水汽吸收和下垫面发射率对晴空大气红外窗区遥感影响的综合分析     

巴桑  许丽生  刘海磊  丁继烈  邓小波  刘志红 《地理与地理信息科学》2011,27(2):41-45

从数学上探讨了晴空大气红外窗区通道遥感陆面特性水汽吸收和陆面发射率的综合影响。首先,基于辐射传输方程推导出大气水汽含量和陆面发射率(ε)引起红外窗区通道遥感陆面亮温(Tg)变化的数学表达式,指出红外辐射在传输过程中水汽吸收衰减的影响主要是引起大气透过率的变化;分析了在高温高湿和低温干燥等不同地区,红外窗区通道的大气透过率所受到的不同程度的衰减,以及水汽吸收衰减和陆面发射率对不同的红外窗区通道的影响。此外,还建立了一个红外窗区通道遥感陆面温度与地面亮温差ΔT=(Ts-Tg,imax)与水汽含量变化Δq和陆面发射率ε的二元多项式拟合方程,进一步分析大气水汽含量和陆面发射率对不同的红外窗区通道遥感的影响;指出红外短波窗区通道不但受太阳辐射污染严重,而且受陆面发射率变化的影响激烈,特别是在寒冷干燥的亚北极冬季。最后强调,为了精确地反演陆面温度,最好采用热红外窗区通道;必须考虑大气订正,特别是在高温高湿区;同时应该考虑陆面发射率等因子的作用。  相似文献   

钦州湾潮流深槽的成因与稳定性探讨     

张伯虎  陈沈良  谷国传  丰爱平 《海岸工程》2010,29(3):43-50

据钦州湾2007年1—2月的实测潮流,结合径流、潮汐等资料,经水动力和港湾地形综合分析揭示:钦州湾的潮流深槽是潮流作用于葫芦形复式港湾的必然产物,是在内湾纳潮蓄能、湾颈狭道强流、颈口岛礁分流喷射冲刷而成的。通过对潮流流路和强度的分析,对潮流深槽的稳定性进行了探讨;进而通过湾颈流速-内湾纳潮关系计算,给出了潮流深槽稳定的临界条件。  相似文献   

Effects of sediment pulses on bed relief in bar‐pool channels          下载免费PDF全文

John P. P. Zunka  Desiree D. Tullos  Stephen T. Lancaster 《地球表面变化过程与地形》2015,40(8):1017-1028

To further develop prediction of the range of morphological adjustments associated with sediment pulses in bar‐pool channels, we analyze channel bed topographic data collected prior to and following the removal of two dams in Oregon: Marmot Dam on the Sandy River and Brownsville Dam on the Calapooia River. We hypothesize that, in gravel‐bed, bar‐pool channels, the response of bed relief to sand and gravel sediment pulses is a function of initial relief and pulse magnitude. Modest increases in sediment supply to initially low‐relief, sediment‐poor cross‐sections will increase bed relief and variance of bed relief via bar deposition. Modest increases in sediment supply to initially high‐relief cross‐sections, characteristic of alternate bar morphology, will result in decreased bed relief and variance of relief via deposition in bar‐adjacent pools. These hypothesized adjustments are measured in terms of bed relief, which we define as the difference in elevation between the pool‐bottom and bar‐top. We evaluate how relief varies with sediment thickness, where both relief and mean sediment thickness at a cross‐section are normalized by the 90th percentile of observed relief values within a reach prior to a sediment pulse. Field measurements generally supported the stated hypotheses, demonstrating how introduction of a sediment pulse to low‐relief reaches can increase mean and variance of relief, while introduction to high‐relief reaches can decrease the mean and variance of bed relief, at least temporarily. In general, at both sites, the degree of impact increased with the thickness of sediment delivered to the cross‐section. Results thus suggest that the analysis is a useful step for understanding the morphological effects of sediment pulses introduced to gravel‐bed, bar‐pool channels. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

Morphodynamics of steep mountain channels          下载免费PDF全文

Francesco Brardinoni  Luca Mao  Alain Recking  Dieter Rickenmann  Jens M. Turowski 《地球表面变化过程与地形》2015,40(11):1560-1562

  相似文献   

复式河道滩槽交互区水沙运动机理          下载免费PDF全文

吉祖稳  胡春宏 《水科学进展》2017,28(3):321-328

滩槽复式河道是冲积河流中最为常见的一种形态,也是河流动力学研究最为重要的内容之一。以复式河道概化试验数据和水沙运动的区域性特征为依据,在提出滩槽复式断面主槽平衡区、滩槽交互区、滩地平衡区以及边壁区4个分区的基础上,将水流流态最为复杂的滩槽交互区进一步划分为对数流速区（内区）和非对数流速区（外区）,通过引入描写动植物生长过程的S型曲线,提出了内外区分界线的确定方法。以滩槽交互区横向分布公式为基础,通过线性假定和积分变换,给出了滩槽交互区内断面平均流速和含沙量的计算公式,并对不同分区内的流速和含沙量的差异性进行了比较分析。  相似文献   

Modeling uncertainty in the three-dimensional structural deformation and stratigraphic evolution from outcrop data: Implications for submarine channel knickpoint recognition     

《Marine and Petroleum Geology》2017

Digital outcrop models help to constrain the interactions of stratigraphic and structural heterogeneity on ancient depositional systems. This study uses a stochastic approach that incorporates stratigraphic and structural modeling to interrogate the three-dimensional morphology of deep-water channel strata outcropping on Sierra del Toro in the Magallanes Basin of Chile. This approach considers the relative contributions, and associated uncertainty, of erosional downcutting versus post-depositional structural folding and small-offset faulting on the present-day configuration of the submarine channel complexes. Paleodepositional channel-belt gradients were modeled using a combination of three-dimensional visualization, stochastic surface modeling, palinspastic restoration, and decompaction modeling that are bound with errors constrained by stratigraphic and structural uncertainty. Modeling results indicate that at least 100 m of downcutting occurs over 6 km, and the resultant thalweg gradient of 64–125 m/km (decompacted) suggests that the Cerro Toro axial channel belt is an out-of-grade depositional system. Furthermore, the presence of steeper segments (100–175 m/km decompacted) suggests the preservation of one or more knickpoints that are similar in magnitude to tectonically-induced knickpoints on the modern seafloor. The interpreted knickpoints are correlated with a decreasing channel width-depth ratio and an increase of channel depth. These results indicate that stochastic surface modeling using digital outcrop models can constrain stratigraphic interpretations and post-depositional structural heterogeneity.  相似文献   

Supraglacial melt channel networks in the Jakobshavn Isbræ region during the 2007 melt season          下载免费PDF全文

D. J. Lampkin  J. VanderBerg 《水文研究》2014,28(25):6038-6053

Supraglacial channels are an important mechanism for surface water transport over the ablation zone of western Greenland. The first assessment of the spatio‐temporal distribution of surface melt channels and their relationship to supraglacial lakes over the Jakobshavn Isbræ region of Western Greenland was analysed using Landsat Enhanced Thematic Mapper Plus panchromatic images during the 2007 melt season. A total of 1188 melt channels were delineated and show an increase in the number of melt channels throughout the season, reaching a peak on 9 August. Water‐filled melt channels advanced to a maximum elevation of 1647 m on 9 August and attained a minimum average slope of 0.009 on 8 July. The ablation zone demonstrates two hydrologic modes, where crevasse and moulin terminating channels dominate at elevations <800 m and higher‐order channel networks >800 m. Development of higher‐order networks is interrupted by flow divergence due to partitioning of melt water into vertical infiltration through moulins and crevasse fields prevalent at lower elevations. Tributary and connector networks between 800 and 1200 m in elevation are correlated with fewer lake occurrences, lower surface velocities (~50 m a^?1), and ice flow dominated by internal deformation over basal sliding. High‐order channels are associated with lake basins that exceed melt water storage capacity. Evolution of channel networks is coupled to changes in melt water production, runoff, and ice dynamics with implication for the englacial and subglacial environments. © 2013 The Authors. Hydrological Processes Published by John Wiley & Sons, Ltd.  相似文献   

Benchmark on the numerical simulations of the hydrodynamic and morphodynamic evolution of tidal channels and tidal inlets     

N. Tambroni  C. Ferrarin  A. Canestrelli 《Continental Shelf Research》2010

A correct understanding of the hydrodynamics and morphodynamics of tidal basins is of fundamental importance for the fate of the Venice Lagoon, Italy. If on one hand, the development of sophisticated numerical models is called for in order to reproduce the complexity of the mechanisms governing the morphodynamic evolution of many natural environments, including lagoons, on the other hand, a clear knowledge of the reliability and limits of the results provided by these models is crucial in order to establish the condition under which they can be safely applied. To this aim, researchers involved in numerical modeling in the framework of the recent Corila research programmes, agreed to perform an accurate comparison of results provided by three different numerical models, applying them to the test case offered by the experimental investigations performed under controlled conditions by Tambroni et al. (2005a). Here, we consider the following numerical models: (i) a 2D finite element hydrodynamic model coupled with a 2D finite volume morphodynamic model (5 and 3); (ii) a 2D finite element morphodynamic model (Ferrarin et al., 2008); (iii) a 2D depth-averaged model for the inlet region, coupled with a 1D model for the channel (Tambroni et al., 2005b). A first set of simulations concerns the fixed bed case and shows that all the models provide similar results: in particular, they are able to predict the observed free surface oscillations satisfactorily, while comparison with the measured velocity field is less satisfactory. Moreover, as far as the flow field at the inlet is concerned, the models describe accurately the potential flow into the channel during the flood phase, while they are not able to adequately reproduce the occurrence of the fine structure of the shear layers shed by the inlet edges during the ebb phase. This limit is related to the shallow water character of the models. As for the morphodynamics, the long term equilibrium configurations of the bottom of the channel and of the near inlet region show qualitative agreement with the experimental observations, although in this case the differences between the results provided by the distinct numerical approaches are more marked.  相似文献   

Sediments and water fluxes in a muddy coastline: interplay between waves and tidal channel hydrodynamics     

S. Fagherazzi  A. M. Priestas 《地球表面变化过程与地形》2010,35(3):284-293

Tidal channels are ubiquitous in muddy coastlines and play a critical role in the redistribution of sediments, thus dictating the general evolution of intertidal landforms. In muddy coastlines, the morphology of tidal channels and adjacent marshes strongly depends on the supply of fine sediments from the shelf and on the resuspension of sediments by wind waves. To investigate the processes that regulate sediment fluxes in muddy coastlines, we measured tidal velocity and sediment concentration in Little Constance Bayou, a tidal channel in the Rockefeller State Wildlife Refuge, Louisiana, USA. The tidal measurements were integrated with measurements of wave activity in the bay at the mouth of the channel, thus allowing the quantification of feedbacks between waves and sediment fluxes. Results indicate that the sediment concentration in the channel is directly related to the wave height in the adjacent bay during flood and high slack water, whereas the concentration during ebb depends on local channel velocity. Moreover, the sediment flux during ebb is of the same order of magnitude as the sediment flux during the previous flood, indicating that only a small fraction of transported sediments are stored in the marsh during a tidal cycle. Finally, very low tides, characterized by high ebb velocities, export large volumes of sediment to the ocean. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Statistical characteristics of flow as indicators of channeling in heterogeneous porous and fractured media     

R. Le Goc  J.-R. de Dreuzy  P. Davy 《Advances in water resources》2010

We introduce two new channeling indicators D_ic and D_cc based on the Lagrangian distribution of flow rates. On the basis of the participation ratio, these indicators characterize the extremes of both the flow-tube width distribution and the flow rate variation along flow lines. The participation ratio is an indicator biased toward the larger values of a distribution and is equal to the normalized ratio of the square of the first-order moment to the second-order moment. Compared with other existing indicators, they advantageously provide additional information on the flow channel geometry, are consistently applicable to both porous and fractured media, and are generally less variable for media generated using the same parameters than other indicators. Based on their computation for a broad range of porous and fracture permeability fields, we show that they consistently characterize two different geometric properties of channels. D_ic gives a characteristic scale of low-flow zones in porous media and a characteristic distance between effectively flowing structures in fractured cases. D_cc gives a characteristic scale of the extension of high-flow zones in porous media and a characteristic channel length in fractured media. D_ic is mostly determined by channel density and permeability variability. D_cc is, however, more affected by the nature of the correlation structure like the presence of permeability channels or fractures in porous media and the length distribution in fracture networks.  相似文献