bluuebunny/crossref_metadata_2025_split huggingface dataset:
A thermosphere‐ionosphere‐mesosphere‐electrodynamics general circulation model (time‐GCM): Equinox solar cycle minimum simulations (30–500 km)
Authors: Roble R. G. , Ridley E. C. 
Published: February 2004

A new simulation model of the mesosphere, thermosphere, and ionosphere with coupled electrodynamics has been developed and used to calculate the global circulation, temperature and compositional structure between 30–500 km for equinox, solar cycle minimum, geomagnetic quiet conditions. The model incorporates all of the features of the NCAR thermosphere‐ionosphere‐electrodynamics general circulation model (TIE‐GCM) but the lower boundary has been extended downward from 97 to 30 km (10 mb) and it includes the physical and chemical processes appropriate for the mesosphere and upper stratosphere.The first simulation used Rayleigh friction to represent gravity wave drag in the middle atmosphere and although it was able to close the mesospheric jets it severely damped the diurnal tide. Reduced Rayleigh friction allowed the tide to penetrate to thermospheric heights but did not close the jets. A gravity wave parameterization developed by Fritts and Lu (1993) allows both features to exist simultaneously with the structure of tides and mean flow dependent upon the strength of the gravity wave source, The model calculates a changing dynamic structure with the mean flow and diurnal tide dominant in the mesosphere, the in‐situ generated semi‐diurnal tide dominating the lower thermosphere and an in‐situ generated diurnal tide in the upper thermosphere. The results also show considerable interaction between dynamics and composition, especially atomic oxygen between 85 and 120 km.
The Freja Project
Authors: Lundin R. , Haerendel G. , Grahn S. 
Published: February 2004

Freja is a joint Swedish and German scientific satellite project to study the interaction between hot magnetospheric plasma and the topside atmosphere/ionosphere. This interaction leads to a strong energization of magnetospheric and ionospheric plasma and an associated erosion and loss of matter from the terrestrial atmosphere. Using novel plasma instruments and a high data rate Freja have provided a number of “firsts” in high resolution plasma diagnostics from satellites. Freja's high spatial/temporal resolution permits studies of meso‐ and micro‐scale phenomena in the 100‐m range for particles and in the 10‐m range for electric and magnetic fields.The Freja satellite was successfully launched on October 6, 1992 into an orbit with 63° inclination, an apogee of 1750 km and perigee of 600 km.
Finding sets of acceptable solutions with a genetic algorithm with application to surface wave group dispersion in Europe
Authors: Lomax Anthony , Snieder Roel 
Published: February 2004

We discuss the use of a genetic algorithm (GA) to invert data for many acceptable solutions, in contrast to inversion for a single, “optimum” solution. The GA is a directed search method which does not need linearization of the forward problem or a starting model, and it can be applied with a very large model‐space. Consequently, fewer assumptions are required and a greater range of solutions is examined than with many other inversion methods.We apply the GA to fundamental Rayleigh group dispersion estimates for paths across Central Europe and across the East European Platform to determine “average”, layered S velocity models separately for each region. The use of the GA allows an identical model parameterization and broad parameter search range to be used for both regions. The scatter of acceptable solutions shows velocity‐depth trade‐offs around the Moho, indicates the depth resolution of the inversion, and shows the uncertainty in upper mantle, S velocity estimates. The results indicate that a thicker crust and up to 0.3 km/sec (7%) higher S wave velocities in the upper 100 km of the mantle under the older East European Platform than under Central Europe explain most of the differences in the data sets.
Mesospheric temperature inversions as seen by ISAMS in December 1991
Authors: Leblanc Thierry , Hauchecorne Alain , Chanin Marie‐Lise , Rodgers Clive , Taylor Fred , Livesey Nathaniel 
Published: February 2004

A large number of mesospheric temperature inversion layers have been observed locally in recent decades, notably by the network of French lidars. It is shown in this paper that the Improved Stratospheric and Mesospheric Sounder on board the Upper Atmosphere Research Satellite is able to detect the presence of temperature inversions, and thus allows the study of their occurrence and characteristics on a global scale. During December 1991, inversions of large amplitude (greater than 20 K) are seen almost every day, especially in mid latitudes, with extent varying typically from 105 to 106 km². Several particularly large inversions were observed at the end of the month. Their correlation with assimilated stratospheric winds is consistent with the interpretation that gravity waves propagate unfiltered through the stratosphere in the regions of strong winds, and break in the mesosphere.The combination of high resolution lidar measurements and global satellite coverage is expected to lead to a better understanding of this significant feature of the winter mesosphere at middle latitudes.
Timescales of orogeny: Jurassic construction of the Klamath Mountains
Authors: Hacker Bradley R. , Donato Mary M. , Barnes Calvin G. , McWilliams M. O. , Ernst W. G. 
Published: February 2004

An electronic supplement of this material may be obtained on a diskette or Anonymous FTP from KOSMOS.AGU.ORG (LOGIN to AGU’s FTP account using ANONYMOUS as the username and GUEST as the password. Go to the right directory by typing CD APEND. Type LS to see what files are available. Type GET and the name of the file to get it. Finally, type EXIT to leave the system.) (Paper 94YCJ2454, Timescales of orogeny: Jurassic construction of the Klamath Mountains, B.R. Hacker, M.M. Donato, C.G. Barnes, M.O. McWilliams, and W.G. Ernst). Diskette may be ordered from American Geophysical Union, 2000 Florida Avenue, N.W., Washington, DC 20009; $15.00. Payment must accompany order.Classical interpretations of orogeny were based on relatively imprecise biostratigraphic and isotopic age determinations that necessitated grouping apparently related features that may in reality have been greatly diachronous. Isotopic age techniques now have the precision required to resolve the timing of orogenic events on a scale much smaller than that of entire mountain belts. Forty‐five new 40Ar/39Ar ages from the Klamath Mountains illuminate the deformation, metamorphism, magmatism, and sedimentation involved in the Jurassic construction of that orogen, leading to a new level of understanding regarding how preserved orogenic features relate to ancient plate tectonic processes. The new geochronologic relationships show that many Jurassic units of the Klamath Mountains had 200 Ma or older volcanoplutonic basement. Subsequent formation of a large ∼170 Ma arc was followed by contractional collapse of the arc. Collision with a spreading ridge may have led to large‐scale NW–SE extension in the central and northern Klamaths from 167 to ∼155 Ma, coincident with the crystallization of voluminous plutonic and volcanic suites. Marked cooling of a large region of the central Klamath Mountains to below ∼350°C at ∼150 Ma may have occurred as the igneous belt was extinguished by subduction of colder material at deeper structural levels. These data demonstrate that the Klamath Mountains—and perhaps other similar orogens—were constructed during areally and temporally variant episodes of contraction, extension, and magmatism that do not fit classical definitions of orogeny.
Geographical differences in the UV Measured by intercompared spectroradiometers
Authors: Seckmeyer G. , Mayer B. , Bernhard G. , McKenzie R. L. , Johnston P. V. , Kotkamp M. , Booth C. R. , Lucas T. , Mestechkina T. , Roy C. R. , Gies H. P. , Tomlinson D. 
Published: February 2004

Five UV spectroradiometers representative of the types used in monitoring programs on several continents were intercompared at the Fraunhofer Institute for Atmospheric Environmental Research (IFU), Garmisch‐Partenkirchen, Southern Germany, during a campaign in August 1994. Global spectral irradiances between 290 and 410 nm were measured over a range of solar zenith angles from 30° to 80°. Scans were synchronized to enable useful comparisons to be made under changing weather conditions, which included overcast, partly cloudy, and clear skies.No exchange of data was allowed between participating groups until after the campaign. At wavelengths longer than 310 nm, the spectra generally agreed to within ±5%. At wavelengths shorter than 310 nm, differences between instruments were larger, especially at larger solar zenith angles. Causes of differences are discussed. For all instruments, deviations in erythemally weighted irradiances were always less than 7% from the mean. The agreement between measurement systems is sufficient to allow an investigation of geographical differences in UV, under all observing conditions. UV doses measured at sites in the southern hemisphere are systematically larger than those measured at the corresponding northern latitudes. During the summer months the daily doses at the South Pole exceed those at mid‐latitudes in the Northern Hemisphere. Further investigations must be performed to establish a global UV‐climatology.
Observational studies of the role of polar regions in mid‐latitude ozone loss
Authors: Jones R. L. , MacKenzie A. R. 
Published: February 2004

Recent analysis of global measurements of ozone distributions using satellites have revealed widespread declines in mid‐latitude ozone, with regional reductions approaching ∼1% per annum (Stolarksi et al., 1991). The existence of mid‐latitude ozone losses has prompted much debate over whether and how perturbations to the chemical composition at high latitudes within the polar vortex may contribute to the reduced ozone amounts observed at lower latitudes (e.g. Schoeberl et al., 1992; Proffitt et al. 1990, 1992, Tuck et al., 1992, 1993, 1994). The export of polar air to low latitudes during each winter can bring air that has undergone recent ozone depletion or air in which chlorine activation has occurred, both potentially contributing to mid‐latitude ozone loss. If this ‘vortex outflow’ is large enough, it may influence the relationship between atmospheric chlorine loading and ozone loss, and knowledge of this process is thus essential for prediction models.In this paper in‐situ observations of nitrogen compounds from both hemispheres are used to quantify the transport of chemically perturbed polar air to lower latitudes, and show that the transport of air from the polar vortex, at least above the 400K potential temperature surface, appears small.
Nannofossil assemblages, fine fraction stable isotopes, and the paleoceanography of the Valanginian‐Barremian (Early Cretaceous) North Sea Basin
Authors: Williams John R. , Bralower Timothy J. 
Published: February 2004

Calcareous nannofossil assemblages have been investigated in three sections from around the margins of the Early Cretaceous North Sea Basin. Both absolute (number of nannofossils per gram) and relative (percent of the assemblage of different taxa) abundance data have been collected. Absolute abundances (up to 10 billion nannofossils per gram) are somewhat higher than those reported previously from other stratigraphic intervals. Stratigraphic correlation of trends in assemblage data in different sections points toward the existence of large, uniform water masses, stable over long (0.5 to 1 m.y.) time periods. These water masses contained a characteristic nannoplankton, which appears to have been driven largely by variations in fertility possibly tied to changes in sources of surface waters, which in turn may have been controlled by relative sea level. Fine fraction isotopic data show fluctuations on shorter time periods (0.1 to 0.5 m.y.). We postulate that some of these isotopic fluctuations were controlled by relative changes in sea level which affected the balance of surface waters derived from runoff and those imported from the Boreal Sea. These oceanographic changes appear to have affected nannofossil assemblages only in discrete intervals.Data are available with entire article on microfiche. Order from American Geophysical Union, 2000 Florida Avenue, N.W., Washington, DC 20009. Document P95‐001; $2.50 payment must accompany order.
Recent progress in snow hydrology
Authors: Bales Roger C. , Harrington Robert F. 
Published: February 2004

Though limited in extent, seasonal snowpacks in the Earth's mountain ranges account for the major source of the runoff for stream flow and groundwater recharge over wide areas of the mid‐latitudes. In most alpine regions, snowmelt runoff is responsible for the annual maximum instantaneous discharge and most of the annual flow. It is therefore important to understand the processes controlling snowmelt runoff and its chemical composition for both water resources as well as ecological reasons.Progress in snow hydrology over the past quadrennium has been heavily influenced by the availability and anticipated future availability of remote sensing data at times and spatial scales appropriate for addressing local, regional and global hydrologic issues [Dozier, 1992]. Recent research has examined topics contributing to better estimation of snowpack properties, snow distribution, snowmelt, and related chemical and biological questions. This review focuses mainly on seasonally snow‐covered alpine areas, but includes other research potentially applicable to alpine areas of the Earth.
The atmospheric oxygen cycle: The oxygen isotopes of atmospheric CO2 and 02 and the 02/N2 ratio
Authors: Keeling Ralph F. 
Published: February 2004

Oxygen is the most abundant element in the earth's crust, it accounts for 89% of the mass of the ocean, and it is the second most abundant element in the earth's atmosphere. Much work on the oxygen cycle has focused on the question of the origin of atmospheric 02 and its variations over geologic time [see Kump et al, 1991, and references therein]. This review focuses on several other aspects of the oxygen cycle including the short‐term controls on the oxygen isotopic abundance of atmospheric CO2 and O2, and the short‐term variabilitiy in the O2/N2 ratio.These aspects of the oxygen cycle depend mainly on material exchanges between the atmosphere and living organisms at the earth's surface or in the ocean. Like several other atmospheric variables which have received much attention recently, e.g., the abundances of CO2, CH4, and N2O, the oxygen isotopic content of CO2 and O2 and the O2/N2 ratio have atmospheric lifetimes that are long relative to the time scale of atmospheric mixing and thus reflect an integration of material exchanges over the globe. Recently, our knowledge of these variables has expanded through laboratory experiments exploring the exchange pathways, and through measurements on contemporary air samples or in ancient air samples extracted from polar ice cores. This review summarizes recent literature on these subjects, and also emphasizes how these aspects of the global oxygen cycle can provide new information on the material exchanges between the atmosphere and biota integrated over large areas.
Recent developments in hydrologic data assimilation
Authors: McLaughlin Dennis 
Published: February 2004

Data assimilation is a term that is most closely associated with the atmospheric sciences. It arises from the meteorological custom of constructing daily weather maps which show how environmental variables such as pressure and wind velocity vary over space (see Daley [1991] for a good historical review). Such maps are useful both for short‐term forecasting, where they provide initial conditions for numerical weather prediction models, and for more long‐term climatic analysis, where they can be used to reveal regional trends [Bengtson and Shukla, 1988; National Research Council, 1991; Shubert et al, 1993].For many years weather maps were derived from a limited number of measurements collected from surface stations and radiosondes. The mapping process required a good understanding of atmospheric physics and was typically carried out by hand, using the methods of ‘subjective analysis’. In the first half of the twentieth century efforts were made to standardize and automate meteorological mapping. The quantitative procedures which grew out of these efforts were commonly called ‘objective analysis’ methods [Gandin, 1963]. Objective analysis algorithms provide spatially distributed descriptions of atmospheric conditions which are consistent both with observed data and with kinematic (‘diagnostic’) principles (such as the geostrophic requirement that the pressure gradient and Coriolis force must balance). These algorithms produce ‘snapshots’ portraying conditions everywhere in a given region at a particular time.
Recent advances associated with flood forecast and warning systems
Authors: Krzysztofowicz Roman 
Published: February 2004

Floods remain one of the most frequent and devastating natural hazards worldwide. In the United States alone, there are 20,000 flood‐prone communities; 3,000 of them receive site‐specific flood forecasts from the National Weather Service (NWS), and 1,000 have local warning systems; the remaining communities receive county‐wide warnings. Between 1965 and 1985, floods accounted for 63% of the federally declared disasters (337 out of 531), took 1,767 lives, and caused $5 billion worth of damage annually, on the average.The Great Flood of 1993, documented by the National Oceanic and Atmospheric Administration [NOAA, 1994], provided a vivid demonstration of Cromwell's rule: one should never assign the exceedance probability of zero to any prior observation. The duration (from March to November), the extent (over nine states) and the magnitude (exceeding previous floods of record at 95 forecast points) made this the most catastrophic flooding in modern U.S. history: 54,000 persons were evacuated, 50,000 homes were damaged, and economic losses of $15–20 billion have been estimated. The event also tested the limits of the Nation's forecast and warning services as flood stages were exceeded at about 500 forecast points.
Marine biological diversity: Some important issues, opportunities and critical research needs
Authors: Butman Cheryl Ann , Carlton James T. 
Published: February 2004

Marine biological diversity is changing, dramatically in some cases, and most recent changes are due to broad‐scale human activities. Knowledge of “biodiversity” — the variety of genomes (the genetic material specifying all characteristics and functions within an organism), species and ecosystems — is the foundation for understanding and predicting how human and natural effects can change the ocean's ecosystems. Evaluating the scale and ultimate consequences to life in the sea of a plethora of anthropogenic effects is difficult, however, because there is inadequate knowledge of both the patterns of and the processes that control marine biodiversity.Recognizing change and evaluating its consequences require sufficient knowledge of present and historical natural patterns of biodiversity, and sufficient understanding of how and why these patterns vary in space and time. Data on biodiversity patterns and their causes are sorely lacking for most marine ecosystems. Adequate understanding of what creates and maintains diversity must be the scientific underpinning for policy decisions regarding pollutant and waste disposal, habitat alteration, fisheries management and the preservation of threatened or endangered species. The inability, at this time, to provide such information to policy makers may have important implications for the conservation of marine life [Norse, 1993].
Measurement of the latitudinal distribution of NO2 column density and layer height in Oct. / Nov. 1993
Authors: Senne T. , Stutz J. , Platt U. 
Published: February 2004

In October/November 1993 DOAS measurements of total columns of NO2 and O3 were performed on a ship cruise from Germany to South Africa. The results are compared to data collected during an earlier campaign with a similar setup [Kreher et al. 1995], which took place in 1990, before the eruption of the Pinatubo volcano. Overall no general trend for NO2 in 1993 in comparison to 1990 could be detected.The O3 vertical column densities in 1993 are mostly around 280 Dobson Units, showing a significant increase to over 330 DU south of 25°S, and significantly lower O3 values south of 50°S. The height of the NO2 concentration maximum was calculated from the NO2 am/pm ratio and data from ozonesondes. The resulting heights are mostly round 29 km, except in the region (south of ≈ 45°S) where the lowest ozone column densities occurred, there the calculated height is ≈ 22 km.
Reply to “Dicing with earthquakes,” by Paul W. Burton
Authors: Varotsos P. , Lazaridou M. 
Published: February 2004

The paper by Burton [1996], besides its unusual title, contains a lot of points that are inaccurate, or erroneous. A clear misuse of statistics is made by Burton, because he handles values of one parameter (i.e., magnitude) without paying attention to essential points like the following: the magnitude value of a prediction referring to a main shock in an area, which becomes very rarely active with such events, cannot be treated equally with a prediction that may have the same magnitude value, but refers to an aftershock in another area. By using simple rules of statistics, we show that the statistical treatment used by Burton is obviously wrong and can “reject” even an ideal prediction method. Furthermore, we show that Burton's criticism on the magnitudes predicted by VAN, is based on a clear misinterpretation of the true meaning of the experimental error and of Gutenberg‐Richter relation; the related Burton's claims, contradict the physical expectation.The appropriate spatial resolution of an earthquake prediction is also discussed. For magnitudes between 5.5 and 6.0, the spatial resolution usually achieved by VAN is around 50km; such a value is reasonable from practical point of view, if we also consider the dimensions of the source. For larger magnitudes, i.e., around 7.5, a spatial resolution of ∼150km would be accepted. Therefore, Burton's [1996] claims for VAN to increase the spatial resolution are unjustified, as they have some basis only for smaller events (∼5.0‐units) which, however, have no much practical interest.Last but not least, Burton uses unusual phrases like “a posteriori demonstration of predictions prevailed,” “unclear retrospective filters” or “too much is often claimed from too little,” but does not mention facts, e.g., that during the three years period under discussion (i.e., 1987–1989) VAN issued only one public alarm, which was followed by the most strong and destructive activity during this period.