bluuebunny/crossref_metadata_2025_split huggingface dataset:
The wake south of the Alps: Dynamics and structure of the lee‐side flow and secondary potential vorticity banners
Authors: Flamant C. , Richard E. , Schär C. , Rotunno R. , Nance5 L. , Sprenger M. , Benoit R. 
Published: June 2004

AbstractThe dynamics and structure of the lee‐side flow over the Po valley during a northerly föhn event, which occurred in the framework of the Mesoscale Alpine Programme Special Observation Period (on 8 November 1999 during Intensive Observation Period 15), has been investigated using aircraft data and high‐resolution numerical simulations. Numerical simulations were performed with the mesoscale non‐hydrostatic model Meso‐NH, using three nested domains (with horizontal resolutions 32, 8 and 2 km), the 2 km resolution domain being centred on the Po valley. The basic data–model comparison, and back‐trajectory and tracer release analyses, provided evidence that the jet/wake structure of the flow above the Po valley could be reasonably identified with the mountain pass/peak distributions. Measurements from three aircraft flying below the Alps crestline (at 2700, 1500 and 600 m above sea level) along two 350 km east–west legs, designed to be approximately perpendicular to the northerly synoptic flow, were used to compute the potential vorticity (PV) experimentally assuming the lee‐side flow to be two‐dimensional. (The simplified form of the PV under these assumptions is hereafter referred to as SPV). Due to increasing lee‐side flow curvature with decreasing altitude (caused by flow splitting at the scale of the Alps), the experimentally derived SPV was compared to its simulated counterpart. In situ measurements showed that coherent secondary PV banners (PVB2s) do exist downstream of the complex Alpine terrain, as observations show oscillations between positive and negative values of SPV as expected from the simulations. The details of the structure of the SPV field simulated with Meso‐NH were found to be different from the observations (i.e. the location of observed maxima and minima of SPV did not match their simulated counterparts at particular points). This is because the correspondence between observed and modelled velocity and potential temperature fields was not good enough to expect good correspondence between differentiated quantities such as vorticity and potential temperature gradient (since less‐reliable shorter‐scale features are thereby accentuated). Parametrized processes such as surface drag and internal diffusion, and ‘numerical’ processes, such as model filters, to which PV production mechanisms are sensitive and whose role is difficult to assess, also contribute to the poor agreement between observed and modelled SPV fluctuations. Finally, simulations suggest that lowlevel gravity‐wave breaking was the main mechanism responsible for the formation of the elongated PVB2 modelled/observed over the Po valley.
A finite‐element scheme for the vertical discretization of the semi‐Lagrangian version of the ECMWF forecast model
Authors: Untch A. , Hortal M. 
Published: June 2004

AbstractA vertical finite‐element (FE) discretization designed for the European Centre for Medium‐Range Weather Forecasts (ECMWF) model with semi‐Lagrangian advection is described. Only non‐local operations are evaluated in FE representation, while products of variables are evaluated in physical space. With semi‐Lagrangian advection the only non‐local vertical operations to be evaluated are vertical integrals. An integral operator is derived based on the Galerkin method using B‐splines as basis functions with compact support. Two versions have been implemented, one using piecewise linear basis functions (hat functions) and the other using cubic B‐splines. No staggering of dependent variables is employed in physical space, making the method well suited for use with semi‐Lagrangian advection.The two versions of the FE scheme are compared to finite‐difference (FD) schemes in both the Lorenz and the Charney–Phillips staggering of the dependent variables for the linearized model. The FE schemes give more accurate results than the two FD schemes for the phase speeds of most of the linear gravity waves. Evidence is shown that the FE schemes suffer less from the computational mode than the FD scheme with Lorenz staggering, although temperature and geopotential are held at the same set of levels in the FE scheme too. As a result, the FE schemes reduce the level of vertical noise in forecasts with the full model. They also reduce by about 50% a persistent cold bias in the lower stratosphere present with the FD scheme in Lorenz staggering (i.e. the operational scheme at ECMWF before its replacement by the cubic version of the FE scheme described here) and improve the transport in the stratosphere. Copyright © 2004 Royal Meteorological Society
Convective mixing in a tropopause fold
Authors: Reid H. J. , Vaughan G. 
Published: June 2004

AbstractWe present a case study of the passage of a tropopause fold over the UK behind a cold front, with emphasis on the mixing caused by convection extending into the fold. The event took place on 15–16 January 1999, and was the subject of intensive observations using the Met Office C130 aircraft and the mesosphere–stratosphere–troposphere (MST) radar at Aberystwyth. Here we concentrate on radar and satellite observations during the afternoon of 16 January, when the surface cold front had passed over the UK. A tongue of moist air moved north‐eastwards over Wales at 700 hPa at this time, which, because of the very dry air in the fold above, resulted in potential instability. The resulting convection was clearly observed in NOAA satellite images. The MST radar depicted the passage of the cold front and tropopause fold as a layer of high‐echo power and vertical wind shear ascending with time. Spectral widths showed the fold to be free of turbulence until 1200 UTC on 16 January, when convection was observed reaching into the frontal zone and generating turbulence. Eddy dissipation and diffusivity rates of 8.6 mW kg−1 and 8.5 m2s−1, respectively, were derived for this event. To place these figures in context, they are compared with corresponding rates derived for sixteen other passages of tropopause folds over the radar, each resulting from shear rather than convective instability. The convective event is found to be comparable to the strongest shear events, and to correspond to moderate turbulence as experienced by an aircraft. This process is of potential importance for atmospheric chemistry because it mixes boundary layer air directly with stratospheric air over a timescale of 1–2 hours. Copyright © 2004 Royal Meteorological Society
A canopy model of mean winds through urban areas
Authors: Coceal O. , Belcher S. E. 
Published: June 2004

AbstractAn urban canopy model is developed for spatially averaged mean winds within and above urban areas. The urban roughness elements are represented as a canopy‐element drag carefully formulated in terms of morphological parameters of the building arrays and a mean sectional drag coefficient for a single building. Turbulent stresses are represented using a mixing‐length model, with a mixing length that depends upon the density of the canopy and distance from the ground, which captures processes known to occur in canopies. The urban canopy model is sufficiently simple that it can be implemented in numerical weather‐prediction models.The urban canopy model compares well with wind tunnel measurements of the mean wind profile through a homogeneous canopy of cubical roughness elements and with measurements of the effective roughness length of cubical roughness elements. These comparisons give confidence that the basic approach of a canopy model can be extended from fine‐scale vegetation canopies to the canopies of large‐scale roughness elements that characterize urban areas.The urban canopy model is also used to investigate the adjustment to inhomogeneous canopies. The canonical case of adjustment of a rural boundary layer to a uniform urban canopy shows that the winds within the urban canopy adjust after a distance x0 = 3Lc lnK, where Lc is the canopy drag length‐scale, which characterizes the canopy‐element drag, and ln K depends weakly on canopy parameters and varies between about 0.5 and 2. Thus the density and shape of buildings within a radius x0 only determine the local canopy winds. In this sense x0 gives a dynamical definition of the size of a neighbourhood.The urban canopy model compares well with observations of the deceleration of the wind associated with adjustment of a rural boundary layer to a canopy of cubical roughness elements, but only when the sectional drag coefficient is taken to be somewhat larger than expected. We attribute this discrepancy to displacement of streamlines around the large‐scale urban roughness elements, which yields a stress that decelerates the wind. A challenge for future research is to incorporate this additional ‘dispersive stress’ into the urban canopy model. Copyright © 2004 Royal Meteorological Society
The semi‐direct aerosol effect: Impact of absorbing aerosols on marine stratocumulus
Authors: Johnson B. T. , Shine K. P. , Forster P. M. 
Published: June 2004

AbstractAerosols that absorb solar radiation may lead to a decrease of low‐cloud cover and liquid‐water path (LWP), leading to a positive radiative forcing. A large‐eddy model was used to investigate this ‘semi‐direct effect’ for marine stratocumulus and examine the dependency on the vertical distribution of the aerosol. In this study, the aerosols influenced clouds by directly altering the short‐wave heating rate (the semi‐direct effect), but did not interact with the cloud microphysics (i.e. indirect aerosol effects are excluded). Absorbing aerosols within the boundary layer (BL) decreased LWP by 10 g m−2, leading to a positive semi‐direct forcing. Even for mildly absorbing aerosols (mid‐visible single‐scattering albedo of 0.96), the semi‐direct forcing was three times stronger, and opposite in sign, to the aerosol direct forcing. The semi‐direct forcing was found to be proportional to aerosol single‐scattering co‐albedo (tested to a value of 0.12). Conversely, with the absorbing aerosol layer above the cloud, the LWP increased by 5 to 10 g m−2, leading to a negative semi‐direct forcing. Absorbing aerosols located in the BL heat the cloud layer, enhancing the daytime decoupling and thinning of the stratocumulus layer. Absorbing aerosols immediately above the BL increased the contrast in potential temperature across the inversion, leading to a lower cloud‐top entrainment rate. With aerosol both within and above the BL, the semidirect forcing was positive but half the magnitude of that experienced when aerosol was only in the BL. As marine stratocumulus covers about 20% of the globe, the semi‐direct effect could significantly influence the radiative forcing by absorbing aerosols. Copyright © 2004 Royal Meteorological Society
A new parametrization of turbulent orographic form drag
Authors: Beljaars Anton C. M. , Brown Andrew R. , Wood Nigel 
Published: June 2004

AbstractA new parametrization is presented for the representation in large‐scale models of turbulent form drag due to subgrid orography with horizontal scales smaller than around 5000 m. The scheme is based on earlier work in which surface stress and its vertical distribution is formulated in terms of a slope parameter for sinusoidal hills. The new elements of the current parametrization are: (i) the spectrum of the orography is represented by a piecewise empirical power law, (ii) the turbulent form drag scheme integrates over the spectral orography to represent all the relevant scales, and (iii) the wind forcing level of the drag scheme depends on the horizontal scale of the orography, which implies that the smaller scales respond to lighter winds than do the larger scales.The scheme is controlled by a single parameter, namely the spectral density of the orography at scales of a few kilometres, as can be accurately obtained from a global 1 km data set. The empirical orographic power‐law spectrum is derived by analysing fine resolution data as available for the USA. In order to be applicable in a large‐scale model, simplifications are applied. Single‐column simulations are performed to assess the consequences of these simplifications. Comparisons of single‐column simulations with output from fine‐scale simulations for sinusoidal hills show that the approximations are within the uncertainty of the fine‐scale models. Furthermore, it is felt that the scheme is sufficiently accurate given the uncertainty in the characterization of the orography with current global datasets. © Royal Meteorological Society, 2004. Contributions by A. R. Brown and N. Wood are Crown copyright.
Estimation of turbulence parameters in the lower atmosphere from MST radar observations
Authors: Satheesan K. , Murthy B. V. Krishna 
Published: June 2004

AbstractUsing the Mesosphere‐Stratosphere‐Troposphere (MST) radar observations at Gadanki (13.5°N,79.2°E) in the troposphere and lower stratosphere, the nature of the temporal spectrum of the vertical wind in the inertial sub‐range is investigated. It is found that the slope of the spectrum depends upon the background horizontal wind speed. The turbulent‐kinetic‐energy dissipation rate ε has been estimated using the MST radar observations by (i) the Doppler spectral‐width method, (ii) the backscatter signal‐power method, and (iii) the velocity‐variance method. A detailed comparison of the ε in the troposphere and lower stratosphere estimated by the three methods has been carried out. It is found that ε by the variance method differs from that by the other two methods very significantly in the troposphere where the background horizontal wind is high. In the lower stratosphere with low background horizontal wind, ε from the three methods is different in each case. It appears that turbulence in the regions of high background horizontal wind in the troposphere is anisotropic and the differences between the estimates of ε by the variance method and the other two methods are attributed to the presence of anisotropic turbulence. Copyright © 2004 Royal Meteorological Society
Detection of cloud‐affected AIRS channels using an adjacent‐pixel approach
Authors: Joiner J. , Poli P. , Frank D. , Liu H. C. 
Published: June 2004

AbstractHigh‐spectral‐resolution infrared sounders such as the Atmospheric InfraRed Sounder (AIRS), flying on the National Aeronautics and Space Administration Earth Observing System (EOS) Aqua satellite, provide information about vertical temperature and humidity structure that is potentially useful for data assimilation and numerical weather prediction. Tropospheric channels from infrared sounders are frequently affected by cloud. The methods currently used operationally to account for cloud effects are screening to eliminate cloud‐contaminated data and cloud‐clearing. For either approach, it is important to determine which channels peak sufficiently above the cloud so that they are not contaminated. Depending on the sounding, different combinations of channels are cloud‐contaminated, thus making cloud detection difficult.This paper proposes a new method of identifying clear or unaffected channels using adjacent pixels. Unlike other proposed or implemented methods, this approach does not rely heavily on having accurate background information about the atmospheric state or estimates of its error. The method also does not make any assumptions about cloud spectral properties. Instead, it assumes that clouds will produce adjacent‐pixel variability. The approach requires an estimate of clear‐scene adjacent‐pixel homogeneity that can be obtained with real data.We apply the methodology to simulated AIRS data using Monte Carlo experiments. We then apply the algorithm to real AIRS data and use brightness temperature departure statistics as an independent check for residual cloud contamination. We also make qualitative comparisons with cloud properties derived from the EOS Aqua Moderate‐Resolution Imaging Spectroradiometer instrument. Copyright © 2004 Royal Meteorological Society
High‐frequency estimation of rainfall from thunderstorms via satellite infrared and a long‐range lightning network in Europe
Authors: Chronis Themis G. , Anagnostou Emmanouil N. , Dinku Tufa 
Published: June 2004

AbstractA rain retrieval technique called Omvrios, that combines geostationary satellite infrared (IR) observations and cloud‐to‐ground (CG) lightning information retrieved from a long‐range lightning detection network (Zeus) in Europe, is presented. Cloud systems are defined in the IR temperature array by the 255 K isotherm. Bulk parametrizations that relate cloud top IR temperature, morphological characteristics and CG lightning information (location and flash rate) are used to discriminate rainy from non‐rainy cloud systems, and to evaluate the convective and stratiform rain areas and associated area‐averaged rain rates of the rainy systems. The technique's parameters were calibrated using collocated and instantaneous rain fields derived from Special Sensor Micro‐wave/Imager passive microwave data. Retrieved rain estimates are aggregated to 0.1° grid resolution and 6 h temporal accumulation. The technique is validated during the warm season from May to August 2002, based on independent 6 h rain accumulation measurements from a network of 700 rain‐gauges located across Europe. Statistical analysis shows high correlation with gauge rainfall data (0.88) and low overall systematic difference (∼5%). Besides direct validation against rain‐gauge data, Omvrios has been compared to existing passive microwave‐calibrated IR rain‐retrieval techniques. It is shown that lightning information can lead to a significant (25–40%) reduction in the random error of IR retrievals and to an increase of nearly 0.3 in correlation with gauges. In terms of systematic differences (retrieval bias) Omvrios is shown to be consistent, as conditional and unconditional biases are nearly equal (within 5%), while for the other IR rain retrievals the variation between conditional and unconditional biases was significant (34–75%). Copyright © 2004 Royal Meteorological Society
Phase IV Trial Evaluating the Effectiveness and Safety of Dofetilide
Authors: Guanzon Anna V , Crouch Michael A 
Published: June 2004

BACKGROUND: Dofetilide gained Food and Drug Administration approval for persistent atrial fibrillation/flutter (AFF) based on 2 randomized, placebo-controlled, dose-ranging studies. Concerns of proarrhythmia have prompted the manufacturer to develop specific treatment guidelines. OBJECTIVE: To determine the effectiveness and safety of dofetilide in clinical practice as well as to ascertain whether clinicians are following established dosing guidelines. METHODS: This retrospective analysis evaluated guideline adherence and safety in patients who received dofetilide at a tertiary care medical center. Safety assessment included monitoring for the occurrence of excessive QTc interval prolongation and torsade de pointes. Excessive QTc interval prolongation was defined as >15% above baseline after the first dose or >500 msec following any dose (>550 msec in patients with ventricular conduction abnormalities). Patients were included in the effectiveness assessment if they received at least 36 hours of dofetilide for persistent AFF, received an appropriate dose per guidelines, and did not receive direct current cardioversion during the evaluation period. We compared the 36–hour conversion rate with dofetilide in this study with that observed in the EMERALD and SAFIRE-D trials using the Z test, and we evaluated the incidence of excessive QTc interval prolongation in high-risk subgroups by χ2 analysis. RESULTS: Investigators identified 107 patients. The primary indication for dofetilide was AFF, with 58.9% receiving the drug for paroxysmal disease. Prescribing followed established guidelines, except that it was used intermittently by nonconfirmed prescribers (5.6%) and/or at inconsistent doses (14%). Excessive prolongation of the QTc interval occurred in 17.8% of patients after the first dose and 26.2% during subsequent doses; prolongation was more common in those with structural heart disease (p < 0.01). No patients developed torsade de pointes. In the effectiveness assessment (n = 25), the conversion of persistent AFF at 36 hours was higher than in previous studies (48% vs 27.2%; p = 0.05). CONCLUSIONS: In clinical practice, the conversion of persistent AFF with dofetilide is at least comparable to premarketing studies, with a similar safety profile. Institutions should continue to emphasize adherence with established treatment guidelines.
Reversible Ageusia after Chemotherapy with Pegylated Liposomal Doxorubicin
Authors: Kiewe Philipp , Jovanovic Sergije , Thiel Eckhard , Korfel Agnieszka 
Published: June 2004

OBJECTIVE: To report a case of reversible ageusia in a patient with multiple myeloma receiving pegylated liposomal doxorubicin. CASE SUMMARY: A 67–year-old man with a history of arterial hypertension and persisting left bundle-branch block was diagnosed with multiple myeloma. He was initially treated with cyclophosphamide 200 mg/m2 (days 1–4), pegylated liposomal doxorubicin 20 mg/m2 (day 1), and dexamethasone 40 mg (days 1–4) (CLAD). That treatment was followed by high-dose melphalan therapy and autologous peripheral stem-cell transplantation. The disease recurred 18 months later, and renal failure developed. The patient was again treated with the CLAD protocol. After the first cycle, almost complete ageusia occurred, along with weight loss and severe depression. Chemotherapy was continued, but pegylated liposomal doxorubicin was replaced by conventional doxorubicin. Within 12 weeks, the patient's sense of taste returned to normal. DISCUSSION: Pegylated liposomal anthracyclines are increasingly being used as a less cardiotoxic alternative to conventional doxorubicin in first- and second-line therapy of multiple myeloma. Whereas cardiotoxicity and unspecific reactions are seen less frequently, palmar—plantar erythrodysesthesia is a common reaction to pegylated liposomal anthracyclines. No other reasons for ageusia in our patient could be identified. Based on the Naranjo probability scale, ageusia was rated as a probable reaction to pegylated liposomal doxorubicin. CONCLUSIONS: As with all new and innovative drugs, thorough documentation of infrequent adverse events is necessary. We would like to raise awareness for ageusia, which appears to be a rare but severely impairing adverse reaction to a relatively new pharmacologic agent.
Toward Resolving the Challenges of Sepsis Diagnosis
Authors: Carrigan Shawn D , Scott George , Tabrizian Maryam 
Published: June 2004

AbstractSepsis in the United States has an estimated annual healthcare cost of $16.7 billion and leads to 120 000 deaths. Insufficient development in both medical diagnosis and treatment of sepsis has led to continued growth in reported cases of sepsis over the past two decades with little improvement in mortality statistics. Efforts over the last decade to improve diagnosis have unsuccessfully sought to identify a “magic bullet” proteic biomarker that provides high sensitivity and specificity for infectious inflammation. More recently, genetic methods have made tracking regulation of the genes responsible for these biomarkers possible, giving current research new direction in the search to understand how host immune response combats infection. Despite the breadth of research, inadequate treatment as a result of delayed diagnosis continues to affect approximately one fourth of septic patients. In this report we review past and present diagnostic methods for sepsis and their respective limitations, and discuss the requirements for more timely diagnosis as the next step in curtailing sepsis-related mortality. We also present a proposal toward revision of the current diagnostic paradigm to include real-time immune monitoring.