bluuebunny/crossref_metadata_2025 huggingface dataset:
Context
Authors: Graham Alan
Published: November 2020

The interaction between vegetation and the environment over time is one of the most complex of the Earth’s integrated systems. In addition to the direct methodologies of paleopalynology and paleobotany, there are other techniques that provide independent sources of information for interpreting this interaction. These include paleotemperature analysis, sea-level changes, and faunal history. The first two are also forcing mechanisms as discussed in Chapter 2, but for this survey the summary curves can also serve as convenient context information. Each is a vast subject with an extensive literature, and all are presently generating considerable discussion. For paleotemperature analysis, unsettled issues include the extent of temperature change in equatorial waters during the Early and Middle Tertiary, which would affect the poleward transport of heat by conveyer-belt mechanisms. Estimates range from surface waters as warm or warmer than the present to considerably cooler. For the Neogene, CLIMAP estimates based on the ecology of coccolithophores, diatoms, radiolarians, and especially foraminifera are that temperatures in the tropics did not cool significantly; modeling results, terrestrial paleontological evidence, and new Barbados coral data suggest they cooled by ~5°C. There is uncertainty as to when glaciations began on Antarctica; recent estimates range from the Early Eocene to late Middle Eocene to Middle Oligocene (45-35 Ma; Birkenmajer, 1990; Leg 119 Shipboard Scientific Party, 1988). This affects interpretation of 18O values during the Paleogene because they could reflect temperature alone or could be due to ocean water temperature and ice volume changes. Another challenge is to unravel the extent to which benthic temperature records track insolation-induced changes in water temperature versus new thresholds in ocean bottom-water circulation. Discussions of sea-level fluctuation are presently focused on their causes during the preglacial Early Cenozoic. In faunal history the timing of the North American Land Mammal Ages (NALMAs) or provincial ages are being revised. For vegetational history much of the older literature describes events in terms of geofloras, but this conceptual context, at minimum, requires substantial renovation, and the boreotropical hypothesis is emerging as an alternative for envisioning biotic events in the high northern latitudes.
Soil Chemistry
Authors: Juo Anthony S. R. , Franzluebbers Kathrin
Published: November 2020

Soil chemistry deals with the chemical properties and reactions of soils. It is essentially the application of electrochemistry and colloid chemistry to soil systems. Major topics include surface charge properties of soil colloids, cation and anion sorption and exchange, soil acidity, soil alkalinity, soil salinity, and the effects of these chemical properties and processes on soil biological activity, plant growth, and environmental quality. The ability of the electrically charged surface of soil colloids to retain nutrient cations and anions is an important chemical property affecting the fertility status of the soil. There are two major sources of electrical charges on soil organic and inorganic colloids, namely, permanent or constant charges and variable or pH-dependent charges. Permanent or constant charges are the result of the charge imbalance brought about by isomorphous substitution in a mineral structure of one cation by another of similar size but differing valence (see also section 2.3.2). For example, the substitution of Mg2+ for Al3+ that occurs in Al-dominated octahedral sheets of 2:1 clay minerals results in a negative surface charge in smectite, vermiculite, and chlorite. The excess negative charges are then balanced by adsorbed cations to maintain electrical neutrality. Permanent negative charges of all 2:1 silicate minerals arise from isomorphous substitutions. The l:l-type clay mineral, kaolinite, has only a minor amount of permanent charge due to isomorphic substitution. The negative charges on kaolinite originate from surface hydroxyl groups on the edge of the mineral structure and are pH-dependent. Variable or pH-dependent charges occur on the surfaces of Fe and Al oxides, allophanes, and organic soil colloids. This type of surface charge originates from hydroxyl groups and other functional groups by releasing or accepting H+ ions, resulting in either negative or positive charges. Other functional groups are hydroxyl (OH) groups of Fe and/or Al oxides and allophanes and the COOH and OH groups of soil organic matter. Variable-charge soil colloids bear either a positive or a negative net surface charge depending on the pH of the soil. The magnitude of the charge varies with the electrolyte concentration of the soil solution.
To Reconcile Historical Geology with Isostasy: Continental Drift
Authors: Oreskes Naomi
Published: November 2020

Alfred Wegener (1880–1930) first presented his theory of continental displacement in 1912, at a meeting of the Geological Association of Frankfurt. In a paper entitled “The geophysical basis of the evolution of the large-scale features of the earth’s crust (continents and oceans),” Wegener proposed that the continents of the earth slowly drift through the ocean basins, from time to time crashing into one another and then breaking apart again. In 1915, he developed this idea into the first edition of his now-famous monograph, Die Entstehung der Kontinente und Ozeane, and a second edition was published in 1920. The work came to the attention of American geologists when a third edition, published in 1922, was translated into English, with a foreword, by John W. Evans, the president of the Geological Society of London and a fellow of the Royal Society, in 1924 asThe Origin of Continents and Oceans. A fourth and final edition appeared in 1929, the year before Wegener died on an expedition across Greenland. In addition to the various editions of his book, Wegener published his ideas in the leading German geological journal, Geologische Rundschau, and he had an abstract read on his behalf in the United States at a conference dedicated to the topic, sponsored by the American Association of Petroleum Geologists, in 1926. The Origin of Continents and Oceans was widely reviewed in English-language journals, including Nature, Science, and the Geological Magazine. Although a number of other geologists had proposed ideas of continental mobility, including the Americans Frank Bursey Taylor, Howard Baker, and W. H. Pickering, Wegener’s treatment was by far the best developed and most extensively researched. Wegener argued that the continents are composed of less dense material than the ocean basins, arid that the density difference between them permitted the continents to float in hydrostatic equilibrium within the denser oceanic substrate. These floatin continents can move through the substrate because it behaves over geological time as a highly viscous fluid. The major geological features of the earth, he suggested — mountain chains, rift valleys, oceanic island arcs—were caused by the horizontal motions and interactions of the continents.
Handbook of Soils for Landscape Architects
Authors: Keefer Robert F.
Published: November 2020

Written in a clear, accessible style, this book covers the fundamental aspects of soil science with an emphasis on topics useful to landscape architects and professionals in related fields. The book begins with a discussion of soil surveys developed in different countries, followed by a concise description of soil components and how the interactions between air, water, and nutrients affect plant growth. It examines methods for controlling erosion, particularly in light of modern irrigation techniques. It describes the chemistry of plant growth, devotes four chapters to macro- and micro-nutrients, and features a detailed discussion of ways to diagnose and correct plant disorders. It also looks at the engineering aspects of soils and includes a detailed list of references for further information. Written by an experienced teacher with an extensive background in landscape architecture, this volume will be an invaluable source for students and researchers in architecture, horticulture, and urban planning.
Demographic Models and Branching Processes
Authors: Chu C. Y. Cyrus
Published: November 2020

All models describing the dynamic pattern of human population have two common features. First, the human population is usually divided into several types, and second, each type has a type-specific stochastic reproduction rate. The traditional literature of demography has been dominated by the age-specific models of Lotka (1939) and Leslie (1945,1948), where the type refers to the age of an individual and the type-specific reproduction rates refer to the age-specific vital rates in a life table, It has been shown that, mathematically, these age-specific models can be analyzed in a more general framework, namely, the multitype branching process. Most demography researchers, however, do not bother to pursue properties of the general branching process. They prefer to follow Lotka’s (1939) age-specific renewal equation approach in proceeding with their analysis because that renewal equation is technically convenient, whereas the steady-state and dynamic properties of a general branching process are usually much more difficult to derive. Although the analytical convenience of the age-specific models has facilitated the research on age-related topics, it also tends to obscure the fact that the age-specific model is merely a special kind of branching process. When female fertility becomes a decision variable of the family and the fertility-related family decision problems expand, these age-specific models are often unworkable. Despite the difficulties inherent in applying the traditional age-specific models to these decision dimensions, researchers still hesitate to go back to the general, but more difficult, branching process for solutions. This is perhaps why, as we mentioned in chapter 1, the demand-side theory of demography has not made much progress in describing the macro aggregate pattern of the population. In this chapter, I separate the discussion into the age-specific branching process and general branching processes. I show that the steady states and ergodic properties of these models can both be established under some regularity conditions. Although the material in this chapter is mostly a reorganization of previously established mathematical results, I believe that my summary is systematic and will be helpful to most readers. All the results summarized will be used in later chapters, but aspects of branching processes that are irrelevant to our purposes will not be discussed.
Age-Distribution Dynamics During Demographic Transitions
Authors: Chu C. Y. Cyrus
Published: November 2020

Everyone knows that population aging refers to the phenomenon of a growing proportion of old people. This may happen 60 years after a “baby boom”, as the “baby boomers” begin to reach their old age. Population aging may also be a natural consequence of demographic transitions, for we know that the proportion of old people will increase as the fertility rale declines. Although there have been numerous economics research papers on topics related to population aging, the focus of most of these research projects has not been on the process and dynamics of population aging but rather on the various problems of the elderly (such as housing, pension, medical care, savings, and retirement) that will grow as the population ages. The typical example is the series of research projects on the economics of aging undertaken by the National Bureau of Economic Research. These research reports were edited by David Wise into several books on aging. In order to make some policy suggestions, however, we must be able to derive the future dynamic pattern of the age distribution, so that the macro level prediction of some age-related variables can be arrived at analytically instead of numerically. Unfortunately, little analytical work has been done along these lines. The purpose of this chapter is to derive the analytical pattern of the age distribution dynamics, which not only helps us calculate the aggregate value of age-related variables but also gives us some insight into finding reasonable aging indexes. Previous researchers often adopted the common measure of population aging, “the proportion of the population older than a critical age,” which is called the “head-count ratio” of the aged. As the head-count ratio of the aged rises above 10%, by instinct one may realize the seriousness of the aging problem. But since we know little about either the formal dynamics or the economic implications of population aging, we do not even know whether the head-count ratio is an appropriate index for characterizing the seriousness of the aging problem. We will show in later sections how information on age distribution dynamics helps us identify reasonable indexes of population aging.
Coenzymes I: Organic Coenzymes
Authors: Frey Perry A. , Hegeman Adrian D.
Published: November 2020

Most enzymatic reactions proceed with chemical changes that cannot be brought about by the side chains of amino acid residues. These enzymes function in cooperation with coenzymes and cofactors, which lend physicochemical potentialities not found in amino acids. Many coenzymes are organic molecules incorporating functional groups with chemical properties that enable them to facilitate reactions of certain types. These molecules bind to active sites tailored for them through evolution and equipped to assist in their coenzymatic functions. Many of these coenzymes were derived from vitamins, and in early biochemistry investigations, vitamins and coenzymes were often regarded as closely linked and even synonymous. However, vitamins such as vitamin D are more akin to hormones than to coenzymes, and in modern biochemistry, the newly discovered coenzymes are not related to vitamins and have identities independent of any nutritional origin. More than 25 biological molecules may be regarded as coenzymatic in nature. In this book, the most common coenzymes and their functions are described in two chapters, the organic coenzymes in this chapter, and the metallo-coenzymes in chapter 4. Each coenzyme and cognate enzyme form a union that allows them to act as a single catalytic entity functioning in concert to bring about a difficult chemical transformation. Each coenzyme provides the chemistry required for a class of enzymatic processes, and the mechanisms of enzymatic catalysis are often revealed through the actions of the participating coenzymes. Nicotinamide adenine dinucleotide (NAD+) is the coenzymatic form of the vitamin niacin (vitamin B1). The structural formula for NAD+ is shown in fig. 3-1 along with the biochemically reactive bonds and their importance in metabolism. NADH is the reduced form of NAD+ and is produced in the dehydrogenation of substrates. The closely related forms NADP+ and NADPH are phosphorylated at the 2′-hydroxyl group of the adenosyl moiety. NADP+ and NADPH generally participate in biosynthesis (anabolism), whereas NAD+ and NADH generally participate in biodegradative metabolism (catabolism). NAD+ and NADH were formerly known as DPN+ and DPNH, for diphosphopyridine nucleotide, and TPN+ and TPNH, for triphosphopyridine nucleotide. The most frequent function of NAD+ is as an acceptor of a hydrogen atom and two electrons, a hydride equivalent, in reactions of oxidoreductases, commonly known as dehydrogenases.
Addition and Elimination
Authors: Frey Perry A. , Hegeman Adrian D.
Published: November 2020

Most elimination and addition reactions in biochemistry proceed by α,β-elimination/addition mechanisms. In the case of elimination, the leaving group is β to an activating functional group in the substrate. The activating group may be the carbonyl group of a ketone or aldehyde, the iminium group derived from an aldehyde or ketone, or the acyl-carbonyl of a carboxylic acid or ester, and the proton is α to the activating group. Addition reactions in this class are the same reactions in reverse, and they follow the course of the Michael addition in organic chemistry. The generic process is illustrated in scheme 9-1. Substituents among the activating and leaving groups are diverse and are presumed to account for the significant variations among enzymes in the class. A few enzymes in this class catalyze elimination/addition without the assistance of a coenzyme or cofactor. They presumably incorporate sufficiently acidic (A—H) or basic (:B) amino acid side chains to catalyze the proton transfer processes, or they may stabilize carbanionic intermediates by low-barrier hydrogen bonding. Others employ divalent metal ions, pyridoxal-5'-phosphate (PLP), [4Fe–4S] centers, or NAD+ to facilitate the reactions. Cofactors and coenzymes increase the acidity of Cα—H or improve the propensity of the leaving group Y to depart. In most cases, the major barrier consists of increasing the acidity of the Cα—H group, which decreases the pKa. In a few cases, as when the leaving group is a carboxylic acid or a phosphate, no catalysis is required for it to depart. Limited space prevents discussion of the many enzymes that catalyze cofactor-independent α, β-eliminations. We address the actions of fumarase and crotonase because of the historic emphasis on the biochemical significance of these enzymes. Many other dehydratases and ammonia lyases also belong in this group. In the tricarboxylic acid cycle, fumarate arises from the action of succinate dehydrogenase, and fumarase (EC 4.2.1.2) catalyzes the addition of water to form S-malate. The reaction can be monitored in either direction, and in various studies, the kinetic parameters may be quoted as such (e.g., fumarate formation, or malate formation). The body of knowledge about the action of fumarase is surprisingly incomplete, given the importance of the enzyme in metabolism.
The Uptake Properties of the Root System
Authors: Tinker Peter B. , Nye Peter
Published: November 2020

The uptake of nutrient and other ions into the root from the surrounding soil is the main topic of this book. To understand it, we need to know how the nutrient uptake and demand of the plant is expressed at the root surface. The main interest is on how the demand at the root surface can be quantitatively defined in terms of its uptake characteristics. For this reason, our explanation of the ion uptake mechanism of the root itself is brief, and is intended mainly for readers who have not studied the subject deeply. The subject has become considerably more complex since 1977, but this detailed knowledge has not yet coalesced into a full model of how ions are absorbed, such as ultimately will allow root uptake properties to be predicted. There have been many good reviews in the recent past, and the following may be consulted: Clarkson & Hanson 1980; Glass 1983; Luttge 1983; Clarkson 1985; Sanders 1990; Clarkson & Luttge 1991; Marschner 1995. We will describe the structure of a single root only briefly here, since this information can be found in standard texts (Troughton 1957; Esau 1965; Cutter 1978; Fahn 1982). Figures 5.1-5.5 show the general structure, but here we stress points that have a special bearing on the process of ion uptake or root behaviour in soil. Byrne (1974) noted that the anatomy of soil-grown roots may differ somewhat from that of solution-grown roots. The architecture of whole root systems in soil is dealt with in chapter 9.The root tip is a highly important part of the root. The apical meristem (the ‘quiescent centre’) is a fraction of a millimetre behind the visible root tip; cells that form behind the centre of this develop into the root, whereas those in front of the centre form the root cap. These cells gradually reach the surface of the cap, and there are rubbed off and lost into the soil at a rate of several thousand per day in maize. Often, these cells are visible in the mucigel that forms from the base of the root cap and covers the young root (section 8.1.3), and can remain alive in the gel for a period.
Vanishing Assets: Conservation Status of U.S. Species
Authors: Master Lawrence L. , Kutner Lynn S.
Published: November 2020

“The air was literally filled with pigeons; the light of noonday was obscured as by an eclipse.” So observed John James Audubon, the eminent naturalist and bird artist, of a mass migration of passenger pigeons (Ectopistes migratorius) passing through Kentucky in 1813. For three days the pigeons poured out of the Northeast in search of forests bearing nuts and acorns. By Audubon’s estimate, the flock that passed overhead contained more than I billion birds, a number consistent with calculations made by other ornithologists. As the pigeons approached their roost, Audubon noted that the noise they made “reminded me of a hard gale at sea passing through the rigging of a close-reefed vessel.” Indeed, they were so numerous that by some accounts every other bird on the North American continent was probably a passenger pigeon at the time of European colonization (Schorger 1955). Yet despite this extraordinary abundance, barely 100 years later the last passenger pigeon, a female bird named Martha, died in the Cincinnati Zoo. The vast flocks of passenger pigeons moved around eastern North America, feeding mostly on the fruits of forest trees such as beechnuts and acorns. Two factors conspired to seal their fate. Because of their huge numbers, the birds were easy to hunt, especially at their roosting sites. Hunters were ingenious in developing increasingly efficient ways to slaughter the birds. Armed with sticks, guns, nets, or sulfur fires, hunters swept through the enormous roosting colonies, carting away what they could carry and feeding the remaining carcasses to their pigs. One of these methods, in which a decoy pigeon with its eyes sewn shut was attached to a perch, or stool, gave rise to the term stool pigeon. As the railroads expanded west, enormous numbers could be sent to major urban markets like New York, where pigeons became the cheapest meat available. They were so cheap and abundant that live birds were used as targets in shooting galleries. At the same time that this frontal assault on the pigeons was under way, human settlers were expanding into the interior of the country, clearing large areas of the forests on which the flocks depended for food.
Sex, Religion, and the Making of Modern Madness
Authors: Goldberg Ann
Published: November 2020

How did the affliction we now know as insanity move from a religious phenomenon to a medical one? How did social class, gender, and ethnicity affect the experience of mental trauma and the way psychiatrists diagnosed and treated patients? In answering these questions, this important volume mines the rich and unusually detailed records of one of Germany's first modern insane asylums, the Eberbach Asylum in the duchy of Nassau. It is a book on the historical relationship between madness and modernity that both builds upon and challenges Michel Foucault's landmark work on this topic, a bold study that gives generous consideration to madness from the patient's perspective while also shedding new light on sexuality, politics, and antisemitism in nineteenth-century Germany. Drawing on the case records of several hundred asylum patients, Sex, Religion, and the Making of Modern Madness reconstructs the encounters of state officials and medical practitioners with peasant madness and deviancy during a transitional period in the history of both Germany and psychiatry. As author Ann Goldberg explains, this era witnessed the establishment of psychiatry as a legitimate medical specialty during a time of social upheaval, as Germany underwent the shift toward a capitalist order and the modern state. Focusing on such "illnesses" as religious madness, nymphomania, and masturbatory insanity, as well as the construct of Jewishness, she probes the daily encounters in which psychiatric categories were applied, experienced, and resisted within the settings of family, village, and insane asylum. The book is a model of microhistory, breaking new ground in the historiography of psychiatry as it synthetically applies approaches from "the history of everyday life," anthropology, poststructuralism, and feminist studies. In contrast to earlier, anecdotal studies of "the asylum patient," Goldberg employs diagnostic patterns to illuminate the ways in which madness--both in psychiatric practice and in the experience of patients--was structured by gender, class, and "race." She thus examines both the social basis of rural mental trauma in the Vormärz and the political and medical practices that sought to refashion this experience. This study sheds light on a range of issues concerning gender, religion, class relations, ethnicity, and state-building. It will appeal to students and scholars of a number of disciplines.
Managed Care and Informed Consent
Authors: Berg Jessica W. , Appelbaum Paul S. , Lidz Charles W. , Parker Lisa S.
Published: November 2020

In the last decade, American medicine has been transformed by a series of changes in the economic arrangements governing clinical practice that have come to be known genetically as “managed care.” Since the nature of these changes is complex and the process of evolution incomplete, managed care evades efforts at easy definition. However, it is probably fair to say, as Iglehart has, that “[a]ll forms of managed care represent attempts to control costs by modifying the behavior of doctors, although they do so in different ways”. Managed care’s alteration of some of the basic premises of the physicianpatient relationship, has raised serious questions about its effect on the doctrine of informed consent. To take but one example, if the physician is now subject to incentives from a managed care organization to decrease the amount and cost of care provided, would this information be material to the decision making of a reasonable patient? Should the law therefore require that such information be disclosed? If so, who should disclose this information, and when should the disclosure be made? At this stage, most of the questions that can be framed are, like this one, not susceptible to definitive answers from a legal or ethical perspective. But the potential impact of these new means of authorizing and paying for medical treatment is so substantial that there is value in laying out the issues to which jurists and legislators will have to respond, and in providing some initial guidance to clinicians and administrators. These are the goals of this chapter. To understand the changes wrought by managed care in the practice of medicine— and their possible relevance for informed consent law—one needs to begin by recalling the economic framework of medical care during the development of the doctrine of informed consent. With the growth of employer-provided health insurance following World War II, most middle-class Americans and their families were freed of the spectre of bankruptcy attending serious medical illness (2).
Graphite Intercalation Compounds and Applications
Authors: Enoki Toshiaki , Endo Morinobu , Suzuki Masatsugu
Published: November 2020

Graphite intercalation compounds are a new class of electronic materials that are classified as graphite-based host guest systems. They have specific structural features based on the alternating stacking of graphite and guest intercalate sheets. The electronic structures show two-dimensional metallic properties with a large variety of features including superconductivity. They are also interesting from the point of two-dimensional magnetic systems. This book presents the synthesis, crystal structures, phase transitions, lattice dynamics, electronic structures, electron transport properties, magnetic properties, surface phenomena, and applications of graphite intercalation compounds. The applications covered include batteries, highly conductive graphite fibers, exfoliated graphite and intercalated fullerenes and nanotubes.
Cirrus: History and Definition
Authors: Lynch David K.
Published: November 2020

The most distinguishing physical property of cirrus (cirrostratus and cirrocumulus) is their composition. Cirrus are made predominantly or wholly of ice, whereas the majority of clouds (both in name and number) are composed of water droplets. That most clouds were composed of water droplets was probably well known to the ancients, who must surely have encountered fog in valleys and mountains. Yet the presence of ice in cirrus is not easily experienced in everyday life. To answer the question Who discovered that cirrus are made of ice? we have to trace developments in meteorology back almost 2500 years. Anaxagoras of Clazomenae (c. 500-428 B.C.) might have deduced that cirrus were made of ice. Using an inductive approach based on measurements and observations, Anaxagoras knew that clouds were made of water and that air was colder aloft. He believed that warm, moist air convected upward and that the water vapor cooled, condensed, and ultimately froze at great heights to become hail. We do not know if Anaxagoras considered cirrus explicitly because what little is left of his writings do not mention any cloud recognizable as cirrus (Gershenson and Greenberg 1964). Two thousand years passed before any substantial progress was made on cirrus. In 1637 Descartes (1596-1650) published Discours de la methode (Descartes 1637) in three parts: Dioptrics, Meteorology, and Geometry. In Dioptrics he set forth the law of refraction (Snell’s law) and in Meteorology he applied the law to the rainbows by performing numerical ray traces. Although he almost certainly knew the principle of minimum deviation, there is nothing in his writings that explicitly refers to it. In the ninth discourse on Meteorology, Descartes conjectures that the common 22° halo was due to refraction through ice crystals. . . . around the heavenly bodies there sometimes appear certain circles . . . they are round . . . and always surround the sun or some other heavenly body . . . they are colored, which shows that there is refraction. But the circles are never seen where it rains, which shows that they are not caused by the refraction which occurs in drops of water or in hail, but by that which is caused in those small little stars of transparent ice . . . those that we have observed most often have had their diameters at around 45° . . . (Olscamp 1965) . . .
Mid-latitude and Tropical Cirrus: Microphysical Properties
Authors: Heymsfield Andrew J. , McFarquhar Greg M.
Published: November 2020

Cirrus, a principal cloud type that forms at low temperatures in the upper troposphere, is composed almost always of ice crystals (Heymsfield and Miloshevich 1989) and on average cover about 20% of the earth's surface (Hartmann et al. 1992). The purpose of this chapter is to characterize the microphysical properties of cirrus clouds. The Glossary of Meteorology (Huschke 1970) defines cirrus clouds as detached clouds in the form of white, delicate filaments, or white or mostly white patches, which are composed of ice crystals. This cloud type forms primarily in the upper troposphere, above about 8km (25,000 feet), where temperatures are generally below -30° C. There are a number of types of cirrus clouds, with the most frequent ones occurring in layers or sheets with horizontal dimensions of hundreds or even thousands of kilometers. Because horizontal dimensions are much greater than vertical extent, this particular type of cirrus cloud is called cirrostratus. Cirrus can also form in a patchy or tufted shape, when the ice crystals are large enough to acquire an appreciable fall velocity (the rate at which ice crystals fall in the vertical) so that trails of considerable vertical extent may form. These trails curve irregularly or slant, sometimes with a commalike shape, as a result of changes in the horizontal wind velocity with height and variations in the fall velocity of the ice crystals. A wispy, layered cloud that forms at the top of a cumulonimbus cloud, termed an “anvil” because of its shape, is a cirrus that consists essentially of ice debris which spreads outward from the convective parts of the storm. Anvils do not include the white, dense portions of thunderstorms or the active convective column. Anvils can spread to form large, widespread cloud layers. Tropical cirrus clouds are thought to arise primarily from cumulonimbus clouds. Unlike the thin, wispy cirrus typifying mid-latitudes, the high altitudes and extensive lateral and vertical development that often characterize tropical cirrus impose substantial large-scale radiative effects in the atmosphere and at the earth's surface (Hartmann et al. 1992; Collins et al. 1996). The cirrus-like low-level ice clouds and ice fogs of the Arctic are not considered cirrus.
Satellite Remote Sensing of Cirrus
Authors: Minnis Patrick
Published: November 2020

The determination of cirrus properties over large spatial and temporal scales will, in most instances, require the use of satellite data. Global coverage at resolutions as fine as several meters are attainable with instruments on Landsat, and temporal coverage at 1-min intervals is now available with the latest Geostationary Operational Environmental Satellite (GOES) imagers. Extracting information about cirrus clouds from these satellite data sets is often difficult because of variations in background, similarities to other cloud types, and the frequently semitransparent nature of cirrus clouds. From the surface, cirrus clouds are readily discerned by the human observer via the patterns of scattered visible radiation from the sun, moon, and stars. The relatively uniform background presented by the sky facilitates cloud detection and the familiar textures, structures, and apparent altitude of cirrus distinguish it from other cloud types. From satellites, cirrus can also be detected from scattered visible radiation, but the demands of accurate identification for different surface backgrounds over the entire diurnal cycle and quantification of the cirrus properties require the analysis of radiances scattered or emitted over a wide range of the electromagnetic spectrum. Many of these spectra and high-resolution satellite data can be used to understand certain aspects of cirrus clouds in particular situations. Intensive study of well-measured cases can yield a wealth of information about cirrus properties on fine scales (e.g., Minnis et al. 1990; Westphal et al. 1996). Production of a global climatology of cirrus clouds, however, requires compromises in spatial, temporal, and spectral coverage (e.g., Schiffer and Rossow 1983). This chapter summarizes both the state of the art and the potential for future passive remote sensing systems to aid the understanding of cirrus processes and to acquire sufficient statistics for constraining and refining weather and climate models. Theoretically, many different aspects of cirrus can be determined from passive sensing systems. A limited number of quantities are the focus of most efforts to describe cirrus clouds. These include the areal coverage, top and base altitude or pressure, thickness, top and base temperatures, optical depth, effective particle size and shape, vertical ice water path, and size, shape and spacing of the cloud cells.
Structural and Optical Properties of Cirrus from LIRAD-type Observations
Authors: Platt C. Martin R.
Published: November 2020

The problem of cirrus clouds, their formation and interactions with solar and infrared (IR) radiation, has been studied over the past two or three decades. Considerable progress has been made over that time through ground-based, satellite, and aircraft observations. This has led to the implementation of fairly sophisticated parameterizations in global circulation models (GCMs; e.g., Rotstayn 1997). However, many problems concerning cirrus properties and their formation remain (e.g., Lee and Somerville 1996; Lohmann and Roeckner 1996). The lidar/radiometer (LIRAD) method was originally formulated to obtain cirrus radiative properties from the ground, with the long-range aim of improving models of the earth's climate (Platt and Gambling 1971; Platt 1973). The method enables many repeated observations easily, once the initial equipment is assembled. The method is essentially a way of obtaining cloud height and depth (from which cloud temperature can be obtained from radiosonde data) simultaneously with a measurement of infrared radiance. This is accomplished in the atmospheric window (8-13 μm), where water vapor or other gaseous absorption is small enough to allow measurement of cirrus cloud radiance without too much error. A cirrus IR emittance can then be calculated, given the cloud depth and temperature. This simple scheme can reveal other facets of the cirrus cloud, such as information on cloud microphysics and particle size. A second lidar channel for detecting depolarized radiation gives information on cloud phase, and even cloud ice crystal habit in the case of hexagonal plate crystals. This chapter describes LIRAD measurements taken over many years in both mid-latitude and tropical cirrus. The observations described by Platt (1973), Platt and Dilley (1981), and Platt et al. (1987, 1998) are then compared to some LIRAD-type observations made by other workers in the field. The LIRAD method uses a calibrated lidar and narrow-beam spectral infrared radiometer placed in close proximity, with both axes aligned accurately to observe the same volume of cloud. The secret of the method is to use compatible field apertures in both instruments and to use a sensitive radiometer that is fast enough to record the rapid fluctuations in cloud emission that can occur (e.g., Platt and Dilley 1981). The lidar is calibrated carefully against a known molecular atmosphere.
Subvisual Cirrus
Authors: Lynch David K. , Sassen Kenneth
Published: November 2020

Starting during World War II, pilots flying high over the tropics reported “a thin layer of cirrus 500ft above us”. Yet as they ascended, they still observed more thin cirrus above them, leading to the colloquialism “cirrus evadus.” With the coming of lidar in the early 1960s, rumors and unqualified reports of subvisual cirrus were replaced with validated detections, in situ sampling, and the first systematic studies (Uthe 1977; Barnes 1980, 1982). Heymsfield (1986) described observations over Kwajalein Atoll in the western tropical Pacific Ocean, where pilots and lidars could clearly see the cloud but DMSP (U.S. Defense Meteorological Satellite Program) radiance measurements and ground observers could not. The term “subvisual” is a relatively recent appellation. Prior terminology included cirrus haze, semitransparent cirrus, subvisible cirrus veils, low density clouds, fields of ice aerosols, cirrus, anvil cirrus, and high altitude tropical (HAT) cirrus. Subvisual cirrus clouds (SVC) are widespread (Winker and Trepte 1998; see chapter 12, this volume) and virtually undetectable with existing passive sensors. Orbiting solar limb occupation systems such as the Stratospheric Aerosol and Gas Experiment (SAGE) can detect these clouds, but only by looking at them horizontally where the optical depths are significant. SVC appear to affect climate primarily by heating the planet, though to what extent this may happen is unknown. Much of what we know is based on work by Heymsfield (1986), Platt et al. (1987), Sassen et al. (1989, 1992), Flatau et al. (1990), Liou et al. (1990), Hutchinson et al. (1991, 1993), Dalcher (1992), Sassen and Cho (1992), Takano et al. (1992), Lynch (1993), Schmidt et al. (1993), Schmidt and Lynch (1995), and Winker and Trepte (1998). SVC are defined as any high clouds composed primarily of ice (WMO 1975) and whose vertical visible optical depth is 0.03 or less (Sassen and Cho 1992). Such clouds are usually found near the tropopause and are less than about 1 km thick vertically. SVC do not appear to be fundamentally different from ordinary, optically thicker cirrus. They do, however, differ from average cirrus by being colder (-50-90°C), thinner (<0.03 optical depths at 0.694 μm), and having smaller particles (typically about <50μm diameter).
Radiative Transfer in Cirrus Clouds: Light Scatting and Spectral Information
Authors: Liou K.N. , Gu Y.
Published: November 2020

The importance of cirrus clouds in climate has been recognized in the light of a number of intensive composite field observations: the First ISCCP Regional Experiment (FIRE) I in October-November 1986; FIRE II in November-December 1991; the European experiment on cirrus (ICE/EUCREX) in 1989; Subsonic Aircraft: Contrail and Cloud Effect Special Study (SUCCESS) in April 1996. Based on observations from the ground-based lidar and radar, airborne instrumentation, and satellites, cirrus clouds are typically located in the upper troposphere and lower stratosphere (Liou 1986). The formation, maintenance, and dissipation of cirrus clouds are directly associated with synoptic and mesoscale disturbances as well as related to deep cumulus outflows. Increases of high cloud cover have been reported at a number of urban airports in the United States based on surface observations spanning 40 years (Liou et al. 1990; Frankel et al. 1997). These increases have been attributed to the contrails and water vapor produced by jet airplane traffic. Satellite observations from NOAA polar-orbiting High-Resolution Infrared Radiation Sounder (HIRS) using the CO2 slicing method (Wylie et al. 1994) also show that cirrus cloud cover substantially increased between 60° S and 60° N during a 4-year period from June 1989 to September 1993. Understanding the role of cirrus clouds in climate must begin with reliable modeling of their radiative properties for incorporation in climate models as well as determination of the global variability of their composition, structure, and optical properties. Development of the remote sensing methodologies for the detection and retrieval of the ubiquitous visible and subvisual cirrus clouds requires the basic scattering, absorption, and polarization data for ice crystals in conjunction with appropriate radiative transfer models. We present the fundamentals involving radiative transfer in cirrus clouds and review pertinent research. In section 13.1, an overview of the subject of light scattering by ice crystals is presented in which we discuss a unification of the geometric optics approach for large ice particles and the finite-difference time domain numerical solution for small ice particles, referred to as the unified theory. Section 13.2 presents radiative transfer in cirrus clouds involving two unique properties: orientation of nonspherical ice crystals and cloud inhomogeneity.
GCM Simulations of Cirrus for Climate Studies
Authors: Del Genio Anthony D.
Published: November 2020

One of the great challenges in predicting the rate and geographical pattern of climate change is to faithfully represent the feedback effects of various cloud types that arise via different mechanisms in different parts of the atmosphere. Cirrus clouds are a particularly uncertain component of general circulation model (GCM) simulations of long-term climate change for a variety of reasons, as detailed below. First, cirrus encompass a wide range of optical thicknesses and altitudes. At one extreme are the thin tropopause cirrus that barely affect the short-wave albedo while radiating to space at very cold temperatures, producing a net positive effect on the planetary radiation balance and causing local upper troposphere warming, thus stabilizing the lapse rate. At the other extreme are thick cumulus anvil cirrus whose bases descend to the freezing level; these clouds produce significant but opposing short-wave and long-wave effects on the planetary energy balance while cooling the surface via their reflection of sunlight. In fact, satellite climatologies show a continuum of optical thicknesses between these two extremes (Rossow and Schiffer 1991). In a climate change, the net effect of cirrus might either be a positive or a negative feedback, depending on the sign and magnitude of the cloud cover change in each cloud-type category and the direction and extent of changes in their optical properties (see Stephens et al. 1990). Second, the dynamic processes that create cirrus are poorly resolved and different in different parts of the globe. In the tropics, small-scale convective transport of water from the planetary boundary layer to the upper troposphere is the immediate source of a significant fraction of the condensate in mesoscale cirrus anvils (see Gamache and Houze 1983), and ultimately the source of much of the water vapor that condenses out in large-scale uplift to form thinner cirrus. However, many observed thin cirrus cannot directly be identified with a convective source, suggesting that in situ upper troposphere dynamics and regeneration processes within cirrus (see Starr and Cox 1985) are important. In mid-latitudes, although summertime continental convection is a source of cirrus, in general cirrus is associated with mesoscale frontal circulations in synoptic-scale baroclinic waves and jet streaks (see Starr and Wylie 1990; Mace et al. 1995).
Ice Clouds in Numerical Weather Prediction Models: Progress, Problems, and Prospects
Authors: Jakob Christian
Published: November 2020

The properties of cirrus, as well as the role ice clouds play in the atmosphere, have been extensively described in the previous chapters. To represent the effects of cirrus in atmospheric models, several intimately linked processes need to be described. These processes include the generation and dissipation of ice clouds as well as their interaction with the radiative fluxes throughout the atmosphere. In this chapter the cloud parameterization aspects of this problem (i.e., the treatment of the generation and dissipation of ice clouds), are discussed in the context of global numerical weather prediction (NWP) models. Aspects of the radiative transfer in ice clouds can be found in chapter 13. The main focus of the current chapter is on the cloud parameterization used in the global forecast model of the European Centre for Medium-Range Weather Forecasts (ECMWF). This parameterization will serve as an example in highlighting the progress made, the problems encountered, and the prospects for improving the representation of ice clouds in atmospheric models. The principles of representing clouds in global NWP models are identical to those in general circulation models (GCMs) used for climate research (see chapter 15). Although ice clouds are the focus of this book, a substantial part of this chapter will be concerned with the overall treatment of clouds in numerical models of the atmosphere. In fact, many models used in NWP today distinguish ice clouds from mixed-phase and water clouds only as a function of temperature. Cloud parameterizations in GCMs have evolved rapidly over the last few years. Section 16.2 is a general overview of the progress made. Section 16.3 will describe the cloud parameterization that is currently used in the ECMWF forecast model as a specific example for a state-of-the-art cloud parameterization in NWP. General aspects of the simulation of ice clouds with this model will be presented. GCM simulations of the atmosphere are very sensitive to the treatment of clouds in general (Senior and Mitchell 1993; Rasch and Kristjansson 1998) and to assumptions about cloud ice in particular (Fowler et al. 1996; Jakob and Morcrette 1995). Section 16.4 gives an example of those sensitivities and the model design problems that can arise when model sensitivities exist in combination with a lack of observations, as noted for cloud ice by Stephens et al. (1998).