Temporal variability in hydrological response within a small catchment with badland areas,central Pyrenees     

《水文科学杂志》2013,58(3):629-639

Abstract

The lower Araguás catchment, central Pyrenees, is characterized by extensive badlands (25% of the total catchment), whereas the upper catchment is covered by dense plantation forest. The catchment (45 ha) has been monitored since October 2005 with the aim of studying its hydrological response. The 44 floods recorded over this period were analysed to identify the factors that control the rainfall—runoff relationship. The first relevant feature of the catchment was its responsiveness. The catchment reacted to all rainfall events, but the irregular nature of the hydrological response was the most characteristic feature of the response. No single variable could explain the response of the Araguás catchment. It was found that stormflow coefficients mainly depend on the combination of rainfall volume and antecedent baseflow. A significant correlation was observed between maximum rainfall intensity and peak flow values. The shapes of the different hydrographs are very similar, regardless of the peak flow magnitude; they show a short time lag, relatively narrow peak flow, and steep recession limb. This indicates a large contribution by overland flow, resulting mainly from the generation of infiltration excess runoff in badland areas.  相似文献   

On natural and laboratory generated dose response curves for quartz of different grain sizes from Romanian loess     

《Quaternary Geochronology》2013

One of the most important foundations of luminescence dating is the assumption that the growth of the luminescence signal in nature can be reproduced under laboratory conditions by performing irradiations with a calibrated beta or gamma source. When optically stimulated luminescence (OSL) of quartz with a dominant fast component is measured using the single aliquot regenerative dose (SAR) protocol, laboratory dose response curves that display continuing growth at high doses are increasingly reported in literature. In this study we investigate fine (4–11 μm) and coarse (63–90 μm) quartz extracted from 25 samples taken from L1, S1 and L2 units from the loess-palaeosol section at Costineşti in Romania. Our results indicate that the growth of the OSL signal in nature does not correspond to the laboratory generated laboratory dose response curve. The growth of the signal in nature is consistent with a single saturating exponential function, with the signal of coarse grains starting to saturate at 100–200 Gy, and for fine grains at 200–300 Gy, respectively. Laboratory dose response curves continue to grow for high doses (>300 Gy) for both quartz fractions. The differences observed between the natural and the laboratory dose response for the two quartz fractions are believed to be a cause for the different chronologies previously reported using the two grain sizes of quartz on Romanian loess. In addition, we have applied the single aliquot regeneration and added dose (SARA) procedure to both fine and coarse grains from the youngest sample. Our findings question the reliability of obtaining high equivalent doses for quartz samples displaying laboratory dose response curves obtained by the SAR protocol for which a single saturating exponential model does not describe the data.  相似文献   

钻井液侵入海洋含水合物地层的一维数值模拟研究   总被引：1，自引：0，他引：1       下载免费PDF全文

宁伏龙  张可霓  吴能友  蒋国盛  张凌  刘力  余义兵 《地球物理学报》2013,56(1):204-218

本文以墨西哥湾水合物区域为背景,利用数值模拟方法研究了过平衡钻井条件下,当钻井液温度高于地层中水合物稳定温度时,水基钻井液侵入海洋含水合物地层的动态过程及其一般性规律.与侵入常规油气地层相比,耦合水合物分解和再形成是钻井液侵入海洋含水合物地层的主要特征.模拟结果表明,钻井液密度、温度和盐度都对侵入过程有影响.在一定条件下,钻井液密度越大,温度和含盐量越高,则钻井液侵入程度越深,热量传递越远,水合物分解程度越大.分解的水气在合适条件下又会重新形成水合物,影响了钻井液进一步侵入.而重新形成的水合物的饱和度甚至可能高于原位水合物饱和度,在井周形成一个"高饱水合物"环带.这一现象归因于钻井液侵入的驱替推挤、水合物分解的吸热以及地层传热的滞后等因素共同作用.在地层物性一定的条件下,高饱水合物环带的出现与否主要受钻井液温度和盐度控制.水合物分解以及高饱水合物环带的出现对井壁稳定和电阻率测井解释有很大影响.因此,为维护井壁稳定、确保测井准确和减少水合物储层伤害,就必须对钻井液密度、温度和滤失量进行严格控制,防止地层中的水合物大量分解.最好采用控制压力钻井(MPD)和深侧向测井方式,同时尽量选用低矿化度的含水合物动力学抑制剂的钻井液体系,采取低温快速循环方式.  相似文献   

Autumn NDVI contributes more and more to vegetation improvement in the growing season across the Tibetan Plateau     

《International Journal of Digital Earth》2013,6(11):1098-1117

ABSTRACT

Detecting changes in vegetation, distinguishing the persistence of changes, and seeking their causes during multiple periods are important to gaining a deeper understanding of vegetation dynamics. Using the Global Inventory Modeling and Mapping Studies Normalized Difference Vegetation Index (NDVI) version NDVI_3g dataset in the Tibetan Plateau, the trends in the seasonal components of NDVI and their linkage with climatic factors were analyzed over 14 asymptotic periods of 18–31 years since 1982. Dynamic trends in vegetation experienced an obvious increase at regional scale, but the increases of vegetation activity mostly tended to stall or slow down as the studied time period was extended. At pixel scale, areas with significant browning significantly expanded over 14 periods for all seasons, but for significant greening significantly increased only in autumn. The changes of vegetation activity in spring were the most drastic among three seasons. Increased increments of NDVI in summer, spring, and autumn took turns being the main reason for the enhanced vegetation activity in the growing season in the nested 14 periods. Vegetation activity was mainly regulated by a thermal factor, and the dominant climatic drivers of vegetation growth varied across different seasons and regions. We speculate that the increase of NDVI will continue but the increments will decline in all seasons except autumn.  相似文献   

层状各向异性地层中三维感应测井响应快速计算及资料处理   总被引：3，自引：1，他引：2       下载免费PDF全文

肖加奇  张国艳  洪德成  杨善德 《地球物理学报》2013,56(2):696-706

本文采用广义反射系数法推导了水平层状各向异性地层中电磁场的积分解析解,并利用快速汉克尔变换技术实现了三维感应仪器测井响应的快速计算.三维感应测井响应与地层水平电导率、垂直电导率和井斜角及仪器方位角同时有关,单一分量的测井曲线不能满足资料解释的需要.通过对仪器测量分量响应特征的考察,本文提出了一种基于组合量测井曲线的资料直观解释方法.数值模拟显示,交叉分量相关组合量可准确划分地层纵向边界,并可直观识别各向异性层;与单独分量相比,主分量相关组合量提高了纵向分辨率、减弱了与地层电导率参数的非线性关系.  相似文献