bluuebunny/crossref_metadata_2025 huggingface dataset:
Theoretical Calculations on Electronic Structure and Catalytic Reaction of Organo-f-element Complexes
Authors: Luo Yi , Selvam Parasuraman , Koyama Michihisa , Kubo Momoji , Miyamoto Akira
Published: May 2004

The use of lanthanide complexes as catalysts in organic synthesis is currently of intense interest. In particular, organolanthanide complexes are of rapidly growing importance, and hence the understanding of the binding behavior of f orbital as well as the ionic/covalent characteristics of lanthanocene-based complexes is of significance with respect to their reactivity and their role as catalyst in organic synthesis. The purpose of this review is to give a survey of recent progress in theoretical studies on organo-f-element complexes and to highlight successful applications of density functional and quantum chemical molecular dynamics methods.
Construction of Organic Monolayers with Electron Transfer Function on a Hydrogen Terminated Si(111) Surface via Silicon–Carbon Bond and Their Electrochemical Characteristics in Dark and Under Illumination
Authors: Masuda Takuya , Uosaki Kohei
Published: May 2004

An organic monolayer with a functional group of electron mediation capability, viologen, was constructed on a hydrogen-terminated Si(111) surface via Si–C bond by photochemical attachment of 4-vinylbenzyl chloride followed by a surface quarternization reaction with 1-methyl-4-(4-pyridyl)pyridinium iodide. Furthermore, Pt particles were deposited on the monolayer by ion exchange reaction with PtCl42− followed by reduction by hydrogen gas. The mediation of electron transfer by viologen moieties was proved and electrochemical hydrogen evolution reaction rates were enhanced after the Pt deposition.
Synthesis and Adsorption Property of Calixarene-p-sulfonate-intercalated Layered Double Hydroxides
Authors: Sasaki Satoru , Aisawa Sumio , Hirahara Hidetoshi , Sasaki Akira , Narita Eiichi
Published: May 2004

The synthesis of the p-sulfonate[4]calixarene (CS4)/M2+–Al layered double hydroxides (Mg–Al and Zn–Al/CS4/LDHs) has been investigated as well as their adsorption behavior of benzyl alcohol (BA) in aqueous solution. The CS4/LDHs were easily synthesized by the conventional coprecipitation method. The basal spacing of the CS4/LDHs was expanded to 1.33 (Mg–Al) and 1.61 nm (Zn–Al), which indicates that CS4 cavity axis was oriented vertically (Mg–Al) and parallel (Zn–Al) to the LDH basal layer, respectively. In particular, the Zn–Al/CS4/LDH was found to have 2 types of micro pore, the CS4 cavity and the intermolecular space. The adsorption of BA to the CS4/LDH was influenced by the amount and orientation of CS4 ion in the interlayer of the LDHs.
Effect of Additives on Electrochemical Reduction of Oxygen in the Presence of Methanol
Authors: Shiroishi Hidenobu , Ayato Yusuke , Kunimatsu Keiji , Okada Tatsuhiro
Published: May 2004

Methanol oxidation on platinum has been suppressed and selective oxygen reduction was achieved in sulfuric acid – methanol aqueous solution by adding organic ligands or their complexes which have pyridyl structures.
Complementary Multicomplexation of Desymmetrized 2,2′-Bipyridine Ligands on Square Planar Pd(II) Centers
Authors: Tominaga Masahide , Kusukawa Takahiro , Sakamoto Shigeru , Yamaguchi Kentaro , Fujita Makoto
Published: May 2004

Upon complexation with Pd(II) ion, desymmetrized chelating ligand, 6-methyl-2,2′-bipyridine (1), gives only anti Pd·(1)22+ complex. This regioselective complexation is applied to complementary multicomplexation of liner molecular strands: namely, a strand containing two methyl-substituted 2,2′-bipyridine units is selectively complexed on Pd(II) with its counterpart strand in which methyl groups are complementarily substituted.
Guaiacol Oxidation Products in the Enzyme-Activity Assay Reaction by Horseradish Peroxidase Catalysis
Authors: Tonami Hiroyuki , Uyama Hiroshi , Nagahata Ritsuko , Kobayashi Shiro
Published: May 2004

In the horseradish peroxidase (HRP)-catalyzed oxidation of guaiacol (1), trimeric products, and diastereomers of biphenoquinones have been newly identified. The oxidation product was analyzed by HPLC, liquid chromatography electrospray ionization mass spectrometry (LC-ESIMS), and 1H NMR spectroscopy.
Pressure-dependent Activity of Dihydrofolate Reductase from a Deep-sea Bacterium Shewanella violacea Strain DSS12
Authors: Ohmae Eiji , Kubota Kazumasa , Nakasone Kaoru , Kato Chiaki , Gekko Kunihiko
Published: May 2004

A new dihydrofolate reductase (svDHFR) was purified from a deep-sea bacterium, Shewanella violacea strain DSS12, isolated from the Ryukyu Trench (5110 m). In contrast with E. coli DHFR, the enzyme activity of svDHFR increased with increasing hydrostatic pressure up to 100 MPa, suggesting that the enzyme kinetics and structural fluctuation of svDHFR are adapted to a high-pressure environment.
Large‐eddy simulation of turbulent flow in a street canyon
Authors: Cui Zhiqiang , Cai Xiaoming , J. Baker Chris
Published: June 2004

The turbulent flow inside an idealized urban street canyon with an aspect ratio of one is studied by means of large‐eddy simulation. The Regional Atmospheric Modelling System is configured to simulate the turbulent flow in a neutrally stratified atmosphere with the initial wind perpendicular to the street canyon axis. The mean velocity components, resolved‐scale turbulent kinetic energy (RS‐TKE), the skewness and kurtosis of the resolved‐scale velocity components (u along the canyon and w vertically) are compared with wind‐tunnel measurements. The comparison indicates that a reasonable agreement is achieved. The simulation slightly underestimates the intensity of the primary eddy. It is found that distribution of the RS‐TKE is very asymmetric: high in the vicinity of the downstream wall, and uniformly low in the vicinity of the upstream wall. The analyses of skewness and kurtosis indicate that there is a layer just below the rooftop in the canyon where ejection events dominate. Quadrant analysis of resolved‐scale velocity fluctuations, u′ and w′, under the rooftop at the centre of the canyon reveals that the exchange of momentum across the canyon top is contributed unevenly by different events. Weak ejection events dominate the frequency of occurrences, but fewer strong sweep events contribute the majority of the total momentum transfer. The features of momentum transfer are further investigated by analysing the spatial–temporal variations of u′, w′,and u′w′ at the roof level. It is found that the variation of these variables is highly intermittent and is associated with multi‐scale turbulent events. The period of eddies containing high RS‐TKE is attributed to the Kelvin–Helmhotz instabilities. These results improve our understanding of the turbulent structure in street canyon flow. Copyright © 2004 Royal Meteorological Society
Large‐eddy simulation of atmospheric convection on Mars
Authors: Michaels Timothy I. , Rafkin Scot C. R.
Published: June 2004

Large‐eddy simulations are performed using the Mars Regional Atmospheric Modeling System (a nonhydrostatic, mesoscale model) in order to obtain a detailed, three‐dimensional understanding of the daytime Mars atmospheric boundary layer. These microscale runs utilize the full radiative‐transfer (including a static dust profile) routines of the mesoscale model and a multi‐level, prognostic subsurface thermal model. Surface albedo, thermal inertia, Coriolis parameter and solar forcing are homogeneously set to values at the Mars Pathfinder landing site (19.33°N,33.55°W (IAU1991); Ls=143°). The initial state is obtained from a previous mesoscale simulation, and is representative of the Mars Pathfinder landing site during summer.

The convective boundary layer of Mars is found to exhibit structures and turbulent statistics outwardly similar to those of earth's convective boundary layer. However, direct infrared radiative heating of the near‐surface atmosphere is the primary mechanism for the transfer of energy from the solar‐heated surface, and affects the behaviour of the convection. Mars convection is more intense than that on earth, primarily due to lesser gravity and atmospheric mass. Also, certain empirical scaling constants within the subgrid‐scale turbulence parametrization (originally developed for terrestrial large‐eddy simulations) appear to require significant reduction in order for the scheme to perform adequately on Mars. The simulation results are used to further meaningfully interpret spacecraft images of convective clouds. The results also compare favourably with Mars Pathfinder in situ meteorological measurements, and help reconcile large daytime variances in that dataset. Copyright © 2004 Royal Meteorological Society
A simulation study of 1D variational cloud retrieval with infrared satellite data from multiple fields of view
Authors: Szyndel M. D. E. , Collard A. D. , Eyre J. R.
Published: June 2004

A method for retrieving cloud‐top height using one‐dimensional variational analysis with multiple pixels is examined. The method is tested for a range of cloud scenarios using simulated multi‐spectral infrared imagery. The skill of the multiple pixel method is compared to the skill of the single‐field‐of‐view method. It is found that, when applied to two pixels, the multiple‐field‐of‐view method considerably increases the skill of retrieval for the less cloudy pixel, and marginally improves the skill of retrieval for the cloudier pixel in the majority of cases. It is also found that, when applied to six pixels, the multiple‐field‐of‐view method has a positive impact in many cases. © Crown copyright, 2004. Royal Meteorological Society
Evolution and dynamics of summertime blocking over the Far East and the associated surface Okhotsk high
Authors: Nakamura Hisashi , Fukamachi Tomohiro
Published: June 2004

Time evolution and dynamics of an upper‐level blocking ridge over the Far East and the associated surface high over the Sea of Okhotsk that give rise to abnormal summertime coolness over eastern Japan are investigated through a composite analysis applied to distinct surface high events. The formation mechanism and vertical structure of the blocking differ fundamentally between May and July, attributable to seasonal changes in the jet structure, storm‐track activity over the Far East and the land–sea thermal contrast within the Okhotsk region. In May, forcing from migratory eddies is strong enough for precursory anticyclonic anomalies retrograding slowly over the North Pacific to develop into a blocking ridge. The ridge remains equivalent barotropic under the weak land–sea thermal contrast in the Okhotsk region. In contrast, the eddy forcing is no longer the primary factor for the blocking formation in July, in the presence of the weakened and split westerlies. Rather, the propagation of a stationary Rossby wave packet that has emanated from precursory anticyclonic anomalies over northern Europe stagnates over the Far East, and the subsequent local breaking of the packet leads to the blocking formation. In a particular case in July 1993, a wave packet involved in blocking formation could be traced back as far upstream as the east coast of North America over the two previous weeks. Acting on the strong thermal contrast in July between the cool sea surface and a warm land mass to the west, the anomalous surface easterlies induced by the blocking ridge can build up a cold surface anticyclone through cold advection, rendering the blocking anomalies distinctly baroclinic. Copyright © 2004 Royal Meteorological Society
The role of the south‐east Asian monsoon and other seasonal features in creating the ‘tape‐recorder’ signal in the Unified Model
Authors: Bannister R. N. , O'neill A. , Gregory A. R. , Nissen K. M.
Published: June 2004

A multi‐year simulation with an atmospheric general‐circulation model (AGCM), the Unified Model, is shown to simulate the main features of seasonal variations in the concentrations of water vapour in the stratosphere—the so‐called tape‐recorder signal. An off‐line transport model, utilizing winds from the AGCM, is used to synthesize the signal from local contributions. During June–July–August, the most significant localized contribution to the moist phase of the signal comes from an air stream emanating from the South‐East Asian monsoon. The moist air does not enter the stratosphere immediately above the monsoon in a localized ‘fountain’. Rather, the air stream moves southward, via the monsoon's upper level anticyclone, into the tropical stratosphere while moving steadily upwards across isentropic surfaces in a field of radiative heating in the tropical tropopause layer (TTL). As a result of this steady ascent during equatorward movement, not all the airstream is freeze dried in the cold cap of low temperatures which exists in the TTL above the monsoon. The water vapour mixing ratios of air entering the stratospheric tape‐recorder are therefore not entirely set by the minimum temperatures near the equator, but in part by physical conditions outside the inner tropical region used to define the tape‐recorder signal. During December–January–February, the flow near the tropopause is simpler. Dry air enters the stratosphere by slow upglide through the localized temperature minimum near the tropical tropopause over the western Pacific. The mixing ratios during the dry phase are set largely by freeze drying in this region. The simple tape‐recorder model, which envisages that mixing ratios are set by the minimum temperature near the tropical tropopause is therefore an oversimplification. Copyright © 2004 Royal Meteorological Society
Observations and simulations of the 8 November 1999 MAP mountain wave case
Authors: Smith S. A.
Published: June 2004

A joint aircraft sortie took place over the Swiss Alps as part of the Mesoscale Alpine Program (MAP) on 8 November 1999. The synoptic situation is documented here and the Met Office Unified Model is shown to be capable of producing accurate simulations of the large‐scale flow over and around the Alps by a comparison of model profiles with data from the many radiosonde ascents available on this day. Upstream flow splitting, a cold pool over the Po valley and lee‐side föhn flow are all present in the simulation, and the upstream Scorer parameter and Froude numbers are predicted accurately. Trapped lee waves and vertically propagating waves are predicted at the correct wavelengths. However, the wave amplitudes are underpredicted. This is particularly true at higher levels, where the limited model resolution means that the inversion at the tropopause and its instabilities are not captured. The problems inherent in interpreting aircraft observations along a single transect which is not oriented along the wave vector are highlighted in this study, and an accurate high‐resolution simulation is essential to understanding the otherwise misleading aircraft data. © Crown copyright, 2004. Royal Meteorological Society
A laboratory study of the influence of ice crystal growth conditions on subsequent charge transfer in thunderstorm electrification
Authors: Saunders C. P. R. , Bax‐Norman H. , Avila E.E. , E. Castellano N.
Published: June 2004

Laboratory studies of a thunderstorm charging mechanism involving rebounding collisions between ice crystals and riming graupel pellets, have shown the importance of the growth conditions of the interacting ice particles on the sign of the charge transferred. The present study shows a new result: if an ice crystal is not in thermal equilibrium with the environment (immediately following the mixing of two clouds at different saturations) the crystal surface may experience an enhanced growth rate that can influence the sign of the charge transfer and promote negative rimer charging. Furthermore, when an ice crystal in ice saturation conditions is introduced to a cloud at water saturation, leading to transient growth and heating, the period of thermal non‐equilibrium is shown to be sufficiently brief that the enhanced negative rimer charging is short lived. These results suggest that the earlier conclusions of Berdeklis and List—that the cloud saturation conditions around a growing ice crystal impart to the crystal surface a property that is carried with it and that influences the sign of subsequent charge transfer—are unfounded. The discrepancy is because in their laboratory simulations of thunderstorm conditions there is adequate time for the growing ice crystal surface to come to equilibrium with its environment. The established concept of the relative diffusional growth rate of the interacting surfaces controlling the sign of charge transfer, such that the faster growing surface charges positively, is consistent with the observations. Copyright © 2004 Royal Meteorological Society
Structure, genesis and scale selection of the tropical quasi‐biweekly mode
Authors: Chatterjee Piyali , Goswami B. N.
Published: June 2004

The quasi‐biweekly mode (QBM) and the 30–60 day mode are two major intraseasonal oscillations (ISOs) in the tropics. The QBM is known to have a major influence in determining the active and break conditions of the Indian monsoon during the northern summer. A westward‐propagating equatorial Rossby wave with quasi‐biweekly period influences the Australian monsoon during the northern winter. Universality between the summer and winter QBM is established through analysis of daily circulation and convection data for 10 years. It is shown that the mean spatial structure of the QBM in circulation and convection resembles that of a gravest meridional mode equatorial Rossby wave with wavelength of about 6000 km and westward phase speed of approximately 4.5 m s−1. However, the maximum zonal wind occurs at around 5°N (5°S) during the northern summer (winter). The wave structure appears to be translated northward (southward) by about 5° during the northern summer (winter). The relationship between outgoing long‐wave radiation and circulation data indicates that the mode is driven unstable by coupling with moist convection. Similarity in temporal and spatial characteristics of the mode during the two seasons leads us to propose that the same mechanism governs the genesis and scale selection of the mode in both the seasons.

An acceptable mechanism for genesis and scale selection of the QBM has been lacking. In the present study, a mechanism for genesis and scale selection of the observed QBM is proposed. A simple 2½‐layer model that includes a steady Ekman boundary layer (BL) formulation incorporating effect of entrainment mixing is constructed for the convectively coupled equatorial waves. Without influence of the background mean flow, moist feedback in the presence of frictional BL convergence drives the gravest meridional mode equatorial Rossby wave unstable with observed wavelength and period but with zonal winds symmetric about the equator. Potential temperature perturbation associated with the Rossby wave is in phase with relative vorticity perturbation at low level. The BL drives moisture convergence in phase with the relative vorticity at the top of the BL. Release of latent heat associated with the BL convergence enhances the potential temperature leading to a positive feedback. The mean flow over the Indian Ocean and western Pacific at low levels is such that the zero ambient absolute vorticity or the ‘dynamic equator’ shifts to around 5°N (5°S) during summer (winter) and results in a shift of the unstable Rossby waves towards the north (south) by about 5°. The resulting structure of the unstable Rossby mode resembles the observed structure of the biweekly mode. It is shown that neither evaporation–wind feedback nor vertical shear of the mean flow is crucial for the existence of the mode. However these processes marginally modify the growth rate and make the structure of the unstable wave more realistic. Copyright © 2004 Royal Meteorological Society
Short‐wave radiative effects of biomass burning aerosol during SAFARI2000
Authors: Osborne Simon R. , Haywood James M. , Francis Peter N. , Dubovik Oleg
Published: June 2004

We present data from two case‐studies during the Southern AFricAn Research Initiative (SAFARI2000) of the radiative effects of a biomass burning plume advecting over the ocean. In situ aircraft measurements were made of the aerosol vertical structure, the aerosol microphysics, and the aerosol optical properties (scattering and absorption coefficients). Remote sensing measurements of the upwelling broadband short‐wave (SW) radiative fluxes (0.3–3.0µm) were made above the plume. Together with modelling of the clear‐air flux using a flexible radiation scheme, we have been able to determine the local mean direct radiative effects of the aerosol column for the two cases. Aerosol optical depths were derived using a number of techniques: the upwelling fluxes, vertical integration of the in situ extinction coefficient, and using downwelling sky radiances. These optical depths are compared and discussed; discrepancies are revealed through instrument sampling problems and horizontal inhomogeneity of the aerosol. Spectrally resolved downwelling SW sky radiances as a function of scattering angle were measured and modelled. The modelling technique illustrates the importance of including unpolluted marine boundary‐layer aerosol as part of the aerosol column. A retrieval algorithm that uses the measured downwelling sky radiances as input has also been utilized. This algorithm derives a columnar aerosol size distribution for comparison against the measured biomass burning and marine boundary‐layer size distributions. The retrieved columnar size distribution is acceptable in representing the atmospheric aerosol in terms of describing the effect on scattered radiances. © Crown copyright, 2004. Royal Meteorological Society
Simulation of the diurnal cycle in a climate model and its evaluation using data from Meteosat 7
Authors: Slingo A. , Hodges K. I. , Robinson G. J.
Published: June 2004

The representation of the diurnal cycle in the Hadley Centre climate model is evaluated using simulations of the infrared radiances observed by Meteosat 7. In both the window and water vapour channels, the standard version of the model with 19 levels produces a good simulation of the geographical distributions of the mean radiances and of the amplitude of the diurnal cycle. Increasing the vertical resolution to 30 levels leads to further improvements in the mean fields. The timing of the maximum and minimum radiances reveals significant model errors, however, which are sensitive to the frequency with which the radiation scheme is called. In most regions, these errors are consistent with well documented errors in the timing of convective precipitation, which peaks before noon in the model, in contrast to the observed peak in the late afternoon or evening. When the radiation scheme is called every model time step (half an hour), as opposed to every three hours in the standard version, the timing of the minimum radiance is improved for convective regions over central Africa, due to the creation of upper‐level layer‐cloud by detrainment from the convection scheme, which persists well after the convection itself has dissipated. However, this produces a decoupling between the timing of the diurnal cycles of precipitation and window channel radiance. The possibility is raised that a similar decoupling may occur in reality and the implications of this for the retrieval of the diurnal cycle of precipitation from infrared radiances are discussed. Copyright © 2004 Royal Meteorological Society
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

The 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

A 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

We 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

An 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

Aerosols 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

A 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

Using 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

High‐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

A 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.
Fechner as a statistician
Authors: Sheynin Oscar
Published: June 2004

The work of Gustav Theodor Fechner (1801–1887) related to probability and statistics and, in particular, to the treatment of observations is described. From a mathematical point of view his arguments were often insufficient, but his work proved to be highly fruitful, and the relevant comments of such scholars as Pearson and von Mises are presented. As the originator of psychophysics, Fechner opened up a new field for quantification. Subsequent workers rejected some of his findings, while at the same time acknowledging their debt to him.
Bayesian model comparison of nonlinear structural equation models with missing continuous and ordinal categorical data
Authors: Lee Sik‐Yum , Song Xin‐Yuan
Published: June 2004

Missing data are very common in behavioural and psychological research. In this paper, we develop a Bayesian approach in the context of a general nonlinear structural equation model with missing continuous and ordinal categorical data. In the development, the missing data are treated as latent quantities, and provision for the incompleteness of the data is made by a hybrid algorithm that combines the Gibbs sampler and the Metropolis‐Hastings algorithm. We show by means of a simulation study that the Bayesian estimates are accurate. A Bayesian model comparison procedure based on the Bayes factor and path sampling is proposed. The required observations from the posterior distribution for computing the Bayes factor are simulated by the hybrid algorithm in Bayesian estimation. Our simulation results indicate that the correct model is selected more frequently when the incomplete records are used in the analysis than when they are ignored. The methodology is further illustrated with a real data set from a study concerned with an AIDS preventative intervention for Filipina sex workers.