bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Hydrologic Cycles and Global Circulation
Authors: Oki Taikan 
Published: April 2006

Abstract
The role of hydrological cycles in earth system, the amount of water on the Earth's surface and its distribution in various reserves are first introduced together with the water cycles on the Earth. The concept of mean residence time, water stored in various parts over the Earth surface as various phases, such as glacier, soil moisture, water vapor, and water flux among these reserves, such as precipitation, evaporation, transpiration, and runoff, are briefly explained with their role in global climate system, and their quantitative estimates are presented. Detailed annual water balances over land estimated by land surface models are introduced, as well. Water balance requirements over land, atmosphere, and their coupled system are explained with some application of the concept, and the role of rivers in the global hydrological cycle is quantitatively shown. Finally, the impact of increasing magnitude of anthropogenic activities on global water system and its relationships with global changes are briefly discussed.
Organization and Process
Authors: Kirkby Mike 
Published: April 2006

Abstract
Water, its movement, changes of state, and chemistry, is fundamental to the nature of planet Earth. It is involved in the most important processes near the surface and supports life as we know it. Hydrological sciences potentially address all aspects of water movement and transformation, although with major divisions between hydrology, which is essentially focused on the principle of conservation of mass; hydraulics, based on conservation of momentum (Newton's laws of motion); and meteorology, based on the laws of thermodynamics. This review of processes takes a primarily hydrological viewpoint, concerned with where water is, its pathways, and impacts on other aspects of the environment. A good understanding of these processes is an essential prerequisite to modeling and forecasting the behavior of water, and much of the history of hydrological science reflects changes in our conceptual understanding of how and where water moves. The main theme of this article is the way in which the landscape influences the flow of water, particularly surface hydrology, and how the hydrology in turn influences the form of the landscape.
Fundamental Hydrologic Equations
Authors: Beckie Roger 
Published: April 2006

Abstract
In this article our goal is to present an overview of the fundamental principles that are the basis of most models used in hydrology. We develop the fundamental principles of mass, momentum, and energy conservation and express them in mathematical form. We first outline the general approach that can be used to develop a mathematical statement of a conservation law, using a so‐called Eulerian framework, where we consider volumes fixed in time and space through which material may flow. We then derive the general conservation equations for mass, momentum, and energy for the case of flowing fluids. We next provide examples from hydrology that illustrate the application of the general conservation principles. We begin with relatively straightforward applications of the conservation equations and progress to more complex and less direct applications. Our first and simplest example is the advection–dispersion equation, which is a relatively transparent application of the conservation of mass principle, augmented with a so‐called gradient‐flux model, Fick's law, which describes the dispersion and diffusion of solute mass within the bulk flowing fluid. Next we present the Navier–Stokes equations, which are the conservation of momentum equations for a Newtonian fluid. The next suite of examples involves flow in porous media, which is described by more than one conservation principle applied simultaneously. Our last example is from engineering hydraulics, the Saint Venant equations, which are gross but practical simplifications of the general conservation statements.
Principles of Hydrological Measurements
Authors: Western Andrew W , Grayson Rodger B , Costelloe Justin F 
Published: April 2006

Abstract

This article highlights several key considerations in a successful measurement programme. These are:

The need to have a clear set of objectives or hypotheses to be tested

An understanding of the temporal and spatial variability of the phenomena of interest.

An understanding of the characteristics of the instruments available for measurement, including errors.

Matching of the temporal and spatial characteristics of the measurement with those of the processes of interest.

Considering the trade‐offs inherent in sampling including the number of measurements and accuracy.

Considering a range of practical issues related to setup in the field and the need to check and manage the data as it is collected.

Successful monitoring programs are well designed, well resourced, and analysis will occur during the monitoring program. Timely analysis allows an ongoing review of performance and appropriate modification, which is critical to success.
New and emerging sensor technologies, as well as the ever‐increasing availability of remote sensing information, bode well for the future of hydrological measurement. The synthesis of “smart measurements” with theoretical developments and modeling will yield the greatest advances in the coming years.
Methods of Analyzing Variability
Authors: Gottschalk Lars 
Published: April 2006

AbstractIn an introductory part basic concepts from probability theory, and specifically from the theory of random processes, are introduced as a basis for the characterization of variability of hydrological time series, space processes and time‐space processes. A partial characterization of the random process under study is adopted in accordance with three different schemes:Characterization by distribution function (one dimensional),Second moment characterization, andKarhunen–Loève expansion, that is, a series representation in terms of random variables and deterministic functions of a random process.The article follows the same division into three major sections. In the first one, distribution functions of frequent use in hydrology are shortly described as well as the flow duration curve. The treatment of second‐order moments includes covariance/correlation functions, spectral functions and semivariograms. They allow establishing the structure of the data in space and time and its scale of variability. They also give the possibility of testing basic hypothesis of homogeneity and stationarity. By means of normalization and standardization, data can be transformed into new data sets owing these properties.The section on Karhunen–Loève expansion includes harmonic analysis, analysis by wavelets, principal component analysis, and empirical orthogonal functions. The characterization by series representation in its turn assumes homogeneity with respect to the variance–covariance function. It is as such a tool for analyzing spatial‐temporal variability relative to the first‐ and second‐order moments in terms of new sets of common orthogonal random functions.
Co‐Evolution of Climate, Soil and Vegetation
Authors: Berry Sandra L , Farquhar Graham D , Roderick Michael L 
Published: April 2006

Abstract
The myriad of interactions between the vegetation, the soil, the climate, and the air involve transfers of energy and matter between the atmosphere and the lithosphere. In this article, these interactions are investigated mainly from the perspective of the vegetation. Most of the water taken up from the soil by plants is evaporated from the leaves via stomata during the process commonly referred to as transpiration. Transpiration of water is necessary for the uptake of carbon dioxide from the atmosphere for photosynthesis. Through transpiration and photosynthesis, the vegetation links the energy, water, and carbon and other biogeochemical cycles. This linkage provides the backbone to the article. Sections deal with: energy and water limitations to transpiration and plant growth at the catchment scale; the relationship between plant water use and photosynthesis; ecological strategies and temporal variability of water use and volume of soil involved in exchange with the atmosphere; soil water holding capacity and mineral nutrient availability; and catchment scale relationships between vegetation, soil, and climate. In the final sections, the concept of optimality between climate, vegetation, soil, and air is introduced, and the potential application of the optimality approach to hydrology is reviewed.
Pattern, Process and Function: Elements of a Unified Theory of Hydrology at the Catchment Scale
Authors: Sivapalan Murugesu 
Published: April 2006

Abstract
Catchment hydrology is presently operating under an essentially reductionist paradigm, dominated by small‐scale process theories. Yet, hydrology is full of examples of highly complex behavior, including strong nonlinearities and thresholds, and paradoxes that defy causal explanation through these small‐scale process theories. There are strong interactions and feedbacks between processes, leading to apparent simplicities in the overall catchment response, yet the laws governing these feedbacks are not well understood. Routine measurements and specialized field experiments have been valuable for observing catchment responses and understanding the underlying process controls, but there has been little progress in extrapolating the local knowledge and understanding gained from these well studied (or gauged) catchments to ungauged catchments. Efforts at generalization are hampered by the lack of an appropriate quantitative framework, for example, a classification system, to help identify interesting and useful patterns in the observations. There are many theories governing different elements of catchment hydrology, but not a unified theory that connects these seemingly disparate elements. This article presents the broad outlines of an emerging new, unified theory of hydrology at the catchment scale, and the approaches being used to develop it. The new theory embraces multiscale heterogeneities as a natural and intrinsic part of catchment hydrology. Instead of relying solely on current process theories, it seeks to discover new catchment‐scale process theories that embed within them the effects of natural heterogeneities. Instead of attempting to prescribe in detail the actual patterns of heterogeneity in every catchment, it will seek to incorporate the geomorphic or landforming processes that may have generated them in the first place, and their ecological, pedological, and geomorphological functions. Instead of using our rather meagre observations to calibrate complex models that are based on small‐scale theories, the theory will emphasize the use of patterns in the observations to formulate and test alternative hypotheses about the underlying process controls. Instead of using field measurements to learn more and more about individual catchments, it will seek to find connections between observations in different catchments, to identify broad‐scale or general patterns. The defining feature of the new theory of catchment hydrology will be a sharp focus on the interconnection and feedbacks between pattern and process, over a range of scales, and their interpretation in terms of their “function”, that is, the reason that these connections arise. The renewed focus on pattern, process, and function will revolutionize hydrology, elevate its place within the earth system sciences, and strengthen the scientific foundations of its practice.
Data‐Driven Modeling and Computational Intelligence Methods in Hydrology
Authors: Solomatine Dimitri P 
Published: April 2006

AbstractAlong with the physically based (process) models based on mathematical descriptions of hydrological processes, the so‐called data‐driven models (DDM) are becoming popular. They are based on the use of methods of computational intelligence and machine learning and assume the presence of considerable amount of data describing the modeled phenomenon. The article covers various aspects of DDM, including the data preparation and a brief overview of the used techniques – neural networks, regression and model trees, instance‐based learning, and nonlinear dynamics. A number of references to the successful application of data‐driven methods are provided along with the links to the relevant web sites and software packages. An example where several data‐driven methods were used in a hydrologic forecasting problem is provided.
Storm Systems
Authors: Doswell Charles A 
Published: April 2006

Abstract
The concept of a storm is defined as a weather disturbance that, in the context of hydrological science, produces precipitation or affects the formation and distribution of precipitation. Storm systems are reviewed in terms of their spatial and temporal scale, with the dominant storm system on large scales in midlatitudes being the so‐called extratropical cyclones. Not only do such storms produce considerable weather in their own right, but they provide a setting in which the so‐called mesoscale storm systems can develop. Mesoscale weather is not dominated by any particular form of disturbance, but can take many different forms. The intensity of the weather, including precipitation rates, in mesoscale systems can be much greater than in extratropical cyclones although the duration of such weather is typically less than in large‐scale systems. Small‐scale storms are dominated by convective storms, which can produce the most violent weather of all, including large hail, strong winds, tornadoes, and torrential rainfalls.
Clouds and Precipitation
Authors: Isaac George A , Hallett John 
Published: April 2006

Abstract

Clouds and the precipitation that comes from them are important elements of the hydrological cycle. Clouds provide a blanket for our Earth, both shielding it from radiation from the Sun and trapping heat escaping from the surface. They also generate precipitation through the condensation‐coalescence mechanism, which involves only liquid cloud drops, or through ice initiation leading to large ice particles and eventually snow or rain. Mean annual precipitation amounts reach a maximum near the equator, near 8 mm day
−1
, and decrease poleward to about 1 mm day
−1
. A good understanding of both cloud and precipitation processes is very important for climate and weather predictions. This paper outlines some of the most important processes and provides reference material where more detailed information can be obtained.
Topographic Effects on Precipitation
Authors: Austin Geoffrey L , Dirks Kim N 
Published: April 2006

Abstract
Topography and orography can drastically alter the wind patterns in the atmosphere that in turn can have a major effect on the geographical distribution of precipitation. The processes involved include the upslope enhancement of existing rainfall or the triggering of new rainfall in mountainous regions, and the effect of temperature or humidity contrasts between boundary layer air masses over land and oceanic areas. These processes can result in rainfall patterns ranging from a single triggered thunderstorm to widespread torrential rainfall, as occur when tropical cyclone air masses are pushed up steep coastal mountain ranges. Since the magnitude and distribution of the resulting precipitation pattern can depend critically on the wind speed and direction, as well as the terrain itself, the topographical precipitation processes often determine not only the climatic rainfall patterns of a region but also the interannual variability of this distribution.
Human Impacts on Weather and Climate
Authors: Schneider Stephen H , Mastrandrea Michael D 
Published: April 2006

Abstract
Climate change is a worldwide environmental, social, and economic challenge. It includes issues of air pollution, land use, toxic waste, transportation, industry, energy, government policies, development strategies, and individual freedoms and responsibilities. Human use of the atmosphere as an unpriced dumping space has led to the buildup of gases and particles such as carbon dioxide and methane that can alter the energy exchange between the Earth's surface and space. There is a great deal of confusion among policy makers and the public about just how much is known about our climate, and what makes it change. However, although many aspects of the science of climate change are laced with major uncertainties, many others are actually scientifically well established. Human modification of the climate system has far‐reaching implications for human welfare and the health of our planet. Are our actions causing the climate to change in ways or at rates that will threaten natural systems or make human adaptation difficult? This chapter outlines the current state of scientific knowledge regarding human impacts on the climate system.
Climate Change – Past, Present and Future
Authors: Hengeveld Henry 
Published: April 2006

Abstract
Local climate is a major determinant of both the composition and behavior of a region's ecosystems and of the infrastructure and culture of human society residing within the region. Hence, climatic statistics are an important factor in ecosystem management and planning for socioeconomic development. However, although decision makers often treat these statistics as a constant, there is clear evidence that climate has changed, is changing, and will change. Large natural changes have occurred in the geologic past. However, these have been relatively modest during the past few millennia. On the other hand, human interference with the climate system, primarily through land use change and changes in atmospheric composition, is now adding an unprecedented and increasingly dominant force for change. There is convincing evidence that this interference has already caused a substantial increase in global mean temperatures over the past 50 years. Projected changes for the next century will likely exceed anything yet experienced in human history and could rival the magnitude of very large changes during the past million years, but at a much more rapid rate. Such rapid change will have dramatic implications for, inter alia, the global hydrological cycle and the frequency and severity of extreme weather events.
Rainfall Measurement: Gauges
Authors: Sevruk Boris 
Published: April 2006

AbstractIt is difficult to measure precipitation without introducing systematic errors or biases. The quality of any measurement will depend on the type of gauge used and the details of the installation, as well as the characteristics of the gauge site including exposure and the prevailing weather. All precipitation measurements using can‐type gauges are subject to systematic errors, mostly due to deformation of the wind field above the precipitation gauge orifice, wetting and evaporation losses, splash‐out and splash‐in, blowing snow, and so on. Because these measurement errors are systematic, precipitation gauges frequently show different precipitation figures. This is the case when the gauges are of different construction, or the same construction, but from different manufacturers, or are installed at different heights at the same site near each other, or under different gauge site exposure. With the exception of measurements of blowing and drifting snow, they show less precipitation than the “true” precipitation falling on the ground. Correction procedures are different for rain and snow. They were developed for different types of precipitation gauges and various time intervals according to the availability of necessary input data. Corrections are based either on empirical field methods using the World Meteorological Organization reference standard, laboratory experiments, or numerical simulation.
Surface Radiation Balance
Authors: Unsworth Michael H 
Published: April 2006

Abstract
The surface radiation balance is the algebraic sum of the net solar radiation and the net long‐wave radiation received by a surface. It may be measured directly with a net radiometer, deduced from measurements of its upwelling and downwelling components, or modeled from climatological, geographical, and atmospheric data. Methods of modeling and measuring each of the components are discussed. Downwelling solar radiation from cloudless skies may be modeled from knowledge of atmospheric properties, but effects of clouds require more empirical approaches most suitable for monthly means. Downwelling long‐wave radiation below cloudless skies is well related to temperature and humidity near the ground. An empirical method to account for clouds is given. Reflection coefficients and emissivities of natural surfaces are tabulated for use in calculating upwelling short and long‐wave radiation. Net radiometer designs are reviewed, and examples are given of the surface radiation balance and its components over forest and grass. Issues of spatial variability of the surface radiation balance are discussed.
Transpiration
Authors: Roberts John 
Published: April 2006

Abstract

The transpiration process is the uptake of water by plant roots, transport through the plant and evaporation from the leaf through pores called stomata. Evaporation of water from the leaf is determined by atmospheric conditions such as radiation, temperature and humidity deficit but the plant can limit transpiration by partial or complete stomatal closure. Generally stomata open in response to increasing radiation but tend to close with increasing air humidity deficit and reduced availability of soil moisture. Because the stomata have to be open in daylight for the entry of carbon dioxide into the leaf for the photosynthesis process, water loss is an inevitable consequence. Nevertheless transpiration itself has important roles. Nutrients are brought into the plant when water is taken up from the soil and evaporation of transpired water prevents leaf temperature reaching supra‐optimal levels. There are numerous ways that transpiration might be measured. These include measurements of soil water changes below vegetation or changes in atmospheric humidity above vegetation. Alternatively measurements can be made on individual plants or leaves. In most circumstances the source of water for transpiration is the soil and principally the surface soil layers where most roots are found. In the future, increased levels of atmospheric CO
2
are expected to reduce transpiration through reduction in stomatal aperture.
Principles of Radiative Transfer
Authors: Drusch Matthias , Crewell Susanne 
Published: April 2006

AbstractThe article gives an introduction to classical vector radiative transfer theory (RTT). It comprises a brief summary of the fundamental quantities in RTT and the corresponding definitions. Based on these quantities, the transfer equation for radiation will be introduced in its basic form for a plane‐parallel, horizontally homogeneous atmosphere. Polarization and the Stokes vector are introduced, which extend the scalar radiative transfer equation to the more general form of the vector radiative transfer equation. Scattering processes and interactions with the surface are discussed within the mathematical framework given in the first part of the paper. As an example, the theoretical concept presented is then applied to passive microwave remote sensing. A solution for the radiative transfer equation, which is commonly used for the retrieval of atmospheric quantities (e.g. water vapor) and land surface properties (e.g. soil moisture), is derived based on approximations and simplifications. More general approaches to solve the radiative transfer equation including multiple scattering are described and discussed in a separate section.