bluuebunny/crossref_metadata_2025_split huggingface dataset:
An axisymmetric model of a mature tropical cyclone incorporating azimuthal vorticity
Authors: Pearce Robert P. 
Published: February 2004

AbstractThe inner core of an axisymmetric mature hurricane‐type vortex is first constructed using the gradient‐wind‐balance condition by specifying the tangential wind, v, and the mean temperature excess of the eye, which is assumed to be at rest. These parameters are used to define the configuration of the eye wall. A relation is then obtained relating the eye radius to a parameter α in the relation rαv=constant, defining the inflow tangential wind at radius r, a parameter Γ involving v(=vR) at a radius R of order 100 km, and the eye temperature. This relation is shown to be readily adaptable to a model with an eye in solid rotation.A meridional circulation is constructed by specifying its azimuthal vorticity, η, and then calculating the temperature field required to maintain a steady state; the full azimuthal vorticity equation rather than the gradient‐wind‐balance approximation is used for this purpose. The main additional terms are those arising from vorticity advection by the meridional flow and a vorticity source related to the temperature lapse rate. The latter is the dominant additional term and implies model tangential winds which are about 5% supergradient near the eye wall.The role of the meridional circulation in both exporting the heat and importing the angular momentum required by the surface transfers is examined. The observed restriction of α to a narrow band between 0.5 and 0.6 is shown to be consistent with its being determined by the ratio given by the strength of the surface heating divided by the mean temperature excess in the eye. (=ΔTE), which must itself be restricted within a narrow band and can be regarded as determining α. It is inferred that the model's maximum wind is effectively determined solely by ΔTE. On the other hand, the eye radii of similar systems are roughly proportional to R, i.e. larger systems of similar intensities have larger eyes.Finally a conceptual model of the intensification phase is presented. After first demonstrating that a ring of deep convection must contract, it is shown that the intensification process can be characterized as a downwards and inwards penetration of the eye wall from the convective ring outflow near the tropopause, limiting the contraction. Copyright © 2004 Royal Meteorological Society
Specification and prediction of monthly and seasonal rainfall over the south‐west peninsula of England
Authors: McGregor Glenn R. , Phillips Ian D. 
Published: February 2004

AbstractAn assessment of the extent to which atmospheric variables add to the specification and predictability of rainfall over the south‐west peninsula of England (SWPE), as provided by North Atlantic sea surface temperatures (SSTs), is undertaken. To this end multivariate specification and prediction models are developed, describing rainfall variations over the SWPE at monthly and seasonal time‐scales. Results reveal that synchronous variations in atmospheric circulation characteristics are the main specifiers of monthly and seasonal rainfall variability, chiefly mean monthly sea‐level pressure, vorticity and atmospheric water vapour flux. In contrast, the predictability of rainfall for one‐ and two‐months, and one‐ and two‐seasons ahead is more dependent on SST than atmospheric circulation variability. Both the tropical Atlantic and the Greenland–Iceland (Norwegian Sea) regions of the North Atlantic appear important as centres of action in terms of SST–SWPE rainfall links. Although SSTs account for the majority of variance in monthly and seasonal rainfall, a moderate improvement of rainfall prediction is achieved with the inclusion of atmospheric water vapour flux in prediction models for one‐month to two‐seasons ahead, as it acts as an atmospheric bridge between the ocean and land in terms of precipitation delivery. The empirical relationships revealed between SWPE rainfall, and atmospheric and SST variability are discussed in terms of the main components of the North Atlantic climate system. Copyright © 2004 Royal Meteorological Society
Variational data assimilation in the tropics: The impact of a background‐error constraint
Authors: Žagar Nedjeljka , Gustafsson Nils , Källén Erland 
Published: February 2004

AbstractGeostrophic adjustment theory predicts that wind information is a primary information source in the tropics. We ask whether this is true when variational data assimilation including a background‐error constraint is applied. The question is investigated by carrying out three‐ and four‐dimensional variational (4D‐Var) data assimilation experiments with nonlinear shallow‐water equations and idealized waves. The contribution to the analysis from mass and wind field observations is contrasted to that of spectral characteristics and multivariate relationships of equatorial waves built into a background‐error covariance matrix. A background‐error term for the analysis is built by using the tropical eigenmodes and the observed variability is used to determine the relative weights for different modes.Single observation sensitivity experiments illustrate an important impact of Kelvin and mixed Rossby–gravity waves in reducing the coupling between the mass and wind fields, found when only equatorial Rossby waves are utilized in the background‐error constraint.The assimilation experiments demonstrate two main features. First, the wind field information is of greater value than the mass field information, in spite of the known error statistics. A second intriguing feature is that the assimilation of wind observations better resolves smaller‐scale features of the height field than the assimilation of height data. When height data are used, a somewhat different analysis response is obtained for the zonal and meridional wind components, due to the strong projection onto the Kelvin wave structure for height observations. Finally, a comparison of different time windows for 4D‐Var illuminates the sensitivity of height field assimilation to the length of the assimilation window. Copyright © 2004 Royal Meteorological Society
Instability in a class of explicit two‐time‐level semi‐Lagrangian schemes
Authors: Durran Dale R. , Reinecke P. Alexander 
Published: February 2004

AbstractRecently Gospodinov and collaborators derived a family of second‐order two‐time‐level semi‐Lagrangian schemes that contain an undetermined parameter α. It is shown that, when using one of these schemes to approximate the forcing terms in partial differential equations in a semi‐Lagrangian coordinate frame, the choice of α has a critical influence on the absolute stability of the method. Optimal stability properties are obtained by choosing α = ¼ which corresponds to the SETTLS scheme proposed by Hortal. Copyright © 2004 Royal Meteorological Society
Physically based two‐moment bulkwater parametrization for warm‐cloud microphysics
Authors: Chen Jen‐Ping , Liu Sen‐Tsong 
Published: February 2004

AbstractA two‐moment bulkwater parametrization scheme for warm‐cloud microphysics is developed via statistical analyses of results from a detailed parcel model. This computationally efficient scheme is quite accurate and produces bulkwater properties which resemble the results from a fully explicit microphysical model. It responds sensitively to the effect of aerosol types on the cloud drop number concentration and the timing of rain initiation. Diagnostic formulae are also provided for the group fall velocity, number and mass sedimentation fluxes, the radar reflectivity factor, and the effective radii of cloud drops and raindrops. This physically sound and easy to use parametrization scheme could be useful in improving the microphysical representation in regional‐ and cloud‐scale models. Copyright © 2004 Royal Meteorological Society
Contour‐advective semi‐Lagrangian algorithms for many‐layer primitive‐equation models
Authors: Mohebalhojeh A. R. , Dritschel D. G. 
Published: February 2004

AbstractFor an f‐plane many‐layer primitive‐equation isopycnal model, three ‘contour‐advective semi‐Lagrangian’ (CASL) algorithms and a standard pseudo‐spectral (PS) algorithm are compared as regards their representation of balance and imbalance during the evolution of a highly complex vortical flow with substantial activity in small horizontal and vertical scales. The three CASL algorithms employ (q,h,δ), (q,δ,γ), and (q,γ,Ξ) as their prognostic variables, where q is the Rossby potential vorticity, h is layer thickness, δ is horizontal divergence, γ and Ξ represent departures of vorticity from, respectively, geostrophic and Bolin–Charney balance. It is demonstrated that the CASL algorithm with (q,δ,γ) improves on the algorithm with (q,h,δ) across nearly the whole range of applicability of the algorithms, i.e. practically up to the limit where overturning and diabatic effects may dominate. Unlike in the PS algorithm, the improvement is achieved without sacrificing the accuracy of the vortical part of the flow by excessive damping. Copyright © 2004 Royal Meteorological Society
Climate response to tropospheric absorbing aerosols in an intermediate general‐circulation model
Authors: Cook J. , Highwood E. J. 
Published: February 2004

AbstractThis study uses idealized aerosol distributions with the Reading Intermediate General‐Circulation Model (IGCM) to assess and explain the climate response in that model to absorbing tropospheric aerosol. We find that the sign of the direct aerosol radiative forcing is not a good indication of the sign of the resulting global and annual mean surface temperature change. The climate sensitivity parameter for aerosols which absorb some solar radiation is much larger than that for CO2or solar experiments with the same model.Reasons for the enhanced surface temperature response in the presence of aerosol are examined. Significant changes in cloud amount occur, some of which appear most influenced by the change in surface temperature and may be generic to any mechanism that warms the surface. A reduction in low cloud amount occurs when the aerosol single‐scattering albedo is less than 0.95; the so‐called ‘semi‐direct’ effect of aerosols is clearly evident in this model. We suggest that this aerosol–cloud feedback is present in all GCMs which include absorbing tropospheric aerosol but remains largely undiagnosed. Comparisons with a previous study and further sensitivity tests suggest that the magnitude of this effect and the mechanisms behind it are strongly dependent on the cloud scheme employed. Copyright © 2004 Royal Meteorological Society
Effects of shear sheltering in a stable atmospheric boundary layer with strong shear
Authors: Smedman Ann‐Sofi , Högström Ulf , Hunt J. C. R. 
Published: February 2004

AbstractData from two marine field experiments in the Baltic Sea with stable stratification have been analysed. The purpose was to test the concept of the ‘detached’ or ‘top‐down’ eddies and the ‘shear‐sheltering’ mechanism in the presence of a low‐level wind speed maximum in the atmosphere. Data used include turbulence and profile measurements on two 30 m towers and concurrent wind profiles throughout the boundary layer obtained from pilot‐balloon soundings.Measurements show that large eddies are being suppressed when there is a low‐level wind speed maximum present somewhere in the layer 40–300 m above the water surface and when the stratification is slightly stable. The effect is seen both in normalized standard deviations of the velocity components and in corresponding component spectra. In previous work it was argued that the relatively large eddies, which dominate the low wave number spectra in measurements in the surface layer, are detached or top‐down eddies generated higher up in the boundary layer, that interact with the surface layer. The low‐level wind maximum introduces a distinct layer with strong vorticity which, according to the shear‐sheltering hypothesis, prevents these eddies from penetrating downwards.In the limit of the wind maximum occurring at a very low height (less than about 100 m), usual turbulence statistics characteristic of the ‘canonical’ boundary layer are found. Combining all the statistics, it is demonstrated that the wavelength of maximum spectral energy is locally related to a turbulence length‐scale, which shows that for values of the Richardson number of unity or less the effect of the local wind gradient is greater than that of static stability. The reduction of length‐scale with the strength of a low‐level wind maximum, explains the observed reduction (by a factor of two) of the turbulent flux of sensible heat at the surface. This result indicates that the shear‐sheltering mechanism is likely to play an important role in the turbulent exchange process at the surface in sea areas where low‐level wind maxima are a frequently occurring phenomenon, such as the Baltic and other large water bodies surrounded by landmasses. Copyright © 2004 Royal Meteorological Society
Portable method for the determination of snoring site by sound analysis
Authors: Bieger-Farhan A. K. , Chadha N. K. , Camilleri A. E. , Stone P. , McGuinness K. 
Published: February 2004

It has been shown that computerized sound frequency analysis can be used todistinguish between different snoring sites. The aim of this study was to investigate whether aportable recording method using audiotapes and digital minidisc formats could produce waveformssimilar to a computer recording.The snores of 12 subjects in their natural sleep were recorded onto audiotape, minidisc and directly onto a computer. For each snorer and recording method 30 snore samples were analysed and their power ratio was calculated indicating the relative amount of sound below and above a set frequency. It was found that the power ratios from audiotape recordings were significantly different to those from computer recordings for all snoring sites (p = 0.0007), whereasthere was no significant difference between minidisc and computer recordings (p = 0.41).These results indicate that it would be possible to base a portable snore analysis system for site determination on minidisc, but not on audiotape recordings.
Non-recurrent inferior laryngeal nerve in thyroid surgery: report of three cases and review of the literature
Authors: Abboud Bassam , Aouad Rony 
Published: February 2004

The non-recurrent inferior laryngeal nerve (NRILN) is a nerve anomaly that can be associated with an increased risk of vocal fold paralysis. The purpose of this study wasto report three new cases of this anomaly, underline the necessity of recognizing its possibility for the prevention of intra-operative nerve damage and a review of the literature.Three cases of thyroid surgery associated with right NRILN are reported.Two patients underwent bilateral thyroidectomy for a multinodular goitre and for a toxic multinodular goitre respectively. The third patient had a right lobectomy and isthmectomy for a thyroid nodule. All patients had identification of the recurrent laryngeal nerve on the left sideand NRILN on the right side. The diagnosis of the NRILN was made per-operatively on all cases. A post-operative computed tomography (CT) scan in two patients, showed a retrooesophageal aberrant right subclavian artery. Post-operatively, all patients had normal vocal fold function on laryngoscopy.The NRILN is a rare anomaly but overlooking its possibility may lead to severe operative morbidity. This is an additional argument in favour of systematic dissection of the recurrent inferior laryngeal nerve during thyroid surgery.
Vibration Perception Thresholds Assessed by Two Different Methods in Healthy Subjects
Authors: Zamyslowska-Szmytke Ewa , Szymczak Wieslaw , Sliwinska-Kowalska Mariola 
Published: February 2004

The values of vibration perception threshold (VPT) should be related to the equipment and methods of measurement that differ between European countries. ISO Standard 13091-1-2001 specifies the general guidelines regarding device facilities and measurement methodology. This study was designed to compare VPTs in healthy subjects by using two different methods of measurement. The first one was a standard technique applied currently in Poland and the second one was based on the principles of the International Standard ISO 13091-1-2001. The study comprised 187 healthy subjects, aged 17–57 years, not occupationally exposed to vibration. Both measurements of VPTs were performed using the same equipment (P-8, EmsonMat). The main differences in methodology between the Polish standard method and the method of ISO included: different mode of stimuli presentation (ascending in standard vs. Bekesy in ISO method), frequency range applied (63–500 Hz vs. 4–125 Hz), probe contact force (larger in Polish method), probe diameter (12 mm vs. 5 mm) and its surface (plane vs. rough). The results obtained found that the mean VPTs differed significantly at the overlapping frequencies depending on the method used, the differences varied from 2.2 to 6.4 dB at frequencies 125 and 250Hz, respectively. The correlation between the thresholds obtained by both methods at these frequencies was moderate (correlation coefficients about 0.6), although statistically significant. In the ISO method, the best VPTs were found at 4 and 125 Hz. There was a poor correlation between the thresholds at the extreme frequencies (i.e. 125 and 4 Hz) and rather high between adjacent frequencies (i.e. 25 and 32 Hz). Age, weight and height were significant covariates in both measurements. The model to calculate the normative values of VPTs adjusted for explanatory factors was set up in this study. It was concluded that different methods of VPT measurement are not comparable. The ISO method seems to supply more information about skin receptors and different kinds of tough sense than the Polish standard method. In order to perform international cohort studies there is a need to establish a unified standardised method of vibrotactile sense assessment.
Ground Vibration Generated by a Harmonic Load Moving in a Circular Tunnel in a Layered Ground
Authors: Sheng X , Jones C J C , Thompson D J 
Published: February 2004

All modes of transport impact on e environment. Although railways are seen as environmentally advantageous in many ways, the issues of noise and vibration are often seen as their weakness. For trains running in tunnels where direct airborne noise is effectively screened, structure-borne or ‘ground-borne’ noise caused by vibration propagated through the ground is the most important concern. The vibration of interest in this case has frequency components from about 15 Hz to 200 Hz. To understand the mechanisms of vibration propagation from tunnels, a predictive model has been developed for ground vibration generated by a stationary or moving harmonic load applied in a circular lined or unlined tunnel in a layered ground. This study is the first step towards the use of discrete wavenumber methods to model ground vibration from underground trains. Discrete wavenumber methods fall into three categories: the discrete wavenumber fictitious force method, the discrete wavenumber finite element method and the discrete wavenumber boundary element method. This study uses the discrete wavenumber fictitious force method. Based on the moving Green's functions for a layered half-space and those for a cylinder of infinite length, boundary integral equations over the tunnel-soil interface are established. Unlike the conventional boundary integral equation in elastodynamics, the method used here only requires the displacement Green's function. This is achieved by introducing the excavated part of the ground as an extra substructure. The boundary integral equations are further transformed into a set of algebraic equations by expressing each quantity involved in the boundary integral equations in terms of a Fourier series. Results presented in this paper illustrate the effect of a tunnel on vibration propagation at the ground surface and the difference between a lined tunnel and an unlined tunnel.
Wind Shear Extremes at Possible Offshore Wind Turbine Locations
Authors: Hansen Kurt S. , Larsen Gunner Chr. 
Published: February 2004

Positive and negative short-term extreme wind shear distributions (conditioned on the mean wind speed) are determined and compared for a number of offshore sites. The analysis is based on rapidly sampled field measurements (1–8 Hz) extracted from the “Database on Wind Characteristics” ( www.winddata.com ). Three different averaging periods (2, 5 and 10 seconds) are considered, and for each averaging period a relation between the resulting extreme shear distributions and the averaging time are presented. The short-term extreme shear analysis is based on different spatial distances, and extrapolation to a spatial distance of 100 m has been investigated. Such distances are appropriate for the next generation of offshore wind turbines. The paper concludes with an estimation of the short-term extreme shear values, which are compared to the values specified in the IEC-61400 code. The extreme IEC shear values seems to be rather conservative for an offshore location, compared to the estimated values based on measurements.
Technical Note: Impact Sound Reduction for Cross-Linked and Non-Cross-Linked Polyethylene Foams in Suspended Concrete Floor Structures
Authors: Díez-Gutiérrez S. , Rodríguez-Pérez M.A. , Machimbarrena M. , González J. , de Saja J.A. 
Published: February 2004

The acoustic behaviour of two building systems, a traditional concrete structure and an innovative one involving expanded polystyrene (EPS) elements have been compared using field measurements. The results indicate that the airborne sound insulation is very similar for both construction methods, whereas impact sound insulation is better for the innovative system. The improvement obtained by introducing polyethylene foams in floating floor constructions has also been investigated for the EPS system using field measurements. Also, the impact sound insulation improvement obtained with two different polyethylene foams has also been analysed by performing laboratory experiments. Whilst both materials are adequate for this application, results indicate that the non cross-linked foam has a better performance.
Small Firms and Their Difficulties with Contractual Relationships: Implications for Legal Policy
Authors: Lewis P. 
Published: February 2004

This paper is based on interviews with and documents supplied by the owners, directors and managers of 40 small businesses in the UK. It analyses the contractual arrangements made for business purposes, investigates the firms' experiences of litigation and attempts to classify the legal problems faced by small firms in their contractual relationships. The firms' legal problems were more in the area of private business relations than public administration and many of the actions arising out of contractual relations were statutory rather than contractual. The most common type of problem related to firms' inadequate response to the legal environment rather than to deficiencies in the law or legal system. There was only a limited professional legal input into contract formation although the use of standard terms was widespread. There were doubts on the part of some of the firms about whether the contractual framework they had adopted offered sufficient legal protection. It is submitted that it is right that small firms should not be excluded from legal duties placed upon employers more generally but the conclusion here is that they are badly placed to fulfil these duties because of a difficulty in gaining access to legal resources. The main implication for legal policy is that small firms may require a publicly-subsidized legal service if they are to conduct their contractual relationships lawfully, particularly as these relationships come to be regulated increasingly by statute. It is noted that some steps consistent with such an approach are being considered by the government in relation to employment law.