bluuebunny/crossref_metadata_2025 huggingface dataset:
Sexual and seasonal variation in the diet and foraging behaviour of a sexually dimorphic carnivore, the honey badger (Mellivora capensis)
Authors: Begg C. M. , Begg K. S. , Du Toit J. T. , Mills M. G. L.
Published: June 2003

The honey badger, or ratel, Mellivora capensis has not been well studied despite its extensive distribution. As part of the first detailed study, visual observations of nine habituated free‐living individuals (five females, four males) were used to investigate seasonal, annual and sexual differences in diet and foraging behaviour. Theory predicts that generalist predators ‘switch’ between alternative prey species depending on which prey species are currently most abundant, and diet breadth expands in response to decreased availability of preferred food types. There were significant seasonal differences in the consumption of eight prey categories related to changes in prey availability but no seasonal differences in food intake per kg of body mass. As predicted, the cold‐dry season diet was characterized by low species richness and low foraging yield but high dietary diversity, while the reverse was true in the hot‐dry and hot‐wet seasons. In accordance with these predictions, results suggest that the honey badger maintains its intake level by food switching and by varying dietary breadth. Despite marked sexual size dimorphism, male and female honey badgers showed no intersexual differences in prey size, digging success, daily food intake per unit body weight or foraging behaviour. Results do not support the hypothesis that size dimorphism is primarily an adaptation to reduce intersexual competition for food.
The ontogeny of bite‐force performance in American alligator (Alligator mississippiensis)
Authors: Erickson Gregory M. , Lappin A. Kristopher , Vliet Kent A.
Published: June 2003

American alligators Alligator mississippiensis undergo major transformations in morphology and ecology during development. These include several thousand‐fold changes in body mass, modified snout and dental proportions, and shifts in diet from small, delicate foodstuffs to the inclusion of increasingly larger, more robust prey. How these changes in anatomical form contribute to actual physical performance and niche use is largely unknown. In the present study, bite‐force measurements for 41 specimens of A. mississipiensis, were made throughout ontogeny (hatchling–older adults) using a series of precision force transducers. How this performance indicator scaled with respect to cranial and whole‐body measurements was determined. Bite‐force production throughout development was contrasted with ontogenetic changes in trophic ecology. The influences of this performance measure on these changes were then analysed. The results showed a 800‐fold range (12–9452 N) of bite forces with values positively correlating with increases in body size. Scaling of biting forces through ontogeny showed positive allometry with respect to body mass, head length, jaw length, snout–vent length and total length. These patterns may be attributable to allometric growth of individual skeletal elements (and associated musculature), and/or progressive fusion and ossification of skull and jawbones during development. The overall pattern of force increase throughout ontogeny did not vary in association with major shifts in diet. Notably, the bite‐force values for adult A. mississippiensis are the highest measured for any living animal and represent the first measures for a large crocodilian. Additionally, these data provide the first documentation of how bite force changes during ontogeny in a reptile. By bridging the rich morphological and ecological databases for these animals, this study opens the door to a comprehensive understanding of feeding in A. mississippiensis. Furthermore, it provides groundwork for standardized comparative studies of feeding among crocodilian, reptilian, or other gnathostome vertebrates.
Primal scenes: Verdi in analysis
Authors: SMART MARY ANN
Published: June 2003

Anniversary years always prompt revaluation as well as celebration, and the centenary of Verdi's death in 2001 was no exception. The conference for which the articles in this issue were written came at the end of a year packed with Verdi celebrations in both opera houses and academic settings. In terms of performance, a handful of ostentatious critical failures in 2001 sparked new debate about two old issues – the pros and cons of revisionist staging in general, and the degree to which contemporary productions should be faithful to what we can glean of the composer's intentions. These edgy, sometimes irreverent productions prompted the critic for the New Yorker magazine, Alex Ross, to declare that Verdi should be exempt from the rigours and indignities of Regietheater. While the abstraction of Wagnerian drama might reward updated settings spiked with flashes of contemporary social critique, he suggested, Verdi's operas work because the composer ‘meant every word’ and because their dramatic force is propelled by unadulterated emotion and sharp juxtapositions, qualities too direct and ‘site-specific’ to tolerate stagings that draw out hidden contexts or ironize dramatic conventions. In what quickly began to sound like a back-handed defence, Ross pronounced: ‘To the analytical mind such music can look crude, even vulgar on the page. Only in live performances, when the momentum begins to build and the voices become urgent, does it catch fire. But how do you go about analyzing momentum and urgency?’
‘… qualche cosa d’incredibile …': Hearing the invisible in Macbeth
Authors: HUDSON ELIZABETH
Published: June 2003

‘Fu qualche cosa d’incredibile …': ‘it
was something unbelievable, something new, unprecedented’.
Thus wrote Marianna Barbieri-Nini, the singer who created the role of Verdi's
Lady Macbeth, in reference to the famous Act I duet between Macbeth and Lady
Macbeth. Indeed, this duet seems to have been one of the most effective pieces in the opera for
nineteenth-century audiences. Verdi himself wrote about it as one of the ‘two principal
numbers’ of the opera, together with the sleepwalking scene, upon which the opera's
dramaturgy depended. The reception of this piece at the
1847 première was stupendous. Antonio Calvi cites it as one of the opera's three
excellent pieces, in which ‘maestro Verdi has arrived at Shakespeare’s
sublimity'. The duet's opening section
(‘Fatal mia donna’), according to various press releases during the opera's
first few runs, was regularly encored three, four, even five times an evening. Abramo Basevi waxed
eloquent over the piece, calling it ‘the culminating number of the opera’, ‘a true
flash of Verdian genius’. And by the time the revised version was premièred in
Paris in 1865, this duet had become entrenched in the repertory in a way the entire opera had not:
one reviewer noted that the Act I duet ‘has always been considered the best duet Verdi has
ever written’.
‘Bewitched, bothered and bewildered’: Lady Macbeth, sleepwalking, and the demonic in Verdi's Scottish opera
Authors: BERNSTEIN JANE A.
Published: June 2003

‘Nothing is but what is not’. These words uttered by Macbeth
after his bizarre first encounter with the three weird sisters could serve as a motto for the
whole of Shakespeare's tragedy; for ‘the Scottish play’, as the superstitious
have called it for centuries, is ruled by uncertainty, the questionable, the netherworld, where
the only thing that is absolute is evil. It is about ambiguous forces that violate
ife's natural order – witches, ghosts, a moving forest, an invisible dagger –
what we call the macabre, what Freud called the uncanny, and what Verdi called ‘un genere
fantastico’. Shakespeare constructs a world of binary opposites where boundaries, as
Marjorie Garber has observed, are ‘continually transgressed, and marked by a series of
taboo border crossings’.
‘The firmness of a female hand’ in The Corsair and Il corsaro
Authors: HADLOCK HEATHER
Published: June 2003

The dramatic climax of Byron's poem The Corsair comes when Gulnare,
a harem slave, seizes a weapon to free herself and Conrad, the pirate whom she loves, from the
prison of their common enemy the Pasha Seyd.
‘Chi piange, qual forza m'arretra?’: Verdi's interior voices
Authors: ESSE MELINA
Published: June 2003

It all started with voices – voices not meant to be heard.
Verdi's demand that at crucial moments in Macbeth the performers stifle vocal
expression is by now famous. Again and again he urged that the duet and sleepwalking scene be sung
‘sotto voce’, ‘with mutes’, that the singers should speak more than sing,
that their voices should sound ‘harsh’, ‘stifled’,
‘hollow’, ‘veiled’. Verdi's wilful insistence that his singers not sing has
been understood as part of the composer's struggle to curb the excesses of primo
ottocento opera and invest it with a new psychological
depth.
Gilles de Van, for example, argues that the suppression of the voice in Macbeth
creates a shadowy subjective interiority, and claims further that the decision represents a shift
in Verdi's aesthetic orientation from ‘melodrama to music drama’. De Van
understands Verdi's inward turn as a renunciation of the kind of extroverted display upon
which melodrama relies, as a ‘turning point, the beginnings of a dramaturgy of interiority
that does away with the superb transparency of traditional melodrama and marks Verdi’s new
awareness of the aura of confusion and ambiguity that can inhabit the human
soul'.
‘Teco io sto’: Strategies of seduction in Act II of Un ballo in maschera
Authors: SENICI EMANUELE
Published: June 2003

‘La sventurata rispose’ [the poor wretch answered].
This sentence, among the most famous of Italian literature, appears in chapter 10 of Alessandro
Manzoni's I promessi sposi (The Betrothed, first published in 1827 and
revised in 1840), where it functions as stitches trying to heal the deep wound caused by a radical
surgical intervention, the excision of pages and pages devoted to a description of seduction. In the
best Gothic tradition, the first version of the novel, entitled Fermo e Lucia
(1821–23), contained a long account of the seduction of the Nun of Monza by a young
libertine, but religious and, apparently, aesthetic considerations convinced Manzoni to cut this
episode and replace it with those three words. The rhetorical figure of reticence, so prominent in
chapter
10 of I promessi sposi, dominates the tradition of Italian ‘high’
Classicist and Romantic literature, which seems to have considered seduction unfit as a literary
theme, to be left to the gutter of the popular novel.
Masked balls
Authors: HEXTER RALPH
Published: June 2003

In the course of his insightful analysis of Act II of Un ballo in
maschera, Harold Powers recurs to two critics of earlier generations who hyperbolically describe
how, to cite his more measured summary, ‘the drama has turned into music as the opera was being
composed. The music is the drama for an audience habituated to its conventions, its style,
its genres’. Powers first quotes Gabriele Baldini, who describes the libretto of Il
trovatore as ‘a phantom libretto, which became completely engulfed by the music and,
once the opera was finished, disappeared as an individual entity’, and then the earlier Bruno
Barilli, in whose view ‘the grotesque libretto is only the causal element that provokes the
explosion, after which it collapses, annihilated – a confused scattering of
rhymes, syllables, babblings – to vanish forever without a
trace’. Although Powers and
other more recent scholars tend to pay operatic words greater respect, I begin with an invocation of
views that might seem anathema to a scholar of texts for the inspiring idea that the text can
be ‘annihilated’ as one moves to another level of the work. In what follows, I intend to
annihilate both text and music in order to dissolve to a yet higher level of analysis and to
recuperate a specific history in which Verdi's Un ballo in maschera, I maintain,
participates.
Don Carlos as Bildungsoper: Carlos's last act
Authors: ROSEN DAVID
Published: June 2003

The scene upon which I focus here – the final duet – was a late addition to the list of primal scenes for this conference. The Don Carlos scenes on the original list were the Posa–Philippe duet and the Quartet, and thus we almost had a session on Don Carlos without the Prince of Spain. Perhaps this is not surprising. Carlos has not fared well in recent writing about the opera.
Philippe and Posa Act II: The shock of the new
Authors: PARKER ROGER
Published: June 2003

One of the contemporary production books for Don Carlos
thus austerely sums up the Philippe–Posa duet in Act II (of the five-act version);
its none-too-subtle indication of grand themes handled seriously is one that has consistently
driven the piece's reception. As so often, Verdi himself encouraged the
trend – most significantly by treating the duet to more substantial
revision than any other major piece in his entire output. Some drastic cutting occurred even during
rehearsals, so that the supposed Urfassung predates the first performance. What is
commonly referred to as the ‘original’ version corresponds, then, to the music
performed at the 1867 Paris première. This was substantially refashioned for Naples in
1872 (with Italian text only), and given an even more thorough overhaul in 1884. The four versions
have been much discussed: indeed, revisions such as these were one of the proving grounds on which
Verdi (and thus his admirers) became musicologically
respectable. Where would we stand today without
those four versions and their many Verdian copains? Possibly on some other,
less comfortable podium.
Verdi's Egyptian spectacle: On the colonial subject of Aida
Authors: BERGERON KATHERINE
Published: June 2003

In June 1867 Ismail Pasha, the new Viceroy of Egypt, arrived in Paris to
represent his country at the Exposition universelle. The Egyptian pavilion, erected on a
large corner of the Champs de Mars, featured a marvellous collection of architectural spaces that
included a pharaoh's temple, a mediæval palace ‘richly decorated in the Arabic
style’, and a modern-day bazaar showing all manner of merchants and artisans at work. If the
temple, designed by the French archaeologist Auguste Mariette, was intended to display artefacts
from the most remote corners of Egypt's history, other spaces transported spectators directly
to the present, offering what one French commentator called ‘a living Egypt, a picturesque
Egypt, the Egypt of Ismail Pasha’. An enormous
panorama of the Isthmus of Suez, created by the Suez Canal Company with the help of M.
Rubé, set designer from the Opéra, drew long queues of paying customers.
Elsewhere visitors could gaze at authentic Egyptian peasants, or Bedouins on white dromedaries,
all the races governed by the Viceroy ‘personified by individuals selected with care’,
as the critic Edmond About put it. Most dazzling of all was the exhibit within the
refabricated royal palace, where the Viceroy himself was the featured attraction: poised on a
divan in a bedroom painted to look exactly like the place of his birth, he smoked a hookah
and daily received guests from the best Parisian society. The whole sumptuous spectacle, About
would conclude, ‘spoke to the eyes as well as to the mind. It expressed a
political idea’.
‘O patria mia’: Patriotism, dream, death
Authors: HUEBNER STEVEN
Published: June 2003

Idealized mother figure, great protectress, unsurpassed magician, devoted
wife of Osiris: the goddess Isis assumed multiple roles in ancient Egyptian
mythology. Verdi's Aida reflects this polysemy. Concordant with its
general attention to Egyptological detail (though not without inaccuracies even by the standards of
the day), Auguste Mariette's early synopsis for the opera refers to Isis only once, at the
beginning of Act III when Aida awaits Radames: ‘May Isis, protectress of love, guide him to
her who wants to belong only to him’.
Aida's flutes
Authors: CRUZ GABRIELA
Published: June 2003

After years spent reflecting on Western imperial practices, critic Edward
Said wrote that Giuseppe Verdi's Aida is ‘a kind of curatorial art’,
a work

whose rigorous and unbending frame recall[s], with relentless mortuary logic, a precise
historical moment and a specifically dated aesthetic form, an imperial spectacle designed to
alienate and impress an almost exclusively European audience.
Shedding light on the audience: Hans Neuenfels and Peter Konwitschny stage Verdi (and Verdians)
Authors: RISI CLEMENS
Published: June 2003

‘Scandal’, ‘uproar’ and ‘sensation’ are words that are often used by critics when writing about operatic stagings of directors Hans Neuenfels and Peter Konwitschny. Neuenfels' 1981 staging of Aida in Frankfurt/Main aroused a veritable furore, as did his interpretation of Nabucco (Berlin, 2000); similar reactions greeted Konwitschny's Graz Aida (1994) and his Hamburg Don Carlos (2001). Neuenfels and Konwitschny continually undermine traditional concepts of operatic staging: the provocative statements advanced by their powerful images regularly elicit bewildered reactions.
Comparing notes: Amelia/Maria and the ‘larve del passato’
Authors: CAMPANA ALESSANDRA
Published: June 2003

In his recent book on Hamlet, Stephen Greenblatt writes:

What
there is again and again in Shakespeare, … is a sense that ghosts, real or imagined, are good
theatre – indeed, that they are good for thinking about theatre's
capacity to fashion realities, to call realities into question, to tell compelling stories, to
puncture the illusions that these stories generate, and to salvage something on the other side of
disillusionment.
Learning to curse at sixty-seven
Authors: TOMLINSON GARY
Published: June 2003

What makes Bernard Shaw, for us, the most perfect of Wagnerites
is that he did not mince words when he judged the master to have taken a wrong turn. Such a
turn came in Das Rheingold, and Shaw was quick to expose it, even though he had just
spent a chapter elaborating the profound political allegory he discerned in the work:

In the midst of these far-reaching ideas, it is amusing to find Wagner still full of his ingrained
theatrical professionalism, and introducing effects which now seem old-fashioned and stagey
with as much energy and earnestness as if they were his loftiest inspirations. When Wotan
wrests the ring from Alberic, the dwarf delivers a lurid and blood-curdling stage curse,
calling down on its every future possessor care, fear, and death. The musical phrase
accompanying this outburst was a veritable harmonic and melodic bogey to mid-century
ears, though time has now robbed it of its terrors. It sounds again when Fafnir slays Fasolt,
and on every subsequent occasion when the ring brings death to its holder. This episode
must justify itself purely as a piece of stage sensationalism. On deeper ground it is
superfluous and confusing, as the ruin to which the pursuit of riches leads needs no curse
to explain it; nor is there any sense in investing Alberic with providential powers in the
matter.
Quantitative testing of bedrock incision models for the Clearwater River, NW Washington State
Authors: Tomkin Jonathan H. , Brandon Mark T. , Pazzaglia Frank J. , Barbour Jonathan R. , Willett Sean D.
Published: June 2003

The incision of rivers in bedrock is thought to be an important factor that influences the evolution of relief in tectonically active orogens. At present, there are at least six competing models for incision of bedrock rivers, but these models have received little quantitative testing. We statistically evaluate these models using observations from the Clearwater River in northwestern Washington State, which crosses the actively rising forearc high of the Cascadia margin. A previous study has used fluvial terraces along the Clearwater to estimate bedrock incision rates over the last ∼150 kyr. They show that incision rates have been steady over the long‐term (>50 kyr), consistent with other evidence based on isotopic cooling ages, for steady long‐term (>1 Myr) erosion rates. The steady state character of the river allows us to use the relatively simple time‐invariant solutions for the various incision models and also to estimate long‐term sediment discharge along the river, which is a critical variable for some incision models. An interesting feature of the Clearwater River is that it has a downstream decrease in the rate of incision, from ∼0.9 mm/yr in the headwater to <0.1 mm/yr at the coast. None of the incision models, including the shear stress model, successfully accounts for this relationship. This result may be due to the simple way in which these models are used, commonly without consideration for the distribution of discharge with time, and the variable capacity of the river channel to contain peak flows along its course. We suggest some general improvements for the incision models, and also guidelines for selecting those rivers that will allow good discrimination between competing models.
Changes in the modeled ice thickness distribution near the Surface Heat Budget of the Arctic Ocean (SHEBA) drifting ice camp
Authors: Lindsay R. W.
Published: June 2003

In the polar oceans the ice thickness distribution controls the exchange of heat between the ocean and the atmosphere and determines the strength of the ice. The Surface Heat Budget of the Arctic Ocean (SHEBA) experiment included a year‐long field program centered on a drifting ice station in the Beaufort and Chukchi Seas in the Arctic Ocean from October 1997 through October 1998. Here we use camp observations and develop methods to assimilate ice thickness and open water observations into a model in order to estimate the evolution of the thickness distribution in the vicinity of the camp. A thermodynamic model is used to simulate the ice growth and melt, and an ice redistribution model is used to simulate the opening and ridging processes. Data assimilation procedures are developed and then used to assimilate observations of the thickness distribution. Assimilated observations include those of the thin end of the distribution determined by aircraft surveys of the surface temperature and helicopter photographic surveys and aircraft microwave estimates of the open water fraction. The deformation of the ice was determined primarily from buoy and RADARSAT Geophysical Processor System (RGPS) measurements of the ice velocity. Because of the substantial convergence and ridging observed in the spring and summer, the estimated mean ice thickness increases by 59%, from 1.53 to 2.44 m, over the year in spite of a net thermodynamic ice loss for most multiyear ice.
Near‐bed turbulence and bottom friction during SandyDuck97
Authors: Smyth C. , Hay Alex E.
Published: June 2003

Remote acoustic measurements of turbulence intensity profiles are investigated as a function of wave energy and bedstate, from low energy vortex ripples to high energy flat bed. Outside the wave boundary layer, velocity power spectral densities increase with increasing wave energy for all bedstates at frequencies across the wave and turbulence bands up to the Nyquist frequency of the measurements, 8 to 10 Hz. The power spectra of the horizontal and vertical velocity exhibit the −5/3 slope characteristic of inertial subrange turbulence. As the seafloor is approached, the slopes of the vertical velocity spectra in this subrange become progressively less steep, reaching values between −1.2 and −0.6 within the wave boundary layer where the spectral densities are independent of bedstate and incident wave energy. Consistent with laboratory turbulence spectra showing similarly reduced spectral roll‐off for the transverse velocity component at microscale Reynolds numbers below 1000 [Sreenivasan, 1996], these field observations indicate that near‐bed turbulence generated by irregular waves above a mobile bed is probably anisotropic. Ensemble‐averaged vertical turbulence intensity profiles exhibit a peak within the wave boundary layer at heights of O(1 cm) above bottom for all bedstates. The peak is less pronounced for higher energy bedstates. Consistent with the observed spectral convergence within the boundary layer, these peak average turbulence intensities are relatively independent of bedstate, varying by no more than 50% despite a factor of 7 variation in average wave energy. This remarkable observation can be understood from the corresponding decrease in the physical roughness of the bed, associated with the different observed bedstates, as wave energy increases. Estimated wave friction factors are highest for low‐energy rippled beds and smallest for flat bed conditions, and within the uncertainty of the measurements, are generally consistent with predictions from the model by Tolman [1994].
Export production in the central Arctic Ocean evaluated from phosphate deficits
Authors: Anderson Leif G. , Jones E. Peter , Swift James H.
Published: June 2003

Primary productivity in the central Arctic Ocean has recently been reported as being much higher than earlier thought. If a significant fraction of this primary production were exported from the immediate surface region, present estimates of the carbon budget for the Arctic Ocean would have to be reassessed. Using the deficit of phosphate in the central Arctic Ocean, we show that the export production is very low, on an average less than 0.5 gC m−2 yr−1. This is at least an order of magnitude lower than the total production as measured or estimated from oxygen data, thus indicating extensive recycling of nutrients in the upper waters of the central Arctic Ocean and very little export production.
Ice shelf tidal motion derived from ERS altimetry
Authors: Shepherd Andrew , Peacock Neil R.
Published: June 2003

Ocean tides beneath floating ice shelves can affect heat and water circulations within the subshelf cavity, which may influence patterns of basal melting. Accurate tidal predictions are essential to eliminate vertical tide motions when mapping the flow speeds and thickness changes of floating ice. Global ocean tide solutions are typically accurate to 2–3 cm in amplitude. However, their coarse resolution limits their utility in coastal regions. Moreover, the absence of satellite and extensive gauge station data in the polar regions has resulted in significant differences between recent tide model solutions around the Antarctic continent. We use 9 years of high‐resolution European Remote Sensing (ERS) satellite radar altimeter range measurements and a modified form of the orthotide method to generate tidal solutions for a series of ice shelves around the Antarctic Peninsula. We compare our tidal solution at George VI Ice Shelf on the western coast of the Antarctic Peninsula to direct measurements from British Antarctic Survey tide gauge records and contrast the results with solutions from the FES99 and Kantha2.0 (global) and the CATS01.02 (Antarctic) ocean tide models. The average root mean square vector difference between the tide gauge and tide model predictions of amplitude and phase was 10.9, 17.1, 4.2, and 15.4 cm for the ERS ice shelf, Kantha2.0, CATS01.02, and FES99 models, respectively. Tidal predictions derived from the ERS ice shelf model are closer to the tide gauge recordings than those of the global models, and the inclusion of ERS altimeter data may lead to improved global model performance.
Evidence for shear failure in forming near‐equatorial lineae on Europa
Authors: Spaun Nicole A. , Pappalardo Robert T. , Head James W.
Published: June 2003

Global stress models for Europa are unable to readily explain the orientations of lineae in the equatorial region of Europa's trailing hemisphere if lineae originate as tension cracks. Our analysis of two equatorial, trailing regions reveals that lineae are predominantly oriented NE and NW, and E‐W lineae are rare, contrary to predictions of stress and formation models. The measured orientations are consistent with an origin by shear failure. The studied regions are located near the point of maximum differential stress and minimum surface tensile stresses, where shear faulting may surmount tension fracturing. Several types of lineae are recognized; their relative abundance is inferred to have changed with time, consistent with formation models suggesting lineae evolve from simple troughs to complex ridges. The opening of crevasse‐like tensile fractures is not required for generation of all lineae; the observations are consistent with ridge formation models where troughs (formed in tension or shear) experience shear heating from tidal deformation, allowing warm ice to buoyantly uplift, creating ridges. The stratigraphic relationships indicate the following: ridged plains formed first, followed by continued formation of a wide range of lineae, and lastly emplacement of lenticulae and continued linea formation. This sequence is consistent with an early thin, brittle lithosphere that thickened with time and was subject to repetitive diurnal tides during ∼30°–90° of nonsynchronous rotation. Ultimately, the thickened shell underwent thermally induced solid‐state convection, producing lenticulae. The young surface age of Europa implies that this entire stratigraphic sequence was emplaced in the geologically recent past.
Numerical error in groundwater flow and solute transport simulation
Authors: Woods Juliette A. , Teubner Michael D. , Simmons Craig T. , Narayan Kumar A.
Published: June 2003

Models of groundwater flow and solute transport may be affected by numerical error, leading to quantitative and qualitative changes in behavior. In this paper we compare and combine three methods of assessing the extent of numerical error: grid refinement, mathematical analysis, and benchmark test problems. In particular, we assess the popular solute transport code SUTRA [Voss, 1984] as being a typical finite element code. Our numerical analysis suggests that SUTRA incorporates a numerical dispersion error and that its mass‐lumped numerical scheme increases the numerical error. This is confirmed using a Gaussian test problem. A modified SUTRA code, in which the numerical dispersion is calculated and subtracted, produces better results. The much more challenging Elder problem [Elder, 1967; Voss and Souza, 1987] is then considered. Calculation of its numerical dispersion coefficients and numerical stability show that the Elder problem is prone to error. We confirm that Elder problem results are extremely sensitive to the simulation method used.
Partitioning net ecosystem carbon exchange into net assimilation and respiration using 13CO2 measurements: A cost‐effective sampling strategy
Authors: Ogée J. , Peylin P. , Ciais P. , Bariac T. , Brunet Y. , Berbigier P. , Roche C. , Richard P. , Bardoux G. , Bonnefond J.‐M.
Published: June 2003

The current emphasis on global climate studies has led the scientific community to set up a number of sites for measuring the long‐term biosphere‐atmosphere net CO2 exchange (net ecosystem exchange, NEE). Partitioning this flux into its elementary components, net assimilation (FA), and respiration (FR), remains necessary in order to get a better understanding of biosphere functioning and design better surface exchange models. Noting that FR and FA have different isotopic signatures, we evaluate the potential of isotopic 13CO2 measurements in the air (combined with CO2 flux and concentration measurements) to partition NEE into FR and FA on a routine basis. The study is conducted at a temperate coniferous forest where intensive isotopic measurements in air, soil, and biomass were performed in summer 1997. The multilayer soil‐vegetation‐atmosphere transfer model MuSICA is adapted to compute 13CO2 flux and concentration profiles. Using MuSICA as a “perfect” simulator and taking advantage of the very dense spatiotemporal resolution of the isotopic data set (341 flasks over a 24‐hour period) enable us to test each hypothesis and estimate the performance of the method. The partitioning works better in midafternoon when isotopic disequilibrium is strong. With only 15 flasks, i.e., two 13CO2 nighttime profiles (to estimate the isotopic signature of FR) and five daytime measurements (to perform the partitioning) we get mean daily estimates of FR and FA that agree with the model within 15–20%. However, knowledge of the mesophyll conductance seems crucial and may be a limitation to the method.
Gross primary production and light response parameters of four Southern Plains ecosystems estimated using long‐term CO2‐flux tower measurements
Authors: Gilmanov Tagir G. , Verma Shashi B. , Sims Phillip L. , Meyers Tilden P. , Bradford James A. , Burba George G. , Suyker Andrew E.
Published: June 2003

Gross primary production (GPP) is one of the most important characteristics of an ecosystem. At present, no empirically based method to estimate GPP is available, other than measurements of net CO2 exchange and calculations of respiration. Data sets from continuous CO2 flux measurements in a number of ecosystems (Ameriflux, AgriFlux, etc.) for the first time provide an opportunity to obtain empirically based estimates of GPP. In this paper, using the results of CO2 flux tower measurements during the 1997 season at four sites in Oklahoma (tallgrass prairie, mixed prairie, pasture, and winter wheat crop), we describe a method to evaluate the average daytime rate of ecosystem respiration, Rd, by estimation of the respiration term of the nonrectangular hyperbolic model of the ecosystem‐scale light‐response curve. Comparison of these predicted daytime respiration rates with directly measured corresponding nighttime values, Rn, after appropriate length of the night and temperature correction, demonstrated close linear relationship, with 0.82 ≤ R2 ≤ 0.98 for weekly averaged fluxes. Daily gross primary productivity, Pg, can be calculated as Pg = Pd + Rd, where Pd is the daytime integral of the net ecosystem CO2 exchange, obtained directly from measurements. Annual GPP for the sites, obtained as the sum of Pg over the whole period with Pg > 0 were: tallgrass prairie, 5223 g CO2 m−2; winter wheat, 2853 g CO2 m−2; mixed prairie, 3037 g CO2 m−2; and pasture, 2333 g CO2 m−2. These values are in agreement with published GPP estimates for nonforest terrestrial ecosystems.
Plausibility of the “White Mars” hypothesis based upon the thermal nature of the Martian subsurface
Authors: Urquhart Mary L. , Gulick Virginia C.
Published: June 2003

The “White Mars” hypothesis asserts that CO2 gas‐driven debris flows were responsible for carving the outflow channels, the valley networks and the gullies on Mars rather than liquid water. This model further asserts that liquid water has been confined to the deep subsurface unable to find egress to erode the surface. We show that the subsurface of Mars, especially when major fluvial features formed, is unlikely to have been as cold as this model suggests and that liquid water would be present much closer to the surface than predicted by “White Mars”. The assumptions of the “White Mars” hypothesis regarding globally‐averaged crustal heat flow are below most estimates of the current thermal state of the Martian crust, and well below probable values 2 Gyr or more ago. Likewise, the assumed value of crustal thermal conductivity in “White Mars” is inconsistent with the CO2 dominated cryosphere of the model.
Coupled seismic slip on adjacent oceanic transform faults
Authors: Forsyth Donald W. , Yang Yingjie , Mangriotis Maria‐Daphne , Shen Yang
Published: June 2003

In a four and a half hour period, more than 60 events in an earthquake swarm on the western boundary of the Easter microplate were detected by an array of ocean bottom seismometers. The larger events of the swarm were strike‐slip earthquakes located on two transform faults separated by about 25 km. Slip on the faults was closely coupled, with activity alternating back and forth randomly between the two transforms. Coupled seismic activity is usually attributed to triggering by static stress changes or dynamic stresses in propagating shear waves generated by another earthquake, but these earthquakes are too small for either mechanism to be plausible. We suggest that the swarm may have been the seismic manifestation of a larger, primarily aseismic, slip event or slow earthquake involving both transforms, perhaps triggered by dike injection on the Easter‐Pacific spreading center.
Shear wave splitting and mantle flow beneath LA RISTRA
Authors: Gök Rengin , Ni James F. , West Michael , Sandvol Eric , Wilson David , Aster Richard , Baldridge W. Scott , Grand Stephen , Gao Wei , Tillmann Frederik , Semken Steve
Published: June 2003

Shear‐wave splitting parameters (fast polarization direction and delay time) are determined using data from LA RISTRA (Colorado pLAteau RIo Grande Rift/Great Plains Seismic TRAnsect), a deployment of broadband seismometers extending from the Great Plains, across the Rio Grande Rift and the Jemez Lineament, to the Colorado Plateau. Results show that the fast polarization directions are sub‐parallel to North American absolute plate motion. The largest deviations from the plate motion are observed within the western edge of the Great Plains and in the interior of the Colorado Plateau where lithospheric anisotropy may be significant. Delay times range from 0.8 to 1.8 seconds with an average value of 1.4 seconds; the largest values are along the Jemez Lineament and the Rio Grande Rift which are underlain by an uppermost mantle low velocity zone extending to depths of ∼200 km. The anisotropy beneath the central part of LA RISTRA shows a remarkably consistent pattern with a mean fast direction of 40° ± 6°. Seismic anisotropy can be explained by differential horizontal motion between the North American lithosphere and westerly to southwesterly flow of the asthenospheric mantle. The approximately N‐S fast direction found beneath western Texas is similar to that observed beneath the southern rift and may reflect a different dynamic regime.
Evening co‐rotating patches: A new type of aurora observed by high sensitivity all‐sky cameras in Alaska
Authors: Kubota M. , Nagatsuma T. , Murayama Y.
Published: June 2003

We observed an interesting auroral event at Poker Flat Research Range (PFRR, MLAT ∼65.5°) using an all‐sky imaging system. This aurora, which appeared in the evening (16–19 MLT) during a geomagnetically quiet period, maintained its patch structure and position for more than 40 minutes. These patches were distinct in OI 557.7‐nm and N2+ 427.8‐nm emissions. At this time, PFRR was located at a lower latitude region than the auroral oval. An extended plasmasphere was observed a few hours beforehand with the Akebono satellite in the afternoon sector. This evidence suggests that the particles causing this aurora precipitate from the extended duskside plasmasphere. We believe that the imaging observation from the ground using our technique is an effective method for investigating dynamics around the plasmapause, a still partially‐unexplored region of space.
Geodetic evidence of back‐arc spreading in the Mariana Trough
Authors: Kato Teruyuki , Beavan John , Matsushima Takeshi , Kotake Yoshiko , Camacho Juan T. , Nakao Shigeru
Published: June 2003

Repeated GPS surveys in the Mariana Islands show that the Mariana block is moving apart from the Philippine Sea plate. The velocities of the islands relative to the Philippine Sea plate range from about 15 mm/yr in the northern islands to about 45 mm/yr near Guam. The data also suggest convergence rates for the Mariana forearc with respect to the Pacific plate of 35–45 mm/yr at 19°N increasing to 55–70 mm/yr at 13.5°N. In addition, the velocity vectors show a slight north‐south expansion of the arc. The estimated location of the Euler pole of the Mariana forearc with respect to the Philippine Sea plate is well south of the geographical point where the back‐arc basin narrows to zero width.
Model simulations of melting hydrometeors: A new lidar bright band from melting frozen drops
Authors: Di Girolamo Paolo , Demoz Belay B. , Whiteman David N.
Published: June 2003

This study provides a model simulation of lidar and radar echoes from melting frozen drops. Results are based on a concentric‐sphere Mie scattering code, together with a melting layer model. Simulations reveal the appearance of a lidar bright band in the melting layer, as well as a fainter radar bright band. Both maxima are located approximately 300 m below the freezing level for a core/shell radius of 0.7. In order to achieve a more realistic representation of the melting process, preliminary simulations have also been obtained from an eccentric sphere Mie scattering code that are in general agreement with results obtained with the concentric sphere code. The sensitivity of the algorithms to changes in initial conditions is investigated.
Role of solar wind turbulence in the coupling of the solar wind to the Earth's magnetosphere
Authors: Borovsky Joseph E. , Funsten Herbert O.
Published: June 2003

The correlation between the amplitude of the MHD turbulence in the upstream solar wind and the amplitude of the Earth's geomagnetic activity indices AE, AU, AL, Kp, ap, Dst, and PCI is explored. The amplitude of the MHD turbulence is determined by the fluctuation amplitude of the solar wind magnetic field. This “turbulence effect” in solar wind/magnetosphere coupling is more easily discerned when the interplanetary magnetic field (IMF) is northward, but the effect is also present when the IMF is southward. The magnitude of the effect is the same for northward and southward IMF, accounting for about 150 nT of the variability of the AE index. Tests are performed that conclude (1) that the turbulence effect is not caused by the turbulence amplitude acting as a proxy for ∣B∣ in the solar wind and (2) that reversals of the IMF from northward to southward in the turbulent fluctuations is not the cause of the correlations. An expression is derived for the total viscous‐shear force on the surface of the magnetosphere; improved solar wind/magnetosphere correlations result when this expression is used. With insight from fluid‐flow experiments, the turbulence effect is interpreted as an enhanced viscous coupling of the solar wind flow to the Earth's magnetosphere caused by an eddy viscosity that is controlled by the amplitude of MHD turbulence in the upstream solar wind: more upstream turbulence means more momentum transfer from the magnetosheath into the magnetosphere, resulting in more stirring of the magnetosphere, which produces enhanced geomagnetic activity indices.
Midlatitude ionospheric disturbances during magnetic storms and substorms
Authors: Huang Chao‐Song , Foster J. C. , Goncharenko L. P. , Sofko G. J. , Borovsky J. E. , Rich F. J.
Published: June 2003

We present periodic (∼2 hour) magnetospheric and ionospheric oscillations observed with multiple space‐based and ground‐based instruments during the severe magnetic storm of 25 September 1998. Periodic particle injections were observed at geosynchronous orbit. Ground magnetometers registered very large, as high as 3000 nT, magnetic deviations in the nightside auroral zone. The Millstone Hill incoherent scatter radar at magnetic latitude 55° measured periodic enhancements of ionospheric eastward ion velocity from midnight to ∼1000 MLT. The periodic variations in the magnetometers and Millstone Hill radar were well correlated with the magnetospheric particle injections. The observations are consistent with the occurrence of periodic magnetospheric substorms during a magnetic storm. During each substorm cycle the ionospheric auroral zone expanded to the latitude of the Millstone Hill radar, so the radar was periodically within the auroral zone and detected the auroral plasma return flows. After substorm activity stopped, the Millstone Hill radar measured near‐noon in‐phase periodic oscillations of the ionospheric F‐region electron density and temperature, which may be due to particle precipitation from the ring current and/or plasmasphere into the midlatitude ionosphere. We suggest that magnetospheric substorms during magnetic storms have a cycle time of ∼2 hours. The magnetosphere can sustain similar oscillations for several cycles even though the substorm activity has stopped. All the observed periodic variations in the geosynchronous particle injections, in the auroral magnetic deviations, and in the ionospheric ion velocity are related to the periodic magnetospheric substorms and oscillations.
Characterization and dynamics of the auroral electron precipitation during substorms deduced from IMAGE‐FUV
Authors: Meurant M. , Gérard J. C. , Hubert B. , Coumans V. , Shematovich V. I. , Bisikalo D. V. , Evans D. S. , Gladstone G. R. , Mende S. B.
Published: June 2003

The FUV imager on board the IMAGE satellite provides simultaneous images of the north polar aurora every 2 min in three spectral channels. The Wideband Imaging Camera (WIC) responds primarily to the N2 LBH bands while one of the Spectral Imagers (SI13) includes the OI 135.6 nm emission and nearby LBH bands. The third channel (SI12) is sensitive to Doppler‐shifted Lyman‐α emission at 121.8 nm generated by proton precipitation. The relative magnitude of the WIC and SI13 signals depends on the altitude distribution of the energy deposition, in response to the differential O2 absorption and the altitude dependence of the neutral composition. The ratio of simultaneous images from WIC and SI13 is used to derive the spatial distribution of the characteristic energy of the precipitating auroral electrons and the energy flux they carry. The method is described and the uncertainties introduced by possible perturbations of the neutral composition known to occur in the auroral thermosphere are discussed. The first part of this study describes a validation of this method performed by comparing precipitation characteristics derived from FUV with in situ measurements from two coincident passes of the NOAA‐16 satellite. They are shown to agree within about 45%. The second part applies this ratio method to analyze the time evolution of auroral activity which occured during two substorms on 28 October 2000. The time evolution is displayed in the form of magnetic local time and magnetic latitude keograms. It is shown that the pattern of the electron average energy distribution exhibits both spatial and temporal changes. Comparison with FAST in situ electron spectrograms confirms the ability of IMAGE to detect precipitation events with a ∼200 km spatial scale. However the characteristics of the physical process leading to electron acceleration cannot be identified with FUV. The highest values of the average energy are colocated in time and space with the largest electron precipitation fluxes. A dawnward motion of bright features is observed in the postmidnight at speeds on the order of 5 magnetic local time hours/UT hour.
Effect of equatorial plasma bubbles on the thermosphere
Authors: Schunk R. W. , Demars H. G.
Published: June 2003

Equatorial plasma bubbles are common in the low‐latitude ionosphere at night, particularly at solar maximum. The bubbles form on the bottomside of the F‐layer as a result of the Rayleigh‐Taylor instability and then drift upwards and to the east. As the bubbles evolve, the entire north‐south extent of the plasma flux tubes in the bubbles becomes depleted, and the bubbles take the form of vertically elongated wedges of depleted plasma. The east‐west width of a bubble domain can be several thousand kilometers and the plasma density depletion in the bubbles varies from a factor of 10 to 1000. Because equatorial plasma bubbles could have an appreciable effect on the upper atmosphere, a time‐dependent, three‐dimensional, high‐resolution model of the global thermosphere was used to calculate the response of the neutral gas to “idealized” plasma bubble depletions. The model predicts that there are both neutral density and temperature depressions and enhancements in association with the plasma bubbles. The bubble regions can contain either neutral gas enhancements or depressions depending on the background conditions, which change throughout the night. However, the calculated neutral gas perturbations are small, with maximum neutral density perturbations of 6% and maximum temperature perturbations of about 35°K. Nevertheless, these results support the recent experimental evidence that plasma bubbles produce depletions in the neutral density.