This study aims at evaluating the uncertainty in the prediction of soil moisture (1D, vertical column) from an offline land surface model (LSM) forced by hydro-meteorological and radiation data. We focus on two types of uncertainty: an input error due to satellite rainfall retrieval uncertainty, and, LSM soil-parametric error. The study is facilitated by in situ and remotely sensed data-driven (precipitation, radiation, soil moisture) simulation experiments comprising a LSM and stochastic models for error characterization. The parametric uncertainty is represented by the generalized likelihood uncertainty estimation (GLUE) technique, which models the parameter non-uniqueness against direct observations. Half-hourly infra-red (IR) sensor retrievals were used as satellite rainfall estimates. The IR rain retrieval uncertainty is characterized on the basis of a satellite rainfall error model (SREM). The combined uncertainty (i.e., SREM + GLUE) is compared with the partial assessment of uncertainty. It is found that precipitation (IR) error alone may explain moderate to low proportion of the soil moisture simulation uncertainty, depending on the level of model accuracy—50–60% for high model accuracy, and 20–30% for low model accuracy. Comparisons on the basis of two different sites also yielded an increase (50–100%) in soil moisture prediction uncertainty for the more vegetated site. This study exemplified the need for detailed investigations of the rainfall retrieval-modeling parameter error interaction within a comprehensive space-time stochastic framework for achieving optimal integration of satellite rain retrievals in land data assimilation systems. 相似文献
In engineering projects such as tunnels, dams, foundations, and slope stability, the strength and elastic properties of the intact rock affect both the project design and the construction operation. It is sometimes expensive and time consuming to perform direct tests to evaluate the engineering properties (such as strength, modulus of elasticity, and Poisson's ratio) of the intact rock. The purpose of this work is to investigate the relationships between the engineering properties of the intact rock and the different types of hardness (Schmidt, shore scleroscope, abrasion, and total hardness), which are relatively cheap and easy to evaluate. In this study, dolomite, dolomitic limestone, and shale rocks were used. For simplicity, linear statistical analyses were performed. The results show that there are good relationships between the engineering properties of the intact rock and its hardness. Also, the results of this study are compared well with the results obtained by other investigators conducted on different types of rocks. 相似文献
The systematic decline of in situ networks for hydrologic measurements has been recognized as a crucial limitation to advancing
hydrologic monitoring in medium to large basins, especially those that are already sparsely instrumented. As a collective
response, sections of the hydrologic community have recently forged partnerships for the development of space-borne missions
for cost-effective, yet global, hydrologic measurements by building upon the technological advancements since the last two
decades. In this article, we review the state-of-the-art on flood monitoring in medium and large ungauged basins where satellite
remote sensing can facilitate development of a cost-effective mechanism. We present our review in the context of the current
hydro-political situation of flood monitoring in flood-prone developing nations situated in international river basins (IRBs).
Given the large number of such basins and the difficulty in acquisition of multi-faceted geophysical data, we argue that the
conventional data-intensive implementation of physically based hydrologic models that are complex and distributed is time-consuming
for global assessment of the utility of proposed global satellite hydrologic missions. A more parsimonious approach is justified
at the tolerable expense of accuracy before such missions begin operation. Such a parsimonious approach can subsequently motivate
the identified international basins to invest greater effort in conventional and detailed hydrologic studies to design a prototype
flood forecasting system in an effort to overcome the hydro-political hurdles to flood monitoring. Through a modeling exercise involving an open-book watershed concept, we demonstrate the value of a parsimonious approach
in understanding the utility of NASA-derived satellite rainfall products. It is critical now that real-world operational flood
forecasting agencies in the under-developed world come forward to collaborate with the research community in order to leverage
satellite rainfall data for greater societal benefit for inhabitants in IRBs. 相似文献
Although hydraulic fracturing has been massively studied and applied as a key technique to enhance the gas production from tight formations, some problems and uncertainties exist to accurately predict and analyze the fracture behavior in complex reservoirs, especially in the naturally fractured reservoirs like shale reservoirs. This paper presents a full 3D numerical model (FLAC3D) to study hydraulic fracturing behavior under the impact of preexisting orthogonal natural fractures. In this numerical model, the hydraulic fracture propagation direction is assumed perpendicular to the minimum principal stress and activated only by tensile failure, whereas the preexisting natural fractures can be activated by tensile or shear failure or a combination of them, and only tensile failure can open the natural fracture as well. The newly developed model was used to study the impact of preexisting orthogonal natural fractures on hydraulic fracturing behavior, based on a multistage hydraulic fracturing operation in a naturally fractured reservoir from the Barnett Shale formation, northwest of Texas in USA. In this multistage operation, two more representative stages, i.e., stage 1 with a relatively large horizontal stress anisotropy of 3.3 MPa and stage 4 with a comparatively small one of 1.3 MPa, were selected to conduct the simulation. Based on the numerical results, one can observe that the interaction between hydraulic and natural fracture is driven mainly by induced stress around fracture tip. Besides, the horizontal stress anisotropy plays a key role in opening the natural fracture. Thus, no significant opened fracture is activated on natural fracture in stage 1, while in stage 4 an opened fracture invades to about 90 m into the first natural fracture. Conversely, the hydraulic fracture length in stage 1 is much longer than in stage 4, as some fluid volume is stored in the opened natural fracture in stage 4. In this work, the shear failure on natural fractures is treated as the main factor for inducing the seismic events. And the simulated seismic events, i.e., shear failure on natural fractures, are very comparable with the measured seismic events.
Previous experiments demonstrated that exposure of mummichog to cadmium (Cd) in combination with benzo[a]pyrene (BaP) caused a higher mortality than would be expected from simple additive effects. Experiments are described here that investigated whether BaP exposure inhibits the induction of metallothionein (MT), a major detoxifying protein for Cd, or if reactive BaP metabolites compete with Cd for binding sites on MT. Fish were injected with or without BaP (18 mg/kg) in combination with a low (1 mg/kg) or high (3.2 mg/kg) dose of Cd, and in one treatment BP was dosed 4 days after Cd. The results showed a rapid induction of MT to 1.5 mg/g wet weight liver, 1 day after injecting the low Cd dose. Simultaneous BaP exposure significantly delayed the induction of MT, for both low and high Cd doses, and BaP temporarily lowered the induced MT concentration when dosed 4 days after induction by Cd. To test if binding of BaP metabolites to MT reduces the detoxification potential for Cd, microsomes of CYP1A-induced fish were incubated with MT and radiolabeled BaP. Active metabolism of BaP was observed by high-performance liquid chromatography analysis, but no association of BaP metabolites with MT was found. Neither could this be demonstrated in vivo, in liver MT isolated from mummichog dosed with 3H-BaP and Cd. These results suggest that increased toxicity of Cd in combination with BaP exposure is likely to be caused by inhibited MT synthesis, rather than by interference of BaP metabolites with Cd binding on MT. 相似文献
A slight variation in the magnitude of stream flow can have a substantial influence on the development of water resources. The Songhua River Basin (SRB) serves as a major grain commodity basin and is located in the northeastern region of China. Recent studies have identified a gradual decrease in stream flows, which presents a serious risk to water resources of the region. It is therefore necessary to assess the variation in stream flow and to predict the future of stream flows and droughts to make a comprehensive plan for agricultural irrigation. The simulation of monthly stream flows and the investigation of the influence of climate on the stream flow in the SRB were performed by utilizing the Integrated Water Evaluation and Planning (WEAP) tool coupled with observed precipitation data, as well as the Asian Precipitation-Highly-Resolved Observational Data Integration towards Evaluation of Water Resources (APHRODITE’s Water Resources) precipitation product. The Nash–Sutcliffe coefficient (NSC) was used to assess the WEAP efficiency. During the time of calibration, NSC was obtained as 0.90 and 0.67 using observed and APHRODITE precipitation data, respectively. The results indicate that WEAP can be used effectively in the SRB. The application of the model suggested a maximum decline in stream flow, reaching 24% until the end of 21st century under future climate change scenarios. The drought indices (standardized drought index and percent of normal index) demonstrated that chances of severe to extreme drought events are highest in 2059, 2060 and 2085, while in the remaining time period mild to moderate drought events may occur in the entire study area. The drought duration, severity and intensity for the period of 2011–2099 under all scenarios, [(A1B: 12, ? 1.55, ? 0.12), (A2: 12, ? 1.41, ? 0.09), (max. wetting and warming conditions: 12, ? 1.37, ? 0.11) and (min. wetting and warming conditions: 12, ? 1.69, ? 0.19)], respectively. 相似文献
Lining contact pressure and ground deformation of Raghadan transportation tunnel (Amman, Jordan) were investigated. The tunnel
is 1.1 km in length and 13.5 m in diameter. This study was intended to integrate useful relations among the widely used rock
classification system (RMR: rock mass rating), Hoek–Brown classification, and lining-ground interaction. The materials encountered
along the tunnel alignment were limestone, dolomatic limestone, marly limestone, dolomite, and sillicified limestone. The
ground conditions along the tunnel alignment including bedding planes, joint sets and joint conditions, rock quality, water
flow, and rock strength were evaluated based on the drilled boreholes and rock exposures. Elasto-plastic finite element analyses
were conducted to study the effect of rock mass conditions and tunnel face advance on the behavior of lining-ground interaction.
The results of the analyses showed that lining contact pressure decreases linearly with the increase in RMR value. Also the
results showed that tunnel lining contact pressure and crown inward displacement decreases with the increase in the unsupported
distance (distance between tunnel face and the end of the erected lining). Ground displacement above the tunnel crown was
found to be increases in an increasing rate with the decrease in the depth above the crown. This displacement was also found
to be affected by the RMR value and the unsupported distance. 相似文献