Eliane Gonthier  Pascal Lecroart 《Marine Geology》2007,242(4):247-260

The margin of the Gulf of Cadiz is swept by the deep current formed by the Mediterranean Outflow Water (MOW) flowing from the Mediterranean to the Atlantic. On the northern margin of the Gulf (Algarve Margin, South Portugal), the MOW intensity is low and fine-grained contourite drifts are built up with an alongslope development. From new sedimentological data, this study emphasizes the presence of two types of contourite drifts separated only by a deep submarine canyon incising the slope with a north-south orientation (Portimão Canyon). High-resolution seismic and bathymetry interpretation shows that on the eastern side of the canyon, the MOW forms a thick and large detached drift (Albufeira Drift) prograding toward both north and west, as shown in seismic profiles, with a high sedimentation rate. On this side of the canyon, the MOW intensity is high enough to erode the slope forming a moat channel (Alvarez Cabral). On the western side of Portimão Canyon, the MOW energy is lower, preventing moat channel erosion. Only flat and thin drift develops (Portimão and Lagos Drifts) with slow aggradation and a low sedimentation rate. This difference in drift development is due to the presence of the canyon which generates an important change in hydrodynamic of the MOW, confirmed by temperature-density measurements showing that MOW flows down Portimão Canyon. The canyon is responsible for the deviation of the direction of the MOW as it partly catches the deep-sea current flowing westward (i.e. capture phenomenon). It creates, thus, a decrease of the flow energy, competency and capacity between the east and west sides of the canyon. Through this phenomenon of MOW deep-sea current capture, the canyon constitutes a morphologic feature generating an important change in the contourite deposition pattern.In addition to already known climatic and oceanographic influences, our results show the role of canyons on contourite drift building. This study provides new elements on autocyclic factors influencing the contourite sedimentation, which are important to consider in future sedimentary paleo-reconstruction interpretations.  相似文献   

内河航运之优势与京杭运河山东段续建工程展望     

田仕文 《海岸工程》1997,(4)

内河航运是交通运输业重要的组成部分，具有独特的优越性。京杭运河距今已有近2500年的历史，是世界上开凿最早、最长的人工运河。鲁西南地区具有丰富的煤炭、石膏等矿产资源，长江以南京杭运河南段苏浙沪水网地区，是我国重要的工业生产基地．迫切需要从北方调入大量煤炭，在津浦线运力早已饱含的情况下，京杭运河济宁至徐州段续建工程更显得十分必要。该工程包括：航道、船闸、公路桥、节制闸、港口、船厂、航修站、微波通信等项目。工程总投资14．96亿元，完工后可净增港口吞吐能力1550万t，三级航道的年货物通过能力将达4000万t．京杭运河山东段工程的续建和崛起必将为齐鲁经济和强国富民做出更大贡献。  相似文献   

Morphometric analysis of sediment conduits on a bathymetric high: Implications for palaeoenvironment and hydrocarbon prospectivity     

《Basin Research》2018,30(5):1015-1041

Canyons and other sediment conduits are important components of the deep‐water environment and are the main pathways for sediment transport from the shelf to the basin floor. Using 3‐D and 2‐D seismic reflection data, seismic facies and statistical morphometric analyses, this study showed the architectural evolution of five canyons, two slide scars and four gullies on the southern part of the Loppa High, Barents Sea. Morphometric parameters such as thalweg depth (lowest point on a conduit's base), wall depth (middle point), height, width and base width, sinuosity, thalweg gradient, aspect ratio (width/height) and cross‐sectional area of the conduits were measured at intervals of 250‐m perpendicular to the conduits’ pathways. Our results show that the canyons and slide scars in the study area widen down slope, whereas the gullies are narrow and short with uniform widths. The sediment conduits in the study area evolved in three stages. The first stage is correlated with a time when erosion and bypass were dominant in the conduits, and sediment transferred to the basin in the south. The second stage occurred when basin subsidence was prevalent, and a widespread fine‐grained sequence was deposited as a drape blanketing the canyons and other conduits. A final stage occurred when uplift and glacial erosion configured the entire southern Loppa High into an area of denudation. Our work demonstrates that the morphometric parameters of the canyons, slide scars and gullies generally have increasing linear trends with down‐slope distance, irrespective of their geometries. The morphometric analysis of the sediment conduits in the study area has wider applications for understanding depositional processes, reservoir distribution and petroleum prospectivity in frontier basins.  相似文献   

Biogeochemical processes of incorporation, transformation and migration of organic matter at the marine water-sediment interface: Simulation by C labelled compounds     

R. Buscail 《Organic Geochemistry》1986,10(4-6)

The study of biogeochemical processes at the water-sediment interface must be able to explain the relatively small content of organic carbon in the sediment, compared to the calculated carbon flux in the oceans. The input of an organic molecule at the marine sediment surface (Gulf of Lion, France) was simulated by the injection of a ¹⁴C labelled molecule in the water of a preserved interface. A glutamic acid [¹⁴C(U)] simulated marine organic matter, whereas a catechol [¹⁴C(U)] represented continental organic material. The separation by successive acid and basic extractions of the remaining initial compounds and the resulting products showed the relative importance of biological (respiration, assimilation) and geochemical (adsorption on argillaceous particles and condensation in geopolymers) processes occurring at the water-sediment interface. The evaluation was supported by the determination of the geochemical (humic substances), hydrological (conditions of temperature and degree of oxygénation) and sedimentological characteristics of the environment studied and by the estimation of the benthic activity.  相似文献