bluuebunny/crossref_metadata_2025 huggingface dataset:
Generating Trails Automatically, to Aid Navigation When You Revisit an Environment
Authors: Ruddle Roy A.
Published: October 2008

A new method for generating trails from a person's movement through a virtual environment (VE) is described. The method is entirely automatic (no user input is needed), and uses string-matching to identify similar sequences of movement and derive the person's primary trail. The method was evaluated in a virtual building, and generated trails that substantially reduced the distance participants traveled when they searched for target objects in the building 5–8 weeks after a set of familiarization sessions. Only a modest amount of data (typically five traversals of the building) was required to generate trails that were both effective and stable, and the method was not affected by the order in which objects were visited. The trail generation method models an environment as a graph and, therefore, may be applied to aiding navigation in the real world and information spaces, as well as VEs.
The Comparisons of Heart Rate Variability and Perceived Exertion During Simulated Cycling with Various Viewing Devices
Authors: Huang Shih-Fong , Tsai Po-Yi , Sung Wen-Hsu , Lin Chih-Yung , Chuang Tien-Yow
Published: October 2008

Sympathovagal modulation during immersion in a virtual environment is an important influence on human performance of a task. The aim of this study is to investigate sympathovagal modulation using heart rate variability and perceived exertion during exercise in a virtual reality (VR) environment.

Sixteen young healthy volunteers were tested while using a stationary bicycle and maintained at an anaerobic threshold intensity for exercise sessions of approximately 10 min duration. Four randomized viewing alternatives were provided including desktop monitor, projector, head mounted device (HMD), and no simulation display. The “no simulation display” served as the control group. A quick ramp exercise test was conducted and maintained at an anaerobic threshold intensity for each session to evaluate power spectral density and rating of perceived exertion (RPE). The sampled heart rate data were rearranged by cubic spline interpolation into power spectrums spanning the ultra-low frequency (ULF) to high frequency (HF) range.

A significant difference was found between the no-display and projector groups for total power (TP) and very low frequency (VLF) components. In particular, there was a significant difference when comparing HMD and no-display exercise RPE curves within 6 min of cycling and at the termination of the exercise. A significant difference was also achieved in projector vs. control group comparison at the termination of the exercise.

Our results indicate that the use of HMD and the projected VR during cycling can reduce the TP and VLF power spectral density through a proposed decrease in the renin-angiotensin system, with the implication that this humoral effect may enable anaerobic exercise for longer durations through a reduction in sympathetic tone and subsequent increased blood flow to the muscles.
African Women Scientists and the Politics of Location: The Case of Four Sierra Leonean Women Scientists
Authors: Beoku-Betts Josephine
Published: October 2008

This paper examines the attempts of four Sierra Leonean women scientists to restructure their lives and professional careers in the wake of changing political and economic conditions in their nation state. I show how their emotional affinities to their country of origin are still strong and influence their scientific practices and commitments to their country of origin. I argue that as transnational migrants, their experiences are shaped by the intersection of inequalities of gender, race, and nation and changing economic, social, and political processes in their countries of origin and destination. These conditions may constrain but also enable them to compete, challenge, and negotiate new spheres of lived experience. The analysis is framed around discourses on the brain drain, the concept of transnationalism, and feminist research on gender and migration. The study is based on semi-structured interviews, using narratives to illustrate the lived experiences and perspectives of the study participants. Issues addressed include (1) factors leading to migration, (2) experiences of race, gender, and nationality, (3) ways of practicing science, (4) navigation of emotional commitments to country of origin.
African Women in the New Diaspora: Transnationalism and the (Re) Creation of Home
Authors: Osirim Mary Johnson
Published: October 2008

During the past 25 years, African immigrants have been arriving in the US in increasing numbers due to the push factors of globalization, wars, civil unrest and natural disasters. Drawing on in-depth interviews with African women as immigrants in Greater Boston and Philadelphia, this paper will explore how the intersections of gender, race and class affect their contributions to civil society and business development. This work illustrates how transnational ties, specifically in the form of a new pan-Africanism, lead African immigrants to make significant contributions to community revitalization, particularly in historically African American communities. Although African women immigrants are clearly transnationals, in their civic lives, they differ from their male counterparts in their especially strong commitment to improving the lives of their families and communities on this side of the Atlantic.
Collective Activism: The Domestic Violence Bill becoming Law in Ghana
Authors: Adomako Ampofo Akosua
Published: October 2008

This article reflects on contemporary struggles for citizenship rights through an examination of civil society's advocacy for the passage of domestic violence legislation in Ghana. The National Coalition on Domestic Violence Legislation, established in 2003 specifically to push for the passage of the legislation, at various times worked closely with, and at other times independently of, or even in conflict with, the state. These processes and engagements point to the vibrancy of civil society and suggest the need for new analyses of social movements, political power and democracy that are rooted in Africa's contemporary realities.
Outras Vozes: Women's Writings in Lusophone Africa
Authors: Fêo Rodrigues Isabel , Sheldon Kathleen
Published: October 2008

In this paper we examine the development of women's studies in the Portuguese-speaking African countries of Angola, Mozambique, Cape Verde, Guinea-Bissau, and São Tomé e Príncipe. There are notable variations between these nations, as Mozambique has had a strong Gender Studies unit at Universidade Eduardo Mondlane that has supported a range of research projects and publications on women and the law, women's history, and related topics. The other countries have also produced important studies, often focusing on women's experiences in the anti-colonial liberation struggle, and on more recent issues such as women's legal position. The paper draws out the commonalities and differences in approaches to women's studies by providing an overview of the relevant publications over the past thirty years.
Facing Challenges and Pioneering Feminist and Gender Studies: Women in Post-colonial and Today's Maghrib
Authors: Sadiqi Fatima
Published: October 2008

Starting from the premise that the nature and impact of women's agency can be understood only within specific historical and socio-cultural environments (Sadiqi, 2003), the major aim of this paper is to highlight the multi-faceted agency of women in post-colonial and today's Maghrib. The Maghrib is a North African region that includes Morocco, Algeria, Tunisia, Libya and Mauritania, but I chose to focus on the first three countries given their common historical and socio-cultural background. Not only have women in this region faced challenges, but they have also pioneered feminist and gender studies and raised new issues for these disciplines in the global South as well as the North. Four major interrelated domains where these achievements are significant are considered: women's reproductive rights, women's movements, women's legal rights, and women's knowledge production. Issues related to these domains are analyzed from a broad comparative perspective which involves an overall political and economic contextualization. The paper reveals the positive role that Maghribi women have been playing in the overall development of their countries and the main outcomes show that the future of the Maghrib is significantly linked to the fate of these gains.
"Bottom Power:" Theorizing Feminism and the Women's Movement in Sierra Leone (1981-2007)
Authors: Day Lynda
Published: October 2008

This paper examines the theory and praxis of women's political activism in contemporary Sierra Leone. In spite of the steady upswing in the number of women elected or appointed to positions of political authority, the growing influence of women in politics runs into male resistance which privately and derisively refers to women's newly held positions of authority and public clout as "bottom power." This essay proposes that male pushback results from a neo-liberal women's movement that frames women's economic marginality and lack of access to political power as the result of patriarchy and male privilege, rather than using an African feminist framework which recognizes women's lack of resources as primarily the result of the appropriation of the country's wealth by multinational corporations, lending agencies and members of the elite. If viewed from this perspective, the women's movement would be framed as a socially transformative struggle for all sectors of society, and not as a contest between men and women for power.
Analysing Males in Africa: Certain Useful Elements in Considering Ruling Masculinities
Authors: Ratele Kopano
Published: October 2008

This article examines the questions why and how African males have been analysed, informed by the view that across several societies in Africa undeclared yet public gender wars of words and deeds go on daily, and may even be intensifying. It argues that though interventions with males from feminist perspectives have gained ground over the last few decades, more radical, to the gendered African worlds and masculinities have failed to materialise because analyses of boys and men's lives have tended to be blind to the imbrications of the experience of maleness with the experience of other significant social categorisations, such as being without gainful employment. Consequently, many interventions, such as those around violence against women and girls, have failed to grasp some of the critical factors underlying males' reluctance to support feminist action. The article therefore routes its examination of males through a number of categories of social-psychological experience and practice, namely (a) occupational and income attainment and, (b) age, categories theoretically tied to maleness and to practices geared towards the attainment of ruling masculinity. The article reveals the manner in which the psychosocial and the political inter-penetrate each other in the lives of African males. In conclusion, the recognition of the heterogeneous nature of masculinities also, ironically, affords mounting new feminist interventions into changing traditional ruling ideas of being a man or boy.
The Storm-Gods of the Ancient Near East: Summary, Synthesis, Recent Studies: Part II
Authors: Schwemer Daniel
Published: October 2008

In many regions of the ancient Near East, not least in Upper Mesopotamia, Syria and Anatolia where agriculture relied mainly on rainfall, storm-gods ranked among the most prominent gods in the local panthea or were even regarded as divine kings, ruling over the gods and bestowing kingship on the human ruler. While the Babylonian and Assyrian storm-god never held the highest position among the gods, he too belongs to the group of 'great gods' through most periods of Mesopotamian history. Given the many cultural contacts and the longevity of traditions in the ancient Near East only a study that takes into account all relevant periods, regions and text-groups can further our understanding of the different ancient Near Eastern storm-gods. The study Wettergottgestalten Mesopotamiens und Nordsyriens by the present author (2001) tried to tackle the problems involved, basing itself primarily on the textual record and excluding the genuinely Anatolian storm-gods from the study. Given the lack of handbooks, concordances and thesauri in our field, the book is necessarily heavily burdened with materials collected for the first time. Despite comprehensive indices, the long lists and footnotes as well as the lack of an overall synthesis make the study not easily accessible, especially outside the German-speaking community. In 2003 Alberto Green published a comprehensive monograph entitled The Storm-God in the Ancient Near East whose aims are more ambitious than those of Wettergottgestalten: All regions of the ancient Near East—including a chapter on Yahwe as a storm-god—are taken into account, and both textual and iconographic sources are given equal space. Unfortunately this book, which was apparently finished and submitted to the publisher before Wettergottgestalten came to its author's attention, suffers from some serious flaws with regard to methodology, philology and the interpretation of texts and images. In presenting the following succinct overview I take the opportunity to make up for the missing synthesis in Wettergottgestalten and to provide some additions and corrections where necessary. It is hoped that this synthesis can also serve as a response to the history of ancient Near Eastern storm-gods as outlined by A. Green.
Early Mesopotamian Astral Science and Divination in the Myth of Inana And Šukaletuda
Authors: Cooley Jeffrey
Published: October 2008

The Sumerian tale of Inana and Shukaletuda recounts how the goddess Inana is raped by a homely gardener upon whom she seeks and ultimately finds revenge. Though this general plot has long been understood, certain elements of the story have remained largely unexplored. Previous scholarship has often suggested that within Inana and Shukaletuda, the goddess Inana is often described in her astral manifestation (e.g. S. Kramer 1961, 117; K. Volk 1995, 177-179 and 182-183; B. Alster 1999, 687; J. Cooper 2001, 142-144). Nevertheless, to date there has been no systematic treatment of this assumption and this study seeks to fill this gap. It is my thesis that certain events of the story (i.e. Inana's movements) can be related to a series of observable celestial phenomena, specifically the synodic activity of the planet Venus. This also explains the heretofore enigmatic climax of the story, in which Inana crosses the entire sky in order to finally locate her attacker, as a celestial miracle required by the planet Venus' peculiar celestial limitations. Furthermore, since in ancient Iraq the observation of astronomical phenomena was often done for the purpose of celestial divination, I suggest that certain events within the story may be illuminated if situated within that undertaking.
Arthur in the Alhambra? Narrative and Nasrid Courtly Self-Fashioning in The Hall Of Justice Ceiling Paintings
Authors: Robinson Cynthia
Published: October 2008

This essay reconsiders the "Arthurian" identification of a number of the scenes that compose the ornamental program of the painted ceilings above the northern and southern alcobas of the Alhambra's Hall of Justice, proposing a reading that privileges Castilian versions of well-known courtly romances over French ones. The scenes are read as representations of the stories of Flores y Blancaflor, as well as Tristán de Leonís. Both tales, however, have been further altered and adapted in order to privilege the ideological concerns of the Nasrid court, both as an Islamic political entity with an agenda of jihād and—in a fashion that could easily be viewed as contradictory—as a participant in medieval Iberia's much-discussed frontier culture, which involved a "marriage of convenience" with Castilian allies.
Painting Politics in the Alhambra
Authors: Echevarria Ana
Published: October 2008

This article endeavours to shed new light on the meaning of the ten Muslim male figures depicted in the central vault of the Hall of Justice in the Alhambra. First, new chronologies are attempted for the hall and the painting according to historical evidence contained in chronicles and literary sources. The study of the architectural frame of the paintings, interpreted as a madrasa-zawiya, suggests a relationship between the painting and the books intended to be kept below it. Therefore, an analysis of the emir's literary entourage is basic for the interpretation of the ceiling. Finally, the question of armouries and shields to be found in the vault is taken into account to demonstrate that some of this work may have been re-elaborated by Christians after taking possession of the palaces. The shields and the concept of the Order of the Band are too far from Islamic tradition as to belong to the original design of this painting, as critical examination of the Order's internal code shows.
Hunting in the Borderlands (for Oleg Grabar)
Authors: Dodds Jerrilynn
Published: October 2008

In an article now three decades old, I suggested that the Paintings of the Hall of Justice of the Alhambra used Arthurian iconography as part of a fashionable admiration for Gothic style and the language of chivalry in the Nasrid court, one which was subverted by the polarizing imagery of a Muslim and a Christian fighting. However, I failed at the time to take into full account the extraordinary hunting cycle of the Hall of Justice paintings, discrete groups of hunters and their prey that were interspersed with surprising episodes from romance narratives. These images picture Christians and Muslims as polarized and opposed. In fact, I believe it is in these very images of domination and apparent differentiation that a deep interconnectedness can be found. This study uses the painting cycle from the Hall of Justice of the Alhambra as a means of exploring, not just common styles and motives, but artistic meanings that were held in common between courts. In particular, hunting as an attribute of lordship and sovereignty is key here, in a world in which relationships between Nasrids and Castilians were still largely feudal and many meanings shared, allying the parties we once supposed to be 'other.' There, hunting as iconographic shorthand for ownership of the land appears in surprising and deflected ways. Through a discussion of the Palace of Pedro I at the Alcázar of Seville, contemporary literary evocations of the courtly tradition and of the practice and meaning of the hunt, as these were known on the Iberian peninsula, and the exploration of narrative and emblematic languages of form, I hope to reveal an imagery which suggests domination but masks a complicit, symbiotic interaction. Hunting imagery becomes the means by which both Nasrids and Castilians act out a ceremonial opposition to another with whom they are socially and culturally intertwined.
The Forested Frontier: Commentary in the Margins of the Alhambra Ceiling Paintings
Authors: Borland Jennifer
Published: October 2008

This paper argues that important notions are imbedded within the seemingly marginal backgrounds of the ceiling paintings in the Alhambra's so-called "Hall of Justice." The shared European and Islamic iconographies evident in the paintings' settings, and the creatures that appear therein, reiterate the complexities inherent in the multicultural context of the Alhambra. Through the processes of intercultural appropriation, interpretation and adaptation, these plants and animals seem to transcend their many individual cultural resonances, generating new meanings based on the particular convergences fostered by the Nasrid court. The paintings' backgrounds, on the edges of the central courtly dramas, literally visualize the cultural "outsideness" of forests, which, as spaces for seclusion and distance from the distractions of daily life, also may have served as a metaphor for the Nasrid court in Granada. At the same time, these newly reconstituted meanings often seem to speak directly to the nature of the relationships between the figures depicted in the main scenes. Displaying integrated associations deliberately culled from the visual repertoires of several cultures, these paintings appear to offer something of an oasis, where intellectuals of various religious and cultural affiliations would have been encouraged to engage in contemplation and dialogue with one another.
Walk on the Wild Side
Authors: Pinet Simone
Published: October 2008

The figure of the wild man is one that crosses artistic disciplines and genres in the cultures of medieval Iberia. In this article I show how the wild man operates within a variety of meanings in diverse literary contexts that, working simultaneously at different narrative levels, cross over from literature into daily life and spectacles, from legal to political discourses. The figure's continued presence from the medieval period into the sixteenth and seventeenth centuries suggests its use as a commonplace, as a motif with a number of fixed meanings that are put to work through context, providing the possibility of different, perhaps even contradictory readings. As commonplace, then, the wild man is presented as a case study for the reconsideration of other elements in the paintings of the Hall of Justice of the Alhambra, often interpreted to have a specific or fixed meaning, and thus programmed within a particular narrative. Seen in its entirety as a repository of commonplaces, I interpret the complex of the lateral paintings of the Hall of Justice in relation to the central one, in which a set of ten kings in Nasrid dress are depicted as conversing, as pretexts for narration that can be of a literary or juridical nature. I then go on to provide a possible itinerary of reading for the wild man scene not only in its immediate context, but as part of he overall visual project in a political key that illustrates the productive makeup of the paintings as pedagogical and ideological enterprise.
Love's Subjects: The Alhambra Ceilings, Sentimental Fiction and Allegory
Authors: Martín Oscar
Published: October 2008

This article analyzes the way in which allegorical and narrative motifs work in the fourteenth-century Alhambra ceilings and in fifteenth-century Castilian sentimental fiction. It argues that while the Alhambra ceilings, based on courtly allegory, convey a dignified statement concerning the potential of allegory to structure a political lesson while at the same time registering cultural assimilation and social crisis, allegory in sentimental fiction is problematized from the outset, showing that the genre's evolution renders allegory ineffective to account for love's subjectivity as it was attached to an outmoded courtly subjectivity. In this way, the painted ceilings of the Alhambra can be interpreted as a stage in the use of allegory in courtly context in the Iberian Peninsula within a larger group of works that make use of similar codes.
Spatiotemporal Mapping of Temperature and Precipitation for the Development of a Multidecadal Climatic Dataset for Wisconsin
Authors: Serbin Shawn P. , Kucharik Christopher J.
Published: October 2008

Results from the generation of a multidecadal gridded climatic dataset for 57 yr (1950–2006) of daily and monthly precipitation (PTotal), maximum temperature (Tmax), and minimum temperature (Tmin) are presented for the important agricultural and forest products state of Wisconsin. A total of 176 climate stations were used in the final gridded dataset that was constructed at 8-km (5.0′) latitude–longitude resolution using an automated inverse distance weighting interpolation. Accuracy statistics for the interpolated data were based on a rigorous validation step using 104 first- and second-order climate observation stations withheld in the production of the gridded dataset. The mean absolute errors (MAE) for daily minimum and maximum temperatures averaged 1.51° and 1.31°C, respectively. Daily precipitation errors were also reasonable, ranging from −0.04 to 0.08 mm, on average, across all climate divisions in the state with an overall statewide MAE of 1.37 mm day−1. Correlation analysis suggested a high degree of explained variation for daily temperature (R2 ≥ 0.97) and a moderate degree for daily precipitation (R2 = 0.66), whereby the realism improved considerably for monthly precipitation accumulation totals (R2 = 0.87). Precipitation had the best interpolation accuracy during the winter months, related to large-scale, synoptic weather systems, and accuracy was at a minimum in the wetter summer months when more precipitation originates from local-to-regional-scale convective forcing. Overall the grids showed coherent spatial patterns in temperature and precipitation that were expected for this region, such as the latitudinal gradient in temperature and longitudinal gradient in precipitation across the state. The grids will prove useful for a variety of regional-scale research and ecosystem modeling studies.
Numerical Simulations of Local Circulation and Cumulus Generation over the Loess Plateau, China
Authors: Nishikawa Masanori , Hiyama Tetsuya , Tsuboki Kazuhisa , Fukushima Yoshihiro
Published: October 2008

The Loess Plateau of China consists of dissected flat tablelands with steep gullies. To evaluate the effect of topography on local circulation and cumulus generation over the Loess Plateau, numerical simulations of atmospheric boundary layer (ABL) development were conducted using a cloud-resolving nonhydrostatic model. Two types of numerical simulation were carried out under two sets of bottom boundary conditions: real terrain and flat terrain. The differences in ABL development and cumulus generation between the flat- and real-terrain conditions are described and the local circulation structures induced by ABL development are illustrated. More cumulus clouds were generated over the real terrain than over the flat terrain. In the real-terrain case, large amounts of cumulus cloud were generated on the windward slopes and on the edge of the tableland, with updrafts caused by thermal generation and a local circulation developing with horizontal and vertical scales of several kilometers. Cumulus clouds clearly developed at the top of the ABL because the water vapor is nonhomogeneously lifted by the local circulation on windward slopes and on edge of the tableland. Thus, the topography of the Loess Plateau plays an important role in cumulus generation.
Correlative Evolutions of ENSO and the Seasonal Cycle in the Tropical Pacific Ocean
Authors: Xiao Heng , Mechoso Carlos R.
Published: October 2008

This study examines whether shifts between the correlative evolutions of ENSO and the seasonal cycle in the tropical Pacific Ocean can produce effects that are large enough to alter the evolution of the coupled atmosphere–ocean system. The approach is based on experiments with an ocean general circulation model (OGCM) of the Pacific basin, in which the seasonal and nonseasonal (interannually varying) components of the surface forcing are prescribed with different shifts in time. The shift would make no difference in terms of ENSO variability if the system were linear. The surface fluxes of heat and momentum used to force the ocean are taken from 1) simulations in which the OGCM coupled to an atmospheric GCM produces realistic ENSO variability and 2) NCEP reanalysis data corrected by Comprehensive Ocean–Atmosphere Data Set climatology for the 20-yr period 1980–99. It is found that the response to the shifts in terms of eastern basin heat content can be 20%–40% of the maximum interannual anomaly in the first experiment, whereas it is 10%–20% in the second experiment. In addition, the response to the shift is event dependent. A response of this magnitude can potentially generate coupled atmosphere–ocean interactions that alter subsequent event evolution. Analysis of a selected event shows that the major contribution to the response is provided by the anomalous zonal advection of seasonal mean temperature in the equatorial band. Additional OGCM experiments suggest that both directly forced and delayed signals provide comparable contributions to the response. An interpretation of the results based on the “delayed oscillator” paradigm and on equatorial wave–mean flow interaction is given. It is argued that the same oceanic ENSO anomalies in different times of the oceanic seasonal cycle can result in different ENSO evolutions because of nonlinear interactions between equatorially trapped waves at work during ENSO and the seasonally varying upper-ocean currents and thermocline structure.
Consistent Scale Interaction of Gravity Waves in the Doppler Spread Parameterization
Authors: Becker Erich , McLandress Charles
Published: October 2008

The standard Doppler spread parameterization of gravity waves, which was proposed by C.-O. Hines and has been applied in a number of middle atmosphere general circulation models, is extended by the inclusion of all effects associated with vertical diffusion. Here the Wentzel–Kramers–Brillouin (WKB) approximation is employed to calculate the vertical propagation of the wave spectrum in the presence of wave damping. According to the scale interaction between quasi-stationary turbulence and the larger nonturbulent flow, all vertical diffusion applied to the resolved flow should damp the parameterized gravity waves as well. Hence, the unobliterated part of the gravity wave spectrum is subject to diffusive damping by the following processes: 1) the background diffusion derived from the model’s boundary layer vertical diffusion scheme, which may extend into the middle atmosphere, 2) molecular diffusion, and 3) the turbulent diffusion resulting from the truncation of the gravity wave spectrum by Doppler spreading, which thus feeds back on the unobliterated gravity waves. The extended Doppler spread parameterization is examined using perpetual July simulations performed with a mechanistic general circulation model. For reasonable parameter settings, the convergence of the potential temperature flux cannot be neglected in the sensible heat budget, especially in the thermosphere. Less gravity wave flux enters the model thermosphere when vertical diffusion is included, thus avoiding the need for artificial means to control the parameterized gravity waves in the upper atmosphere. The zonal wind in the tropical middle and upper atmosphere is found to be especially sensitive to gravity wave damping by diffusion.
Linear Theory Calculations for the Sea Breeze in a Background Wind: The Equatorial Case
Authors: Qian Tingting , Epifanio Craig C. , Zhang Fuqing
Published: October 2008

The equatorial coastal circulation is modeled in terms of the linear wave response to a diurnally oscillating heat source gradient in a background wind. A diurnal scaling shows that the solution depends on two parameters: a nondimensional coastal width ℒ and a nondimensional wind speed 𝒰. The solutions are interpreted by comparing to the 𝒰 = 0 theory of Rotunno.

For 𝒰 ≠ 0 the Fourier integral solution consists of three distinct wave branches. Two of these branches correspond to the prior no-wind solution of Rotunno, except with Doppler shifting and associated wave dispersion. The third branch exists only for 𝒰 ≠ 0 and is shown to be broadly similar to flow past a steady heat source or a topographic obstacle. The relative importance of this third branch is determined largely by the parameter combination 𝒰/ℒ. For sufficiently large 𝒰/ℒ the third branch becomes the dominant part of the solution.

The spatial structures of the three branches are described in terms of group velocity arguments combined with a desingularized quadrature method.
A Note on the Numerical Representation of Surface Dynamics in Quasigeostrophic Turbulence: Application to the Nonlinear Eady Model
Authors: Tulloch Ross , Smith K. Shafer
Published: October 2008

The quasigeostrophic equations consist of the advection of linearized potential vorticity coupled with advection of temperature at the bounding upper and lower surfaces. Numerical models of quasigeostrophic flow often employ greater (scaled) resolution in the horizontal than in the vertical (the two-layer model is an extreme example). In the interior, this has the effect of suppressing interactions between layers at horizontal scales that are small compared to Nδz/f (where δz is the vertical resolution, N the buoyancy frequency, and f the Coriolis parameter). The nature of the turbulent cascade in the interior is, however, not fundamentally altered because the downscale cascade of potential enstrophy in quasigeostrophic turbulence and the downscale cascade of enstrophy in two-dimensional turbulence (occurring layerwise) both yield energy spectra with slopes of −3. It is shown here that a similar restriction on the vertical resolution applies to the representation of horizontal motions at the surfaces, but the penalty for underresolving in the vertical is complete suppression of the surface temperature cascade at small scales and a corresponding artificial steepening of the surface energy spectrum. This effect is demonstrated in the nonlinear Eady model, using a finite-difference representation in comparison with a model that explicitly advects temperature at the upper and lower surfaces. Theoretical predictions for the spectrum of turbulence in the nonlinear Eady model are reviewed and compared to the simulated flows, showing that the latter model yields an accurate representation of the cascade dynamics. To accurately represent dynamics at horizontal wavenumber K in the vertically finite-differenced model, it is found that the vertical grid spacing must satisfy δz ≲ 0.3f/(NK); at wavenumbers K > 0.3f/(Nδz), the spectrum of temperature variance rolls off rapidly.
Nonlinear Saturation of Vertically Propagating Rossby Waves
Authors: Giannitsis Constantine , Lindzen Richard S.
Published: October 2008

The interaction between vertical Rossby wave propagation and wave breaking is studied in the idealized context of a beta-plane channel model. Considering the problem of propagation through a uniform zonal flow in an exponentially stratified fluid, where linear theory predicts exponential wave growth with height, the question is how wave growth is limited in the nonlinear flow. Using a numerical model, the authors examine the behavior of the flow as the bottom forcing increases through values bound to lead to a breakdown of the linear solution within the computational domain. Focusing on the equilibrium flow obtained for each value of the bottom forcing, an attempt is made to identify the mechanisms involved in limiting wave growth and examine in particular the importance of wave–wave interactions. The authors also examine the case in which forcing is continuously increasing with time so as to enhance effects peculiar to transiency; it does not significantly alter the main results.

Wave–mean flow interactions are found to dominate the dynamics even for strong bottom forcing values. Ultimately, it is the modification of the mean flow that is found to limit the vertical penetration of the forced wave, through either increased wave absorption or downward reflection. Linear propagation theory is found to capture the wave structure surprisingly well, even when the total flow is highly deformed. Overall, the numerical results seem to suggest that wave–wave interactions do not have a strong direct effect on the propagating disturbance. Wave–mean flow interactions limit wave growth sufficiently that a strong additional nonlinear enstrophy sink, through downscale cascade, is not necessary. Quantitatively, however, wave–wave interactions, primarily among the lowest wavenumbers, prove important so as to sufficiently accurately determine the basic state and its influence on wave propagation.
The Roles of CO2 and Orbital Forcing in Driving Southern Hemispheric Temperature Variations during the Last 21 000 Yr*
Authors: Timmermann Axel , Timm Oliver , Stott Lowell , Menviel Laurie
Published: October 2008

Transient climate model simulations covering the last 21 000 yr reveal that orbitally driven insolation changes in the Southern Hemisphere, combined with a rise in atmospheric pCO2, were sufficient to jump-start the deglacial warming around Antarctica without direct Northern Hemispheric triggers. Analyses of sensitivity experiments forced with only one external forcing component (greenhouse gases, ice-sheet forcing, or orbital forcing) demonstrate that austral spring insolation changes triggered an early retreat of Southern Ocean sea ice starting around 19–18 ka BP. The associated sea ice–albedo feedback and the subsequent increase of atmospheric CO2 concentrations helped to further accelerate the deglacial warming in the Southern Hemisphere. Implications for the interpretation of Southern Hemispheric paleoproxy records are discussed.
Stratosphere–Troposphere Coupling in a Relatively Simple AGCM: The Importance of Stratospheric Variability
Authors: Gerber Edwin P. , Polvani Lorenzo M.
Published: October 2008

The impact of stratospheric variability on the dynamical coupling between the stratosphere and the troposphere is explored in a relatively simple atmospheric general circulation model. Variability of the model’s stratospheric polar vortex, or polar night jet, is induced by topographically forced stationary waves. A robust relationship is found between the strength of the stratospheric polar vortex and the latitude of the tropospheric jet, confirming and extending earlier results in the absence of stationary waves. In both the climatological mean and on intraseasonal time scales, a weaker vortex is associated with an equatorward shift in the tropospheric jet and vice versa.

It is found that the mean structure and variability of the vortex in the model is very sensitive to the amplitude of the topography and that Northern Hemisphere–like variability, with a realistic frequency of stratospheric sudden warming events, occurs only for a relatively narrow range of topographic heights. When the model captures sudden warming events with fidelity, however, the exchange of information both upward and downward between the troposphere and stratosphere closely resembles that in observations. The influence of stratospheric variability on variability in the troposphere is demonstrated by comparing integrations with and without an active stratosphere. A realistic, time-dependent stratospheric circulation increases the persistence of the tropospheric annular modes, and the dynamical coupling is most apparent prior to and following stratospheric sudden warming events.
Retrieval of an Available Water-Based Soil Moisture Proxy from Thermal Infrared Remote Sensing. Part I: Methodology and Validation
Authors: Hain Christopher R. , Mecikalski John R. , Anderson Martha C.
Published: October 2008

A retrieval of available water fraction ( fAW) is proposed using surface flux estimates from satellite-based thermal infrared (TIR) imagery and the Atmosphere–Land Exchange Inversion (ALEXI) model. Available water serves as a proxy for soil moisture conditions, where fAW can be converted to volumetric soil moisture through two soil texture dependents parameters—field capacity and permanent wilting point. The ability of ALEXI to provide valuable information about the partitioning of the surface energy budget, which can be largely dictated by soil moisture conditions, accommodates the retrieval of an average fAW over the surface to the rooting depth of the active vegetation. For this method, the fraction of actual to potential evapotranspiration ( fPET) is computed from an ALEXI estimate of latent heat flux and potential evapotranspiration (PET). The ALEXI-estimated fPET can be related to fAW in the soil profile. Four unique fPET to fAW relationships are proposed and validated against Oklahoma Mesonet soil moisture observations within a series of composite periods during the warm seasons of 2002–04. Using the validation results, the most representative of the four relationships is chosen and shown to produce reasonable (mean absolute errors values less than 20%) fAW estimates when compared to Oklahoma Mesonet observations. Quantitative comparisons between ALEXI and modeled fAW estimates from the Eta Data Assimilation System (EDAS) are also performed to assess the possible advantages of using ALEXI soil moisture estimates within numerical weather predication (NWP) simulations. This TIR retrieval technique is advantageous over microwave techniques because of the ability to indirectly sense fAW—and hence soil moisture conditions—extending into the root-zone layer. Retrievals are also possible over dense vegetation cover and are available on spatial resolutions on the order of the native TIR imagery. A notable disadvantage is the inability to retrieve fAW conditions through cloud cover.
Northwest Territories and Nunavut Snow Characteristics from a Subarctic Traverse: Implications for Passive Microwave Remote Sensing
Authors: Derksen Chris , Silis Arvids , Sturm Matthew , Holmgren Jon , Liston Glen E. , Huntington Henry , Solie Daniel
Published: October 2008

During April 2007, a coordinated series of snow measurements was made across the Northwest Territories and Nunavut, Canada, during a snowmobile traverse from Fairbanks, Alaska, to Baker Lake, Nunavut. The purpose of the measurements was to document the general nature of the snowpack across this region for the evaluation of satellite- and model-derived estimates of snow water equivalent (SWE). Although detailed, local snow measurements have been made as part of ongoing studies at tundra field sites (e.g., Daring Lake and Trail Valley Creek in the Northwest Territories; Toolik Lake and the Kuparak River basin in Alaska), systematic measurements at the regional scale have not been previously collected across this region of northern Canada. The snow cover consisted of depth hoar and wind slab with small and ephemeral fractions of new, recent, and icy snow. The snow was shallow (<40 cm deep), usually with fewer than six layers. Where snow was deposited on lake and river ice, it was shallower, denser, and more metamorphosed than where it was deposited on tundra. Although highly variable locally, no longitudinal gradients in snow distribution, magnitude, or structure were detected. This regional homogeneity allowed us to identify that the observed spatial variability in passive microwave brightness temperatures was related to subgrid fractional lake cover. Correlation analysis between lake fraction and Advanced Microwave Scanning Radiometer for Earth Observing System (AMSR-E) brightness temperature showed frequency dependent, seasonally evolving relationships consistent with lake ice drivers. Simulations of lake ice thickness and snow depth on lake ice produced from the Canadian Lake Ice Model (CLIMo) indicated that at low frequencies (6.9, 10.7 GHz), correlations with lake fraction were consistent through the winter season, whereas at higher frequencies (18.7, 36.5 GHz), the strength and direction of the correlations evolved consistently with the penetration depth as the influence of the subice water was replaced by emissions from the ice and snowpack. A regional rain-on-snow event created a surface ice lens that was detectable using the AMSR-E 36.5-GHz polarization gradient due to a strong response at the horizontal polarization. The appropriate polarization for remote sensing of the tundra snowpack depends on the application: horizontal measurements are suitable for ice lens detection; vertically polarized measurements are appropriate for deriving SWE estimates.
An Adjoint Sensitivity Analysis of the Southern California Current Circulation and Ecosystem
Authors: Moore Andrew M. , Arango Hernan G. , Di Lorenzo Emanuele , Miller Arthur J. , Cornuelle Bruce D.
Published: October 2008

Adjoint methods of sensitivity analysis were applied to the California Current using the Regional Ocean Modeling Systems (ROMS) with medium resolution, aimed at diagnosing the circulation sensitivity to variations in surface forcing. The sensitivities of coastal variations in SST, eddy kinetic energy, and baroclinic instability of complex time-evolving flows were quantified. Each aspect of the circulation exhibits significant interannual and seasonal variations in sensitivity controlled by mesoscale circulation features. Central California SST is equally sensitive to wind stress and surface heat flux, but less so to wind stress curl, displaying the greatest sensitivity when upwelling-favorable winds are relaxing and the least sensitivity during the peak of upwelling. SST sensitivity is typically 2–4 times larger during summer than during spring, although larger variations occur during some years.

The sensitivity of central coast eddy kinetic energy to surface forcing is constant on average throughout the year. Perturbations in the wind that align with mesoscale eddies to enhance the strength of the circulation by local Ekman pumping yield the greatest sensitivities.

The sensitivity of the potential for baroclinic instability is greatest when nearshore horizontal temperature gradients are largest, and it is associated with variations in wind stress concentrated along the core of the California Current. The sensitivity varies by a factor of ∼1.5 throughout the year. A new and important aspect of this work is identification of the complex flow dependence and seasonal dependence of the sensitivity of the ROMS California Current System (CCS) circulation to variations in surface forcing that was hitherto not previously appreciated.
Basin and Channel Contributions to a Model Antarctic Circumpolar Current
Authors: Nadeau Louis-Philippe , Straub David N.
Published: October 2008

The idea that basinlike dynamics may play a major role in determining the Antarctic Circumpolar Current (ACC) transport is revisited. A simple analytic model is developed to describe the relationship between the wind stress and transport. At very low-wind stress, a nonzero minimum is predicted. This is followed by two distinct dynamical regimes for stronger forcing: 1) a Stommel regime in which transport increases linearly with forcing strength; and 2) a saturation regime in which the transport levels off. The baroclinic structure of the Sverdrup flux into the Drake Passage latitude band is central to the analytic model, and the geometry of characteristics, or geostrophic contours, is key to predicting the transition between the two regimes. A robustness analysis is performed using an eddy-permitting quasigeostrophic model in idealized geometries. Many simulations were carried out in large domains across a range of forcing strengths. The simulations agree qualitatively with the analytic model, with two main discrepancies being related to zonal jet structures and to a western boundary inertial recirculation. Eddy fluxes associated with zonal jets modify the baroclinic structure and lower the saturation transport value. Inertial effects increase the transport, although this effect is mainly limited to smaller domains.
Tatian
Authors: Foster Paul
Published: October 2008

Tatian, Christian apologist and author of the most famous gospel harmony, was a disciple of Justin Martyr. His single complete surviving work, Oratio ad Graecos , is an example of the apologetic genre, which sought to offer a robust defence of the Christian faith. By contrast, his gospel harmony, the Diatessaron , survives only in fragmentary form, or embedded in later gospel harmonies, as well as being partially recoverable via Ephrem's Commentary on the text. What can be reconstructed of this work is potentially important for more fully understanding the textual form of the gospels in the second century. Later writers charge Tatian with heresy due to his association with Encratite Christianity. Such a perspective reflects the concerns of subsequent generations, and for this reason there appears to be no clear `error' attributed to Tatian.
The Date of Ignatius
Authors: Barnes Timothy D.
Published: October 2008

The present article seeks to transcend the terms of the traditional debate over the date and authenticity of the Ignatian letters by showing that Ignatius knew the writings of the Gnostic Ptolemaeus. Since Eusebius' dating of Ignatius to the reign of Trajan (98—117) cannot be regarded as authoritative, it is suggested that the letters were probably written in the 140s.