祁连山七一冰川暖季能量平衡及小气候特征分析   总被引：8，自引：6，他引：2  

蒋熹  王宁练  杨胜朋  贺建桥  宋高举 《冰川冻土》2010,32(4)

利用2007年7月1日至10月10日安装在七一冰川消融区的自动气象站资料,计算和讨论了能量平衡方程中的净辐射、感热和潜热通量、冰雪的热传输和降雨加热项.结果表明:净辐射是七一冰川的主要能量来源,其次是湍流感热.消融期消融耗热是主要的能量耗散,到消融末期,潜热耗热的比重开始增加.冰雪的热传导量值较小.同时还分析了暖季七一冰川区的小气候特征.  相似文献   

兰州马衔山多年冻土特征及变化趋势分析   总被引：2，自引：2，他引：0  

谢昌卫  赵林  吴吉春  乔永平 《冰川冻土》2010,32(5)

马衔山是目前黄土高原地区唯一证实有多年冻土发育的山脉.残存的多年冻土被誉为黄土高原地区多年冻土的"活化石".近20a来马衔山多年冻土发生了明显的退化,目前仅在小湖滩有岛状多年冻土残存,属于典型的高温多年冻土,1990年代初在其它区域发现的零星多年冻土已经基本消失.马衔山岛状多年冻土地温从10～16m的-0.2℃向上和向下升高,地温梯度±0.01℃·m-1左右,相比1990年代初,多年冻土地温上升了0.1～0.2℃,年升温率为0.006～0.012℃·a-1,小于青藏高原高温多年冻土平均升温速率.马衔山多年冻土最大厚度约40m,正在发生着上引式和下引式退化,而岛状冻土边缘区域侧引式退化起主导作用.马衔山多年冻土发育有丰富的地下分凝冰,根据地下冰发育特征和埋藏有机质层14C测试资料分析,马衔山多年冻土在新冰期形成后发生过多次地表重复堆积,共生共长作用是地下冰形成的重要原因.丰富的地下冰和厚层有机质层的保护作用,以及区域寒冷的微气候环境,应该是马衔山多年冻土残存的主要原因.  相似文献   

沙漠及绿洲不同覆被下大气CO2浓度的梯度变化   总被引：4，自引：1，他引：3  

苏培玺  赵爱芬  张立新  杜明武  刘新民 《中国沙漠》2002,22(4):377-382

运用美国生产的开环气体交换系统LI-6400便携式光合作用测定系统,研究了沙漠及绿洲不同覆被下大气CO₂浓度的梯度变化。结果表明,2001年巴丹吉林沙漠南缘大气CO₂浓度为366μmol·mol^-1,秋季大气CO₂浓度梯度在1~ 10m高度范围内为0,CO₂浓度与气温呈线形正相关,相关系数为0.87;与空气相对湿度呈线形负相关,相关系数为 -0.86。秋季绿洲区CO₂浓度高于沙漠区,人类活动向大气排放CO₂,是绿洲区CO₂浓度高于沙漠区的主要原因。绿洲不同覆被类型其CO₂浓度梯度明显不同,影响CO₂浓度梯度的主要因素为:人类活动、覆被变化、气象因子。覆被变化研究得出,杨树林初秋光合作用最强时在10m高度范围内CO₂浓度可降低22μmol·mol^-1;另外得出,降雨能够明显降低空气CO₂浓度。  相似文献   

Long-term large wood load fluctuations in two low-order streams in Southern Chile     

Andrés Iroumé  Manuel Cartagena  Luisa Villablanca  Daniel Sanhueza  Bruno Mazzorana  Lorenzo Picco 《地球表面变化过程与地形》2020,45(9):1959-1973

The eco-hydrogeomorphic significance of large wood (LW) and its potential for increasing downstream hazards during extreme floods have been widely recognized. We used LW data collected for a 10-year period from the two low-order streams of Pichún (Pi) and Vuelta de Zorra (VZ) in Southern Chile to (a) determine if the abundance and dimensions of individual LW pieces change with time, (b) quantify wood load fluctuations during the 10-year period, and (c) assess the role of LW recruitment from the riparian forests to explain wood load fluctuations during the study period. Nine years after the first survey, the number of LW pieces in Pi and VZ diminished by 60 and 40%, respectively. Despite the reduction in these numbers, in Pi, the LW dimensions did not change significantly during the study. In VZ, the dimensions exhibited statistically significant differences, despite being within the same class. In both catchments, the LW load fluctuated during a 10-year period, but the drivers of change differed. Although tree toppling was the recruitment mechanism responsible for LW in both stream cases, the high wood load measured in Pi at the beginning of the study suggested massive tree recruitments before the first survey, followed by wood exports which were higher than inputs in the subsequent 10-year period. In VZ, LW load decreased during the first 9 years (mean annual rate of ~9.2 m³ year⁻¹) and then increased by ~12.1 m³ year⁻¹ in year 10. At VZ, the inputs consisted of single trees that were recruited from the riparian area and by upstream flotation, while exports occurred by downstream fluvial transport. Wood inputs and exports occurred asynchronously and led to LW load fluctuations at decadal and annual intervals. Land management and tree species thus exert a major influence on wood inventory and budget in streams. © 2020 John Wiley & Sons, Ltd.  相似文献   

Remotely sensed rivers in the Anthropocene: state of the art and prospects     

Hervé Piégay  Fanny Arnaud  Barbara Belletti  Mélanie Bertrand  Simone Bizzi  Patrice Carbonneau  Simon Dufour  Frédéric Liébault  Virginia Ruiz-Villanueva  Louise Slater 《地球表面变化过程与地形》2020,45(1):157-188

The rivers of the world are undergoing accelerated change in the Anthropocene, and need to be managed at much broader spatial and temporal scales than before. Fluvial remote sensing now offers a technical and methodological framework that can be deployed to monitor the processes at work and to assess the trajectories of rivers in the Anthropocene. In this paper, we review research investigating past, present and future fluvial corridor conditions and processes using remote sensing and we consider emerging challenges facing fluvial and riparian research. We introduce a suite of remote sensing methods designed to diagnose river changes at reach to regional scales. We then focus on identification of channel patterns and acting processes from satellite, airborne or ground acquisitions. These techniques range from grain scales to landform scales, and from real time scales to inter-annual scales. We discuss how remote sensing data can now be coupled to catchment scale models that simulate sediment transfer within connected river networks. We also consider future opportunities in terms of datasets and other resources which are likely to impact river management and monitoring at the global scale. We conclude with a summary of challenges and prospects for remotely sensed rivers in the Anthropocene. © 2019 John Wiley & Sons, Ltd.  相似文献   

Riparian vegetation and island formation along the gravel‐bed Fiume Tagliamento,Italy     

A. M. Gurnell  G. E. Petts  D. M. Hannah  B. P. G. Smith  P. J. Edwards  J. Kollmann  J. V. Ward  K. Tockner 《地球表面变化过程与地形》2001,26(1):31-62

After more than 300 years of river management, scientific knowledge of European river systems has evolved with limited empirical knowledge of truly natural systems. In particular, little is known of the mechanisms supporting the evolution and maintenance of islands and secondary channels. The dynamic, gravel‐bed Fiume Tagliamento, Italy, provides an opportunity to acquire baseline data from a river where the level of direct engineering intervention along the main stem is remarkably small. Against a background of a strong alpine to mediterranean climatic and hydrological gradient, this paper explores relationships between topography, sediment and vegetation at eight sites along the active zone of the Tagliamento. A conceptual model of island development is proposed which integrates the interactions between large woody debris and vegetation, geomorphic features, sediment calibre and hydrological regime. Islands may develop on bare gravel sites or be dissected from the floodplain by channel avulsion. Depositional and erosional processes result in different island types and developmental stages. Differences in the apparent trajectories of island development are identified for each of the eight study sites along the river. The management implications of the model and associated observations of the role of riparian vegetation in island development are considered. In particular, the potential impacts of woody debris removal, riparian tree management, regulation of river flow and sediment regimes, and changes in riparian tree species' distribution are discussed. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

Fractal dimensions of suspended solids in streams: comparison of sampling and analysis techniques     

Dirk H. de Boer  Mike Stone 《水文研究》1999,13(2):239-254

Fluvial suspended sediment typically consists of a variety of complex, composite particles referred to as flocs. Floc characteristics are determined by factors such as the source, size and geochemical properties of the primary particles, chemical and biological coagulation processes in the water column and shear stress and turbulence levels in the stream. Studies of floc morphology have used two contrasting methods of sampling and analysis. In the first method, particles settle on a microscope slide and are observed from below using an inverted microscope. The second method uses filtration at no or low vacuum and particles deposited on the filter are observed with a microscope. Floc morphology can be quantified using fractal dimensions. The aims of the present study were to examine the effect of the two sampling methods on the fractal dimensions of particle populations, and to evaluate for each method how well the fractal dimensions at the various sampling sites reflect basin conditions. Suspended solids were collected in triplicate on inverted microscope slides and on 0·45 μm Millipore HA filters in two southern Ontario streams with contrasting riparian zones during a minor runoff event resulting from the melt of a freshly fallen snowpack. An image analysis system was used to determine area, longest axis and perimeter of particles. The morphology of the particle population of each sample was characterized using four fractal dimensions (D, D₁, D₂ and D_K). Systematic differences in fractal dimensions obtained with the two methods were observed. For the settling method, outlines of larger particles were frequently blurred because of the distance between the focal plane (the top of the inverted microscope slides) and the plane of the particle outline. In this method, the blurring of large particles can cause an increase in the projected area and length of the particle. The effect on the particle perimeter is unpredictable because it depends on the amount of detail lost through blurring and its effect on the apparent increase in particle size. Because of blurring, D and D₁ tend to be systematically lower for the settling method, whereas the net effect on D₂ is unpredictable. Particle size distributions derived from settling are typically coarser because small, low density particles may remain in the water column and all particles may not deposit on the slides. This loss of fines results in systematically lower D_K values for the settling method compared with the filtration method. Fractal dimensions and particle size distributions obtained with the filtration method were sensitive to and clearly indicated differences between drainage basins and between sites within each basin. These differences were explained by basin characteristics and conditions. Fractal dimensions and particle size distributions obtained with the settling method were less sensitive to drainage basin characteristics and conditions, which limits their usefulness as process indicators. Copyright © 1999 John Wiley & Sons, Ltd.  相似文献   

荒漠河岸林地下水位时空动态及其对地表径流的响应   总被引：1，自引：0，他引：1       下载免费PDF全文

张经天  席海洋 《干旱区地理》2020,43(2):388-397

荒漠河岸林是干旱地区重要的生态系统之一,受间歇性河流补给的浅层地下水是河岸林植物生存的主要水分来源。基于额济纳荒漠河岸林地下水位观测断面具有高时空分辨率的地下水位数据,分析了荒漠河岸林浅层地下水的时空变化及分水事件中河水对地下水的补给特征。结果表明：额济纳绿洲河岸林地下水位在季节尺度上具有植物生长季下降,非生长季上升的变化特征;在植物生长季内,地下水位具有白天下降,夜间上升的日周期变化特征,且日波动幅度主要受不同植被类型及植物不同生长期地下水蒸散速率的影响。黑河下游河水的河道渗漏是沿岸浅层地下水的主要补给来源,在分水过程中,距河道不同距离的地下水位对河水补给的响应时间随距离增加而增大,分水结束时的地下水位上升幅度随距离增加而减小,分水总径流量、分水持续时间和日均径流量是影响地下水补给宽度的主要因素。河道径流渗漏水量的绝大部分都通过蒸散发过程损失,从2013—2015年6次分水事件结束后,地下水估算补给量占其与蒸散量总和的平均比例为23.6%。  相似文献