塔河油田四区奥陶系古岩溶流域的倒淌河及其成因研究

在现代岩溶区,由于构造运动、岩性差异以及地貌起伏等因素,常常出现水系袭夺现象,并随之伴生一系列反常的水文地貌现象,如分水岭迁移和破坏、袭夺肘、风峡、断头河和倒淌河等。基于三维地震资料,应用层拉平技术、精细相干分析技术及相关地震成图技术,对塔河油田四区中—下奥陶统顶部海西早期的岩溶古地貌和古水系进行了恢复识别,发现也存在类似的反常水文地貌现象。借鉴现代水系袭夺理论,证实了塔河油田四区东部岩溶流域早期为南向汇流结构,而后期由于构造运动引起西北部侵蚀基准面下降,并通过地下途径对邻近南向流域北缘进行逐步袭夺,形成了大型倒淌河,再现了本区岩溶古水系及流域的阶段性演化过程,从而为揭示塔河油田奥陶系古岩溶发育规律提供了重要的依据。     

中国东部主要河流稀土元素地球化学特征

在2007年底至2008年初的枯水期间,系统采集了中国东部流域面积和径流量较大的33条河流沉积物、悬浮颗粒物和水样,采用等离子质谱法、X荧光光谱法等方法测定了14种稀土元素含量以及常量组分和水体pH值等理化指标。研究发现中国河流稀土元素浓度总体高于世界均值,且南方河流沉积物、悬浮物稀土元素含量高于北方河流,南方河流悬浮物态中稀土、重稀土呈现一定程度的相对富集,与我国上地壳稀土丰度和稀土矿产种类的南北分异相吻合。展示了以中国东部泥质岩稀土元素丰度标准化后的稀土配分模式及Ce、Eu异常特征,发现河流沉积物的中、重稀土元素相对富集,悬浮物轻稀土相对富集,溶解相重稀土富集的特征;北方河流溶解相稀土元素浓度明显大于南方河流,且除小清河外,溶解相Eu不同于沉积物与悬浮物而呈强烈的正异常,主要与河水理化性质影响下的稀土分异有关。研究发现小清河等少数河流沉积物中稀土元素为异常高值,经Al标准化处理、计算拟合剩余值后,认为小清河等河流稀土元素已受人为污染的影响。     

Spatially distributed hydrotope‐based modelling of evapotranspiration and runoff in mountainous basins

River basins in mountainous regions are characterized by strong variations in topography, vegetation, soils, climatic conditions and snow cover conditions, and all are strongly related to altitude. The high spatial variation needs to be considered when modelling hydrological processes in such catchments. A complex hydrological model, with a great potential to account for spatial variability, was developed and applied for the hourly simulation of evapotranspiration, soil moisture, water balance and the runoff components for the period 1993 and 1994 in 12 subcatchments of the alpine/pre‐alpine basin of the River Thur (area 1703 km²). The basin is located in the north‐east of the Swiss part of the Rhine Basin and has an elevation range from 350 to 2500 m a.s.l. A considerable part of the Thur Basin is high mountain area, some of it above the tree‐line and a great part of the basin is snow covered during the winter season. In the distributed hydrological model, the 12 sub‐basins of the Thur catchment were spatially subdivided into sub‐areas (hydrologically similar response units—HRUs or hydrotopes) using a GIS. Within the HRUs a hydrologically similar behaviour was assumed. Spatial interpolations of the meteorological input variables wereemployed for each altitudinal zone. The structure of the model components for snow accumulation and melt, interception, soil water storage and uptake by evapotranspiration, runoff generation and flow routing are briefly outlined. The results of the simulated potential evapotranspiration reflect the dominant role of altitudinal change in radiation and albedo of exposure, followed by the influence of slope. The actual evapotranspiration shows, in comparison with the potential evapotranspiration, a greater variability in the lower and medium altitudinal zones and a smaller variability in the upper elevation zones, which was associated with limitations of available moisture in soil and surface depression storages as well as with the evaporative demand of the local vegetation. The higher altitudinal dependency and variability of runoff results from the strong increase in precipitation and the decrease in evaporation with increased altitude. An increasing influence of snow cover on runoff as well as evapotranspiration with altitude is obvious. The computed actual evapotranspiration and runoff were evaluated against the observed values of a weighting lysimeter and against runoff hydrographs. Copyright © 1999 John Wiley & Sons, Ltd.     

长江中下游河湖洪水演进的数值模拟

以长江中下游(宜昌-大通)防洪系统为对象,在水文、河道及湖盆地形现状条件下,建立了一个能适应各种复杂条件的一二维非恒定流模型,来进行长江干流、河网、湖泊、分蓄洪区垸及水库的洪水演进和调度仿真.所建模型的洞庭湖部分采用无结构网格二维非恒定有限体积格式,以适应湖区复杂的边界形状和保持水量平衡.河网区部分采用一维非恒定流显隐结合的分块三级算法,以准确实现河网汊点流量的自动分配和往复流动.为了提高模拟精度和扩展模拟功能,在水流数值模拟的范围内侧重讨论了内外动边界处理、分蓄洪运用及阻力项计算等环节,提出了合理可行的数值处理方法.采用20世纪80年代至90年代共6年汛期洪水资料对所建模型进行了严格的率定和检验,高精度的模拟结果证实了模型的合理性和有效性.     

雪冰中NO_3~-浓度记录的研究进展

NO3-是雪冰中含量最高的含氮无机离子,雪冰中NO3-浓度记录的解读已成为研究全球变化的重要内容之一.近年来国内外已经就极地与中低纬高海拔地区雪冰中NO3-浓度记录开展了大量的研究,关于NO3-所指示的环境意义形成了一系列的认识.从雪冰中NO3-的可能性来源(包括太阳活动、陆源粉尘、闪电等自然源以及其他人类源)、时空变化特征以及气-雪-冰界面转化过程等方面综述了近年来该领域的研究成果,并结合全球变化的背景对其研究前景进行了展望.     

松花江白山河段冰情数值计算及分析

根据水动力学、河流动力学、热力学、河冰水力学及固体力学等原理,针对松花江上游白山河段具体特征,建立了河冰数学模型,并应用有限差分计算方法,对白山河段冬季冰情演变进行了精确模拟。应用该河段1958-1973年共15年完整的地形、气象、水文、热力、冰情等原型观测资料,分别进行了模型参数率定及冰情数值模拟。研究结果表明:白山河段的封冻首先开始于白山坝址下游4 km的大崴子河段,然后封冻边缘逐渐上溯,最终到达松14断面;计算的白山河段冰花堆积体外形与河床纵剖面呈相似趋势;各种水力及冰情要素的数值计算结果和实测值吻合较好,所建立的数值模型能较好地模拟该河道的冰情。研究结果对东北地区河流冬季冰情研究及冰害防治具有一定的借鉴意义。     

Numerical study on salinity stratification in the Pamlico River Estuary

The variations of current circulation, salt intrusion, and vertical stratification under different river flow and wind conditions in the Pamlico River Estuary (PRE) were investigated in this paper using a three-dimensional numerical model. The model was calibrated and verified against water level variation, temperature, and salinity variations during 2003 and 2001, respectively. Eight sensitivity tests were conducted with different river flow and wind conditions specified in the model. Model results show that salinity intruded further upstream under scenarios with low flow, downriver local wind, and remote-wind-caused water level set-up conditions. In contrast, the responses of salinity stratification to different environmental forcing functions were different in different portions of the estuary. Salinity stratification was enhanced under high flow condition at the lower part of the estuary, under upriver wind near the river mouth, under downriver wind at the upstream to middle portion of the estuary, and under remote-wind-caused water level set-up condition at the majority of the estuary except near the river mouth. Model results also show that across-channel wind tended to reduce salt intrusion and salinity stratification in the PRE through increased vertical mixing.     

Linking the northern hemisphere sea-ice reduction trend and the quasi-decadal arctic sea-ice oscillation

The nature of the reduction trend and quasi-decadal oscillation in Northern Hemisphere sea-ice extent is investigated. The trend and oscillation that seem to be two separate phenomena have been found in data. This study examines a hypothesis that the Arctic sea-ice reduction trend in the last three decades amplified the quasi-decadal Arctic sea-ice oscillation (ASIO) due to a positive ice/ocean-albedo feedback, based on data analysis and a conceptual model proposed by Ikeda et al. The theoretical, conceptual model predicts that the quasi-decadal oscillation is amplified by the thinning sea-ice, leading to the ASIO, which is driven by the strong positive feedback between the atmosphere and ice-ocean systems. Such oscillation is predicted to be out-of-phase between the Arctic Basin and the Nordic Seas with a phase difference of 3/4, with the Nordic Seas leading the Arctic. The wavelet analysis of the sea ice data reveals that the quasi-decadal ASIO occurred actively since the 1970s following the trend starting in the 1960s (i.e., as sea-ice became thinner and thinner), as the atmosphere experienced quasi-decadal oscillations during the last century. The wavelet analysis also confirms the prediction of such out-of-phase feature between these two basins, which varied from 0.62 in 1960 to 0.25 in 1995. Furthermore, a coupled ice-ocean general circulation model (GCM) was used to simulate two scenarios, one without the greenhouse gas warming and the other having realistic atmospheric forcing along with the warming that leads to sea-ice reduction trend. The quasi-decadal ASIO is excited in the latter case compared to the no-warming case. The wavelet analyses of the simulated ice volume were also conducted to derive decadal ASIO and similar phase relationship between the Arctic Ocean and the Nordic Seas. An independent data source was used to confirm such decadal oscillation in the upper layer (or freshwater) thickness, which is consistent with the model simulation. A modified feedback loop for the sea-ice trend and ASIO was proposed based on the previous one by Mysak and Venegas and the ice/albedo and cloud/albedo feedabcks, which are responsible for the sea ice reduction trend.     

Assessment of flow paths and confluences for saltwater intrusion in a deltaic river network

Saltwater intrusion is a serious issue in estuarine deltas all over the world due to rapid urban sprawl and water shortage. Therefore, detecting the major flow paths or locations at risk of saltwater intrusion in estuarine ecosystems is important for mitigating saltwater intrusion. In this paper, we introduce a centrality index, the betweenness centrality (BC), to address this problem. Using the BC as the weighted attribute of the river network, we identify the critical confluences for saltwater intrusion and detect the preferential flow paths for saltwater intrusion through the least‐cost‐path algorithm from a graph theory approach. Moreover, we analyse the responses of the BC values of confluences calculated in the river network to salinity. Our results show that the major flow paths and critical confluences for saltwater intrusion in a deltaic river network can be represented by the least cost paths and the BC values of confluences, respectively. In addition, a significant positive correlation between the BC values of confluences and salinity is determined in the Pearl River Delta. Changes in the salinity can produce significant variation in the BC values of confluences. Therefore, freshwater can be diverted into these major flow paths and critical confluences to improve river network management under saltwater intrusion. Copyright © 2015 John Wiley & Sons, Ltd.     

2002~2020年刚果河流域陆地水储量变化分析

利用德克萨斯大学空间研究中心（CSR）发布的GRACE时变重力场模型,基于最大信噪比准则确定RL06球谐系数模型（spherical harmonics,SH）的最优高斯滤波半径,在此基础上反演2002-04~2020-05刚果河流域陆地水储量变化,结合水文与降雨、蒸散资料分析其驱动因素。研究结果表明,GRACE模型估计的刚果河流域水储量变化和水文模型估计的地表水储量变化的周年振幅一致,表明刚果河流域的陆地水储量周年变化驱动因素为地表水。对于年际变化,2002-04~2020-05陆地水储量变化呈轻微增加趋势,2002-04~2006-12明显减少,RL06 SH模型估计结果为-2.30±0.24 cm/a;2007-01~2010-12呈现增加趋势,为0.38±0.24 cm/a;2011-01~2020-05水储量增速变大,为0.92±0.12 cm/a,该结果与CSR Mascon估计结果一致。