bluuebunny/crossref_metadata_2025 huggingface dataset:
Turbulent flow similarity over an array of cubes in near-neutrally stratified atmospheric flow
Authors: INAGAKI A. , KANDA M.
Published: November 2008

The main objective of this study is to examine the robustness of the inner-layer scaling similarity of near-wall turbulence. The turbulent boundary layer of interest is over a very rough surface with a very high Reynolds number and significant outer-layer disturbances. This is not consistent with the canonical turbulent flows studied in laboratories, but it is common in urban areas. The investigation was conducted using the comprehensive outdoor scale model (COSMO) facility. COSMO is composed of a regular array of 1.5 m concrete cubes on a 50×100 m2flat concrete base. This unique facility allows us to obtain the turbulent dataset within the vertical constant stress region under near-neutral stratification at high Reynolds numbers. The turbulent spectra and the standard deviation of velocity fluctuations from COSMO were compared with the values obtained over rural and urban surfaces, and in wind-tunnel experiments.

The results confirmed that the inner-layer scaling similarity was robust for the wall-normal fluctuations and the Reynolds stress, independent of the roughness types and the outer-layer conditions. The inner-layer scaling similarity failed for the horizontal velocity fluctuations owing to the influence of the outer-layer disturbance. The relative importance of outer-layer turbulence to inner-layer-scale eddies in the horizontal velocity fluctuations was successfully quantified in terms of the roughness scale normalized by the outer-layer scale.
Universality of shear-banding instability and crystallization in sheared granular fluid
Authors: ALAM MEHEBOOB , SHUKLA PRIYANKA , LUDING STEFAN
Published: November 2008

The linear stability analysis of an uniform shear flow of granular materials is revisited using several cases of a Navier–Stokes-level constitutive model in which we incorporate the global equation of states for pressure and thermal conductivity (which are accurate up to the maximum packing density νm) and the shear viscosity is allowed to diverge at a density νμ (<νm), with all other transport coefficients diverging at νm. It is shown that the emergence of shear-banding instabilities (for perturbations having no variation along the streamwise direction), that lead to shear-band formation along the gradient direction, depends crucially on the choice of the constitutive model. In the framework of a dense constitutive model that incorporates only collisional transport mechanism, it is shown that an accurate global equation of state for pressure or a viscosity divergence at a lower density or a stronger viscosity divergence (with other transport coefficients being given by respective Enskog values that diverge at νm) can induce shear-banding instabilities, even though the original dense Enskog model is stable to such shear-banding instabilities. For any constitutive model, the onset of this shear-banding instability is tied to a universal criterion in terms of constitutive relations for viscosity and pressure, and the sheared granular flow evolves toward a state of lower ‘dynamic’ friction, leading to the shear-induced band formation, as it cannot sustain increasing dynamic friction with increasing density to stay in the homogeneous state. A similar criterion of a lower viscosity or a lower viscous-dissipation is responsible for the shear-banding state in many complex fluids.
Imbibition in geometries with axial variations
Authors: REYSSAT MATHILDE , COURBIN LAURENT , REYSSAT ETIENNE , STONE HOWARD A.
Published: November 2008

When surface wetting drives liquids to invade porous media or microstructured materials with uniform channels, the penetration distance is known to increase as the square root of time. We demonstrate, experimentally and theoretically, that shape variations of the channel, in the flow direction, modify this ‘diffusive’ response. At short times, the shape variations are not significant and the imbibition is still diffusive. However, at long times, different power-law responses occur, and their exponents are uniquely connected to the details of the geometry. Experiments performed with conical tubes clearly show the two theoretical limits. Several extensions of these ideas are described.
Pressure-gradient-dependent logarithmic laws in sink flow turbulent boundary layers
Authors: DIXIT SHIVSAI AJIT , RAMESH O. N.
Published: November 2008

Experiments were done on sink flow turbulent boundary layers over a wide range of streamwise pressure gradients in order to investigate the effects on the mean velocity profiles. Measurements revealed the existence of non-universal logarithmic laws, in both inner and defect coordinates, even when the mean velocity descriptions departed strongly from the universal logarithmic law (with universal values of the Kármán constant and the inner law intercept). Systematic dependences of slope and intercepts for inner and outer logarithmic laws on the strength of the pressure gradient were observed. A theory based on the method of matched asymptotic expansions was developed in order to explain the experimentally observed variations of log-law constants with the non-dimensional pressure gradient parameter (Δp=(ν/ρU3τ)dp/dx). Towards this end, the system of partial differential equations governing the mean flow was reduced to inner and outer ordinary differential equations in self-preserving form, valid for sink flow conditions. Asymptotic matching of the inner and outer mean velocity expansions, extended to higher orders, clearly revealed the dependence of slope and intercepts on pressure gradient in the logarithmic laws.
Lack of balance in continuously stratified rotating flows
Authors: SUTYRIN GEORGI G.
Published: November 2008

Periodic linear waves in a vertically sheared flow are considered in a continuously stratified layer of rotating fluid between homogeneous layers along a sloping bottom. This generalized Phillips' configuration has cyclonic horizontal shear and supports the Rossby modes related to the thickness variations of the homogeneous layers and inertia–gravity waves (IGW). While long Rossby modes with streamwise wavenumber κ < f/V (f is the Coriolis parameter, V is the maximum velocity) can be approximated by a neutral balanced solution, short waves with κ > f/V are found to have an inertial critical level and unbalanced gravity-wave-like structure beyond this level. Such ageostrophic unstable normal modes are shown explicitly to couple short Rossby waves with Doppler-shifted gravity waves. They exist even for small Froude number, although the growth rate of ageostrophic unstable modes is exponentially small in Froude number as in the Eady model. This lack of balance in continuously stratified flows agrees with the ultraviolet problem for Ripa's sufficient conditions of stability in a multi-layer model when the number of layers tends to infinity.
Instability of higher harmonic electrostatic ion cyclotron waves in a negative ion plasma
Authors: ROSENBERG M. , MERLINO R. L.
Published: November 2008

We present a kinetic theory analysis of the electrostatic ion cyclotron (EIC) instability in a plasma containing positive ions, electrons, and negative ions that are much more massive than the positive ions. Conditions are investigated for exciting the fundamental and the higher harmonic EIC waves associated with each ion species. We find that as the concentration of heavy negative ions increases, the wave frequencies increase, the unstable spectrum in general shifts to longer perpendicular wavelengths, and the growth of higher harmonic EIC waves tends to increase within certain parameter ranges. Applications to possible laboratory plasmas are discussed.
Cosmopolitanism and the Modern Girl: A Cross-Cultural Discourse in 1930s Penang
Authors: LEWIS SU LIN
Published: November 2008

In the 1920s and 1930s, the Modern Girl emerged in advertisements, cinema and public discourse all over the globe. While she was implicated in nationalist projects of social reform in post-war Britain and Japan, in multicultural, port-city environments such as Penang, the Modern Girl was central to a discourse of ‘cosmopolitanism’. Lively debates about the Modern Girl in Penang's English press wrestled with the tensions between cultural authenticity, diversity and modernity. Male and female readers of theStraits Echo, from different ethnic backgrounds, engaged with each other in a shared public space about issues ranging from education and politics to women's liberality and fashion. The Modern Girl thus represents a new way of looking at the history of colonial Malaysia in the interwar period: one not focused on ethnic nationalism and communalism, but on a shared, multi-ethnic mode of belonging rooted in the globalist environment of the late colonial port-city.
Isolation and genetic characterization of Neospora caninum from asymptomatic calves in Spain
Authors: REGIDOR-CERRILLO J. , GÓMEZ-BAUTISTA M. , PEREIRA-BUENO J. , ADURIZ G. , NAVARRO-LOZANO V. , RISCO-CASTILLO V. , FÉRNANDEZ-GARCÍA A. , PEDRAZA-DÍAZ S. , ORTEGA-MORA L. M.
Published: November 2008

Neospora caninum is a cyst-forming parasite that causes abortion in cattle. Despite this parasite's ubiquitous distribution and wide host range, the number of N. caninum isolates obtained to date is limited. In vitro isolation of the parasite is arduous and often unsuccessful. In addition, most isolates have been obtained from clinically affected hosts and therefore could be biased towards more virulent isolates. In this report, an improved isolation approach from transplacentally infected newborn calves was undertaken and 9 new isolates were obtained. Moreover, a microsatellite technique was applied to investigate the genetic diversity of these isolates. Most isolates showed specific genetic profiles. However, the Nc-Spain10 isolate was identical to the previously described Nc-Spain1H isolate and Nc-Spain3H was identical to Nc-Spain4H. These isolates were likely to have identical genotypes because they were isolated from distinct calves of the same herd. Future pathogenic characterization of these isolates will contribute to the investigation of the relationship between isolate virulence and the outcome of infection, as well as other epidemiological features, such as transmission.
Evolutionary history of trypanosomes from South American caiman (Caiman yacare) and African crocodiles inferred by phylogenetic analyses using SSU rDNA and gGAPDH genes
Authors: VIOLA L. B. , ALMEIDA R. S. , FERREIRA R. C. , CAMPANER M. , TAKATA C. S. A. , RODRIGUES A. C. , PAIVA F. , CAMARGO E. P. , TEIXEIRA M. M. G.
Published: November 2008

In this study, using a combined data set of SSU rDNA and gGAPDH gene sequences, we provide phylogenetic evidence that supports clustering of crocodilian trypanosomes from the Brazilian Caiman yacare (Alligatoridae) and Trypanosoma grayi, a species that circulates between African crocodiles (Crocodilydae) and tsetse flies. In a survey of trypanosomes in Caiman yacare from the Brazilian Pantanal, the prevalence of trypanosome infection was 35% as determined by microhaematocrit and haemoculture, and 9 cultures were obtained. The morphology of trypomastigotes from caiman blood and tissue imprints was compared with those described for other crocodilian trypanosomes. Differences in morphology and growth behaviour of caiman trypanosomes were corroborated by molecular polymorphism that revealed 2 genotypes. Eight isolates were ascribed to genotype Cay01 and 1 to genotype Cay02. Phylogenetic inferences based on concatenated SSU rDNA and gGAPDH sequences showed that caiman isolates are closely related to T. grayi, constituting a well-supported monophyletic assemblage (clade T. grayi). Divergence time estimates based on clade composition, and biogeographical and geological events were used to discuss the relationships between the evolutionary histories of crocodilian trypanosomes and their hosts.
Differential inhibition of high and low Mrthioredoxin reductases of parasites by organotelluriums supports the concept that low Mrthioredoxin reductases are good drug targets
Authors: McMILLAN P. J. , PATZEWITZ E. M. , YOUNG S. E. , WESTROP G. D. , COOMBS G. H. , ENGMAN L. , MÜLLER S.
Published: November 2008

Thioredoxin reductase (TrxR), a NADPH-dependent disulfide oxidoreductase, is vital in numerous cellular processes including defence against reactive oxygen species, cell proliferation and signal transduction. TrxRs occur in 2 forms, a high Mrenzyme characterized by those of mammals, the malaria parasitePlasmodium falciparumand some worms, and a low Mrform is present in bacteria, fungi, plants and some protozoan parasites. Our hypothesis is that the differences between the forms can be exploited in the development of selective inhibitors. In this study, cyclodextrin- and sulfonic acid-derived organotelluriums known to inhibit mammalian TrxR were investigated for their relative efficacy againstP. falciparumTrxR (PfTrxR), a high Mrenzyme, andTrichomonas vaginalisTrxR (TvTrxR), a low Mrform of TrxR. The results suggest that selective inhibition of low MrTrxRs is a feasible goal.
Effects of front surface plasma expansion on proton acceleration in ultraintense laser irradiation of foil targets
Authors: McKenna P. , Carroll D.C. , Lundh O. , Nürnberg F. , Markey K. , Bandyopadhyay S. , Batani D. , Evans R.G. , Jafer R. , Kar S. , Neely D. , Pepler D. , Quinn M.N. , Redaelli R. , Roth M. , Wahlström C.-G. , Yuan X.H. , Zepf M.
Published: November 2008

The properties of beams of high energy protons accelerated during ultraintense, picosecond laser-irradiation of thin foil targets are investigated as a function of preplasma expansion at the target front surface. Significant enhancement in the maximum proton energy and laser-to-proton energy conversion efficiency is observed at optimum preplasma density gradients, due to self-focusing of the incident laser pulse. For very long preplasma expansion, the propagating laser pulse is observed to filament, resulting in highly uniform proton beams, but with reduced flux and maximum energy.
Trajectory optimization of flexible link manipulators in point-to-point motion
Authors: Korayem M. H. , Nikoobin A. , Azimirad V.
Published: November 2008

The aim of this paper is to determine the optimal trajectory and maximum payload of flexible link manipulators in point-to-point motion. The method starts with deriving the dynamic equations of flexible manipulators using combined Euler–Lagrange formulation and assumed modes method. Then the trajectory planning problem is defined as a general form of optimal control problem. The computational methods to solve this problem are classified as indirect and direct techniques. This work is based on the indirect solution of open-loop optimal control problem. Because of the offline nature of the method, many difficulties like system nonlinearities and all types of constraints can be catered for and implemented easily. By using the Pontryagin's minimum principle, the obtained optimality conditions lead to a standard form of a two-point boundary value problem solved by the available command in MATLAB®. In order to determine the optimal trajectory a computational algorithm is presented for a known payload and the other one is then developed to find the maximum payload trajectory. The optimal trajectory and corresponding input control obtained from this method can be used as a reference signal and feedforward command in control structure of flexible manipulators. In order to clarify the method, derivation of the equations for a planar two-link manipulator is presented in detail. A number of simulation tests are performed and optimal paths with minimum effort, minimum effort-speed, maximum payload, and minimum vibration are obtained. The obtained results illustrate the power and efficiency of the method to solve the different path planning problems and overcome the high nonlinearity nature of the problems.
Spatial variation in structural damage to a keystone plant species in the sub-Antarctic: interactions betweenAzorella selagoand invasive house mice
Authors: Phiri Ethel E. , McGeoch Melodie A. , Chown Steven L.
Published: November 2008

On Southern Ocean islands the effects of the house mouse on plants are not well understood. In particular, its influence at the landscape scale has largely been overlooked. To address this issue, we systematically mapped the distribution of a keystone, cushion plant species,Azorella selago, and mouse damage to it across Marion Island. Mouse damage was observed in a third of the sampled sites from sea level to 548 m a.s.l. Damage to individual cushions ranged from single burrows to the disintegration of entire cushions. Mouse damage was high in sites with lowA. selagodensity, suggesting that in areas of low cushion density the impact of mice may be substantial. Moreover, it is not simply direct impacts on theA. selagopopulation that are ecologically significant.Azorella selagocushions serve as nurse plants for many epiphyte species, so increasing the altitudinal range of a variety of them, and also house high densities of invertebrates especially in fellfield landscapes. In consequence, this study demonstrates that mice are having a significant, negative impact at the landscape scale on Marion Island, so adding to the growing list of species and ecosystem-level effects attributable to this invasive rodent.
The First Electroacoustic Pieces by Karlheinz Stockhausen: Technologies and Aesthetics
Authors: Tissot Gaël
Published: November 2008

This article aims to bring to light the links between technology and aesthetics in the first electroacoustic pieces written between 1953 and 1966 by Karlheinz Stockhausen. After reviewing the technological differences of the two aesthetics of musique concrète (France) and elektronische Musik (Germany), it is possible to see how Stockhausen transcended this distinction by gradually creating more diversified material, leading to a ‘world material’, independent from the tools used. This comes along with a more global approach to the sound. The composer, by an appropriate use of the equipment, does not seek an individual control of each element or each parameter, but has a larger-scale view, in which time units are longer and are considered as a whole. This conception, while remaining as precise as an analytical approach, involves a rethinking of the time development, proposed by Stockhausen as the Momentform, a new musical form in which each part is independent and does not constitute the continuation of the preceding one. This reflection on non-linearity in a work, and on relative perception of time, is a key to understanding Stockhausen's music.
The influence of technology on the composition of Stockhausen's Octophonie, with particular reference to the issues of spatialisation in a three-dimensional listening environment
Authors: Clarke Michael , Manning Peter
Published: November 2008

The legacy of Stockhausen's role in developing the art and practice of electroacoustic music is significant, in terms of both the repertory of works he produced for the medium from the early 1950s right up to his death in 2007, and also the supporting documentation he has provided in terms of scores and technical records and his many writings on the medium over the years. What emerges from this documentation is a fascinating and at times significant insight into his compositional methods and underlying aesthetic, itself shaped and influenced by the changing nature of the technology itself. Whereas his earlier works have been subject to close scrutiny in this context far less attention has been paid to those composed in more recent years, involving the use of digital technologies. A key consideration in this context is the distinctive and highly individual nature of his approach to the resources at his disposal, in turn driven by aesthetic considerations which of necessity become embedded in the practicalities of realisation. Thus the study of the changing nature of his techné as new tools became available becomes a crucial consideration. This article examines these issues in the context of Octophonie (1991) and with particular reference to the concepts and practicalities addressed in his use of three-dimensional spatialisation.
A Computer Music Retrospective
Authors: Lyon Eric
Published: November 2008

A composer who has worked in the field of computer music for the last 25 years reflects on how technological developments during that time have affected his work in computer music, instrumental music and hybrid combinations of the two. The compositional trajectories traced here often run parallel to opportunities afforded by the evolution of computer technology suitable for the generation of digital audio.
This is not a C#: What My Computer Means
Authors: Iglesia Daniel
Published: November 2008

Computers contain layers of abstraction between the raw audio bits and the user experience; each layer requires a method of traversal that reflects the attitudes of the programmer/composer/performer. The navigation of this hierarchy results in modes of thought that affect notions of how musical signifiers can be subverted and redefined. This explosion of individualistic technological systems defines meaning for new sonic results, devoid of traditional communicative signs; the manipulations within these systems directly assail the traditional signification of artistic value and of institutional canonisation. A few pieces and scenarios are presented as examples. Additionally presented are two opposing tendencies (with some empirical manifestations) in the creation of live performances systems, here labelled as extensional and algorithmic. The article posits that a performance system cannot amplify human expression without necessarily having either predefined processes or predefined limitations, and that the choice in this design is reflected in the composer's attitude towards layer-traversal.
The Analysis of Generative Music Programs
Authors: Collins Nick
Published: November 2008

Composers have spent more than fifty years devising computer programs for the semi-automated production of music. This article shall focus in particular on the case of minimal run-time human intervention, where a program allows the creation of a musical variation, typically unravelling in realtime, on demand. These systems have the capacity to vary their output with each run, often from no more input information than the seeding of a random number generator with the start time. Such artworks are accumulating, released online as downloads, or exhibited through streaming radio sites such as rand()%. Listener/users and composer/designers may wish for deeper insight into these programs' ontological status, mechanisms and creative potential. These works are challenging to dissect; this article makes a tentative start at confronting the unique problems and rich behaviours of computer-program-based generative music, from the social and historical context to the backwards engineering of programs in relation to their sound world. After a discussion of exemplars and definitions of generative art, strategies for analysis are outlined. To provide practical examples, analyses are provided of two small scale works by James McCartney.
Formalising Form: An Alternative Approach To Algorithmic Composition
Authors: Hedelin Fredrik
Published: November 2008

One main issue in the field of algorithmic composition is the relationship
between the algorithm and the final musical structure. This article investigates
that relationship further and presents a method of algorithmic thinking in which
the musical form is the starting point. Kimon, an object-oriented programming environment for computer-aided
composition in which one creates abstractions of musical form, will be
introduced. The aim is to take algorithmic composition closer to the musical
output in order to work systematically with form and dramaturgy. An
electroacoustic piece that has been conceived and generated in its entirety by
the system will also be presented.
HIEMPA: Hybrid Instruments from Electroacoustic Manipulation and Models of Pütorino and Aquascape
Authors: Whalley Ian
Published: November 2008

The HIEMPA project combined a team of people with technical, artistic, environmental and cultural expertise towards an artistic outcome aiming to extend the New Zealand sonic art tradition. The work involved collecting audio samples from the aquascape of the Ruakuri Caves and Nature Reserve in Waitomo, South Waikato, New Zealand; and samples of a variety of pütorino – a New Zealand Mäori wind instrument. Following a machine learning analysis of this audio material and an analysis of the performance material, hybrid digital instruments were built and mapped to suitable hardware triggers. The new instruments are playable in realtime, along with the electroacoustic manipulation of pütorino performances. The project takes into account the environmental and cultural significance of the source material, with the results to be released as a set of compositions. This paper discusses the background research and process of the project.
Utilization of barley ( Hordeum vulgare L.) landraces in the highlands of West Shewa, Ethiopia
Authors: Eticha Firdissa , Berghofer Emmerich , Grausgruber Heinrich
Published: November 2008

In Ethiopia, barley is used to make various types of foods, and home-made and industrial beverages. The various kinds of end-use of barley grain by rural people in two districts of West Shewa are reported. According to farmers, no other cereal crop can be processed into so many different forms of food. At least 17 kinds of foods and beverages, which are consumed in the form of whole-grain snacks, sauces, soups, drinks and baked foods, were reported. Some are mainly served on special occasions like annual ceremonies and cultural gatherings, while others are served as main dishes. Black- and purple-grained barleys are preferred for malting and home-made alcoholic drinks, whereas white-grained types are used for baking and roasting. Each landrace has its own inherent property that makes it suitable for at least one end-use. Since ancient times, barley foods are also known to farmers as remedies and traditional medicines for many kinds of diseases. The various kinds of utilizations of barley and its value in the socio-cultural lifestyles of farmers play vital roles for the on-farm maintenance of different landraces in West Shewa.
Imperial paths, big comparisons: the late Ottoman Empire
Authors: Emrence Cem
Published: November 2008

The main goals of this article are to review historiographical trends and set new directions for late Ottoman history. First, the paper demonstrates that current research on the late Ottoman Empire still operates within the confines of the centre–periphery model, and sustains dualistic and state-centred narratives. Second, I argue that a ‘historical trajectory’ framework is a better analytical tool and empirical strategy. It is spatial, path-dependent, and comparative. With special reference to the Middle Eastern provinces, I show that the Ottoman Empire was characterized by distinct imperial paths during the nineteenth century, each representing an alternative route to state–society and local–global relations. The article further suggests that a trajectory-specific approach can provide new prospects for understanding Eurasian land-based empires from a comparative perspective.
Knowledge and divergence from the perspective of early modern India
Authors: Roy Tirthankar
Published: November 2008

This article explores the origins of divergent technological pathways in the early modern world, and the role that artisanal knowledge played in this process. It rejects older explanations based on societal differences in entrepreneurial propensities and incentives, and a more modern one based on factor cost. It argues instead for the importance of conditions that facilitated transactions between complementary skills. In India, the institutional setting within which artisan techniques were learned had made such transactions less likely than in eighteenth-century Europe. The cost of acquiring knowledge, therefore, was relatively high in India.
‘Profits sprout like tropical plants’: a fresh look at what went wrong with the Eurasian spice tradec. 1550–1800
Authors: Halikowski Smith Stefan
Published: November 2008

There has been little in the way of fresh thinking on the Eurasian spice trade since the 1980s, partly due to the crisis in economic history, although recent work has both dealt with the agency of non-European actors and started to take Chinese demand into the equation. Starting with problems specific to the Portuguese re-export trade, this article highlights the role of consumers, using research undertaken on the structures of demand to present a theory of cultural demystification. The Portuguese, it is argued, by opening direct trading links to the sources of supply, broke what amounted to a spell that had sustained the trade from the time of Alexander the Great. In concrete terms, the performance of individual spices is disaggregated, and the appearance of rival pepper products brought under scrutiny. While African peppers failed to consolidate the consumer interest they had generated over the fifteenth century, capsicum peppers rapidly spread to southern Europe, where they were domesticated and hence became invisible to international trade. The success of the capsicum pepper was replicated in West Africa, India, and China.
Was fashion a European invention?
Authors: Marco Belfanti Carlo
Published: November 2008

Fashion was arguably a social phenomenon that emerged in Europe during early modern times, and this paper seeks to determine whether it was unknown in the refined civilizations of the East. The conclusion is that fashion was not a European invention. The analysis of the evolution of Indian, Chinese, and Japanese clothing systems underlines how these societies underwent phases in which, thanks to propitious economic conditions, the accentuated propensity towards consumption stimulated behaviour that challenged the traditional hierarchies of appearance, usually regulated by canons of a prescriptive nature. Fashion was not, therefore, a European invention, but it only fully developed as a social institution in Europe, while in India, China, and Japan it only evolved partially, without being able to obtain full social recognition.
High gas‐transfer velocity in coastal regions with high energy‐dissipation rates
Authors: Tokoro Tatsuki , Kayanne Hajime , Watanabe Atsushi , Nadaoka Kazuo , Tamura Hitoshi , Nozaki Ken , Kato Ken , Negishi Akira
Published: November 2008

We measured the gas‐transfer velocity (k) and analyzed factors regulating k at coral reefs and an estuary at Ishigaki Island, Japan, using the floating‐chamber method and the measured energy‐dissipation rate (ɛ) to represent turbulence in a small‐eddy model. We confirmed the validity of the floating‐chamber method quantitatively for the first time by the comparing ɛ values inside and outside the chamber device. We also compared k to ɛ and empirical parameters such as wind and current speeds. Measured k had a low correlation with the empirical parameters and a high correlation with ɛ, as indicated by the small‐eddy model. The high ɛ values may have been regulated by topographic conditions, e.g., corals or seagrasses that generate wakes, and complex coastlines or large‐scale (on the order of kilometers) topographic factors that generate horizontal current shear. Our measurements indicate that coastal k is regulated by ɛ and cannot be accurately determined using wind or current speeds. Topographic conditions in coastal regions are important factors that regulate ɛ; thus, a quantitative analysis of the effects of these conditions is necessary to accurately determine coastal air–water gas flux.
Modeling the diurnal variability of sea surface temperatures
Authors: Pimentel S. , Haines K. , Nichols N. K.
Published: November 2008

In this study a one‐dimensional mixed layer ocean model is customized for the purpose of estimating the diurnal signal of temperature in the near‐surface ocean layer, generically referred to as sea surface temperature (SST). The model is initially run with data from three mooring locations. It is then demonstrated how operational forecast data sets can be utilized to estimate diurnal signals over a wide area. Daily diurnal variability maps are produced for a weeklong period over the Atlantic Ocean. These maps highlight the transient nature of diurnal SST signals with day to day changes in their magnitude and spatial distribution. The resulting diurnal variability maps are evaluated using a combination of infrared and microwave satellite‐derived SST observations taken over the day. These matchups result in a mean error of 0.09°C and a standard deviation of 0.54°C. Advantages of modeling the diurnal cycle as opposed to using a persistence assumption are discussed.
Global budget of ethane and regional constraints on U.S. sources
Authors: Xiao Yaping , Logan Jennifer A. , Jacob Daniel J. , Hudman Rynda C. , Yantosca Robert , Blake Donald R.
Published: November 2008

We use a 3‐D chemical transport model (the GEOS‐Chem CTM) to evaluate a global emission inventory for ethane (C2H6), with a best estimate for the global source of 13 Tg yr−1, 8.0 Tg yr−1 from fossil fuel production, 2.6 Tg yr−1 from biofuel, and 2.4 Tg yr−1 from biomass burning. About 80% of the source is emitted in the Northern Hemisphere. The model generally provides a reasonable and unbiased simulation of surface air observations, column measurements, and aircraft profiles worldwide, including patterns of geographical and seasonal variability. The main bias is a 20%–30% overestimate at European surface sites. Propagation of the C2H6 seasonal signal from northern midlatitudes to the equatorial western Pacific and the southern tropics demonstrates the dominance of northern midlatitudes as a source of C2H6 worldwide. Interhemispheric transport provides the largest C2H6 source to the Southern Hemisphere (1.7 Tg yr−1), and southern biomass burning provides the other major source (1.0 Tg yr−1). The C2H6 emission inventory for the United States from the Environmental Protection Agency (0.6 Tg yr−1) is considerably lower than our estimate constrained by extensive aircraft observations in the continental boundary layer (2.4 Tg yr−1). This appears to reflect a factor 7 underestimate in the fossil fuel source over the south‐central United States. Our estimate of C2H6 emissions, together with observed ratios of CH4:C2H6, suggests that CH4 emissions from energy production in the U.S. may be underestimated by as much as 50%–100%.
Interannual variations of river water storage from a multiple satellite approach: A case study for the Rio Negro River basin
Authors: Frappart Frédéric , Papa Fabrice , Famiglietti James S. , Prigent Catherine , Rossow William B. , Seyler Frédérique
Published: November 2008

Spatiotemporal variations of water volume over inundated areas located in a large river basin have been determined using combined observations from a multisatellite inundation data set, the TOPEX/POSEIDON (T/P) altimetry satellite, and in situ hydrographic stations for the water levels over rivers and floodplains. We computed maps of monthly surface water volume change over the period of common availability of T/P and the multisatellite data (1993–2000). The basin of the Negro River, the largest tributary in terms of discharge to the Amazon River, was selected as a test site. A strong seasonal signal is observed with minima in October and maxima in June. A strong interannual component is also present, particularly important during ENSO years. The surface water change was estimated to be 167 ± 39 km3 between October 1995 (low water) and June 1996 (high water). This result is consistent with previous estimates obtained for the 1995–1996 hydrological cycle over the same area using the JERS mosaic data. The surface water volume change is then compared to the total water volume change inferred from the GRACE satellite for an average annual cycle. The difference between the surface storage change and the total storage change derived from GRACE was computed to estimate the contribution of the soil moisture and groundwater to the total storage change. Our study supports the hypothesis that total water storage is almost equally partitioned between surface water and the combination of soil moisture and groundwater for the Negro River basin. The water volume changes are also evaluated using in situ discharge measurements and the GPCP precipitation product (correlation of 0.61). The results show the high potential for the new technique to provide valuable information to improve our understanding of large river basin hydrologic processes.
Dynamical downscaling: Assessment of model system dependent retained and added variability for two different regional climate models
Authors: Rockel Burkhardt , Castro Christopher L. , Pielke Roger A. , von Storch Hans , Leoncini Giovanni
Published: November 2008

In this paper, we compare the retained and added variability obtained using the regional climate model CLM (Climate version of the Local Model of the German Weather Service) to an earlier study using the RAMS (Regional Atmospheric Modeling System) model. Both models yield similar results for their standard configurations with a commonly used nudging technique applied to the driving model fields. Significantly both models do not adequately retain the large‐scale variability in total kinetic energy with results poorer on a larger grid domain. Additional experiments with interior nudging, however, permit the retention of large‐scale values for both models. The spectral nudging technique permits more added variability at smaller scales than a four‐dimensional internal grid nudging on large domains. We also confirmed that dynamic downscaling does not retain (or increase) simulation skill of the large‐scale fields over and beyond that which exists in the larger‐scale model or reanalysis. Our conclusions should be relevant to all applications of dynamic downscaling for regional climate simulations.
Modeling of thermal runoff response from an asphalt‐paved plot in the framework of the mass response functions
Authors: Kim Kyunghyun , Thompson Anita M. , Botter Gianluca
Published: November 2008

During hot summer months, impervious surfaces within urban areas may store significant amounts of thermal energy, which may be rapidly transferred to stream waters during runoff events. Modeling of heat release from impervious areas to stream waters thus represents a first, necessary step to quantify possible negative impacts of increased stream water temperature on nearby aquatic ecosystems. In this paper, a stochastic Lagrangian approach is developed to simulate heat transfer from an impermeable surface to runoff. The approach is based on the framework of the mass response functions (MRFs), which was originally developed for modeling nonpoint source pollutant transport in watersheds. The MRF approach has been adapted to describe heat transfer from impervious surfaces to runoff by coupling a heat balance at the asphalt/water interface and a one‐dimensional heat diffusion equation within the asphalt. The model incorporates a simplified, physically based description of all the heat fluxes possibly affecting the ensuing thermal response of impervious areas (e.g., solar radiation and evaporation). The model was applied to an asphalt‐paved plot of 90 m2 where it was able to accurately reproduce the temperature variation of the asphalt surface and runoff during an artificially produced rainfall event. Model prediction uncertainty introduced by the estimate of some key parameters involved in the heat balance is analyzed by sensitivity analysis and by checking a posteriori the consistency of the estimated heat fluxes through an overall heat conservation equation. The effect of the heat diffusivity on the surface temperature response to rainfall input was also examined, showing that the effect could be significant depending on vertical temperature distributions of the plot.
Iodine speciation in marine aerosols along a 30,000 km round‐trip cruise path from Shanghai, China to Prydz Bay, Antarctica
Authors: Lai S. C. , Hoffmann T. , Xie Z. Q.
Published: November 2008

Total suspended particle (TSP) samples were collected onboard a round‐trip cruise from Shanghai, China to Prydz Bay, Antarctica from November 2005 to March 2006. Water soluble iodine species were measured using ion chromatography coupled to Inductively Coupled Plasma‐Mass Spectrometry (IC‐ICP‐MS). The results reveal that soluble organic iodine (SOI) is the most abundant fraction, accounting for approximately 70 % of total soluble iodine (TSI) on average. One unidentified organic iodine (UOI) signal was present in almost all of the samples and was responsible for up to 38.3% of TSI. The abundance of inorganic iodine species, iodate and iodide, was less than 30% of TSI. Iodide was significantly correlated with SOI suggesting a link between iodide formation and SOI decomposition. TSI levels varied considerably over the length of the voyage. In the coastal Antarctic enhanced level of TSI were found to be correlated with the air mass transport from the ice front sector.
Human influence on Arctic sea ice detectable from early 1990s onwards
Authors: Min Seung‐Ki , Zhang Xuebin , Zwiers Francis W. , Agnew Tom
Published: November 2008

Human influence has previously been identified in the observed loss of Arctic sea ice, but this hypothesis has not yet been tested with a formal optimal detection approach. By comparing observed and multi‐model simulated changes in Arctic sea ice extent during 1953–2006 using an optimal fingerprinting method, we find that the anthropogenic signal first emerged in the early 1990s, indicating that human influence could have been detected even prior to the recent dramatic sea ice decline. The anthropogenic signal is also detectable for individual months from May to December, suggesting that human influence, strongest in late summer, now also extends into colder seasons.
Solar activity variations of nighttime ionospheric peak electron density
Authors: Chen Yiding , Liu Libo , Le Huijun
Published: November 2008

Monthly median NmF2 (maximum electron density of the F2‐layer) data at Okinawa, Yamagawa, Kokubunji, and Wakkanai have been collected to investigate the solar activity dependence of the nighttime ionosphere. The result shows that there are seasonal and latitudinal differences of the solar activity variation of nighttime NmF2. The main seasonal effects are as follows: nighttime NmF2 increases with F107 linearly in equinoctial months (March and September), and it tends to saturate with F107 increasing in summer solstice month (June). What is peculiar is that there is an amplification trend of nighttime NmF2 with F107 in winter solstice month (December). The latitudinal difference is mainly displayed by the evolvement course of the variation trend between NmF2 and F107. Using hmF2 (peak height of the F2‐layer) data and the NRLMSISE00 model, we estimated the recombination loss around the F2‐peak at different solar activity levels. We found that the solar activity variation of the recombination processes around the F2‐peak also shows seasonal dependence, which can explain the variation trends of nighttime NmF2 with F107 qualitatively, and field‐aligned plasma influx plays an important role in the equatorial ionization anomaly (EIA) crest region. During the first several hours following sunset in December, there are faster recombination processes around the F2‐peak at medium solar activity level in mid‐latitude regions. This feature is suggested to be responsible for inducing the amplification trend in winter. In virtue of the calculation of neutral parameters at 300‐km altitude and hmF2 data, the variation trend of the recombination processes around the F2‐peak with F107 can be explained. It shows that both the solar activity variations of hmF2 and neutral parameters (neutral temperature, density, and vibrational excited N2) are important for the variation trend of nighttime NmF2 with F107. Furthermore, the obvious uplift of hmF2 at low solar activity level following sunset in December is important for the amplification trend.
Prospects for future enhanced solar energetic particle events and the effects of weaker heliospheric magnetic fields
Authors: Kahler S. W.
Published: November 2008

Recent work based on nitrate abundances in ice cores has shown that large solar energetic (E > 30 MeV) particle (LSEP) events during the spacecraft era of observations (1960–present) are diminished in comparison with those of some preceding eras and that LSEP events have occurred during low cycles of solar activity. McCracken et al. (2004) have reported an inverse correlation between those LSEP events and the magnitude of the associated reconstructed heliospheric magnetic field (HMF). A physical explanation by McCracken (2007a, 2007b) is that the lower HMF and coronal magnetic field B imply that fast coronal mass ejections (CMEs) produce shocks with enhanced Alfvenic Mach numbers MA and higher compression ratios r, leading to more numerous and energetic LSEP events. From a possible decline of the HMF over the next several solar cycles, he has warned of a return to the environment of the more intense LSEP events preceding the current spacecraft era. We formulate and discuss seven questions using recent published observational, modeling, and theoretical work to assess the assumptions and the validity of his explanation and watch. We conclude that a return to more intense LSEP events is certainly possible, but (1) the inferred large increase in HMF characterizing the spacecraft era is in doubt; (2) there is no good evidence to connect more intense LSEP events with weaker HMFs; (3) a new Gleissberg minimum, with lower HMF, may not be imminent; (4) a lower active region B should result in slower CME speeds V less likely to produce shocks; (5) the average CME V increases significantly with SSN; (6) a lower coronal B likely results in a lower VA as the explanation requires; and (7) the lower coronal B leads to weaker, not more intense, LSEP events because of decreased spectral cutoff energies.
Evolution of Kelvin‐Helmholtz activity on the dusk flank magnetopause
Authors: Foullon C. , Farrugia C. J. , Fazakerley A. N. , Owen C. J. , Gratton F. T. , Torbert R. B.
Published: November 2008

Our purpose is to characterize the evolution of the magnetopause Kelvin‐Helmholtz (KH) wave activity with changes in thickness of the adjacent boundary layer, geomagnetic latitude and interplanetary magnetic field (IMF) orientation. As the IMF turns northward, wave activity may be generated at the dayside before propagating down the tail, where the boundary layer is expected to support longer wavelengths. We use two‐point observations on the dusk magnetopause at low latitudes, from Geotail on the dayside and Cluster tailward of the dusk terminator. We quantify the wavelength, power, wavefront steepness and propagation direction at Cluster. An estimate of the thickness of the low‐latitude boundary layer (LLBL) is obtained by correlating normal distances to the magnetopause, derived from two empirical solar‐wind‐driven models, with a systematic relationship (the “transition parameter”) found between the electron number density and temperature; the correlation factor is used to infer the temporal evolution of the thickness of the locally sampled layer. We find that wavelengths are controlled by the IMF clock angle, as expected when generated by the KH mechanism at the dayside, although amplitudes, wavefront steepness and propagation directions are more closely correlated with the layer thickness. A survey of parameter space provides evidence of the contribution of the KH mechanism to the widening of the electron LLBL.