bluuebunny/crossref_metadata_2025 huggingface dataset:
Stress corrosion theory of crack propagation with applications to geophysics
Authors: Anderson Orson L. , Grew Priscilla C.
Published: February 2008

The theory of stress corrosion for slow crack propagation is reviewed in the light of classical Griffith theory of fracture. Experimental data for stress corrosion cracking for glasses, ceramics, and metals are reviewed. We suggest that stress corrosion cracking plays an important role in the intrusion of magmas and in the transport of magmas upward through the lithosphere. It is shown that the effect of decreasing temperature (at progressively shallower levels along the geotherm) would be to decrease the crack velocity by several orders of magnitude if other factors were equal. We also propose that stress corrosion may be an important process in time‐dependent earthquake phenomena such as premonitory behavior and earthquake aftershocks. We suggest that slow cracking in the earth is not seismically detectable but may nevertheless precede the terminal (catastrophic) phase of the fracture that is discerned as an earthquake. The seismically quiet periods before some earthquakes and the seismically quiet regions beneath some volcanoes may in fact be regimes of slow crack propagation. Slow crack propagation in a lithospheric plate may provide access routes for magmas which give rise to prominent linear volcanic chains.
Electric and magnetic fields in the high‐latitude magnetosphere
Authors: Fairfield D. H.
Published: February 2008

The configuration of high‐latitude electric and magnetic fields is reviewed. Various results indicate that high‐latitude magnetic field lines from the outermost regions of the dayside magnetosphere converge toward a point near the noon meridian. This configuration funnels particles toward noon, where they can flow down field lines to form the midday cusp. Plasma convects away from this entry region and is associated with a dawn‐dusk electric field across the polar cap. Plasma flow is enhanced on the side of the polar cap where the components of interplanetary and magnetospheric magnetic fields are in the same direction. The electric fields associated with these flows produce Hall currents on the polar cap which vary with sector structure. Some evidence suggests that polar cap convection may reverse during intervals of strong northward interplanetary field. The flow reversal at the polar cap boundary is probably associated with ‘inverted V’ particle events, auroral arcs, parallel electric fields, and field‐aligned currents. It is concluded that most observations are consistent with an open field magnetosphere model.
Wave propagation in random media, with oceanic applications
Authors: Mysak Lawrence A.
Published: February 2008

A general discussion is presented of the propagation, attenuation, growth, reflection, scattering, and energy transport of waves in the presence of weak but extensive random media or boundaries. Applications of the theory to various types of long‐period waves in the ocean are given: gravity waves, shear waves, internal and inertial waves, Rossby waves, Kelvin and Poincaré waves, and edge waves. The mathematical methods used in this paper to solve the relevant random differential equations are generally of an asymptotic or approximate nature; however, attempts have been made to assess the validity of these methods. A brief discussion is also given of some recent exact methods which have been developed to study wave propagation in the presence of strong random fluctuations. There has been no attempt to summarize the extensive work done on electromagnetic, optical, and acoustic wave propagation in random media, since a number of reviews and books have already appeared on these topics.
Least‐squares collocation
Authors: Moritz Helmut
Published: February 2008

Least‐squares collocation is a mathematical technique for determining the earth's figure and gravitational field by a combination of heterogeneous data of different kinds. The same formulas may be interpreted in very different ways: as the solution of a geophysical inverse problem, as a statistical estimation method combining least‐squares adjustment and least‐squares prediction, and as an analytical approximation to the earth's potential by means of harmonic functions. The present review article attempts a unified presentation of the subject with emphasis on theory.
Interpretations of stratospheric photochemistry
Authors: Johnston Harold S. , Podolske James
Published: February 2008

Trace stratospheric species (parts per billion or less) have negligible effects on ozone (parts per million) unless they interact in catalytic cycles that regenerate the trace species. It is appropriate to regard catalytic cycles, null cycles, and consumptive sequences, rather than the elementary chemical reactions, as the components of ozone photochemistry. A general differential equation for ozone is transformed to an equivalent equation that directly identifies the catalytic cycles and sequences. The novel aspect of this article is the completeness with which this transformation is carried out and used. This method of treating stratospheric photochemistry properly partitions ozone destruction rates among Ox, NOx, HOx, and ClX families of reactions. The features of the methane‐smog chemistry are clearly brought out. From the midvalues of published measurements of NO2and ClO, it appears that NO2, ClO, and O3are sufficient to destroy ozone as fast as it is formed in the range 23–35 km, and NOxreactions and ClX reactions appear to be roughly equal in importance. There is no need to invoke any new or unknown sink for ozone in this region if the midvalues of measured NO2and ClO are representative of the global average. It is improbable that the high values observed for NO2or for ClO are representative of global average values. The magnitude of the contribution of HOxreactions to ozone photochemistry cannot be found by this method because of lack of observations of HOO in the stratosphere. These conclusions depend on the accuracy of the stratospheric observations and certain rate constants. Additional measurements are needed, especially for HOO, NO2, ClO, and HO.
Magnetization of the oceanic crust
Authors: Johnson H. Paul
Published: February 2008

The Vine‐Matthews [1963] model of the magnetic structure of the igneous oceanic crust, in which basement is considered to be made up of alternating normal and reverse magnetic polarity blocks with a one‐to‐one match with linear marine magnetic anomalies, has received wide acceptance in the geological and geophysical community. Comparison of the results from studies of samples obtained by dredging, submersible, and shallow drilling, with magnetic anomaly inversion and modeling are generally consistent with this model if the sections of magnetic crust are considered relatively thin—of the order of a kilometer in vertical thickness. However, work that has taken place in the last four years seems to indicate that the magnetic structure of the oceanic crust is a great deal more complicated than originally envisaged. Recent studies of the oceanic basement basalt recovered by the GLOMAR CHALLENGER, particularly from deep basement holes in the Atlantic, have indicated that the net magnetization of the upper 600 meters of igneous crust may, in some places, appear to be insufficient to contribute much to the overlying anomaly amplitudes.
Magnetospheric substorms
Authors: McPherron Robert L.
Published: February 2008

A magnetospheric substorm is a transient process initiated on the night side of the earth, in which a significant amount of energy derived from the solar wind‐magnetosphere interaction is deposited in the auroral ionosphere and magnetosphere. Substorms are controlled by the interplanetary magnetic field, ceasing when it points northward for long intervals and reappearing when it turns southward. In the simplest case a substorm appears to have three phases: a growth phase in which energy is extracted from the solar wind and stored in the magnetotail; an expansion phase in which energy is explosively released; a recovery phase in which the magnetosphere relaxes to a quiet state. More commonly, however, weak auroral disturbances called pesudobreakups can occur during the growth phase, or more than one expansion phase may follow a single growth phase. Often multiple onsets are so close together that only one expansion phase is evident. At times the magnetosphere undergoes a “convection bay” in which quiet‐time processes are much enhanced but transient processes are not observed in the midnight sector. The processes responsible for onset of the expansion phase are not known although various mechanisms have been suggested such as sudden commencement pressure pulses, interplanetary magnetic field direction fluctuations, near earth plasma sheet thinning, onset of tail current instabilities and the tearing mode instability. The most commonly accepted explanation of substorms is based on a reconnection model in which interplanetary magnetic field lines merge with geomagnetic field lines and draw them back over the polar cap into a long tail. A sudden onset of reconnection at an x‐type neutral line in the near‐earth tail reconnects the earth's field lines, releasing a portion of the tail's magnetic flux and injecting particles into the night side magnetosphere. Many details of substorm morphology are subjects of considerable controversy and alternative explanations not involving reconnection also exist.
Continental collisions
Authors: Roeder Dietrich
Published: February 2008

Continental collision, in the context of plate tectonics (Wilson 1966, 1968), is the aborted subduction of continental crust. Subduction gives way to horizontal compression because the low density of continental crust resists the gravitational re‐incorporation of the subducted lithosphere into the mantle (McKenzie 1969). Continued plate convergence leads to major fields of inhomogeneous strain within adjacent regions of the continental lithosphere. Depending on the composition of the upper plate of a subduction zone involved in collision, it is customary (Dewey and Bird 1970) to distinguish between arc‐continent (A‐C) collisions or, in part, obductions (Coleman 1970, Dewey 1976), arc‐arc (A‐A) collisions (Dewey, 1969), and continent‐continent (C‐C) collisions.
Lithospheric flexure
Authors: Forsyth Donald W.
Published: February 2008

During the last four years, major progress has been made in mapping regional variations in the strength of the lithosphere and in understanding the rheological properties of the upper mantle which are responsible for the plate‐like behavior of the lithosphere. It has long been recognized that the apparently rigid translations of the plates and the support of large topographic loads on the earth's surface require a strong lithosphere overlying a weak asthenosphere. Recently, interest in defining the detailed mechanical properties of the lithosphere has greatly increased, perhaps stimulated by the discovery of a double Benioff zone beneath Japan which may be related to the unbending of the subducted oceanic plate. Many investigators seem to be reaching a general consensus on a model of the oceanic lithosphere which is consistent with thermal models of the upper mantle, experimental rock mechanics, gravity and bathymetrie surveys, and patterns of seismicity and focal mechanisms.
Pore pressure effects in crustal processes
Authors: Martin Randolph J.
Published: February 2008

Perhaps one of the most significant aspects of the earth's crust is that the cracks and cavities within the rocks are not dry. The presence of interstitial water and water vapor has a pronounced effect on many crack related properties of brittle rocks such as fracture strength, frictional strength, creep rate, static fatigue, seismic wave velocity, compressibility, resistivity, to name a few. Although the influence of water on geophysical properties has been known for many years, several recent developments have accentuated the need for more detailed information on the mechanical and chemical effects of pore water in natural situations. First, the energy crisis has focused attention on the development of new geothermal resources as well as the stability of various rock types in areas proposed for nuclear waste disposal.
Precipitation research, 1975–1978
Authors: Court Arnold
Published: February 2008

Precipitation research in the United States during the past quadrennium, 1975–1978, has been directed at all three steps of a scientific discipline: description, explanation, and prediction. Most of the work, however, has been in describing, in various ways, the occurrence of precipitation: instruments and measurements, stochastic and analytic models, and accounts of extremes of precipitation or lack thereof: deep snows, cloudbursts and hurricane rains causing floods, unusually wet periods and droughts.

These observed precipitation patterns were explained, somewhat, in a few papers as arising from variations in the inputs to general circulation models (changes in atmospheric dust or in sea surface temperatures) as well as from local causes: changes due to urbanization, irrigation, or industry, and to the apparent effects of weather modification experiments and operations. Prediction has made considerable progress by using multivariate regressions (“Model Output Statistics”) to relate the probability of precipitation (“PoP"), and even its amount in quantitative precipitation forecasts ("QPF”), to the various predictions, 12, 24, and 36 hours in advance, of operational circulation models (PE, LFM, etc.). Each of these aspects of precipitation research will be discussed in the order given.
Surface water hydrology
Authors: Kibler David F. , Hipel Keith W.
Published: February 2008

Steady progress in many areas of deterministic and stochastic hydrology has occurred in the period 1975–78. In almost every instance, the progress reported here is the result of work continuing from an earlier period and not the result of technical breakthrough during the past four years. With regard to deterministic hydrology, important advances have been made relative to: assessment of spatial variability in the sub‐processes of infiltration, surface depression storage, and surface and sub‐surface runoff; development of simplified methods of flood routing in rivers, reservoirs and storm drain systems; application of conceptual models to hydrologic‐environmental problems; selection of flood frequency models and the analysis of parameter uncertainty; and preliminary assessment of flood frequency methods for ungaged watersheds. In the field of stochastic hydrology, important advances have been made regarding: the Hurst phenomenon; Box‐Jenkins modeling; Kaiman filtering; simulation methods based on Bayesian and multivariate models; spectral methods applied to watershed response; and reservoir theory.
Groundwater in the United States 1975–78
Authors: Rosenshein J. S.
Published: February 2008

During the quadrennial period 1975–78, interest in groundwater in the United States has been at a high level. The water‐related environmental problems associated with energy and mineral resource development, particularly on Federal lands, have contributed in part to this interest. Environmental issues and the progress toward implementation of the Safe Drinking Water Act of 1974 and of the Water Pollution Control Act Amendment of 1972 (Section 208), including planning aspects at the state level, have resulted in a greater awareness of groundwater‐related quality problems. The major drought that occurred during this period in the western and central part of the United States created a greater awareness at National and local levels of the overall water supply and economic significance of the groundwater systems underlying drought‐affected areas.
Geodetic theory
Authors: Eckhardt Donald H.
Published: February 2008

Solutions of problems relating to the redefinition of North American geodetic networks have been important research topics of the National Geodetic Survey. Geodetic network adjustments will be accomplished using higher level Helmert blocking.Snay[1976] derived an improved algorithm for reducing the profile of sparse matrices encountered in geodetic adjustments.Snay[1978a] also used logical geometry to analyze the solvability of geodetic networks. An algorithm to compute the eigenvectors of a symmetric matrix was derived bySchmid[1978].
Internal waves, finestructure, microstructure, and mixing in the ocean
Authors: Gregg M. C. , Briscoe Melbourne G.
Published: February 2008

Progress in measuring, interpreting, and understanding oceanic internal gravity waves and fine and microstructure is reviewed; we emphasize the quadrennium 1975–1978. The context is how these subjects contribute to oceanic mixing. The overlap between the areas is examined, as is the relevance of the subjects to other aspects of oceanography.

Present trends and suggestions for future work are included, and we offer some speculation on possible progress during the next quadrennium, which may be substantial especially for finestructure understanding.
Planetary surfaces
Authors: Mutch Thomas A.
Published: February 2008

This review paper has several aims: first, briefly to characterize planetary photogeology as a scientific discipline; second, to provide some sense of the rapid emergence of this field; third, to systematically review the literature over the past few years; and fourth, to identify the more significant problems for future analysis.

To some degree, the four sections dictated by these goals speak to different audiences. Those unfamiliar with the progress in our understanding of planetary surfaces may be best entertained by a broad overview. Those involved in related science may find more useful the brief citations of the recent literature.
The Global Atmospheric Research Programs's Atlantic Tropical Experiment
Authors: Greenfield Richard S. , Fein Jay S.
Published: February 2008

The Global Atmospheric Research Program (GARP) was described in some detail in the last U.S. National Report (Perry, 1975). The latest GARP activities are discussed in another contribution to this report. In this section, we will describe the major research activities that followed the GARP Atlantic Tropical Experiment (GATE) of 1974.

From the beginning of GARP, the tropics were identified for special attention. The tropical zones, of course, are the primary source of heat driving the general circulation of the atmosphere. The phenomena that transmit the necessary energy to the middle latitudes are not adequately treated in the large‐scale models of the general circulation. To a large extent this inadequacy is due to significant gaps in our understanding of the physical processes involved in deep cumulus convection and the interactions between convection and the other dominant scales of atmospheric phenomena. GATE was designed to obtain data that permit research on the effects of smaller scale tropical systems on the larger scale circulations. The ultimate objective of GATE is to improve and verify tropical numerical models.
Impact cratering: The effect of crustal strength and planetary gravity
Authors: O’Keefe John D. , Ahrens Thomas J.
Published: February 2008

Upon impact of a meteorite with a planetary surface the resulting shock wave both ‘processes’ the material in the vicinity of the impact and sets a larger volume of material than was subjected to high pressure into motion. Most of the volume which is excavated by the impact leaves the crater after the shock wave has decayed. The kinetic energy which has been deposited in the planetary surface is converted into reversible and irreversible work, carried out against the planetary gravity field and against the strength of the impacted material, respectively. By using the results of compressible flow calculations prescribing the initial stages of the impact interaction (obtained with finite difference techniques) the final stages of cratering flow along the symmetry axis are described, using the incompressible flow formalism proposed by Maxwell. The fundamental assumption in this description is that the amplitude of the particle velocity field decreases with time as kinetic energy is converted into heat and gravitational potential energy. At a given time in a spherical coordinate system the radial velocity is proportional to R−z, where R is the radius (normalized by projectile velocity) and z is a constant shape factor for the duration of flow and a weak function of angle. The azimuthal velocity, as well as the streamlines, is prescribed by the incompressibility condition. The final crater depth (for fixed strength Y) is found to be proportional to R0[2(z + 1)uor²/g]1/(z+1), where uor is the initial radial particle velocity at (projectile normalized) radius R0, g is planetary gravity, and z (which varied from 2 to 3) is the shape factor. The final crater depth (for fixed gravity) is also found to be proportional to [ρuor2/Yz]1/(z+1), where ρ and Y are planetary density and yield strength, respectively. By using a Mohr‐Coulomb yield criterion the effect of varying strength on transient crater depth and on crater formation time in the gravity field of the moon is investigated for 5‐km/s impactors with radii in the 10‐ to 107‐cm range. Comparison of crater formation time and maximum transient crater depth as a function of gravity yields dependencies proportional to g−0.58 and g−0.19, respectively, compared to g−0.618 and g−0.165 observed by Gault and Wedekind for hypervelocity impact craters in the 16‐ to 26‐cm‐diameter range in a quartz sand (with Mohr‐Coulomb type behavior) carried out over an effective gravity range of 72–980 cm/s².
A characterization of the inverse gravimetric source problem through extremal measures
Authors: Anger Gottfried
Published: February 2008

Most problems in applications are inverse source problems or identification problems. This review deals with a systematic treatment of the nonnegative sources (measures) relative to the Laplace equation and the heat conduction equation producing the same potential outside a domain Ω ⊂ R³. This set is convex and weakly compact. Therefore the basic theorems on convex sets can be applied to such problems. Sets of extremal measures are characterized by geometric conditions. Almost nothing is known about the structure of the sources which produce the earth’s gravitational field. Therefore these investigations may be of interest for the inverse problem in gravimetry. The following question remains unanswered in this review: to find additional conditions to select uniquely a measure producing the earth’s gravitational field. This question is unanswered in most inverse source problems.
Flow law for polycrystalline ice in glaciers: Comparison of theoretical predictions, laboratory data, and field measurements
Authors: LeB. Hooke Roger
Published: February 2008

Theoretical considerations, laboratory experiments, and limited field data support a value of 3 for the exponent n in the commonly used empirical flow law ϵ = (τ/B)n relating stress and strain rate in polycrystalline ice. If this value is accepted, the viscosity parameter B can be determined for a wide variety of experiments. In a plot of log B against reciprocal temperature, points scatter about a line defined by an empirical equation of the form B = B0 exp {(T0/T) ‐ [C/(Tr ‐ T)k]}, where T is the temperature in kelvins and B0, C, T0, Tr, and k are empirically determined constants. For laboratory data the scatter is equivalent to approximately a factor of 5 variation in strain rate for a given stress and temperature. The cause of this variation is unclear, but because results from any single laboratory are generally internally consistent, sample preparation procedures should be studied. Field experiments yield values of B that are systematically higher than laboratory results. Thus natural ice appears stronger than laboratory ice, despite the coarser texture and the presence of anisotropic fabrics in the natural ice, both of which should tend to soften it. In addition, natural ice in glaciers appears stronger than natural ice deformed in the laboratory. These observations suggest either that the stress is systematically overestimated in field studies or that a flow law based on the von Mises yield criterion (or the second invariant of the stress deviator tensor) does not provide an adequate description of the deformation of ice in multiaxial stress fields.
A survey of fog and related optical propagation characteristics
Authors: Stewart Dorathy A. , Essenwanger Oskar M.
Published: February 2008

A thorough literature survey of drop size distributions, liquid water contents, and vertical thicknesses of fogs throughout the world is discussed and summarized in tables. The information on drop size distributions is then used to obtain estimates of extinction of different wavelengths of electromagnetic energy. The relative attenuations of visible wavelengths and wavelengths near 10 µm depend crucially upon the shape of drop size distributions. Attenuation of wavelengths near 1 mm by fog drops is always less than attenuation by the much shorter wavelengths. However, attenuation by water vapor is significant near 1 mm even in window regions between strong absorption lines. Sample computations on German data compare total attenuation in German fogs in different seasons.
The polar ionosphere
Authors: Heelis R. A.
Published: February 2008

During the International Magnetospheric Study period our understanding of phenomena in the polar ionosphere and the role of this region in the coupling between the ionopshere and the magnetosphere has progressed to a point where many self‐consistent pictures are emerging. In many cases the required relationships between electric currents, conductivity, and electric field can be demonstrated, and observed phenomena can be explained in terms of realistic variations in these parameters. The distribution and composition of plasma can be reconciled with realistic patterns of large‐scale plasma motion and ion production regions. The extent of our understanding is reviewed here. There are, however, gaps in our understanding of the electrodynamic and the plasma properties of the polar ionosphere. But the gaps show promise of being filled by our ability to properly formulate the problems and to provide the necessary measurements from present and future spacecraft missions.
The ionosphere as a source for magnetospheric ions
Authors: Horwitz James L.
Published: February 2008

Ion composition measurements within the past several years have shown O+, He+, and other ions of terrestrial origin to compose a substantial fraction of the magnetospheric ion population. In this review we examine (1) observations of topside ionospheric composition, (2) mechanisms for energization and injection of ionospheric ions into the magnetosphere, and (3) observations of ions of ionospheric origin in various regions of the magnetosphere, including the plasmasphere, ring current, magnetotail plasma sheet and lobes, and boundary layer and magnetosheath.
Geodetic theory
Authors: Jekeli Christopher
Published: February 2008

Spurred by a tremendous increase in new and highly accurate data and by prospects for further improvements, theoretical studies in geodesy have concentrated on devising new methods, or adapting extradisciplinary ones, to process the data efficiently and accurately. Satellite altimetry, the NAVSTAR Global Positioning System, satellite Doppler, satellite‐to‐satellite tracking, satellite laser, VLBI, satellite interferometry, and inertial navigation advancements are all contributing to provide the geodetic, and indeed the geophysical, community with a wealth of new data. Least‐squares collocation has achieved prominence through numerous applications, but for efficiency it must compete with other methods, such as those founded in spectral theory. Also, the improved measurement accuracy has mandated the development of more realistic geodetic models where former approximations can no longer be tolerated.
Status of the geopotential
Authors: Lerch Francis J.
Published: February 2008

Substantial progress has been made in modeling the geopotential field since the last reporting period (Anderle, 1979a). Models of the gravity potential show improvement across the entire gravitational spectrum with resolution down to 1° haIf‐wavelength. Major sources of data utilized for advancing our knowledge of the geopotential field consist of satellite laser ranging (Smith, 1982; Wilson, 1979; Linder, 1981) which contributed to the long wavelength portion of the spectrum, satellite altimetry (GEOS‐3, 1979; SEASAT, 1981) and improved surface gravity anomalies (Rapp, 1981b) both of which contributed to the intermediate and short wavelength features of the spectrum. Uniform global distribution of data in combination solutions is generally achieved by using altimeter data over the ocean and terrestrial gravity anomalies over land.
Polar motion and Earth rotation
Authors: Tapley Byron D.
Published: February 2008

During the period from 1979 through 1982, polar motion and earth rotation activity centered on the development of new observation techniques and the investigations of the relation between the observed motions and geophysical phenomena. Determinations of polar motion through classical techniques continued, but the number of United States observing sites was reduced. However, significant advances in alternate methods for polar motion and earth rotation determination were achieved. Regular polar motion and length of day determinations are being reported now by groups analyzing satellite doppler, laser ranging and very long baseline interferometry (VLBI) data, and preliminary determinations of UT1 by these methods are now being reported.
Geomagnetism of Earth's core
Authors: Benton Edward R.
Published: February 2008

It is widely accepted that terrestrial magnetism, an ancient, ever‐present but highly variable phenomenon, owes its existence to “self‐excited hydromagnetic dynamo action” taking place continuously in Earth's molten outer core. Yet, if the truth be admitted, this fine phrase actually enshrines a dynamical process whose details remain woefully obscure. As a result, geomagnetic dynamo theory should and does remain an active branch of modern geophysics. Some broad main issues at the center of this field include (i) the identification and location within the core of the energy source for the geodynamo; (ii) the form of the resulting fluid motions that both sustain and change the magnetic field; (iii) the strength of the unseen toroidal field in the core and the mechanism responsible for equilibration at that finite amplitude; (iv) the cause of angular tilt of the best‐fitting dipole and slow westward drift of the non‐dipole magnetic field; and (v) the mechanism underlying rapid, sporadic reversals of magnetic polarity.
Paleomagnetism of the moon and meteorites
Authors: Hood L. L. , Cisowski S. M.
Published: February 2008

Magnetization, with varying degrees of stability and probable origins, is a ubiquitous property of lunar and meteoritic materials and of the lunar crust in general, as deduced from orbital surveys. Paleomagnetic investigations of these materials and of planetary surfaces attempt to determine the nature of the magnetizing process and to characterize the magnetizing fields with consequent implications for the histories of the early solar system, meteorite parent bodies, and the moon. During the period 1979–1982, progress toward achieving these goals has been made although fundamental problems remain. In the following, most of the relevant results published in english‐language journals are specifically discussed; inevitably, inadvertent omissions of some contributions may occur for which we apologize. The bibliography is intended to be complete and up‐to‐date through August 1982. For more general but less recent reviews of meteoritic and lunar paleomagnetism, the reader is referred to Nagata (1979c) and Hood (1981a), respectively.
Surface water hydrology—runoff generation and basin structure
Authors: Beven Keith
Published: February 2008

This review addresses the problem of developing a theory of the relationship between runoff generation and basin structure. It is suggested that the current generation of physically based models of basin hydrology cannot predict runoff generation in the field with any adequacy because they are not good descriptors of runoff processes, except under some special circumstances. Some of the complex factors contributing to runoff generation that lead to this conclusion are discussed. Special emphasis is placed on the problems posed by the spatial variability of soil characteristics to the application of physically based models. The way in which basin structure changes with spatial scale is then considered. The ordered nature of drainage basins suggests that it may be possible to develop some parsimonious theory relating basin structure to runoff generation. Finally, the importance of time scale is stressed. Changes in basin structure over time are frequently ignored in hydrological analysis. Over long periods of time these changes are on the average gradual, but over the time scale of years there may be important periods of change induced by extreme events. Such an event may affect runoff generation and the frequency characteristics of events that follow it, particularly in small basins. All these complicating factors affect our ability to predict the response of an ungauged basin using physically based models, one of the ultimate tests of physical hydrology.
The dynamics of large scale atmospheric motions
Authors: Holton James R.
Published: February 2008

Dynamic meteorology is the study of atmospheric motions associated with weather and climate. Traditionally dynamical meteorologists have emphasized motions of synoptic and planetary scale. During the past four years there have been a number of exciting developments in the dynamics of synoptic and plantary scale motions. Many of these are related to various aspects of short term atmospheric variability both internally and externally generated.
Advances in satellite oceanography
Authors: Brown Otis B. , Cheney Robert E.
Published: February 2008

Progress has been made in the past four years by U.S. scientists in the development and application of active and passive satellite remote sensing techniques to the study of oceanic processes. This report summarizes technical advances and recent applications. Major advances have been made in developing and applying quantitative measurements from active and passive satellite based sensor systems launched in the late 1970's and that proven methodologies now exist to observe sea surface temperature, ocean elevation, ocean color, surface wind stress and waves, and to locate free drifting buoy data collection platforms. Many of the advances in technique and application have occurred using sensors which were experimental, i.e., not part of an operational satellite observing system. Consequently future geophysical application and development of advanced techniques to enhance our understanding of the ocean will probably be limited in the next five years by data availability rather than our knowledge of how to apply given satellite observations.
Review of marine organic geochemistry
Authors: Gagosian Robert B.
Published: February 2008

Over the past four years the field of marine organic geochemistry has expanded in many directions. In order to cover the major areas of this expansion in a review of the type presented here, several major topic areas have been selected focusing on the processes responsible for the transport and transformation of organic material. Some of these topics have been discussed in a previous review of future research problems in marine organic chemistry (Gagosian et al., 1978). They include: (1) the atmosphere over the oceans and the air/sea interface, (2) dissolved material in seawater, (3) particulate material as it is transported vertically through the water column, (4) Recent marine sediments, as well as (5) transformation reactions, (6) metal‐organic interactions including adsorption/desorption processes in the ocean, and (7) selected subjects in new areas of research.
Synthetics and theoretical seismology
Authors: Harkrider David G.
Published: February 2008

In the near field, discrete‐finite wave number schemes are economic since they involve fewer wave numbers than most wave number integration schemes. The number of wave numbers is determined by the range and the location of artificial reflectors or fictitious sources inherent in discrete wave number techniques. The number and spacing of wave numbers in wave number integration schemes are determined by the desired accuracy.

The vertical integration schemes used in the near field have been either spectral (Apsel, 1979, Bouchon, 1981) as in the regional techniques or finite‐element (Olson,1982) and finite‐difference in the time domain as in the Alexseev‐Mikhailenko method. The finite element schemes have the disadvantage in that the vertical step size is determined by the desired maximum frequency content, which in turn determines the time step required for stability. This time step is usually many times smaller than the time increment associated with the maximum frequency.
Strong‐motion seismology
Authors: Boore David M.
Published: February 2008

Although this is the first review on this topic to appear in a quadrennial report, the roots of strong‐motion seismology extend back to at least 1932, when far‐sighted engineers in the Seismological Field Survey of the U. S. Coast and Geodetic Survey installed rugged, fieldworthy instruments designed to make on‐scale recordings of large earthquakes (Carder, 1964); these instruments are called accelerographs, for their output closely mimics ground acceleration (Hudson, 1979). The original instruments and their offspring have provided a wealth of information about ground motions of direct use to engineers. Due in large part to the continued devotion of the Seismological Field Survey (now part of the Branch of Engineering Seismology and Geology at the U. S. Geological Survey), the number of recordings has increased substantially, particularly in the last two decades, and multiple recordings of a few California earthquakes have provided the data necessary to begin to unravel the complexities of the ground motions and to predict these motions on an empirical basis. Although seismologists used accelerograph records in studies of earthquake energy and ground motion attenuation as long ago as 1942 (Gutenberg and Richter, 1942, 1956), widespread seismological use of the records began with Aki's (1968) analysis of the 1966 Parkfield earthquake.
The origin and earliest state of the Earth's hydrosphere
Authors: Cogley J. Graham , Henderson‐Sellers A.
Published: February 2008

The origin and earliest history of the earth's hydrosphere, the inventory of excess volatiles defined by Rubey in 1951, can be constrained within wide but useful limits by a consideration of empirical and theoretical evidence from astrophysics and geology. Models for the evolution of the solar system from the protoplanetary nebula and for the growth of the earth to its present dimensions suggest quite strongly that the hydrosphere came into being during accretion. Its format, with H2O mostly in the oceans, CO2mostly in sediments, and a residual atmosphere dominated by N2, CO2, and H2O, was established at a very early date and has persisted without large, destabilizing climatic excursions until the present day. Alternative accounts of early history, in which the earth either loses a massive primordial atmosphere or acquires its secondary atmosphere by gradual degassing, seem improbable on the basis of a series of circumstantial but cumulatively persuasive arguments. The difficulty of dissipating a massive atmosphere of solar composition in reasonable times, the likelihood that accretion was a highly energetic process and that it triggered early segregation of the core, and the tendency of the planet to accumulate volatiles preferentially in the later stages of accretion are examples of arguments favoring an early origin for the hydrosphere. Several geological isotope systems which can be sampled today require early separation of the atmosphere and probably the hydrosphere as a whole; these systems record radiogenic enrichment patterns in the noble gases and stable isotope fractionations which suggest an early origin of the biosphere. Certain geological indicators of atmospheric composition, and the broadly equable character of the rock record, are also consistent with a hydrosphere established in the earliest stages of history and having an initial neutral or weakly reduced composition. The climatic stability of such a hydrosphere poses crucial questions, especially since the early sun was less luminous: we find that it is not paradoxical to have an early earth with surface temperature close to that of the present day if the major hydrospheric constituent is liquid water. A near‐global ocean and a cloudy atmosphere provide thermal feedbacks which suffice to maintain climatic stability against the perils of the “deep freeze” and the “runaway greenhouse.” Large quanltities of atmospheric greenhouse gases are not required for climatic stability, although CO2may well have been present in amounts larger than today's; large expanses of dry land are, however, difficult to accommodate in the picture which we present, but the evidence favors differentiation of the continents later in geological history than the early times which we consider. Localized glacier ice is permitted, and perhaps likely, and may provide a milieu favorable for chemical evolution.
Survey of planetary‐scale traveling waves: The state of theory and observations
Authors: Salby Murry L.
Published: February 2008

There exists a considerable body of evidence relating the gravest‐scale transient components of planetary wave activity (periods shorter than a couple of weeks) to the eigenmodes of an unbounded isothermal atmosphere in uniform rotation. The latter, termed “Lamb modes,” have horizontal structures of Hough functions, with a 10‐km equivalent depth, and the external vertical structure of a Lamb wave. They asymptote, for large total wave number, to normal modes of the nondivergent barotropic vorticity equation. Phase speeds of the gravest modes, however, are significantly retarded by divergence. A historical account of the development of large‐scale traveling waves is presented, culminating with the emergence of global observations and the identification of several modes in atmospheric data. Theoretical ingredients of the simple normal mode problem are reviewed. The relationship between these features and extratropical transients is developed via the notion of a “planetary wave spectrum.” Influences of realistic distributions of dissipation and refractive properties are discussed for a prototypical mode. Calculations for several of the gravest modes are then presented for typical climatological configurations. For all of these the simple eigenstructures are largely preserved at tropospheric levels. Recent observational evidence is collected from global satellite and conventional meteorological analyses and compared with theoretical concepts. An overview of realistic considerations, requisite for an understanding of “particular realizations” of these features, is developed. Response to localized, transient forcing is shown to consist not of any single mode, but rather of a spectrum of normal modes. For sufficiently large amplitudes, Lamb modes can give rise to vacillations in eddy flux fields via modulation of the stationary waves. These, in turn, may be accompanied by vacillations in the basic stream.
Trace gases and other potential perturbations to global climate
Authors: Wang Wei‐Chyung , Wuebbles Donald J. , Washington Warren M. , Isaacs Ronald G. , Molnar Gyula
Published: February 2008

We review the various natural and anthropogenic factors that may affect the climate. The purpose is to summarize our understanding of these factors and their potential future climatic effects so that CO2‐induced climate change can be viewed in a proper context. The factors we discuss include trace gases, anthropogenic and volcanic aerosols, variation of solar constant, change of surface characteristics, and releases of waste heat. We discuss the origins of the various natural and anthropogenic perturbations, the physical and chemical processes and their interactions, model sensitivity calculations, and model projections of their potential future climatic effects. The discussions center on trace gases because of their potentially large climatic effects. It appears that the increases of atmospheric trace gases of other kinds in addition to CO2could have important climatic effects. The model calculations suggest that the combined effect of these other trace gases, and the associated change of atmospheric ozone and water vapor distributions, could potentially warm the climate by an amount comparable in magnitude to the effect of doubling the CO2. Aerosols of anthropogenic origins may have substantial effects on regional climate, while the volcanic aerosols may have an effect on large‐scale climate for up to a few years after injection. Changes of surface characteristics and releases of waste heat may also have substantial effects on the regional climate, but these effects are most likely to be small when compared with the effect of CO2increase. Changes of solar constant could have an effect on the global scale, but the time scale is much longer. There is much more that needs to be learned with regard to the above mentioned natural and anthropogenic factors that may affect the climate. A brief summary of those needs is presented.
The Earth Radiation Budget Experiment: Science and implementation
Authors: Barkstrom Bruce R. , Smith G. Louis
Published: February 2008

This paper gives an overview of the Earth Radiation Budget Experiment. The experiment consists of scanning and nonscanning radiometer packages on three spacecraft. One is a satellite with a 57° inclination orbit which processes around the earth once every 2 months. Packages are also flown on the sun‐synchronous NOAA‐F and NOAA‐G operational meteorological satellites. The scanning radiometer includes three channels: shortwave, long‐wave, and total. The nonscanner package encompasses a pair of wide‐field‐of‐view radiometers and a pair of medium‐field‐of‐view radiometers. Each pair consists of a total and a shortwave radiometer. The scientific importance and objectives of the mission are described, including the need for the three spacecraft and the utility of the complementary types of radiometers.
The Earth Radiation Budget Experiment Nonscanner Instrument
Authors: Luther M. R. , Cooper J. E. , Taylor G. R.
Published: February 2008

Two Earth Radiation Budget Experiment (ERBE) nonscanner instruments are flying with companion scanner instruments to measure the earth's energy budget from low earth orbit. A third set of instruments will be launched in March 1986. This program is the first designed to make a comprehensive set of highly accurate measurements of the earth's energy budget on the spectral, spatial, and temporal scales specified by the scientific community for use in climatological research. The ERBE nonscanner combines the use of the highly accurate active cavity radiometer (ACR) detector with a comprehensive preflight calibration and characterization program and a design which includes operational flexibility and in‐flight calibration checks to achieve and maintain, throughout its 2‐year design life, a measurement accuracy capability not previously possible. This paper describes the ERBE nonscanner instrument, its operation, calibration, and mission profile.