bluuebunny/crossref_metadata_2025 huggingface dataset:
Progress in the design of hydrologic‐data networks
Authors: Moss M. E. , Tasker G. D.
Published: February 2008

The design of hydrologic‐data networks is a topic that previously has not been raised to the status of a separate article in the U.S. National Reports to the International Union of Geodesy and Geophysics. However, three articles (Matalas, 1975; Peck, 1975; Schwarz, 1975) in the 1970–1974 Report considered it significant enough to be included as specific sections. Thus, because of the novelty of this article, some references will be made to work performed prior to the report period of 1975–1978 for the sake of completeness.

The collection of hydrologie data has been perceived as a design problem only within the past few decades. Although some earlier work had been done in the area of precipitation gaging networks, Langbein (1954) presented the first comprehensive description of what needed to be done to manage objectively a hydrologic‐data program.
Land gravimetry
Authors: Strange William E. , Wilcox Luman E.
Published: February 2008

This report covers primarily the major activities of U. S. governmental organizations in the field of land gravimetry. Organizations covered are the National Geodetic Survey (NGS) and National Geophysical and Solar Terrestrial Data Center (NGSDC) of the National Oceanic and Atmospheric Administration (NOAA), the U. S. Geological Survey (USGS), the Department of Energy (DOE), the Nuclear Regulatory Commission (NRC), and several components of the Department of Defense (DoD), the Defense Mapping Agency (DMA), the Air Force Geophysical Laboratory (AFGL), the U. S. Army Engineering Topographic Laboratory (USAETL), the Inter American Geodetic Survey (IAGS), and the U. S. Naval Oceanographic Office (NAVOCEANO). Activities of State organizations, universities, and industry are included where they involve large‐scale surveys or activities of special interest. Several individuals and institutions have provided up‐to‐date information on their projects and work for incorporation in this article.
Earth tides
Authors: Farrell W. E.
Published: February 2008

Three major themes have dominated earth tide research over the past four years. These are the inference of tide parameters from small and slow variations in satellite orbits, the quantitative assessment of the causes of the anomalies in the tidal variations in gravity, tilt and strain, and the incorporation of earth tide effects into numerical computations of ocean tides. Much of the increased understanding of and interest in the tides is a consequence of improved measurement methods, a result of instrumental developments started half a decade or more ago. Among the notable advances in instrumentation have been the dramatic increase in the accuracy with which artificial earth satellites can be tracked, and the perfection of the cryogenic gravity meter and the laser strain meter.
Paleoceanographic events—Recognition, resolution, and reconsideration
Authors: Arthur Michael A.
Published: February 2008

Studies of the last 125 million years of oceanographic and climatic history have benefited greatly from the impetus provided by the Deep Sea Drilling Project. Knowledge of the sedimentary and paleontologic record of the major ocean basins, in conjunction with study of pelagic marine sections exposed on land, has permitted both the testing of old and the development of new hypotheses to explain local and global ocean chemical, sedimentologic and biotic events. Some of the more striking and topical problems in paleoceanography are the oceanic “anoxic events” of early to middle Cretaceous age, the biotic crisis at the Cretaceous/Tertiary boundary, the Eocene/Oligocene extinctions and climatic and circulation events, the Messinian “salinity crisis” (late Miocene) and its effects on the world ocean, and Pleistocene glacial cycles and paleoceanography. Possible explanations of these events, which have been proposed over the last five years, are reviewed in this paper.

Application of new concepts and techniques, especially in micropaleontology and geochemistry, has led to refinements in stratigraphic resolution and in recognition of paleoenvironmental signals. Among the most powerful tools now in use is stable isotope geochemistry. Paleomagnetic studies and statistical techniques for processing micropaleontological data have contributed greatly to stratigraphic resolution.

Although we are beginning to unravel the complex interactions of global sea level changes, climate and ocean chemistry and their influence on life, there are innumerable challenging problems still remaining. As stratigraphic resolution and coverage improve so does our perception of the ocean system.
A review of research on mesoscale ocean currents
Authors: McWilliams James C.
Published: February 2008

Mesoscale ocean currents, for the purposes of this review, are defined as currents in the middle and high latitudes, in the mid‐ocean, of low frequency (i.e., with time scales* greater than or comparable to 105s, which is long compared to the inverse of the Coriolis frequency), and of intermediate spatial scale* (i.e., horizontal scales from tens to hundreds of km). They are geostrophic currents of type 1 in the nomenclature of Phillips (1963). Excluded, therefore, from this review are the following topics: equatorial currents, coastal currents, surface, bottom, and lateral turbulent boundary layers, ageostrophic flow, gyre‐scale transience, seasonal cycles, and the general circulation of the ocean. This review is intended primarily as a record of published contributions on this subject since the last such review written in 1974 (Robinson, 1975), with a broad topical catagorization.
Planetary basalts: Chemistry and petrology
Authors: Papike J. J. , Bence A. E.
Published: February 2008

Basaltic rocks have continued to receive considerable attention in the period 1975‐1978. This is largely due to the recognition of their effectiveness as probes of planetary interiors. Basalts that have formed by partial melting in planetary interiors and have been delivered to the planetary surface without gain or loss of material carry clues to: (1) the formation and earliest differentiation history of the terrestrial planetary bodies, (2) residual mineralogy and phase chemistry of the source region, (3) temporal evolution of the source region, (4) depth of the source region, (5) the thermal history of the planetary body, and (6) the intensive thermodynamic values that obtained during basalt petrogenesis.

Because basalts are key indicators of planetary evolution, an experimental project, entitled “Basaltic Volcanism on the Terrestrial Planets Studies Project,” was organized by the Lunar and Planetary Institute, Houston, Texas. The project, funded in part by NASA, is a pilot project in comparative planetology involving approximately 80 scientists representing a variety of disciplines including observational astronomy, cosmochemistry, geochemistry, geology, geophysics, mineralogy, petrology and volcanology. The project was initiated in 1977 and will culminate in 1980 with a book entitled “Basaltic Volcanism on the Terrestrial Planets,” which will summarize the results of the project. The major advances in our understanding of terrestrial basalt petrogenesis that have occurred in the past four years are to a large extent a consequence of the Deep Sea Drilling Project's crustal drilling program. Deeper penetration and improved recovery on Legs 34, 37, 45‐46, 49, 51‐53, and 55 have provided spatial and temporal controls on sampling of the oceanic crust with a much greater areal coverage than can be achieved by submersibles.
Planetary atmospheres
Authors: Ingersoll Andrew P. , Dobrovolskis Anthony R. , Jakosky Bruce M.
Published: February 2008

Four years is approximately the doubling time for knowledge of extra‐terrestrial planetary atmospheres. During 1975–8 the results of several important missions to Venus, Mars, Jupiter and its satellites were analyzed, and during 1979 more spacecraft will arrive at Jupiter and Saturn. Spacecraft data are supplemented by ground‐based observations, often at higher spectral resolution and extending over longer periods of time. As a result of this rapid growth of information, many first‐order questions concerning the composition, physical state and kinematics of planetary atmospheres have been answered.
Climate studies—A plan for action
Authors: Gates W. Lawrence
Published: February 2008

During the past four years the problem of climate has received unprecedented attention in the atmospheric sciences. The upsurge of interest and concern for a subject whose roots go as far back as science itself is clear testimony to the importance attached to the problem. Part of this activity is due to the recognition by scientists that climate is a challenging problem for which there is the possibility of significant progress by the application of modern methods of data collection and diagnosis, mathematical modeling techniques and impact analysis, and part is due to the recognition by governments that climate continues to exert an important influence on man1s activities and welfare. From either viewpoint, climate is now regarded as a problem “whose time has come.”
Magnetic storm associated perturbations of the upper atmosphere: Recent results obtained by satellite‐borne gas analyzers
Authors: Prölss G. W.
Published: February 2008

This review summarizes some of the recent results on the disturbed upper atmosphere obtained by satellite‐borne gas analyzers. According to these measurements, magnetospheric activity leads to the development of two different disturbance zones. The high‐ and middle‐latitude region is characterized by an increase in the heavier constituents Ar, N2, and O2, by a height‐dependent behavior of O, and by a significant decrease of He. The reaction time of the atmosphere is much smaller than one orbital period. At lower latitudes a moderate increase of all constituents is observed. A comparison between atmospheric and ionospheric data demonstrates that, in contrast to positive effects, negative ionospheric storms are closely coupled to changes in the neutral composition. In addition, model calculations fully support a causal relation between both phenomena. Given this correlation, atmospheric and negative ionospheric disturbance effects have certain variations in common. These include systematic changes with the magnetic storm intensity, with magnetic position, with local time, and with season. Whereas the presently available empirical and theoretical models are quite capable of reproducing the basic properties of the observed atmospheric perturbations, these algorithms are not sophisticated enough for a more detailed description of the data.
Observations of sidereal motions of the Earth's surface
Authors: Knopoff L. , Rydelek P. A.
Published: February 2008

Vertical gravity observations from the geographic south pole are analyzed in the semidiurnal tidal frequency band and show the presence of a sidereal semidiurnal spectral component. This component is not unexpected and probably does not provide evidence for the existence of gravitational waves of extraterrestrial origin.
Geophysical constraints on partial melt in the upper mantle
Authors: Shankland T. J. , O’Connell R. J. , Waff H. S.
Published: February 2008

This paper addresses the conditions under which partial melt can exist in the mantle in order to be observed as a geophysical ‘anomaly.’ Typical observed anomalies are high electrical conductivity of the order of 0.1 S/m or greater, velocity decreases of 7–10%, seismic Q values less than 100, and a frequency band for seismic effects in the region near 1 Hz. Existing theories of electrical conduction in partial melts and of frequency‐dependent seismic properties together with recent measurements of melt electrical conductivity, viscosity, and partial melt texture can be used to establish requirements for melt to be observed by geophysical methods. From electrical anomalies, mainly sensitive to melt volume and its interconnection, one can require a minimum melt fraction of several percent at temperatures close to the solidus (1150°–1300°C). However, seismic models demand only a small volume in very flattened shapes (aspect ratio ⋍0.001, melt fraction ∼0.1%). Further, if melt configuration permits seismic dissipation in bulk, that is, there exist flattened voids intersecting more or less equant voids, then it is possible to infer melt fractions for elastic anomalies that are consistent with the several percent required for electrical anomalies. Observed equilibrium textures of partly melted peridotite together with inferred melt‐solid surface energies suggest that melt on a grain size scale in a gravitational field segregates into a strongly anisotropic pattern. Thus if partial melt causes mantle geophysical anomalies, it should exist in a variety of void shapes and probably of sizes. While the association of electrical and elastic anomalies with indications of reduced density, volcanism, and high heat flow makes the hypothesis of partial melting an attractive explanation, the minimum physical requirement is for existence of relatively high temperature.
Convection in GATE
Authors: Houze Robert A. , Betts Alan K.
Published: February 2008

The difficult problem of parameterizing tropical convection in large‐scale models of the atmosphere led to the Global Atmospheric Research Program’s Atlantic Tropical Experiment (GATE), whose goal was to improve basic understanding of tropical convection and its role in the global atmospheric circulation. A dense network of instrumented ships equipped with upper air sounding equipment and quantitative weather radars were located over the Atlantic Ocean, in the intertropical convergence zone (ITCZ), just west of equatorial Africa. The ship network was supplemented by a fleet of research aircraft and a geosynchronous meteorological satellite. The data obtained show that the deep convection in the ITCZ was concentrated in two types of ‘cloud clusters,’ rapidly moving squall clusters, and slowly moving nonsquall clusters. The clusters were characterized by large mid‐to‐upper level cloud shields, or ‘anvil clouds,’ that emanated from penetrative cumulonimbus convection. Accompanying the deep cumulonimbus in each cluster was a log normal spectrum of smaller convective features ranging from moderate cumulonimbus down to tiny nonprecipitating cumulus. The large cumulonimbus were typically grouped within a cluster into one or more mesoscale precipitation features (or MPF’s), which were apparently triggered in mesoscale regions of intensified low‐level convergence. As an MPF matured it developed a region of stratiform precipitation adjacent to its active deep convective cells. The stratiform precipitation fell from the anvil cloud. Associated with the stratiform precipitation were a mesoscale downdraft below the anvil cloud and an apparent mesoscale updraft within the anvil cloud itself, above the mesoscale downdraft. These mesoscale drafts were distinct from the convective‐scale updrafts and downdrafts of the cumulus and cumulonimbus cells of the cluster. Downdrafts, both convective scale and mesoscale, filled the planetary boundary layer in the vicinity of cumulonimbus with stable air of low moist static energy. These wakes of downdraft air exerted a strong control on where future convection broke out. The results of GATE show that to simulate the effects of tropical convection in large‐scale numerical models of the atmosphere a variety of phenomena must be accounted for, including not only convective‐scale updrafts and downdrafts but anvil clouds with mesoscale updrafts and downdrafts, downdraft‐induced boundary layer transformations, and mesoscale convergence patterns. Experimentation with ways of including some of these features of tropical convection in large‐scale diagnostic and prognostic studies is under way, but much work remains to be done.
The cometary atmosphere and its interaction with the solar wind
Authors: Mendis D. A. , Houpis Harry L. F.
Published: February 2008

The present state of both our knowledge and our understanding of cometary atmospheres and their interactions with the solar wind is critically reviewed. Following the introduction (section 1) the spectrophotometry of the cometary atmosphere and the tail is reviewed in section 2. The existing, rather fragmentary, knowledge about atmospheric abundances and the production rates of various molecular species is given in section 3. The deductions that can be made from these values about the chemical composition of the nucleus and their uncertainties are discussed. Existing models of the cometary atmosphere including the ionosphere are critically evaluated in section 4. The continuing dichotomy between models that concentrate on the chemistry while oversimplifying the dynamics and those that concentrate on the dynamics and thermodynamics while minimizing the chemistry is discussed. The need to combine these two approaches in the future is emphasized. The ionization processes in the cometary atmosphere are discussed in section 5. It is emphasized that besides photoionization and charge exchange ionization with the solar wind protons, other (collisional) ionization processes may play a role in the rapid ionization of cometary neutrals in certain situations. The overall nature of the solar wind‐comet interaction is discussed in section 6 with special emphasis on the strong coupling between the solar wind and cometary plasmas, which is responsible for the observed accelerations in the cometary tails. The complex and time‐varying fine structures observed in the plasma tails of comets are discussed next in section 7. The uses of these to infer the strength and morphology of the magnetic field and the associated currents in the plasma tail on one hand, and the varying conditions in the solar wind on the other, are emphasized. The detailed models of the comet‐solar wind interaction, from the earlier fluid dynamic models to the latest MHD models are critically evaluated in section 8, and their limitations are underscored. It is also pointed out that the nature of the solar wind interaction with the cometary atmosphere is highly variable and that in certain circumstances the nature of both the outer and the inner shocks could change. Also, the need for a detailed study of the solar wind interaction with the fledgling cometary atmosphere at larger heliocentric distances is stressed. The review is concluded with section 9, where the emphasis is on the outstanding problems of cometary atmospheres and their interactions with the solar wind.
A review of recent advances in tornado vortex dynamics
Authors: Snow John T.
Published: February 2008

Advances in understanding the dynamics of tornado vortices since the Lubbock symposium of 1976 are reviewed. The focus is on results obtained from experimental work with laboratory models and from numerical simulations of both real and laboratory events. Progress is shown to have been made in two areas: an increased appreciation for the possible complexities of tornado vortex structure and an improved understanding of the vorticity dynamics of columnar vortices. With respect to the former the evolution of the central core flow from a single‐celled to a two‐celled flow is described, and a mechanism capable of producing the multiple‐vortex phenomenon is discussed. In the latter area the arrangements of vortex lines within the surface inflow layer and in the cores of one‐ and two‐celled vortices are presented. It is seen that both the laboratory work and the numerical simulations indicate a key role in the dynamics of the vortex core played by the vortex breakdown phenomenon. Wherever possible, the theoretical findings are related to recent high‐quality observations of actual tornadoes.
Planetary atmospheres
Authors: Beebe Reta
Published: February 2008

The period from 1979 to 1982 has been characterized by extensive exploration of the Solar System. Pioneer and Voyager missions to Venus, Jupiter, and Saturn combined with ongoing analysis and data collection from the Viking‐Mars mission have contributed greatly to our understanding of planetary atmospheres.

The Pioneer orbiter and the Pioneer multiprobe missions that arrived at Venus in December 1978, yielded results [Donahue, 1979] which have been combined with those from Venera 11 and 12 in December 1979, and Venera 13 and 14 in March 1982, [Moroz, 1981] to provide atmospheric data of significantly higher resolution and precision that has been available previously.
Dynamics of the Earth's thermosphere
Authors: Roble R. G.
Published: February 2008

The earth's thermosphere is that region of the atmosphere above the mesopause (80–90 km) where the neutral gas temperature begins to increase from about 200°K to values as high as 600–2,000°K depending upon solar activity. The dynamics of this region of our atmosphere is primarily governed by solar EUV and UV heating, heat and momentum sources associated with high‐latitude auroral processes, upward‐propagating tides and waves from the lower atmosphere, and ion drag interactions with the ionosphere. The general properties of the thermosphère and the research on thermospheric dynamics prior to 1979 have been reviewed previously in this IUGG series by Dickinson (1975) and Mayr and Harris (1979). Ionospheric processes and large‐scale neutral gas‐plasma interactions have been reviewed by Evans (1975), and reviews covering thermospheric composition have been given by Carrignan (1975) and Hedin (1979).
Cosmic‐ray modulation and the anomalous component
Authors: Jones Frank C.
Published: February 2008

This review is concerned with advances in Cosmic‐Ray Modulation observation and theory and in the study of the anomalous component of the cosmic radiation. It concentrates primarily on advances made in American research and reported in the open literature during the years 1979–1982. This rule is, of course, not rigidly adhered to; certain works that are intimately related to the subject under discussion are cited even though they may lie outside of the above mentioned bounds.

Since the last report in this series there have been two International Cosmic Ray Conferences, in Kyoto in 1979, and in Paris in 1981. A great number of papers that are relevant to our subject were presented at both of these conferences. I have, therefore, cited freely from the proceedings of these conferences with one exception; If I found that a conference paper was subsequently published, by the same authors, in unchanged or expanded form in the open literature, I considered the conference paper to be a “preliminary report” and have cited the final paper instead.
Magnetospheric and interplanetary physics 1979–1982
Authors: Stern David P.
Published: February 2008

The quadrennium 1979–1982 witnessed notable advances in magnetospheric and interplanetary physics, and demonstrated some major trends. Examples of both will be listed below, followed by an evaluation of the state of the discipline and of its future.

Standing out among the advances is the enormous volume of data about the magnetospheres of the giant planets, collected by Voyagers 1–2 and by Pioneer 11. At the start of 1979 the very existence of Saturn's magnetic field was uncertain, and the role of the satellite Io in Jupiter's magnetosphere was only dimly guessed: 4 years later we have extensive information on both magnetospheres, on their underlying planetary fields, ring currents, radio emissions, plasma composition and nightside configuration, and about such matters as Io's plasma torus and the current filament linking Io to Jupiter, Saturn's inner radiation belt (from neutron albedo) and Titan's wake.
Near‐equatorial magnetospheric particles from ∼1 eV to ∼1 MeV
Authors: Young D. T.
Published: February 2008

This report covers near‐equatorial populations of charged particles found within the Earth's magnetosphere. The spacecraft most responsible for advances in our knowledge of near‐equatorial populations over the past four years are listed in Table 1. Note that all spacecraft carried one or more composition‐measuring instruments. This intensive effort has demonstrated the importance of heavy ions (i.e. species heavier than hydrogen) not only as tracers of particle origins and diagnostics of magnetospheric processes, but also as catalysts and major participants in magnetospheric phenomena.
Plasma waves in planetary magnetospheres
Authors: Anderson Roger R.
Published: February 2008

The studies of magnetospheric plasma waves in the 1979–1982 quadrennium have included not only intensive studies of plasma waves in the Earth's magnetosphere but also, for the first time, in situ observations and detailed analyses of plasma waves in the magnetospheres of Jupiter and Saturn. While much of the research has involved the continuing identification and classification of plasma wave phenomena in the magnetospheres, increasingly greater emphasis has been placed on understanding the sources of the plasma waves and the interactions of plasma waves with the particles. Many studies have also shown that plasma wave measurements may be used to discern numerous geophysical boundaries and parameters.

At the earth, significant progress in plasma wave research has been made that has increased our understanding of wave‐particle interactions and their effects, throughout the magnetosphere from the auroral ionosphere out to the bow shock and back into the tail. Observations of auroral kilometric radiation both in the source region and far from it have provided much new information about this intense emission. Details of the fine structure of the radiation and its polarization and propagation characteristics along with particle distribution and other plasma wave measurements in the source region have provided valuable inputs to various generation theories. Similar progress has also been made in understanding electron cyclotron harmonic emissions and nonthermal continuum radiation. Detailed characterizations of plasma wave phenomena reported during this quadrennium in the plasmasphere, outer magnetosphere, magnetopause, magnetosheath and tail regions have been important in assessing the impact of the waves on the particle distributions and vise versa.
Satellite altimetry
Authors: Marsh James G.
Published: February 2008

During the past four years satellite altimetry activities have been primarily concerned with analyses of the GEOS‐3 and Seasat data sets, and the justification and design of next generation altimetric missions and associated instrumentation.

Since the last IUGG Quadrennial review of satellite altimetry [Stanley, 1979a], considerable documentation of altimetric engineering and scientific results has occurred. There has been a special issue of the Journal of Geophysical Research [JGR Vol. 84, B8, 1979] dedicated to scientific results from GEOS‐3. A special issue of Marine Geodesy [Vol. 3, 1980] contains numerous papers on the analysis of altimeter data presented at an International Symposium on Interaction of Marine Geodesy and Ocean Dynamics. A special issue of the IEEE Journal of Oceanic Engineering [OE‐5(2), April 1980] contains a discussion of Seasat sensors and attendant processing algorithms. A special issue of the Journal of the Astronautical Sciences [28(4), Oct‐Dec 1980] was devoted to the problem of orbit determination for Seasat; a subject of importance to users of satellite altimeter data. A special issue of the JGR [Vol. 87, C5, 1982] was dedicated to Seasat geophysical processing algorithms and evaluation. A second Seasat JGR special issue dedicated to scientific results will be published in early 1983, and a special issue of Marine Geodesy devoted to satellite altimetry also will be published in 1983.

This review presents a summary of the geodetic applications of altimeter data, precision orbit determination analyses, the status of the instrumentation and the plans for future altimeter missions. A review of the applications of altimetry to oceanography, including mesoscale current detection and variability, wind and waves, ocean tides and ice is presented in a separate paper by Brown and Cheney [1983].
Main field and recent secular variation
Authors: Alldredge Leroy R.
Published: February 2008

As Cain (1979) indicated might happen in the last IUGG quadrennial report, added resources were made available during the past few years and a real impulse was added to the geomagnetic work in the United States by the launching of the MAGSAT Satellite. This new effort paid off in terms of new charts, additional long wavelength studies, and external source studies. As before, however, the future funding for new starts in geomagnetism does not look bright at the present time.

A single MAGSAT in orbit a little more than seven months did wonders for main field (M.F.) charting, but did little or nothing for secular variation (S.V.) charting. It would take a number of repeated MAGSATS to help the S.V. picture. Meanwhile, the world magnetic observatory net and surface repeat stations remain as the main source of S.V. data.
Polar meteorology and climatology 1979–1982
Authors: Robinson Elmer
Published: February 2008

Polar meteorology and climatology have continued to progress since the past review by Radok (1979), and the emphasis in polar meteorological and atmospheric research has continued to reflect the interests of meteorologists and other scientists in topics of global importance. Thus there is a strong concentration of research related to climatic change with observational, modeling, and theoretical studies. In addition, problems from the mainstream of world activities have intruded in some rather obvious ways into polar research. The possible consequences of air pollutants on these regions began to attract considerable attention.
An overview of passive microwave snow research and results
Authors: Foster J. L. , Hall D. K. , Chang A. T. C. , Rango A.
Published: February 2008

The current state of knowledge of the microwave properties of snow is discussed. Theory behind the microwave emission from snow is reviewed, as are the physical processes of snowpack metamorphism. Field, aircraft, and satellite passive microwave data have been acquired and analyzed for more than 10 years. Results have repeatedly demonstrated the feasibility of employing multifrequency passive microwave data to study snow‐covered area, snow depth, and internal snowpack properties. Radiation emanating from the ground beneath a snowpack is scattered by the snow crystals, and concurrently, the snow itself emits radiation at microwave frequencies. Thus the radiation emerging from the snowpack is the result of a complex series of interactions both within and beneath the snowpack. Future studies recommended by a snowpack properties working group consisting of government and university scientists are discussed in detail. Recommendations include performing extensive laboratory measurements using real and artificial snow, to be coordinated with theoretical modeling and aircraft overflights carrying passive microwave instrumentation. This is considered necessary in order to help to interpret the microwave responses to snow.
Radio emissions from the planets Earth, Jupiter, and Saturn
Authors: Kaiser M. L. , Desch M. D.
Published: February 2008

We review the major observed and inferred features of the three currently known nonthermal radio planets, the earth, Jupiter, and Saturn. Several of the properties of the three planets are quite similar, suggesting that the same processes take place at all three. In addition, Jupiter has two radio components in the low‐frequency range which may not have analogs at the earth or Saturn. We speculate on the expected addition of Uranus to this list of radio planets.
Small‐scale physics of the ocean
Authors: Caldwell Douglas R.
Published: February 2008

Four years ago, we noted that, although there was a widespread belief that the key to many ocean processes must be the communication of energy by internal waves, there had been little progress in definitely relating small‐scale processes to internal waves (Caldwell, 1983a). For example, although it seemed plausible that the energy that supplies spots of turbulence in the thermocline is delivered to those spots by internal waves, the process had neither been directly observed nor shown theoretically in a verifiable calculation. In the past four years there has been some progress; observations have been made which render such connections more plausible and some theoretical ideas have been advanced, but we've seen no breakthrough in this direction.

Instead, progress has come on other fronts. Our picture of turbulent processes in the upper ocean, especially in the equatorial ocean, is becoming more clear (and more complicated). Strong downdrafts in the mixed layer have been discovered. Dissipation in the convective mixed layer has been found to scale very much as it does in similar layers in the atmosphere. The dynamics of intrusions have drawn attention because they may contribute a good deal of the mixing of the oceans. Although significant laboratory experiments are now available, controversy remains concerning the application of laboratory turbulence concepts to the ocean. Bottom‐layer flows have now been carefully defined. One notable development is the increased interest in the effect of mixing conditions on biological activity. Our instrumentation is becoming more routinely deployable, an important step toward obtaining the large amount of sampling required to form a reasonably accurate picture of small‐scale processes in the ocean.
A review of numerical ocean modeling (1983–1986): Midlatitude mesoscale and gyre‐scale
Authors: Evans James C. , Haidvogel Dale B. , Holland William R.
Published: February 2008

For the years 1983 to the present, numerical modeling of midlatitude ocean circulation on the mesoscale and gyre‐scale is reviewed. Numerical results have shown great similarity to recent thermocline theories, but also some important differences. In particular, ventilation of the “pool zone”, caused by convective processes, is substantial; also, solutions employing explicitly‐resolved eddies differ significantly from their equilibrium counterparts. Inverse methods have provided improved estimates of meridional heat transport and tropical upwelling of tracers. The crucial influence of the western boundary on the circulation of the gyre interior is beginning to be understood. Research has focused on the conditions for radiation by jets, the relationship between a jet's structure and its stability, and the generation of deep mean flows by eddy activity near the surface. Constraints on the structure of isolated vortices imposed by instability mechanisms have been explored with new balanced models, which provide an inexpensive but accurate alternative to primitive equation models for many oceanic processes. Transport of salinity by Gulf Stream rings has been found to be comparable to the effects of evaporation and precipitation in the Slope Water. It has also been shown that radial circulation in warm‐core rings cannot be disregarded as a possible cause of ring spin‐down. In anticipation of a dramatic increase in the oceanic observational data base from altimetry, scatterometry, tomography, and in situ measurement, new modeling techniques for data assimilation and prediction are beginning to be developed.
Volatile inventories of the terrestrial planets
Authors: Pepin Robert O.
Published: February 2008

The past few years have seen continuing application of classical theories of thermal and nonthermal atmospheric escape to problems involving the compositional and isotopic evolution of planetary volatile reservoirs. A new emphasis on a previously underappreciated thermal process, hydrodynamic escape, has appeared in interpretations of hydrogen and noble gas fractionation patterns in terrestrial planet atmospheres. Other mechanisms for loss of atmospheric mass, notably by impact‐induced erosion at various scales, have been discussed and roughly modeled. Direct spacecraft exploration of Halley's Comet in 1986 has rekindled interest in cometary matter as a possible early source of planetary volatiles, particularly for Venus.
Planetary atmospheres
Authors: Leovy Conway
Published: February 2008

Rapid advances in our understanding of planetary atmospheres have occurred since the previous quadrennial review (Beebe, 1983), based to a large extent on analyses of planetary spacecraft data from earlier periods. The VEGA mission at Venus and Voyager 2 at Uranus provided new data, as did an active program of remote sensing from Earth and its vicinity.

A number of valuable books and review articles appeared focusing on the origin and evolution of atmospheres as well as their present states (e.g., Lewis and Prinn, 1984; Hunt, 1983; Pollack and Consolmagno, 1984). Clearly, research on atmospheres in the solar system is no longer just exploratory; it has reached the stage of in‐depth study.
Overview of the Atmospheric Sciences Report
Authors: Beasley William H.
Published: February 2008

The first duty of each special associate editor for the quadrennial U.S. National Report to IUGG is to identify the topics that ought to be included, a task that is intellectually challenging, but not labor intensive. The second, more difficult, principal task is to solicit, and if necessary, cajole individual authors to undertake review papers. The objective is a report on U.S. research during the last four years that is within reasonable page limitations, comprehensive, neither redundant nor duplicative of other recent reviews, and yet representative. Whether a particular topic appears in the report depends on the biases and persuasiveness of the special associate editor, coverage or lack of coverage of topics in other forums, and willingness of someone to undertake a paper for the report. It should be clear that the absence of a topic in this report, whether explicitly covered in previous US National Reports to the IUGG or not, does not signify a judgement by the editors that the topic lacks merit.
Solar particle acceleration and propagation
Authors: Lin R. P.
Published: February 2008

Large solar flares are the most energetic natural particle accelerators in the solar system, occasionally accelerating ions to many GeV and electrons to ≳102 MeV energies. The accelerated particles can be studied indirectly, via observations of the electromagnetic emissions produced by the particles in their interactions with the solar atmosphere, or directly by spacecraft and ground‐based observations of the particles which escape into the interplanetary medium. The electromagnetic emissions (X‐ray, gamma‐ray, and radio emission) depend critically on ambient conditions in the solar atmosphere where the accelerated particles reside (the density, magnetic field, and temperature), while the interpretation of the particle fluxes observed in the interplanetary medium depends on the characteristics of the escape and interplanetary propagation processes.

Radio, X‐ray and gamma‐ray, and energetic particle observations obtained before the 1980 solar maximum suggest that there are at least two acceleration processes associated with solar flares. During the impulsive or flash phase, electrons are often accelerated to ∼10–100 keV energies, even in small flares or subflares. For some flares, the energy contained in these electrons may be a substantial fraction of the total flare energy. Thus the primary energy release mechanism for flares may initially convert stored magnetic energy into energetic electrons. These electrons can produce most of the observed impulsive phase flare phenomena through their interactions with the solar atmosphere. In large flares a second acceleration sometimes occurs which accelerates both ions and electrons to MeV energies and above. This second acceleration appears to have a close association with shock waves in the solar atmosphere as observed by type II radio bursts. Based on observations of escaping particles and hard X‐ray and gamma ray bursts, the impulsive phase acceleration events occur on the order of ∼102 times a month near solar maximum while large solar energetic particle (LSEP) events where >10 MeV ions and relativistic electrons are accelerated to observable levels occur a few times a month.
Introduction to the Report on Geodesy
Authors: Goad Clyde C.
Published: February 2008

There is ample evidence over the past four years within the geodesy community that technology is the major driving element for science rather than science driving the technology. The major single example in this respect has been the introduction of electronic equipment capable of measuring the code and carrier phase of the Global Positioning System (GPS) satellite signal transmissions. As predicted by Chovitz (1983) this equipment has spurred an “incipient revolution in geodetic surveying methods.” Consider that only three presentations were given on the initial results using the GPS at the Seventeenth General Assembly, The International Union of Geodesy and Geophysics (IUGG), Hamburg, Federal Republic of Germany, 1983.
Planetary geodesy
Authors: Bills Bruce G. , Synnott Stephen P.
Published: February 2008

This report will attempt to review progress in planetary geodesy during the past four years. We basically restrict the discussion to gravity, topography, rotation and their physical significance. The format has been kept flexible to accommodate the varied amount of information available for the different planets. The bibliography provided is representative but not exhaustive. In addition to previous quadrennial reports by Kaula [1975], Anderson [1975], Ferrari and Bills [1979], and Sjogren [1983], publications by Anderson [1974], Sjogren et al [1976], Phillips and Lambeck [1980], Stevenson [1982], Davies et al [1983, 1986] and Hubbard [1984] provide valuable background information. A summary table of important geodetic parameters is provided.
Strong‐motion seismology
Authors: Joyner William B.
Published: February 2008

Strong‐motion seismology is concerned with earthquake ground motion in the amplitude range that poses the threat of human injury or property damage. Because the occurrence of strong motion cannot be predicted in advance and because the time between significant events at any one place may range from tens to thousands of years, strong‐motion data is recorded on triggered instruments that typically must be maintained in readiness for years between periods of significant recording. As a consequence the strong‐motion data set is sparse. Because of the engineering need for estimates of future ground motion, the scope of the field of strong‐motion seismology encompasses seismic source theory and any other aspect of seismology that can provide insights helpful in making the best possible estimates given the limited data. This relationship with the rest of seismology is a reciprocal one in that strong‐motion data gives perhaps the best information available on earthquake source processes.
Earthquakes of the Holocene
Authors: Schwartz David P.
Published: February 2008

Geologic studies of earthquakes involve mapping of coseismic surface faulting and secondary deformation from historical events, trenching and geomorphic analysis to define the timing and size of past earthquakes, and investigations of fault zone structure and geometry in both unconsolidated sediments and bedrock. This research is now being referred to as paleoseismology, seismic geology, and earthquake geology. Since the mid‐1970s, it has led to some of the most exciting and important contributions to the understanding of earthquake behavior in space and time [Hanks, 1985; Allen, 1986]. The present report is the first of what is hoped will become a regularly contributed summary of the geologic aspects of the study of earthquakes.
Antarctic aerosols: A review
Authors: Shaw Glenn E.
Published: February 2008

The vast ice sheet of Antarctica is isolated geographically but not meteorologically from the rest of the planet. Tropospheric aerosols in or near the accumulation mode size, around a half micron diameter, reside in the atmosphere for tens of days and teleconnect Antarctica with other regions by transport that reaches planetary scales of distances. The aerosol on the ice sheet, therefore, at any time and place represents “memory modules” of events that took place at regions separated from Antarctica by tens of thousands of kilometers. Scientific attention to this collective aerosol system provides insight into long‐range atmospheric transport. Investigations of particles in the ultraclean air over Antarctica were slow to get going mainly because of a failure to recognize the possibility of semiglobal transport of “dust”; as a result, this field is very young, having gone through its “romantic period” of exploratory studies in the late 1960s and entered into a time of synthesis and paradigm building only in the mid‐1970s. An important recent discovery is that the aerosol number concentration (the condensation nuclei (CN)) over this distant ice sheet undergoes a regular, methodical and predictable seasonal variation, nearly disappearing around winter solstice but being relatively robust (i.e., comparable to what one finds over mid‐oceans) in summer. A weakened seasonal modulation of CN is found at coastal sites. Circumstantial evidence indicates that the CN over the ice are produced from gas photolytically. Thus the tiniest particles over Antarctica are products of a slow “chemical” conversion within the atmosphere itself. A major discovery with numerous possible deep geobiological ramifications is that the aerosol over the ice sheet is by mass 70–90% sulfate, in the molecular form of hydrated droplets of sulfuric acid, except during transient events of a few days duration when atmospheric transport forces warm, moist air from the oceans into the interior continental regions. These events are most frequent in late winter‐early spring, accompanying the breakdown of the circumpolar vortex. These “sodium storms” transport large quantities of sea salt to the central ice sheet sporadically. Chemical studies of the submicron ice cap aerosols indicate that there is a uniquely winter and uniquely summer “crustal,” insoluble aerosol that represents <5% of aerosol mass but which has provided an interesting long‐term permanent record of itself going back 2 × 105 years in the ice. In terms of aerosol mass, the aerosol is composed of crustal products (<5%), transported sea‐salt residues (highly variable but averaging ∼ 10%), Ni‐rich meteoric material, and anomalously enriched material with an unknown origin. Most of the Antarctic aerosol, however, is the “natural acid sulfate aerosol” apparently deriving from biological processes taking place in the surrounding oceans.
The magnetosphere, ionosphere, and atmosphere as a system: Dynamics Explorer 5 years later
Authors: Hoffman R. A.
Published: February 2008

The Dynamics Explorer (DE) program summarizes its accomplishments during the first 5 years since the launch of the two DE satellites. This introduction to six review articles provides background information and a brief history of the program, especially citing the contributions of many people to its development. The principal investigators who had primary responsibility to implement the program are listed, together with the instruments they provided. Orbital information and approaches and constraints to data acquisition are explained. The brief description of the ground data processing and analysis system provides information on access to data catalogs and data sets. Each review article is then placed in the context of the categories of scientific objectives of the program.
Foreword
Authors: Heirtzler J. R.
Published: February 2008

The articles in the special section on Atmospheric Sciences in Antarctica of this issue complete the series on current research work by American atmospheric scientists in the Antarctic. The other 10 papers in the series were published earlier in Reviews of Geophysics (vol. 26, no. 1, pages 41–207).