Flow characteristics of a gravity current induced by differential cooling in a small lake     

Elena Roget  Jordi Colomer 《Aquatic Sciences - Research Across Boundaries》1996,58(4):367-377

Extensive field data of a density current driven by the differences in the cooling rates between the two lobes of a small lake are presented. These data illustrate the fact that this gravitational motion affects the whole system and dominates its lakewide circulation. Moreover, data are used to evaluate the entrainment into the density current and also to discuss the regime of the flow from a scaling analysis of the horizontal momentum equations. This analysis is specifically applied to the central area of the lake, where the density current flows from one lobe to the other. Results of this study show that in the longitudinal direction there is a balance between the pressure gradient and the turbulent viscous term. Further, it is found that geostrophy correctly describes the transversal pattern of the passage of the gravity current from the northern lobe to the southern, where it flows confined to the western shoreline.  相似文献   

利用GIS空间分析功能进行矿产资源评价的方法研究   总被引：8，自引：0，他引：8  

张建龙  游丽君 《物探化探计算技术》1997,19(3):283-286

ＧＩＳ（地理信息系统）为矿产资源的评价提供了强有力的工具。作者认为借助于ＧＩＳ所提供的空间分析功能，利用现有的资料，推演地质模型，从而达到矿产资源评价的目的，可为地质工作者提供有益的启示。  相似文献   

新疆胜利达坂地区花岗岩类的地球化学及成岩环境   总被引：4，自引：0，他引：4  

王居里  炎金才 《西北地质科学》1995,16(2):29-35

岩石学、地球化学和同位素地质年代学研究表明，中天山构造带北缘胜利达坂地区的花岗岩类至少是两期岩浆活动的产物，胜利达坂岩体形成于加里东晚期的岛弧构造环境，红色钾长花岗岩形成于华力西晚期，属造山期后花岗岩。  相似文献   

南天山榆树沟高压麻粒岩地体锆石U—Pb定年及其地质意义   总被引：39，自引：1，他引：38  

王润三  李惠民 《地球化学》1998,27(6):517-522

南天山榆树沟高压麻粒岩地体的主体为一套蛇绿岩。从该地体顶部单元的岩石中分离出的锆石绝大部分为浑圆形或椭球形,少量为两端略圆化的四方柱状晶体;镜下粒度分析结果显示分选良好的典型沉积特征;其ＺｒＯ２／ＨｆＯ２比值在４５－５７之间;结合岩石的岩石学和地球化学特征,推测斜长石榴苏辉岩的原岩可能主要由来自洋岛的基性火山激浪沉积碎屑和洋底风化产生的粘土组成。  相似文献   

The ratio between chrysophycean cysts and diatoms in temperate,mountain lakes: some recommendations for its use in paleolimnology   总被引：1，自引：0，他引：1  

Carlos A. Rivera-Rondón  Jordi Catalan 《Journal of Paleolimnology》2017,57(3):273-285

The ratio between chrysophycean cysts and diatom valves (CD ratio) in lake sediments has been suggested as a useful indicator of changing trophic state conditions in oligotrophic lakes. Other environmental factors, however, may influence the CD ratio because chrysophycean cysts usually reflect conditions in the planktonic environment and diatoms reflect benthic conditions. We investigated the CD ratio in 76 mountain lakes in the Pyrenees to determine the environmental drivers that influence the ratio and assess its value for paleoenvironmental inference. The lakes surveyed included a broad range with respect to bedrock type, altitude and surface area, characteristics that cover much of the variability that can be found in cold, oligotrophic mountain lakes. Lake depth and Ca²⁺ concentration explain most of the variation in the CD ratio. Trophic state factors (e.g. total phosphorus, TP) play a secondary role. As a predictor, CD ratio performs primarily as a lake depth indicator. The predictive models can be improved if trophic state (i.e. TP) and chemical conditions (Ca²⁺) are known or can be estimated independently. Use of the CD ratio for inferring Ca²⁺ oscillations only makes sense in lakes with Ca²⁺ <200 µeq/L or in those that oscillate below and above this threshold through time. Other interpretations of the CD ratio (e.g. lake trophic state changes, ice-cover duration) make sense if complementary paleolimnological evidence indicates that neither water depth nor Ca²⁺ concentration changed significantly. Indeed, paleolimnological interpretation of the CD ratio requires considering the particular characteristics of the lake and may vary depending on the temporal scale considered. This study provides some guidelines for evaluating critically the use of the CD ratio.  相似文献   

Hydrodynamic behaviour of compacted granite sawdust from the dimension stone industry of Pontevedra (Spain): experimental and modelling     

Ismael Falcon-Suarez  Ricardo Juncosa-Rivera  Phil Vardon  Dieter Rammlmair  Thomas Günter  Ulla Noell  Jordi Delgado-Martín 《Environmental Earth Sciences》2016,75(5):421

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A Geostatistical Methodology to Evaluate the Performance of Groundwater Quality Monitoring Networks Using a Vulnerability Index     

Hugo Júnez-Ferreira  Julián González  Emmanuel Reyes  Graciela S. Herrera 《Mathematical Geosciences》2016,48(1):25-44

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Analysis and Classification of Natural Rock Textures based on New Transform-based Features     

Rodrigo Lobos  Jorge F. Silva  Julián M. Ortiz  Gonzalo Díaz  Alvaro Egaña 《Mathematical Geosciences》2016,48(7):835-870

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Meromixis origin and recent trophic evolution in the Spanish mountain lake La Cruz   总被引：4，自引：0，他引：4  

Ramon Julià  Francesc Burjachs  Maria J. Dasí  Francesc Mezquita  Maria R. Miracle  Josep R. Roca  Guy Seret  Eduardo Vicente 《Aquatic Sciences - Research Across Boundaries》1998,60(4):279-299

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Changes in Fire and Climate in the Eastern Iberian Peninsula (Mediterranean Basin)   总被引：9，自引：3，他引：9  

Juli G. Pausas 《Climatic change》2004,63(3):337-350

Fire is a dominant ecological factor in Mediterranean ecosystems, and changes in the fire regime can have important consequences for the stability of our landscapes. In this framework I asked firstly, what is the trend in fire number and area burned in the eastern Iberian Peninsula, and then, to what extent is the inter-annual variability of fires determined by climatic factors. To answer these questions I analysed the meteorological data (temperature and precipitation) from 350 stations covering the eastern Iberian Peninsula (1950–2000), and the fire records for the same area (historical data, 1874–1968, and data from recent decades, 1968–2000). The results suggested a slight tendency towards decreasing summer rainfall and a clear pattern of increasing annual and summer temperatures (on average, annual temperatures increased 0.35 °C per decade from 1950 to 2000). The analysis of fire records suggested a clear increase in the annual number of fires and area burned during the last century; however, in the last three decades the number of fires also increased but the area burned did not show a clear trend. For this period the inter-annual variability in area burned was significantly related to the summer rainfall, that is, in wet summers the area burned was lower that in dry summers. Furthermore, summer rainfall was significantly cross-correlated with summer area burned for a time-lag of 2 years, suggesting that high rainfall may increase fuel loads that burn 2 years later.  相似文献