bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sensor Principles and Remote Sensing Techniques
Authors: England Anthony W 
Published: April 2006

AbstractModel‐derived estimates of water stored in the upper few meters of soil, in vegetation, and in snow packs are the objectives of a new satellite microwave remote sensing technology. The most mature of the alternatives, this technology will use a combination of longer wavelength satellite microwave brightness observations and Soil Vegetation Atmosphere Transfer (SVAT) models, forced by solar and thermal radiation and by weather, to produce a near‐daily global field of stored water. While the near‐daily temporal resolution is a unique strength for hydrometeorology, its likely spatial resolution of tens of kilometers is a serious weakness for land‐surface hydrology. This article is intended as a review of the concept and the investigations that have contributed to it. It also includes brief surveys of some technologies, like aperture synthesis radiometry and combined active passive sensing, that are being explored to improve spatial resolution.
Estimation of Precipitation Using Ground‐Based, Active Microwave Sensors
Authors: Steiner Matthias 
Published: April 2006

AbstractGround‐based radar measurements have provided a wealth of information about precipitation systems, how they evolve and organize themselves. Advances in Doppler and polarimetric radar technology, in particular, have yielded unprecedented insight into the dynamics and microphysics of precipitation formation. This paper summarizes the basic components and principals of radar measurements, and discusses how radar can be used to identify different types of precipitation particles as well as recognize nonmeteorological radar echoes, and obtain quantitative precipitation estimates.
Estimation of Surface Insolation
Authors: Pinker Rachel T 
Published: April 2006

Abstract
The incoming solar radiation from the sun (insolation) that reaches the Earth's surface (about 50% of that emitted from the sun) determines the exchange of energy between the land and the atmosphere and consequently, controls climate and climate change. Environmental satellites are considered useful tools for providing information on surface radiative fluxes at various temporal and spatial scales, improving estimation of terrestrial water and energy storage. For several years now, observations from satellites have been used to obtain information on the various components of atmospheric and surface radiative fluxes, initially, retrospectively, and more recently, operationally. In this paper, discussed are the needs for information on radiative fluxes in hydrological applications, methodologies for obtaining such information by methods of remote sensing, accuracy of such estimates, and current status of data availability. Examples of applications in hydrological studies and climate research are provided, and links to international activities and future prospects are indicated.
Estimation of Water Vapor and Clouds Using Microwave Sensors
Authors: Crewell Susanne 
Published: April 2006

Abstract
Both water vapor and clouds play important roles in the energy and water cycle, and their accurate observation is required. Several techniques to measure water vapor distributions and cloud properties exist with each of them having their specific limitations. Measurements in the infrared and visible spectral range are strongly influenced by clouds and cannot be used to observe water vapor under cloudy conditions. Information about cloud properties is limited to the cloud top and base depending on the use of a space‐ or ground‐based system. Microwave techniques can provide information about water vapor and liquid water also under cloudy conditions, but satellite observations are limited to retrievals above ocean surfaces. Therefore, the combination of different measurements needs to be further pursued in order to gain insight into the three‐dimensional distribution of water vapor and cloud properties as well as their temporal variability. Recently, information about the cloud vertical structure including the occurrence of multiple cloud layers and cloud overlap has become available at a few ground‐reference sites through sensor synergy including active and passive instruments. In the near future, the first global measurements of this kind will be carried out from satellites.
Estimation of Surface Temperature and Surface Emissivity
Authors: Schmugge Thomas J 
Published: April 2006

Abstract
Measurements of thermal radiation at infrared wavelengths (7 to 14 µm) yield much information about the land surface. The primary use of these observations is for surface temperature determination as the emissivity is usually close to one. For this purpose, it is fortuitous that the peak in the thermal emission occurs in an atmospheric transmission window. In addition, there are variations in the emissivity of minerals and soils in the 7–14 µm region, which can be interpreted for identification purposes. These also produce significant emissivity variations for arid or desert areas, where there are considerable exposed soils and rocks. The emissivity for vegetative canopies has been found to be close to one, with little spectral variation. Applications of the derived surface temperature to study the surface energy balance and to estimate the energy fluxes from the land surface are discussed.
Estimation of Surface Freeze–Thaw States Using Microwave Sensors
Authors: McDonald Kyle C , Kimball John S 
Published: April 2006

Abstract
The transition of the landscape between predominantly frozen and nonfrozen conditions in seasonally frozen environments impacts climate, hydrological, ecological, and biogeochemical processes profoundly. Satellite microwave remote sensing is uniquely capable of detecting and monitoring a range of related biophysical processes associated with the measurement of landscape freeze/thaw status. This chapter provides an overview of the development, physical basis, current techniques, and selected hydrological applications of satellite‐borne microwave remote sensing of landscape freeze/thaw states for the terrestrial cryosphere. Major landscape hydrological processes embracing the remotely sensed freeze/thaw signal include timing and spatial dynamics of seasonal snowmelt and associated soil thaw, runoff generation, and flooding, ice breakup in large rivers and lakes, and timing and length of vegetation growing seasons and associated productivity and trace gas exchange. This chapter also summarizes the physical principles of microwave sensitivity to landscape freeze/thaw state, recent progress in applying these principles towards satellite remote sensing of freeze/thaw processes over broad regions, and potential for future global monitoring of this significant phenomenon of the global cryosphere.
Estimation of Surface Soil Moisture Using Microwave Sensors
Authors: Jackson Thomas J 
Published: April 2006

Abstract
Soil moisture has been particularly difficult to measure and map using conventional ground‐based point sampling. Microwave remote sensing–based soil moisture retrieval has been demonstrated using tower and aircraft instruments. The translation of this approach to satellites and the implementation in hydrologic applications has been limited by both the technology and the satellite systems that were available. Recent developments in both science and associated technologies now make the exploitation of the microwave region for soil moisture mapping feasible. A number of new and potential satellite missions are reviewed and evaluated for soil moisture applications.
Estimation of Soil Properties Using HyperspectralVIS/IRSensors
Authors: Huete Alfredo R 
Published: April 2006

AbstractKnowledge of soil properties and processes are crucial to the understanding of the terrestrial hydrologic cycle and the functioning of terrestrial ecosystems. In this paper, we present the current state and potential of hyperspectral remote sensing techniques for quantitative retrieval of soil properties. Remote sensing is used to detect chemical and physical soil properties either (i) directly from the bare soil pixels, (ii) through advanced spectroscopy methods in mixed “soil‐vegetation‐litter” pixels, and (iii) by measurements of the overlying vegetated canopy to infer soil properties and moisture status. Optical‐geometric properties of soil surfaces reveal information on soil physical features, such as soil structure, crusting, and erosion. We also investigate the use of vegetation water indices to infer soil drying and wetting in the soil root zone. We conclude with a discussion on future needs and directions for remote sensing of soil properties.
Estimation of Suspended Sediment and Algae in Water Bodies
Authors: Ritchie Jerry C , Zimba Paul V 
Published: April 2006

Abstract
Remote sensing techniques can be use to monitor water quality parameters (i.e., suspended sediments‐turbidity, chlorophyll, temperature). Optical and thermal sensors on shoreline booms, boats, aircraft, and satellites provide both spatial and temporal information needed to monitor changes in water quality parameters for developing management practices to improve water quality. Recent and planned launches of platforms equipped with improved spectral and spatial resolution sensors should lead to greater use of remote sensing techniques to assess and monitor water quality parameters. Integration of remotely sensed data, GPS, and GIS technologies provides a valuable tool for monitoring and assessing waterways. Remotely sensed data can be used to create a permanent geographically located database to provide a baseline for future comparisons. The integrated use of remotely sensed data, GPS, and GIS will enable consultants and natural resource managers to develop management plans for a variety of natural resource management applications. This review paper identifies current knowledge regarding the assessment of water quality, and identifies promising techniques for high resolution assessment.
Estimation of the Surface Energy Balance
Authors: Su Zhongbo 
Published: April 2006

AbstractRadiation and latent and sensible heating are among the most important processes in land–atmosphere exchanges. Hence, quantitative understanding and accurate estimation of these fluxes at large scales are imperative for research and applications in areas ranging from numerical weather forecast, climate research, water cycle study, to water resources management, sustainable agricultural production, and ecological conservation. Quantitative remote sensing is probably the only efficient and economically viable technology to provide regional to global radiometric observations of several physical quantities that are relevant to the estimation of these fluxes. This article examines the physical principles underlying the radiation and turbulent heating, along with exploring the possibilities and difficulties for estimation of these fluxes using remote sensing measurements. Past efforts, recent progresses are reviewed, and future research needs are identified. In particular, the Surface Energy Balance System(SEBS), recently developed in Wageningen, is introduced and its strengths and weakness are analyzed in view of future space‐borne sensor systems. Several applications derived on the basis of SEBS, including estimation of turbulent heat fluxes, evaporative fraction and actual evaporation, estimation of relative soil moisture, and drought monitoring are discussed.
Estimation of River Discharge
Authors: Dingman S Lawrence , Bjerklie David M 
Published: April 2006

AbstractRiver discharge, the volume flow rate through a river cross section, is perhaps the most important single hydrologic quantity. It is a major link in the global hydrologic and geologic cycles and a critical component of climate, and represents the rate at which nature makes water available for human use and management. In the form of floods, it constitutes one of the most destructive natural hazards. Measurement of river discharge thus provides vital information for science and society. Measurement by conventional ground‐based methods is expensive and is declining globally. Using various combinations of active and passive imagery and sensors mounted on satellites or aircraft, it is possible to obtain direct quantitative information on several hydraulic variables, including channel configuration and the area, width, elevation, and velocity of the water surface. Computations using conventionally obtained data indicate that this information can be used in various combinations with statistical models and topographic information to generate quantitative time‐ and location‐specific estimates of discharge. Thus, it appears feasible to produce useful river‐discharge information via remote sensing, especially for locations that are remote or otherwise difficult to observe conventionally. However, it is likely that this capability will be useful only for relatively large rivers and that, even for these, measurement accuracy will be considerably lower than is possible with ground‐based measurements. Given the scientific and societal importance of river‐discharge observations, and the present discharge‐measurement network and unlikely prospects for its expansion, further development and testing of these approaches, development of concurrent sets of pertinent remotely sensed variables, and a more complete evaluation of the spacing and timing of observations possible with satellite systems is warranted.
Soil Water Flow at Different Spatial Scales
Authors: Hopmans Jan W , Schoups Gerrit 
Published: April 2006

AbstractA major challenge in hydrological sciences is the modeling of flow and transport processes and their measurement across a range of spatial or temporal scales. Such needs arise, for example, when watershed processes must be determined from soil hydrological data collected from a limited number of in situ field measurements or analysis of small soil cores in the laboratory. The scaling problem cannot be solved by simple consideration of the differences in space or timescale, for several reasons. First, spatial and temporal variability in soil hydrological properties create uncertainties when changing between scales. Second, flow and transport processes in vadose zone hydrology are highly nonlinear. As a result, vadose zone properties are nonunique and scale‐dependent, resulting in effective properties that vary across spatial scales and merely serve as calibration parameters in hydrologic models. Therefore, their estimation for heterogeneous materials can only be accomplished using scale‐appropriate measurements and models. We present examples of soil water flow at the pore, local, and regional scales. The inherent complexity of flow in heterogeneous soils, and the need to integrate theory with experiment, requires innovative and multidisciplinary research efforts to overcome limitations imposed by current understanding of scale‐dependent soil water flow and transport processes.
Solute Transport in Soil at the Core and Field Scale
Authors: Vanclooster Marnik , Javaux Mathieu , Vanderborght J 
Published: April 2006

Abstract
A detailed understanding of the flow and transport processes of chemicals in soils is needed to implement effective and efficient soil and water management strategies and to meet the current challenges of sustainable development. The solute transport process is a key process determining the mass flow of chemical substances once they are released in the soil solution. The transport process is a highly nonlinear and space‐time dynamic process for which models are still poorly validated at the larger scale. In this article, we review some recent advances in describing solute transport in soil at the macroscopic core scale, corresponding to the scale of most soil measurement devices, and the pedon scale, corresponding to the scale of a small field. After introducing basic concepts, major problems using the classical Convection Dispersion Equation (CDE) model for describing field‐scale solute transport is presented and alternative modeling concepts are introduced.
Determining Soil Hydraulic Properties
Authors: Durner Wolfgang , Lipsius Kai 
Published: April 2006

AbstractHydraulic properties are required for modeling water and solute transport in unsaturated soils. The bottleneck for the successful application of numerical simulation models lays usually in their parameter estimation requirements. Methods to determine hydraulic properties can be classified into indirect and direct approaches. Indirect methods encompass the estimation of hydraulic properties by pedotransfer functions from more easily measured soil properties, and the prediction of the unsaturated hydraulic conductivity function from thewater retention curve(WRC). In direct methods, observations of flow attributes from laboratory or field experiments are evaluated. This article reviews common methods to estimate the hydraulic conductivity function from the water retention characteristic and various direct measurement techniques in the laboratory and the field. We conclude with an outlook on contemporary developments in measurement techniques, stressing the key role of inverse modeling of experiments to derive optimum hydraulic properties and the importance of a future combination of noninvasive measurement techniques with inverse modeling by stochastic data fusion.
Inverse Modeling of Soil Hydraulic Properties
Authors: Vrugt Jasper A , Dane Jacob H 
Published: April 2006

AbstractNumerical‐simulation models of water flow and solute transport in the vadose zone are important tools in environmental research. The accuracy of predictions with these models heavily relies on accurate estimates of the unsaturated soil hydraulic parameters. Initial attempts on the estimation of the soil hydraulic parameters mainly focused on the use of relatively simple static or steady‐state flow experiments. While these laboratory methods have the advantage of being relatively simple to implement, they are typically time consuming and require restrictive initial and boundary conditions to satisfy the assumptions of the corresponding analytical solutions. Significant advances in computational capabilities in the 1980s have stimulated research on the use of Inverse Modelling (IM) for the estimation of soil hydraulic properties. Parameter estimation using IM accommodates much more flexible experimental conditions than required for the static or steady‐state flow methods, thereby enabling a rapid characterization of the hydraulic properties of the considered soil domain. This article explores the historical development of current perspectives on the identification of a single “best” set of soil hydraulic parameters using IM (thereby effectively neglecting the influence of possible sources of uncertainty on the final parameter estimates), and discusses alternative (Bayesian and multiple‐criteria) parameter estimation strategies which can be used to quantify the uncertainty (probabilistic and multiobjective) associated with the inversely estimated soil hydraulic properties. Throughout this article, we use a classical transient laboratory outflow experiment to further illustrate the various aspects of the IM procedure for estimating the soil hydraulic parameters.
Assessing Uncertainty Propagation through Physically Based Models of Soil Water Flow and Solute Transport
Authors: Brown James D , Heuvelink Gerard B M 
Published: April 2006

AbstractSoil hydrological models are inherently imperfect because they abstract and simplify “real” hydrological patterns and processes. Indeed, an important aim of modeling is to establish the simplest description possible for adequately addressing a particular problem. Also, models are frequently based on input data that are known to be inadequate for some practical purpose. Thus, uncertainties in model outputs originate from uncertainties in input data, which include measurement and interpolation errors, and in models that include conceptual, logical, mathematical, and computational errors. Understanding the causes and consequences of uncertainty in soil hydrological modeling is useful for: (i) establishing the utility of data and models as decision‐support tools; (ii) directing resources towards improving data and models, and (iii) seeking alternative ways of managing soils when the opportunities for accurate modeling are limited. This chapter focuses on statistical methods for assessing uncertainty in soil data and models, propagating uncertainties through models, and assessing the contribution of different sources of uncertainty to the overall uncertainties in model predictions. In addition, it explores the impacts of scale, and changes between scales, on the outcomes of an uncertainty analysis. It concentrates on physically based models of soil water flow and solute transport, and provides numerous examples from the literature here
Erosion Prediction and Modeling
Authors: Nearing Mark , Renard Ken , Nichols Mary 
Published: April 2006

Abstract
Models of soil erosion by water historically have been primarily either empirically‐based or process‐based (sometime referred to as physically‐based). The first models of soil erosion were empirically‐based. The prime example of the empirically‐based model is the Universal Soil Loss Equation (USLE). More recent models have been based on equations that describe the physical, biological, and/or chemical processes that cause or affect soil erosion. It is important to understand that both the process‐based and the empirically‐based model possess a major empirical component, in the sense that the constitutive equations use parameters based on experimental data. This chapter details some of the important elements of soil erosion models and factors that influence their use.
Floodplain Sedimentation – Methods, Patterns, and Processes: A Review with Examples from the LowerRhine, theNetherlands
Authors: Middelkoop Hans 
Published: April 2006

AbstractFloodplain sedimentation plays a keyrole in the sediment budget of river basins, but it also relates to river management, flood protection, civil engineering, and ecological rehabilitation of rivers. Understanding of the process, therefore, is essential both from a geomorphologic and river management points of view. This paper provides a review of recent research on floodplain sedimentation, focusing on field‐based methods to reconstruct and document spatial patterns of overbank sedimentation, as well on mathematical modeling approaches. Examples of floodplain sedimentation over various timescales are given for the lower Rhine River in the Netherlands. The final section synthesizes the processes, their controls, and the resulting patterns and amounts of floodplain deposition.
Reservoir Sedimentation
Authors: Annandale George W 
Published: April 2006

AbstractThe storage loss due to reservoir sedimentation has been found to exceed the storage added worldwide by the mid 1990s. Recovery of this lost storage is estimated to range between US$ 10 billion and US$ 20 billion per year, not accounting for the growth in world population. Reservoir sedimentation does not only impact water supply and power supply reliability, but also has significant impacts on the environment, including downstream river degradation, and impacts on recreation, flood management, infrastructure, and the economy. The article illustrates how sediment is trapped in reservoirs, provides empirical techniques for calculating the volume of sediment that can be trapped by reservoirs, outlines sediment management techniques, which includes flushing, dredging, dry excavation, hydrosuction, and bypassing, and introduces the life‐cycle management approach. This approach to reservoir sedimentation management is in contrast to the conventional design life approach, which is inappropriate for the design, construction, and management of dams and their reservoirs. Numerous references for further reading are listed.