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1.
Diandong Ren 《Central European Journal of Geosciences》2010,2(2):83-102
Based on a 2-layer land surface model, a rather general variational data assimilation framework for estimating model state variables is developed. The method minimizes the error of surface soil temperature predictions subject to constraints imposed by the prediction model. Retrieval experiments for soil prognostic variables are performed and the results verified against model simulated data as well as real observations for the Oklahoma Atmospheric Surface layer Instrumentation System (OASIS). The optimization scheme is robust with respect to a wide range of initial guess errors in surface soil temperature (as large as 30 K) and deep soil moisture (within the range between wilting point and saturation). When assimilating OASIS data, the scheme can reduce the initial guess error by more than 90%, while for Observing Simulation System Experiments (OSSEs), the initial guess error is usually reduced by over four orders of magnitude. Using synthetic data, the robustness of the retrieval scheme as related to information content of the data and the physical meaning of the adjoint variables and their use in sensitivity studies are investigated. Through sensitivity analysis, it is confirmed that the vegetation coverage and growth condition determine whether or not the optimally estimated initial soil moisture condition leads to an optimal estimation of the surface fluxes. This reconciles two recent studies. With the real data experiments, it is shown that observations during the daytime period are the most effective for the retrieval. Longer assimilation windows result in more accurate initial condition retrieval, underlining the importance of information quantity, especially for schemes assimilating noisy observations. 相似文献
2.
为研究观测资料稀少情况下土壤质地及有机质对土壤水分同化的影响,发展了集合卡尔曼平滑(Ensemble Kalman Smooth, EnKS)的土壤水分同化方案。利用黑河上游阿柔冻融观测站2008年6月1日至10月29日的观测数据,使用EnKS算法将表层土壤水分观测数据同化到简单生物圈模型(Simple Biosphere Model 2, SiB2)中,分析不同方案对土壤水分估计的影响,并与集合卡尔曼滤波算法(EnKF)的结果进行比较。研究结果表明,土壤质地和有机质对表层土壤水分模拟结果影响最大而对深层的影响相对较小;利用EnKF和EnKS算法同化表层土壤水分观测数据,均能够显著提高表层和根区土壤水分估计的精度,EnKS算法的精度略高于EnKF且所受土壤质地和有机质的影响小于EnKF;当观测数据稀少时,EnKS算法仍然可以得到较高精度的土壤水分估计。 相似文献
3.
The present study assesses the use of support vector machine regression to predict the variation of resilient modulus with post-compaction moisture content of soils commonly encountered in Oklahoma, Pennsylvania and Wisconsin. Results show the prediction model using the support vector regression (SVR) approach is a function of degree of saturation, moisture content and plasticity index. The developed model is compared to current models in the literature. Results indicate the proposed SVR model gives more accurate values than current regression models. This model will better predict changes in the bearing capacity of pavements due to seasonal variations of moisture content. 相似文献
4.
用VIC模型模拟黑河上游流域水分和能量通量的时空分布 总被引：3，自引：3，他引：0
受地形起伏影响, 山区流域的水分和能量通量时空分布差异很大. 利用水文模型VIC (variable infiltration capacity)对黑河上游流域的水文和能量时空分布进行了模拟, 并通过观测对模拟结果进行了验证. 结果表明:VIC模型能够较合理地模拟研究区径流过程, 对净辐射的计算也较准确, 模拟得到的部分水分通量和能量通量(感热、潜热和土壤热通量)在趋势上较一致, 但在数量上存在偏差. 积雪过程对研究区的水文和能量循环有重要影响, VIC模型对积雪的模拟偏差较大, 导致了每年4月左右的模拟径流偏低, 也没有模拟出积雪融化导致的土壤含水量上升; 同时, 积雪模拟的不准确也明显影响到能量通量的模拟. 在研究区, 土壤水分变化受土壤冻融影响明显, VIC模型对气温较高、不发生冻融过程的7-9月土壤水分变化模拟较好, 但是在其他月份, 对积雪及表层土壤消融导致的土壤水分迅速增加和土壤冻结导致的土壤水分迅速减少两个过程的模拟比较差; VIC模型能够给出水分和能量各通量的时空分布, 较好地揭示研究流域各个通量的空间异质性及相互影响. 相似文献
5.
加强塔里木河阿拉尔生态系统综合监测 总被引：3，自引：0，他引：3
塔里木河流域是我国最大的内陆河流域,流域总面积102×104km2,水资源总量为429×108m3,水资源相对贫乏,生态环境十分脆弱.阿拉尔生态系统监测站位于阿克苏河、叶尔羌河、和田河三河和塔里木河交汇处的肖夹克,是平原区重要区域代表站,其生态环境直接关系着塔里木河干流上、中、下游生态和环境安全.查阅模清该区域的生态环境的基本特点、变化规律和演变趋势,对指导塔里木河综合治理,以及当地社会经济和谐发展极其重要.该站始建于1996年7月,监测项目有水文气象;地下水动态;乔、灌、草;土壤、水盐;沙漠化动态5类监测项目.野外监测设施有河道水文断面、气象观测场、第一监测剖面(长22 km).除水文气象监测项目在综合系统监测站附近外,其余4个监测项目均在第一剖面进行. 相似文献
6.
土体含水率监测的线热源法对加热功率要求较高,当热源强度不稳定时,监测结果容易受到影响。为了解决线热源法的不足,提出了土体含水率监测的移动点热源（point
heat source,PHS）法。该方法利用土体热物性与含水率之间的相关性,通过监测土体中PHS的降温规律间接识别含水率。通过数值模拟研究了点热源在含水率均匀分布的土体中的传热规律,根据热源降温曲线的特征,定义了含水率判别指标η,进而建立了含水率与判别指标的拟合关系,并对监测灵敏度的影响因素进行了参数分析。在含水率非均匀分布的土体中开展了点热源降温规律的数值模拟,根据测点降温时程曲线计算含水率判别指标,并利用含水率与判别指标的拟合公式反演含水率分布。结果表明,点热源法反演得到的含水率分布与实际值吻合较好,验证了该方法的理论可行性。通过模型试验进一步验证了该方法的可行性。 相似文献
7.
Celestina Adu-Wusu Ernest K. Yanful Lisa Lanteigne Mike O’Kane 《Geotechnical and Geological Engineering》2007,25(2):215-237
Soil cover systems are widely used for containment of municipal solid waste, hazardous and mine waste, with the objective
of limiting the ingress of precipitation and oxygen. The ability to predict their long-term performance is crucial, as their
failure would result in the release of contaminants to the environment. However, monitoring covers over the long term to derive
the information needed to aid in design is impractical and there are no large-scale covers that have been in use for a long
enough period to generate the data needed. Numerical models have been particularly useful as design tools. To improve their
reliability these models may be calibrated to field data and then used to make long-term predictions of cover performance.
The field performance of two resistive test soil covers on a 20% sloping waste rock platform is predicted using the two-dimensional
soil–atmosphere model Vadose/W. Input data for the model included soil, climate and vegetation data obtained either in the
field or laboratory. Model results were compared to field data to assess the validity of the program. The model reasonably
simulated field response patterns for soil water storage and suction. Divergence between field performance data and model
predictions were significantly influenced by snowmelt, interflow and flow through preferential pathways. 相似文献
8.
Péter Hegedüs Szabolcs Czigány László Balatonyi Ervin Pirkhoffer 《Central European Journal of Geosciences》2013,5(1):97-111
Flash floods are one of the most significant natural hazards of today. Due to the complexity of flash flood triggering factors, to prevent or mitigate flood triggered losses, numeric model based flood forecasting models are capable tools to predict stream water levels. The main goal of the current research was to reproduce two flow peaks with the HEC-HMS rainfall-runoff model and test the model sensitivity for various input parameters. To obtain sufficient input data, we monitored soil depth, maximum infiltration rate, soil moisture content, rainfall, time of concentration and flow. To obtain input data, parameters were calculated, measured in the Sás Valley experimental watershed (SW Hungary) or optimized with the built in function of the HEC-HMS. Soil moisture was monitored in the 1.7 km2 pilot catchment over the period between September 2008 and September 2009. HEC-HMS had a good performance reproducing the two events, however simulated flow time series are highly influenced by the antecedent soil moisture, infiltration rate and canopy storage. Outflow modeled data were verified for two flood events (June 4, 2008 and July 9, 2009). The HEC-HMS was over-sensitive for input soil moisture and with increasing input rainfall and increasing outflow, larger simulation errors were observed. 相似文献
9.
A new monitoring station for debris flows in the European Alps: first observations in the Gadria basin 总被引：1，自引：0，他引：1
F. Comiti L. Marchi P. Macconi M. Arattano G. Bertoldi M. Borga F. Brardinoni M. Cavalli V. D’Agostino D. Penna J. Theule 《Natural Hazards》2014,73(3):1175-1198
Debris-flow monitoring in instrumented areas is an invaluable way to gather field data that may improve the understanding of these hazardous phenomena. A new experimental site has been equipped in the Autonomous Province of Bozen-Bolzano (Eastern Alps, Italy) for both monitoring purposes and testing early warning systems. The study site (Gadria basin) is a 6.3 km2 catchment subjected to frequent debris flows. The monitoring system in the Gadria basin consists of rain gauges, radar sensors, geophones, video cameras, piezometers and soil moisture probes. Transmission of data and alerts from the instruments exploits in part radio technology. The paper presents the data gathered during the first three years of activity, with two debris-flow events recorded at the station varying in magnitude and characteristics, and discusses the perspectives of debris-flow monitoring and related research. 相似文献
10.
The performance of several soil constitutive models was evaluated by comparing experimental results and simulated behavior of a medium plasticity clay. Input parameters for the soil constitutive models were obtained from triaxial compression and extension tests on normally and overconsolidated medium plasticity clay. The soil models employed for this study were the Cam Clay, Modified Cam Clay, 3-SKH, and S-CLAY1 models. In order to investigate the influence of some of the input parameters on the performance of the models, sensitivity analyses were also performed. The comparisons demonstrate that the Cam Clay model was able to predict the normally consolidated compressive behavior of medium plasticity clay. Both 3-SKH and Cam Clay models were able to produce acceptable predictions for stress?Cstrain and stress path behavior for overconsolidated compression of the soil. The 3-SKH model did not perform satisfactorily for predicting pore pressure variations, while the Cam Clay model demonstrated fairly acceptable predictions. For the normally consolidated reduced extension test, the Modified Cam Clay and S-CLAY1 models performed better than the Cam Clay and 3-SKH models in predicting the stress?Cstrain curve, pore pressure variations, and stress path. 相似文献
11.
Soil erosion is a serious environmental problem in Indravati catchment. It carries the highest amount of sediments compared
with other catchments in India. This catchment spreading an area of 41,285 km2 is drained by river Indravati, which is one of the northern tributaries of the river Godavari in its lower reach. In the
present study, USLE is used to estimate potential soil erosion from river Indravati catchment. Both magnitude and spatial
distribution of potential soil erosion in the catchment is determined. The derived soil loss map from USLE model is classified
into six categories ranging from slight to very severe risk depending on the calculated soil erosion amount. The soil erosion
map is linked to elevation and slope maps to identify the area for conservation practice in order to reduce the soil loss.
From the model output predictions, it is found that average erosion rate predicted is 18.00 tons/ha/year and sediment yield
at the out let of the catchment is 22.30 Million tons per annum. The predicted sediment yield verified with the observed data. 相似文献
12.
Mountainous areas surrounding the Campanian Plain and the Somma-Vesuvius volcano (southern Italy) are among the most risky areas of Italy due to the repeated occurrence of rainfall-induced debris flows along ash-fall pyroclastic soil-mantled slopes. In this geomorphological framework, rainfall patterns, hydrological processes taking place within multi-layered ash-fall pyroclastic deposits and soil antecedent moisture status are the principal factors to be taken into account to assess triggering rainfall conditions and the related hazard. This paper presents the outcomes of an experimental study based on integrated analyses consisting of the reconstruction of physical models of landslides, in situ hydrological monitoring, and hydrological and slope stability modeling, carried out on four representative source areas of debris flows that occurred in May 1998 in the Sarno Mountain Range. The hydrological monitoring was carried out during 2011 using nests of tensiometers and Watermark pressure head sensors and also through a rainfall and air temperature recording station. Time series of measured pressure head were used to calibrate a hydrological numerical model of the pyroclastic soil mantle for 2011, which was re-run for a 12-year period beginning in 2000, given the availability of rainfall and air temperature monitoring data. Such an approach allowed us to reconstruct the regime of pressure head at a daily time scale for a long period, which is representative of about 11 hydrologic years with different meteorological conditions. Based on this simulated time series, average winter and summer hydrological conditions were chosen to carry out hydrological and stability modeling of sample slopes and to identify Intensity-Duration rainfall thresholds by a deterministic approach. Among principal results, the opposing winter and summer antecedent pressure head (soil moisture) conditions were found to exert a significant control on intensity and duration of rainfall triggering events. Going from winter to summer conditions requires a strong increase of intensity and/or duration to induce landslides. The results identify an approach to account for different hazard conditions related to seasonality of hydrological processes inside the ash-fall pyroclastic soil mantle. Moreover, they highlight another important factor of uncertainty that potentially affects rainfall thresholds triggering shallow landslides reconstructed by empirical approaches. 相似文献
13.
Ali Lashkari 《国际地质力学数值与分析法杂志》2013,37(8):904-931
Using pile segment analysis, the mobilized shaft resistance of axially loaded nondisplacement piles in sand is investigated here. It is accepted that the shaft capacity of piles constructed in granular soils is highly influenced by the mechanical behavior of soil–structure interfaces forming adjacent the piles skin. Adopting the thin interface layer as a load transfer mechanism, a simple but accurate critical state compatible interface constitutive model is introduced. After evaluation, the interface model in conjunction with the pile segment analysis is applied for the prediction of the shaft resistance mobilized in nondisplacement piles. The proposed approach takes into account the influences of pile diameter and surface roughness together with the effects of the surrounding soil density and stiffness on the mobilized shaft resistance. The performance of the proposed method is verified by comparing its predictions with the experimental data of various model piles covering wide ranges of length, diameter, roughness, and surrounding soil properties. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
14.
Simulation of nitrogen and phosphorus loads in the Dongjiang River basin in South China using SWAT 总被引：1，自引：0，他引：1
Population growth, urbanization, and intensified agriculture have resulted in mobilization of nitrogen and phosphorus, which
is the main cause of river water quality deterioration. Environmental regulation has expedited the necessity for agricultural
producers to design and implement more environmentally suitable practices. Therefore, there is a need to identify critical
nutrients and their loss/transport potential. Watershed model can be used to better understand the relationship between land
use activities/management and hydrologic processes/water quality changes that occur within a watershed. The objective of the
study is to test the performance of the SWAT model and the feasibility of using this model as a simulator of water flow and
nitrogen and phosphorus yields over the Dongjiang River basin in South China.
Spatial data layers of land slope, soil type, and land use were combined with geographic information system (GIS) to aid in
creating model inputs. The observed streamflow and sediment at Boluo station in the Dongjiang River basin were used to calibrate
and validate the model. Time series plots and statistical measures were used to verify model predictions. Predicted values
generally matched well with the observed values during calibration and validation (R
2≥0.6 and Nash-Suttcliffe Efficiency ≥0.5) except for underestimation of sediment peaks and overestimation of sediment valleys
at Boluo. This study shows that SWAT is able to predict streamflow, sediment generation, and nutrients transport with satisfactory
results. 相似文献
15.
Arsalan Ghorbanian Mahmod Reza Sahebi Ali Mohammadzadeh 《Comptes Rendus Geoscience》2019,351(4):332-339
This study suggests a novel approach to the retrieval of soil surface parameters using a single-acquisition single-configuration synthetic-aperture radar (SAR) system. Soil surface parameters such as soil moisture and surface roughness are key elements for many environmental studies, including Earth surface water cycles, energy exchange, agriculture, and geology. Remote sensing techniques, especially SAR data, are commonly used to retrieve such soil surface parameters over large areas. Several backscattering models have been proposed for soil surface parameters retrieval from SAR data. However, commonly, these backscattering models require multi configuration SAR data, including multi-polarization, multi-frequency, and multi-incidence angle. Here we propose a methodology that employs single-acquisition single-configuration SAR data for the retrieval of soil surface parameters. The originality is to use single-acquisition single-configuration SAR data to retrieve the soil surface parameters using an optimization approach by the genetic algorithm (GA); we have used the modified Dubois model (MDM) in HH polarization as the backscattering model. Three HH polarization and C band data sets from Quebec (Radarsat-1), Ontario (SIR-C), and Oklahoma (AIRSAR) were analyzed. The retrieved values of soil moisture and soil surface roughness were then compared to ground truth measurements with corresponding parameters. We employed diverse criteria, including the mean absolute error (MAE), the root mean square error (RMSE), the coefficient of performance (CP), and the correlation coefficient to investigate the performance of the proposed methodology. This analysis suggests the capability of the GA for the retrieval of soil surface parameters. Based on our findings, this method presents a viable alternative approach to the retrieval of soil surface parameters when only single-acquisition single-configuration SAR data is available. 相似文献
16.
利用1998年7月6日至8月9日青藏高原GAME-Tibet试验区MS3608站点的4cm、20cm和100cm的土壤水分观测数据同化SiB2模型输出的表层、根区和深层土壤水分,探讨了一个基于集合卡尔曼滤波和简单生物圈模型的单点土壤水分同化方案。分析和评价了集合大小、同化周期、模型误差、背景场误差以及观测误差对同化系统性能的影响。结果表明:①增加集合数目可以减小土壤水分同化系统的误差,但同时又降低了运行效率;②对于集合卡尔曼滤波,初始场的估计是否准确对同化系统性能影响不大;③模型误差和观测误差的准确估计可以提高土壤水分的估计精度;④利用数据同化的方法对土壤水分的估计有显著提高。 相似文献
17.
Sarat Kumar Das Pijush Samui Akshaya Kumar Sabat T. G. Sitharam 《Environmental Earth Sciences》2010,61(2):393-403
The swelling pressure of soil depends upon various soil parameters such as mineralogy, clay content, Atterberg’s limits, dry
density, moisture content, initial degree of saturation, etc. along with structural and environmental factors. It is very
difficult to model and analyze swelling pressure effectively taking all the above aspects into consideration. Various statistical/empirical
methods have been attempted to predict the swelling pressure based on index properties of soil. In this paper, the computational
intelligence techniques artificial neural network and support vector machine have been used to develop models based on the
set of available experimental results to predict swelling pressure from the inputs; natural moisture content, dry density,
liquid limit, plasticity index, and clay fraction. The generalization of the model to new set of data other than the training
set of data is discussed which is required for successful application of a model. A detailed study of the relative performance
of the computational intelligence techniques has been carried out based on different statistical performance criteria. 相似文献
18.
土壤水分与干旱遥感研究的进展与趋势 总被引：47，自引：2，他引：47
对土壤水分和干旱遥感监测的国内外发展情况进行了回顾,依据土壤水分和干旱遥感监测的原理,围绕着可见光与近红外、热红外、微波光谱波段的使用,分别以土壤和植被为观测对象,对国内外土壤水分与干旱遥感现状与发展趋势进行讨论。重点对微波遥感土壤湿度的算法发展和研究趋势进行了较详细的论述。在总结国内外土壤水分遥感监测研究实验中所用过的方法与原理的基础上,对目前遥感监测土壤水分研究领域的重点、难点和未来的发展方向进行了评述。土壤水分遥感监测是一个复杂的间接过程,波段及变量选择、传感器的性能等因素对土壤水分监测是至关重要的,土壤的各种理化性状、地形的分异作用以及气候变化和人为的土壤管理措施对土壤水分均有不同的影响,地表特征与土壤水分也存在着一定的相关性。改进的热惯量法和作物缺水指数法是当前土壤水分遥感监测中较为成熟的方法。GIS技术的广泛应用、土壤水分遥感监测模型的优化。微波遥感的应用将是该领域的重点研究方向。 相似文献
19.
对滑坡体土壤含水率进行长期和连续的监测,有利于对滑坡体的变形分析和安全预警。为了提高频域反射分析法（FDR法）测量土壤含水率的精度,通过室内标定和现场标定相结合的方式,对使用FDR法测定野外现场滑坡土壤含水率进行了标定。通过对比分析FDR法和烘干法测得的土壤含水率数据,探讨电压信号、含水率、绝对误差和相对误差之间的对应关系,并建立函数模型。试验结果表明:FDR法测定的土壤含水率较烘干法偏高;通过线性、多次曲线及指数形式对试验数据进行拟合和回归分析,最终确定四次曲线作为标定方式,标定后测得的土壤含水率精度明显提高,平均绝对误差可控制在2%以内。该方法可用于类似条件下FDR法测定土壤含水率的标定。 相似文献
20.
The Red River valley experienced one of the worst floods in 1997 because of above average snow accumulation, a blizzard during
the snowmelt period and high soil moisture conditions. A three-dimensional hydrodynamic modeling system is used to study the
impact of the flood on the circulation and contaminant dispersion in Lake Winnipeg. To assess the model performance, we first
simulate the circulation and temperature distribution of the lake in 2007 and compare the model results with the observations
made in the lake during this period. The model showed considerable skill in reproducing the thermal structure, currents and
water levels. The accuracy of these simulations suggests that the model is capable of describing flow and transport of material
required for detailed water quality simulations during the flood. During the flood event, Red River plume movement is primarily
controlled by the wind-driven currents. The winds from the north confined the plume to a small area near the river mouth. 相似文献