bluuebunny/crossref_metadata_2025 huggingface dataset:
Numerical simulation of active separation control by a synthetic jet
Authors: DANDOIS JULIEN , GARNIER ERIC , SAGAUT PIERRE
Published: February 2007

Direct numerical simulation (DNS) and large-eddy simulation (LES) are carried out to investigate the frequency effect of zero-net-mass-flux forcing (synthetic jet) on a generic separated flow. The selected test case is a rounded ramp at a Reynolds number based on the step height of 28 275. The incoming boundary layer is fully turbulent withRθ=1410. The whole flow in the synthetic jet cavity is computed to ensure an accurate description of the actuator effect on the flow field. In a first step, DNS is used to validate LES of this particular flow. In a second step, the effect of a synthetic jet at two reduced frequencies of 0.5 and 4 (based on the separation length of the uncontrolled case and the free-stream velocity) is investigated using LES. It is demonstrated that, with a proper choice of the oscillating frequency, separation can be drastically reduced for a velocity ratio between the jet and the flow lower than one. The low frequency is close to the natural vortex shedding frequency. Two different modes of the synthetic jet have been identified. Avorticity-dominated modeis observed in the low-frequency forcing case for which the separation length is reduced by 54%, while anacoustic-dominated modeis identified in the high-frequency forcing case for which the separation length is increased by 43%. The decrease of the separation length in the low-frequency forcing case is correlated with an increase of the turbulent kinetic energy level and consequently with an increase of the entrainment in the separated zone. A linear inviscid stability analysis shows that the increase of the separation length in the high-frequency forcing case is due to a modification of the mean velocity profile suggested by Stanek and coworkers. The result is a lower amplification of the perturbations and consequently, a lower entrainment into the mixing layer. To our knowledge, it is the first time that Stanek's hypothesis has been assessed, thanks to numerical simulations of fully turbulent flow.
Direct numerical simulation of round turbulent jets in crossflow
Authors: MUPPIDI SUMAN , MAHESH KRISHNAN
Published: February 2007

Direct numerical simulation is used to study a round turbulent jet in a laminar crossflow. The ratio of bulk jet velocity to free-stream crossflow velocity is 5.7 and the Reynolds number based on the bulk jet velocity and the jet exit diameter is 5000. The mean velocity and turbulent intensities from the simulations are compared to data from the experiments by Su & Mungal (2004) and good agreement is observed. Additional quantities, not available from experiments, are presented. Turbulent kinetic energy budgets are computed for this flow. Examination of the budgets shows that the near field is far from a state of turbulent equilibrium – especially along the jet edges. Also – in the near field – peak kinetic energy production is observed close to the leading edge, while peak dissipation is observed toward the trailing edge of the jet. The results are used to comment upon the difficulty involved in predicting this flow using RANS computations. There exist regions in this flow where the pressure transport term, neglected by some models and poorly modelled by others, is significant. And past the jet exit, the flow is not close to established canonical flows on which most models appear to be based.
On the inversion of the von Kármán street in the wake of a confined square cylinder
Authors: CAMARRI SIMONE , GIANNETTI FLAVIO
Published: February 2007

This paper considers the incompressible two-dimensional laminar flow around a square cylinder symmetrically positioned in a channel. In this type of flow, even if vortices of opposite sign are alternately shed from the body into the wake as in the unconfined case, an inversion of their position with respect to the flow symmetry line takes place further downstream. A numerical analysis is carried out to investigate the physical origin of this phenomenon and to characterize the position in the wake at which the vortices cross the symmetry line. It is shown that, for low to moderate blockage ratios, the fundamental cause of the inversion of the vortices is the amount of vorticity present in the incoming flow, and a dynamic interpretation in terms of vorticity interference in the wake is given. Further insight is gained through a linear stability analysis of the vortex shedding instability.
Lee waves from a sphere in a stratified flow
Authors: VOISIN B.
Published: February 2007

Two asymptotic analyses of the generation of lee waves by horizontal flow at velocityUof a stratified fluid of buoyancy frequencyNpast a sphere of radiusaare presented, for either weak or strong stratification, corresponding to either large or small internal Froude numberF=U/(Na), respectively. ForF⋙1, the fluid separates into two regions radially: an inner region of scaleawith three-dimensional irrotational flow unaffected by the stratification, and an outer region of scaleU/Nwith small-amplitude lee waves generated by theO(1) vertical motion in the inner region. ForF⋘1, the fluid separates into five layers vertically: from the lower dividing streamsurface situated at a distanceU/Nabove the bottom of the sphere to the upper dividing streamsurface situated at a distanceU/Nbelow the top, there is a middle layer with two-dimensional horizontal irrotational flow; from the upper dividing streamsurface to the top of the sphere, and from the lower dividing streamsurface to the bottom, there are top and bottom transition layers, respectively, with three-dimensional flow; above the top and below the bottom, there are upper and lower layers, respectively, with small-amplitude lee waves generated by theO(F) vertical motion in the transition layers.

The waves are calculated where they have small amplitudes. The forcing is represented by a source of mass: forF⋙1, the surface distribution of singularities equivalent to the sphere in three-dimensional irrotational flow; forF⋘1, the horizontal distribution of singularities equivalent, in the upper (resp. lower) layer, to the flat cut-off obstacle made up of the top (resp. bottom) portion of the sphere protruding above (resp. below) the upper (resp. lower) dividing streamsurface. The analysis is validated by comparison of the theoretical wave drag with existing experimental determinations. ForF⋙1, the drag coefficient decreases as (lnF+7/4-γ)/(4F4), with γ the Euler constant; forF⋘1, it increases as$(32\surd2)/(15\upi)F^{3/2}$. The waves have the crescent shape of the three-dimensional lee waves from a dipole, modulated by interferences associated with the finite size of the forcing. For strong stratification, the hydrostatic approximation is seen to produce correct leading-order drag, but incorrect waves.
Experimental and numerical studies on the starting effect on the secondary flow in a bend
Authors: BOIRON OLIVIER , DEPLANO VALÉRIE , PELISSIER ROBERT
Published: February 2007

A numerical and experimental modelling study was carried out in a curved tube to analyse the behaviour of unsteady flows in a bend. Based on a test bench, with no mechanical disturbances, the flow behaviour was observed using fluorescein injection. Velocity measurements were performed using hot-film anemometry. In addition, a finite volume method was used to perform three-dimensional unsteady numerical simulations. Womersley parameter values between 8 and 21 and Dean number values between 110 and 420 were used to assess the parameters affecting the flow behaviour. Secondary motions were observed, experimentally and numerically, showing the complexity of the flow patterns. The initiation and subsequent development are explained quantitatively. Based on our analysis of the starting effect, the secondary patterns were found to be highly dependent on both the initial conditions and the flow waveforms.
Macroscopic description of arbitrary Knudsen number flow using Boltzmann–BGK kinetic theory
Authors: CHEN HUDONG , ORSZAG STEVEN A. , STAROSELSKY ILYA
Published: February 2007

We derive, without approximation, a closed-form macroscopic equation for finite Knudsen number flow using the Boltzmann–BGK kinetic theory with constant relaxation time. This general closed-form equation is specialized into a compact integro-differential equation for time-dependent isothermal unidirectional flows and results are presented for channel flow. This equation provides a clear demonstration of the effects of finite Knudsen number, and it also illustrates the limitations of the Boltzmann–BGK theory with constant relaxation time and bounce-back boundary conditions.
Coherent vortices and tracer cascades in two-dimensional turbulence
Authors: BABIANO ARMANDO , PROVENZALE ANTONELLO
Published: February 2007

We study numerically the scale-to-scale transfers of enstrophy and passive-tracer variance in two-dimensional turbulence, and show that these transfers display significant differences in the inertial range of the enstrophy cascade. While passive-tracer variance always cascades towards small scales, enstrophy is characterized by the simultaneous presence of a direct cascade in hyperbolic regions and of an inverse cascade in elliptic regions. The inverse enstrophy cascade is particularly intense in clusters of small-scales elliptic patches and vorticity filaments in the turbulent background, and it is associated with gradient-decreasing processes. The inversion of the enstrophy cascade, already noticed by Ohkitani (Phys. Fluids A, vol. 3, 1991, p. 1598), appears to be the main difference between vorticity and passive-tracer dynamics in incompressible two-dimensional turbulence.
Dream Immorality
Authors: Driver Julia
Published: February 2007

This paper focuses on an underappreciated issue that dreams raise for moral evaluation: is immorality possible in dreams? The evaluatiotial internalist is committed to answering ‘yes.’ This is because the internalist account of moral evaluation holds that the moral quality of a person's actions, what a person does, her agency in any given case is completely determined by factors that are internal to that agency, such as the person's motives and/or intentions. Actual production of either good or bad effects is completely irrelevant to the moral evaluation of that agency. Since agency can be expressed in a dream, the internalist is committed to dream immorality. Some may take this as a reductio of evaluational internalism, but whether or not this is the case the issue reveals what such a theory is committed to.

In this paper I explore the significance of dreams to morality, and argue that the absurdity of dream immorality supports an account of moral evaluation with an externalist component, rather than a purely internalist account of moral evaluation.
The Domain of Authority
Authors: Knowles Dudley
Published: February 2007

If the commands of authority are peremptory and content-independent directives, it is a great puzzle why any rational autonomous agent should accept them as morally binding, as Robert Paul Wolff and others have argued. I analyse the peremptory and content-independent quality of authoritative directives and argue that all earthly authorities operate within a specified domain. I investigate three candidates for the role of universally applicable boundary conditions–morality, harm to self, and absurdity. I conclude that commands are authoritative only when intra vires, i.e. issued within the proper domain of the authority. Wolff's challenge is not met, hut it is shown to be less forbidding.
Wittgenstein, Plato, and the Historical Socrates
Authors: Rowe M.W.
Published: February 2007

This essay examines the profound affinities between Wittgenstein and the historical Socrates. The first five sections argue that similarities between their personalities and circumstances can explain a comparable pattern of philosophical development. The next nine show that many apparently chance similarities between the two men's lives and receptions can be explained by their shared conceptions ofphilosophical method. The last three sections consider the difficulty of practising this method through writing, and examine the solutions which Plato and Wittgenstein adopted.
God and First Person in Berkeley
Authors: Botterill George
Published: February 2007

Berkeley claims idealism provides a novel argument for the existence of God. But familiar interpretations of his argument fail to support the conclusion that there is a single omnipotent spirit. A satisfying reconstruction should explain the way Berkeley moves between first person singular and plural, as well as providing a powerful argument, once idealism is accepted. The new interpretation offered here represents the argument as an inference to the best explanation of a shared reality. Consequently, his use of the first person must be taken as ‘exemplary’ rather than ‘Cartesian’. This explains the freedom of movement in the text between singular and plural. However, it also reveals Berkeley as side-stepping sceptical doubt.
Bertrand Russell's Naturalistic Epistemology
Authors: Kitchener Richard F.
Published: February 2007

Bertrand Russell is widely considered to be one of the founders of analytic philosophy, epistemology, and philosophy of science. Individuals have usually stressed his early philosophical contributions as seminal in this regards. But Russell also had another side–a naturalistic side–leading him towards a naturalistic epistemology and naturalistic philosophy of science of the type Quine later made famous. My goal is to provide an outline of Russell's naturalistic epistemology and the underlying philosophical motivations for such a move. After briefly presenting Russell's conception of the nature of philosophy, I sketch his theory of philosophical method, which is a version of the method of analysis. This provides the underpinnings for a discussion of his Naturalistic Epistemology, which led him to adopt a version of a behavioristic epistemology. Although Russell vacillated on the question of the adequacy of such an account, it provided a major element in his later philosophical views. I suggest that we must reevaluate our conception of the history of analytic philosophy and, in particular, our understanding of Russell's place in the history of 20th century philosophy.
The Good Sense of Nonsense: a reading of Wittgenstein's Tractatus as nonself-repudiating
Authors: Moyal-Sharrock Danièle
Published: February 2007

This paper aims to return Wittgenstein's Tractatus to its original stature by showing that it is not the self-repudiating work commentators take it to be, but the consistent masterpiece its author believed it was at the time he wrote it. The Tractatus has been considered self-repudiating for two reasons: it refers to its own propositions as ‘nonsensical’, and it makes what Peter Hacker calls ‘paradoxical ineffability claims’ – that is, its remarks are themselves instances of what it says cannot be said. I address the first problem by showing that, on Wittgenstein's view, nonsense is primarily a technically descriptive, not a defamatory, qualification, and is not indicative of Wittgenstein rejecting or disavowing his own Tractarian ‘propositions’. I then dissolve the paradoxical ineffability claim by making a technical distinction, based on Wittgenstein's own theory and practice, between saying and speaking.
The temporal relationship between falls and fear-of-falling among Chinese older primary-care patients in Hong Kong
Authors: CHOU KEE-LEE , CHI IRIS
Published: February 2007

Although the association between falls and fear-of-falling has been established by previous studies, the temporal ordering of the two is uncertain. Moreover, the common and unique risk factors that contribute to falls and to fear-of-falling have not been investigated in either primary health-care settings or Asian societies. The aims of this study were to examine the temporal sequencing of fear-of-falling and a fall, and to identify the risk factors associated with the two. A prospective cohort study with three six-month measurement waves was conducted in primary-care settings in Hong Kong. The sample was derived from the waiting list control group of a randomised clinical trial, and 321 respondents participated in the three waves. They were evaluated with the Minimum Data Set for Home Care. It was found that falls and fear-of-falling at baseline were not independent predictors of respectively developing a fear-of-falling and becoming a faller, but that age was a common independent predictor for falls and the onset of a fear-of-falling. Individuals with a fear-of-falling were at risk of both falling and a fear-of-falling at 12 months. The good news is that no vicious cycle of falls and fear-of-falling was found, and modifiable risk factors, including IADL limitations, environmental hazards, and fear-of-falling were identified, so that effective prevention programmes for falls and for fear-of-falling can be designed.
Pension reforms in urban China and Hong Kong
Authors: YU WAI KAM
Published: February 2007

This study of recent pension reforms in Hong Kong and urban China particularly addressed three questions. What are the causes of the pension reforms in these two economies? What are their key features? What difficulties have been faced by the Hong Kong and Beijing governments during their implementation? As well as enhancing our understanding of the pension schemes in these two countries, the paper makes a contribution to the debate on whether government welfare reforms in responses to economic globalisation are converging on one pattern, an ideal mix of pension schemes. This paper shows that both convergent and path-dependent processes explain the forms of the measures introduced by the Hong Kong and Beijing governments. They have responded not only to the challenges brought by economic globalisation but also to the legacy of previous policies. Moreover, the welfare effectiveness of the new schemes has been undermined both by the two governments' non-welfare policies, particularly to promote economic growth, and by the constraints created by the previous welfare measures. The paper also argues that to develop only a non-contributory comprehensive pension scheme is not the solution to the problem of how best to provide old-age income security, but that this welfare goal principle should be more strongly upheld in pensions reforms.
The ‘regulated death’: a documentary analysis of the regulation and inspection of dying and death in English care homes for older people
Authors: FROGGATT KATHERINE
Published: February 2007

In England, processes of regulation and inspection have been established to ensure that older people living in long-term care settings receive quality care. This paper describes how dying and death in care homes for older people is regulated and inspected. A documentary analysis was undertaken of the standard that addresses dying and death in the 2001 Care Homes for Older People: National Minimum Standards. Present in the standard is a ‘good death’ template drawn from constructions of best practice in palliative care. The way in which this national standard is enacted in the inspection process is described using a content analysis of the inspection reports from 226 care homes for older people. These present a narrow focus on dying and death, one that emphasises the older person's wishes and the degree of adherence to policies and procedures concerned with the dying and death event. A regulated death attenuates the ‘good death’ template and reflects both the inspection process and capabilities of the residents of care homes. If the regulation and inspection process is to integrate dying with living, a broader conception and regime of inspection is required. Only then will end-of-life care be provided that meets the diverse needs of older people who live in care homes.
Socio-economic position and quality of life among older people in 10 European countries: results of the SHARE study
Authors: KNESEBECK OLAF VON DEM , WAHRENDORF MORTEN , HYDE MARTIN , SIEGRIST JOHANNES
Published: February 2007

This study examines associations between quality of life and multiple indicators of socio-economic position among people aged 50 or more years in 10 European countries, and analyses whether the relative importance of the socio-economic measures vary by age. The data are from the Survey of Health, Ageing and Retirement in Europe (SHARE) in 2004. 15,080 cases were analysed. Quality of life was measured by a short version of the CASP-19 questionnaire, which represents quality of life as comprising four conceptual domains of individual needs that are particularly relevant in later life: control (C), autonomy (A), self-realisation (S) and pleasure (P). The short version has 12 items (three for each domain). Five indicators of socio-economic position were used: income, education, home ownership, net worth, and car ownership. A multiple logistic regression showed that quality of life was associated with socio-economic position, but that the associations varied by country. Relatively small socio-economic differences in quality of life were observed for Switzerland, but comparatively large differences in Germany. Education, income, net worth, and car ownership consistently related to quality of life, but the association of home ownership was less consistent. There was no indication that the socio-economic differences in quality of life diminished after retirement (i.e. from 65+ years). Conventional measures of socio-economic position (education and income), as well as alternative indicators (car ownership and household net worth), usefully identified the differential risks of poor quality of life among older people before and after the conventional retirement age.
Disturbing life events and wellbeing after 80 years of age: a longitudinal comparison of survivors and the deceased over five years
Authors: CLÉMENCE ALAIN , KARMANIOLA ATHANASSIA , GREEN EVA G. T. , SPINI DARIO
Published: February 2007

This paper assesses the impact of disturbing life events over five years on the wellbeing of 340 people aged 80–84 years at baseline, by analysing data from a longitudinal survey in Switzerland. The guiding proposition was that the negative effect of life events is moderated by the event domain, i.e. health, deaths and changes in family setting and relationships, and by cognitive adaptation to one's own health state (adopting a more or less optimistic view). Multi-level regression that controlled for the effect of socio-demographic and health factors was used. Corroborating the first hypothesis, a model that differentiated the event categories, instead of their additive inclusion, gave the best fit. In support of the second hypothesis, it was shown that the positive impact of self-rated health reduced the negative effect of life events on wellbeing for survivors, but not for those who died within five years. This suggests that the former made more optimistic appraisals of their mental and physical health, while the latter adjusted their subjective health rating to their functional abilities. Survivors had better psychological resources for coping with disturbing life events, while the deceased lacked these resources, which buffered the impact of negative events. The psychological meaning of stressful events at the end of life is discussed. By encouraging optimistic self-evaluations of health, and raising awareness of the range of normal functioning of older people, health- and social-care practitioners can promote the maintenance of meaningful lives in old age.
Increasing gerontological communication
Authors: WARNES TONY
Published: February 2007

I am pleased to report new appointments to the editorial team and plans for expansion of the journal. Last summer Miles Lambert succeeded Jean Wilkinson as the Editorial Assistant, and to the great credit of them both, the transition caused practically no delay in the handling of the submitted papers. Then in November 2006, Mima Cattan of Leeds Metropolitan University was appointed as the journal's first Associate Editor. Mima's academic roots are in medical sociology and anthropology. I find her magnificently thoughtful and constructive, not only about the practicalities and responsibilities of an editor's trade, as with concern for the novice author when they receive an unfavourable decision letter, but also about broad epistemological issues in the production and communication of gerontological understanding. Mima's presence will be creative, stimulating and welcome support. Her appointment is to enable more papers to be published, to which I now turn.
Warnings for pattern matching
Authors: MARANGET LUC
Published: February 2007

We examine the ML pattern-matching anomalies of useless clauses and non-exhaustive matches. We state the definition of these anomalies, building upon pattern matching semantics, and propose a simple algorithm to detect them. We have integrated the algorithm in the Objective Caml compiler, but we show that the same algorithm is also usable in a non-strict language such as Haskell. Or-patterns are considered for both strict and non-strict languages.
A monadic framework for delimited continuations
Authors: Dyvbig R. KENT , JONES SIMON PEYTON , SABRY AMR
Published: February 2007

Delimited continuations are more expressive than traditional abortive continuations and they apparently require a framework beyond traditional continuation-passing style (CPS). We show that this is not the case: standard CPS is sufficient to explain the common control operators for delimited continuations. We demonstrate this fact and present an implementation as a Scheme library. We then investigate a typed account of delimited continuations that makes explicit where control effects can occur. This results in a monadic framework for typed and encapsulated delimited continuations, which we design and implement as a Haskell library.
Brain imaging and courtroom evidence: on the admissibility and persuasiveness of fMRI
Authors: Feigenson Neal
Published: February 2007

Functional magnetic resonance imaging (fMRI) is currently the most advanced technique for measuring and depicting brain function. Functional MRI studies abound in neuroscience, psychiatry and psychology. Inevitably, fMRI-based evidence will be offered in court as proof of matters involving parties’ mental states and capabilities. This paper analyses the likely admissibility of fMRI testimony and images. Cases involving other types of functional neuroimaging (PET and SPECT), which may shed light on judges’ receptivity to fMRI evidence, are briefly surveyed. The conceptual and methodological underpinnings of fMRI are then explored, prompting basic questions about the evidentiary reliability and relevance of fMRI results. The first reported case involving fMRI evidence, which raises several of these questions, is described. Finally, the admissibility and probative value of the fMRI images themselves are discussed. Assuming that the expert testimony that the images are offered to illustrate is admissible, it is argued that the law can obtain the benefits of fMRI science while minimising the judgmental risks by allowing triers of fact to see the images and encouraging experts and lawyers to educate the triers to interpret the images properly.
Strong reciprocity and accountability: behavioural analysis of patients’ legal responses to medical injury
Authors: Dauer Edward A.
Published: February 2007

There is a remarkable resonance between recent findings about medical malpractice litigation and theories about the evolution of co-operation and reciprocity among humans. This should not be altogether surprising: theories of reciprocity seek to explain the behaviours we exhibit when we interact to punish or confer benefits on each other; while civil liability litigation may be just one of modern society’s ways of compelling otherwise unrequited reciprocity. The link between the two fields of study is worth exploring nonetheless. Just as behavioural economics and evolutionary theory offer useful insights for those of us who study legal phenomena, data about the behaviour of people accessing legal institutions may be useful to those who build behavioral theories. This essay is therefore, in a way, a lawyer’s effort to return the favour.
Examining the biological bases of family law: lessons to be learned for the evolutionary analysis of law
Authors: Carbone June , Cahn Naomi
Published: February 2007

This article critically examines the insights that biology (including evolutionary analysis and neuroscience data) offers for understanding the relationship between family law and family stability. The paper initially considers evolutionary analysis, comparative anatomy, and neuroscience data to conclude that while the pair bond appears to be a universal feature of human societies, long-term fidelity is not. The second part of the paper considers the benefits and limitations of evolutionary analysis concluding, first, that evolutionary analysis, without connection to modern neuroscience or sociological data, remains highly speculative; second, that where the evolutionary analysis is borne out by modern neuroscience and/or sociological data, it is more persuasive, but often leads to obvious conclusions; and third, that undertaking this type of examination nonetheless leads to new insights or new questions that should prompt productive research.
Jurors are competent cue-takers: how institutions substitute for legal sophistication
Authors: Boudreau Cheryl
Published: February 2007

What conditions are necessary for juries to work effectively? Legal scholars and social scientists have debated this question, and research in psychology and law demonstrates that jurors are easily confused by scientific evidence and readily swayed by the slick framing of argument. Rather than condemn juries as unworkable, however, I demonstrate experimentally that jurors need not possess legal or scientific sophistication to make reasoned choices during trials. Specifically, I demonstrate that various institutions embedded in our legal system (such as penalties for lying and the threat of verification) can substitute for sophistication and enable even unsophisticated individuals to learn what they need to know. Based on these findings, I argue that rather than advocate blue ribbon juries and bench trials as replacements for citizen juries, scholars should instead seek substitutes for jurors’ lack of sophistication in the institutions of our legal system.
Promulgation and the law
Authors: Grant Claire
Published: February 2007

This is a paper about promulgation, and whether it is a sine qua non of law. The promulgation question has been treated occasionally in the jurisprudential literature, although typically only as a subordinate theorem. This paper does not attempt a thorough conspectus, seeking rather to serve as an introductory to what is a longstanding problem of general interest and concern. An argument for the proposition that laws are things that can be known will be distinguished from two other ways of responding to the promulgation question, which may be attributed respectively to the late H. L. A. Hart and Lon Fuller. The paper defends this proposition about artefactuality and access, and deals with a number of awkward consequences that appear to ensue from its acceptance.
Wohin soll sich die Fachkultur der Arbeits- und Organisationspsychologie entwickeln?
Authors: Heuer Herbert
Published: February 2007

Zusammenfassung. Von Rosenstiel (2004) hat eine Diskussion zur Fachkultur der Arbeits- und Organisationspsychologie angestoßen. In dieser Diskussion wurde eine starke Abgrenzung gegen die Grundlagenfächer sowie eine spezifische Publikationskultur gefordert. Beide Entwicklungen bergen Gefahren für das Fach. Die Abgrenzung gegen die Grundlagenfächer sollte durch ein Kontinuum unterschiedlich anwendungsnaher Forschung ersetzt werden; dem entspricht eine überwiegend internationale Publikationstätigkeit, ergänzt durch deutschsprachige wissenschaftliche und anwendungsorientierte Schriften.
A global climate model study of CH4 emissions during the Holocene and glacial‐interglacial transitions constrained by ice core data
Authors: Harder S. L. , Shindell D. T. , Schmidt G. A. , Brook E. J.
Published: February 2007

Ice core records show atmospheric methane mixing ratio and interpolar gradient varying with climate. Changes in wetland sources have been implicated as the basis for this observed variation in the record, but more recently, modeling studies suggest that changes in the CH4 sink resulting from changes in sea surface temperature (SST) and emissions of other volatile organic carbon (VOC) compounds by vegetation must also be considered. We use the Goddard Institute for Space Studies (GISS) General Circulation Model (GCM) with the GISS Tropospheric Chemistry Model to study the response of the methane mixing ratio to source changes during the Holocene and also to a changing chemical sink during glacial‐interglacial transitions. We combine model results with ice core data to demonstrate a method that provides constraints on changes in northern and tropical methane sources. Results show that within the Holocene, changes in the atmospheric methane mixing ratio and latitudinal gradient are not linear with respect to changing methane emissions. Tropical and northern emissions varied from preindustrial levels by as much as 38% and 15%, respectively, within the Holocene. At glacial‐interglacial transitions the methane mixing ratio is sensitive to changes in both VOC and tropical methane emissions and the sensitivity also depends strongly on the assumed SST shift. Our findings suggest that changes in the ice core methane record are likely the result of changes in both the source and the sink. Changes in the sink become especially important when changes in methane mixing ratio and/or climate are large.
A field investigation into the effects of a kelp forest (Macrocystis pyrifera) on coastal hydrodynamics and transport
Authors: Rosman Johanna H. , Koseff Jeffrey R. , Monismith Stephen G. , Grover Jamie
Published: February 2007

Macrocystis pyrifera (Giant Kelp) forests form important habitats in temperate coastal regions. Hydrodynamics control the transport of nutrients, food particles, larvae and spores at scales ranging from boundary layers around individual blades to entire kelp forests. Our measurements include vertical profiles of current and temperature, and concurrent wave measurements, at a number of different locations in and around a kelp forest at Santa Cruz, California. We find that flow at the site is dominated by variations at diurnal and semidiurnal frequencies. A vertically sheared across‐shore flow, consistent with flow driven by an across‐shore density gradient, is thought to be important for exchange between the kelp forest and the surrounding coastal ocean. Within the kelp forest, currents are reduced by a factor that correlates with surface canopy coverage, higher frequency internal waves are damped, and onshore transport due to waves (Stokes drift) is estimated to be similar in magnitude to that due to currents. Richardson numbers within the kelp forest are higher than those outside the kelp forest and indicate that the water column within the kelp forest is usually stable to turbulence generation by mean velocity shear.
Sensitivity of the MM5 mesoscale model to physical parameterizations for regional climate studies: Annual cycle
Authors: Fernández J. , Montávez J. P. , Sáenz J. , González‐Rouco J. F. , Zorita E.
Published: February 2007

We present an analysis of the sensitivity to different physical parameterizations of a high‐resolution simulation of the MM5 mesoscale model over the Iberian Peninsula. Several (16) 5‐year runs of the MM5 model with varying parameterizations of microphysics, cumulus, planetary boundary layer and longwave radiation have been carried out. The results have been extensively compared with observational precipitation and surface temperature data. The parameterization uncertainty has also been compared with that related to the boundary conditions and the varying observational data sets. The annual cycles of precipitation and surface temperature are well reproduced. The summer season presents the largest deviations, with a 5 K cold bias in the southeast and noticeable precipitation errors over mountain areas. The cold bias seems to be related to the surface, probably because of the excessive moisture availability of the five‐layer soil scheme used. No parameterization combination was found to perform best in simulating both precipitation and surface temperature in every season and subregion. The Kain‐Fritsch cumulus scheme was found to produce unrealistically high summer precipitation. The longwave radiation parameterizations tested were found to have little impact on our target variables. Other factors, such as the choice of boundary conditions, have an impact on the results as large as the selection of parameterizations. The range of variability in the MM5 physics ensemble is of the same order of magnitude as the observational uncertainty, except in summer, when it is larger and probably related to the inaccuracy of the model to reproduce the summer precipitation over the area.
The 2‐μm spectroscopy of Huygens probe landing site on Titan with Very Large Telescope/Nasmyth Adaptive Optics System Near‐Infrared Imager and Spectrograph
Authors: Negrão A. , Hirtzig M. , Coustenis A. , Gendron E. , Drossart P. , Rannou P. , Combes M. , Boudon V.
Published: February 2007

Several ground‐based telescopes followed the event of the Huygens probe descent through Titan's atmosphere (14 January 2005). We used the Nasmyth Adaptive Optics System Near‐Infrared Imager and Spectrograph (NACO) adaptive optics system at the UT‐4 of the Very Large Telescope in Chile to perform both spectroscopic and imaging measurements of Titan. We present here a selected sample of the spectra we acquired on 16 January 2005 in the K band between 2.03 and 2.40 μm. Our spectra include the Huygens landing site and surrounding dark and bright areas. We apply a radiative transfer code using new methane absorption coefficients calculated in the 2‐μm region. The analysis of the data yields information on the atmosphere and surface properties of these areas. The latter seem to indicate a strong decrease of Titan's surface albedo between 2.03 and 2.12 μm in all areas. This is compatible with the presence of ices such as CH4 and H2O at the surface. Sensitivity tests on the influence of the haze profile and the methane absorption on these results were performed.
Assessing methane release from the colossal Storegga submarine landslide
Authors: Paull C. K. , Ussler W. , Holbrook W. S.
Published: February 2007

Marine slope failure involving methane‐gas‐hydrate‐bearing sediments is one mechanism for releasing enormous quantities of methane to the ocean and atmosphere. The Storegga Slide, on the Norwegian margin, is the largest known Holocene‐aged continental margin slope failure complex and is believed to have occurred in sediments that may have initially contained gas hydrate. Here, we report pore water sulfate gradient measurements that are used as a proxy for the relative amounts of methane that exist in continental margin sediments associated with the colossal Storegga Slide. These measurements suggest that a considerable inventory of methane occurs in sediments adjacent to, and unaffected by, the Storegga Slide events, but indicate that methane is notably absent from sediments on the sole of the slide and distal deposits created by the slide events. Either methane was lost during previous Pleistocene failure events or was never present in significant concentrations within the sediments that failed.
Mean age of air and transport in a CTM: Comparison of different ECMWF analyses
Authors: Monge‐Sanz B. M. , Chipperfield M. P. , Simmons A. J. , Uppala S. M.
Published: February 2007

A comparison of the stratospheric circulation achieved by various data assimilation winds has been performed using multiannual simulations of the TOMCAT/SLIMCAT off‐line 3‐D chemical transport model (CTM). Data from the European Centre for Medium‐Range Weather Forecasts (ECMWF) and the U.K. Met Office (UKMO) have been used to drive the CTM. We find that important improvements have been made in the ECMWF stratospheric winds during recent years. Therefore, a more realistic Brewer‐Dobson (B‐D) circulation, and subtropical mixing are achieved when ECMWF operational or new interim reanalyses are used instead of ERA‐40 analyses. Age‐of‐air and trajectory calculations show that more realistic vertical and horizontal transport is achieved with the new ECMWF assimilated winds. The modelled tape recorder signal further shows the improvement in the tropical transport with the new winds. Overall, these results show that with the recent ECMWF reanalyses, off‐line CTMs can produce stratospheric tracer transport over multiannual timescales more realistically than with other previous (re)analyses. Reasons for the improvements in the new reanalysis are discussed.
Size and energy distributions of interplanetary magnetic flux ropes
Authors: Feng H. Q. , Wu D. J. , Chao J. K.
Published: February 2007

In observations from 1995 to 2001 from the Wind spacecraft, 144 interplanetary magnetic flux ropes were identified in the solar wind around 1 AU. Their durations vary from tens of minutes to tens of hours. These magnetic flux ropes include many small‐ and intermediate‐sized structures and display a continuous distribution in size. Energies of these flux ropes are estimated and it is found that the distribution of their energies is a good power law spectrum with an index ∼−0.87. The possible relationship between them and solar eruptions is discussed. It is suggested that like interplanetary magnetic clouds are interplanetary coronal mass ejections, the small‐ and intermediate‐sized interplanetary magnetic flux ropes are the interplanetary manifestations of small coronal mass ejections produced in small solar eruptions. However, these small coronal mass ejections are too weak to appear clearly in the coronagraph observations as an ordinary coronal mass ejection.
Response of Jupiter's UV auroras to interplanetary conditions as observed by the Hubble Space Telescope during the Cassini flyby campaign
Authors: Nichols J. D. , Bunce E. J. , Clarke J. T. , Cowley S. W. H. , Gérard J.‐C. , Grodent D. , Pryor W. R.
Published: February 2007

We provide a first detailed discussion of the relation between the set of Jovian UV auroral images observed by the Hubble Space Telescope (HST) in December 2000 to January 2001 and simultaneous interplanetary data obtained by Cassini during its Jupiter flyby. Examination of the interplanetary data surrounding all seven HST observation intervals shows that by chance six of them correspond to solar wind rarefaction regions, which follow compressions by periods of ∼2 to ∼6 days. Only one imaging interval, on 13 January 2001, corresponds to a compression region of generally elevated, but highly variable, solar wind dynamic pressure and interplanetary field strength. We have thus first examined the images corresponding to rarefaction regions in order to establish the range of behaviors that occur under these known conditions, which then act as a benchmark against which the compression region images can be compared. The rarefaction region images show relatively consistent properties of the main oval auroras, though differing in detail from interval to interval. The polar auroras show more variability, with the patchy (“swirl”) auroras in the central region sometimes forming a diffuse ring structure and at other times being more uniformly distributed, while the “active region” auroras at dusk vary markedly from weak emissions to bright arc‐like forms, the latter possibly being associated with intervals within ∼2–3 days of a previous solar wind compression. The two images obtained in the compression region on 13 January 2001 then show remarkably different properties in all the auroral components. The main oval is found to be brighter over its whole length by factors of two to three compared with the rarefaction region images, while its position remains essentially unchanged, close to the usual reference oval. However, bright contiguous “active region” auroras in the postnoon and dusk sector then widen the overall auroral distribution in that sector by up to ∼5° in the poleward direction. The region of patchy polar auroras is also found to expand to cover essentially the whole of the remaining area of the polar cap, with a much‐narrowed darker zone just poleward of the main oval in the dawn and prenoon sector. We discuss whether these enhanced emissions are characteristic of the few‐day compression region as a whole or of more localized conditions occurring within the compression region and conclude that the latter is more likely. Examination of the relevant interplanetary data then shows that the brightened images are associated with an interval of significant magnetospheric dynamics, involving a modest compression of the magnetosphere followed by an extended major expansion.
Correction to “Energy transport in the thermosphere during the solar storms of April 2002”
Authors: Mlynczak Martin G. , Martin‐Torres F. Javier , Russell James M.
Published: February 2007

We present corrected computations of the infrared power and energy radiated by nitric oxide (NO) and carbon dioxide (CO2) during the solar storm event of April 2002. The computations in our previous paper underestimated the radiated power due to improper weighting of the radiated power and energy with respect to area as a function of latitude. We now find that the radiation by NO during the April 2002 storm period accounts for 50% of the estimated energy input to the atmosphere from the solar storm. The prior estimate was 28.5%. Emission computed for CO2 is also correspondingly increased, but the relative roles of CO2 and NO remain unchanged. NO emission enhancement is still, far and away, the dominant infrared response to the solar storms of April 2002.