bluuebunny/crossref_metadata_2025_split huggingface dataset:
Comment on ‘The local isotropy hypothesis and the turbulent kinetic energy dissipation rate in the atmospheric surface layer’ by M. Chamecki and N. L. Dias (October B, 2004, 130, 2733–2752)
Authors: Smalley R. J. , Antonia R. A. 
Published: March 2006

AbstractThe velocity–velocity‐increment correlation is shown to be an incorrect method for determining the interaction between the energy‐containing and inertial‐range scales of a turbulent flow. As a consequence, the correlation cannot be used as a means for testing the local isotropy hypothesis. Copyright © 2006 Royal Meteorological Society
Reply to a comment by R. J. Smalley and R. A. Antonia on ‘The local isotropy hypothesis and the turbulent kinetic energy dissipation rate in the atmospheric surface layer’ (October B, 2004, 130, 2733–2752)
Authors: Chamecki M. , Dias N. L. 
Published: March 2006

AbstractIn response to Smalley and Antonia's comment, we agree that our statement that closer‐to‐zero velocity–velocity‐increment correlation for larger turbulence intensity values cannot be taken as a measure of homogeneity. We also explain that, although not aware that the velocity–velocity‐increment correlation cannot be zero at finite r1, we concentrated most of our analysis on its tendency towards zero with decreasing r1, since this limit is well known for homogeneous turbulence. Copyright © 2006 Royal Meteorological Society
Life cycles of North Atlantic teleconnections under strong and weak polar vortex conditions
Authors: Walter Katrin , Graf Hans‐F 
Published: March 2006

AbstractThis paper investigates the role of the strength of the polar stratospheric winter vortex in the dynamics of the life cycles of North Atlantic teleconnections. A new set of teleconnection patterns was produced from low‐pass‐filtered daily 300 hPa height data of NCEP (National Centers for Environmental Prediction) reanalysis data 1958–1998. All teleconnections are meridional dipoles, which to a certain degree resemble the North Atlantic Oscillation based on surface pressure data. There are two distinct teleconnections (one over the eastern and one over the western North Atlantic) during episodes of weak polar vortex, and only one, over the central North Atlantic, during strong polar vortex episodes. The teleconnections have periods of about two weeks. Stream function tendency analysis of the life cycles shows that the relatively simple resulting teleconnections evolve from very complex structures. During the growth phase of the teleconnection indices there are strong and systematic differences between the two polar vortex regimes. While in the weak vortex regime the anomaly growth is mainly driven by transient eddy vorticity fluxes from the low‐frequency domain, in the strong vortex regime there is also low‐frequency advection of relative vorticity resulting from the interaction of low‐frequency eddies with stationary eddies. Copyright © 2006 Royal Meteorological Society
Simulation of shallow cumuli and their transition to deep convective clouds by cloud‐resolving models with different third‐order turbulence closures
Authors: Cheng Anning , Xu Kuan‐Man 
Published: March 2006

AbstractThe abilities of a cloud‐resolving model (CRM) with double‐Gaussian based and quasi‐Gaussian based third‐order closures (TOCs) to simulate shallow cumuli and their transition to deep convective clouds are compared in this study. The quasi‐Gaussian based TOC is fully prognostic (FP), while the double‐Gaussian based TOC is intermediately prognostic (IP). The latter only predicts three important third‐order moments while the former predicts all the third‐order moments. A shallow cumulus case is simulated by single‐column versions of the FP and IP TOC models and a large‐eddy simulation (LES). The IP TOC improves the simulation of shallow cumulus greatly over the FP TOC by producing more realistic cloud structures, when both are compared to LES. Large differences of the second‐ and third‐order moments between the FP and IP TOC simulations appear in the cloud layer, because the cloud top height is underestimated by the FP TOC simulation. Sensitivity experiments and analysis of probability density functions (pdfs) used in the TOCs show that both the turbulence‐scale condensation and higher‐order moments are important to realistic simulations of the boundary‐layer shallow cumuli.A shallow to deep convective cloud transition case is also simulated by the two‐dimensional (2‐D) version of the CRM with FP and IP TOCs. Both simulations can capture the transition from the shallow cumuli to deep convective clouds. The IP simulations produce more and deeper shallow cumuli than the FP simulations, but the FP simulations produce larger and wider convective clouds than the IP simulations. The temporal evolutions of cloud and precipitation are closely related to the turbulent transport, the cold pool and the cloud‐scale circulation. The large amount of turbulent mixing associated with the shallow cumuli slows down the increase of the convective available potential energy and inhibits the early transition to deep convective clouds in the IP simulation. When the deep convective clouds fully develop and the precipitation is produced, the cold pools produced by the evaporation of the precipitation are not favourable to the formation of shallow cumuli. As a whole, the IP simulations are able to more realistically capture the transition processes than the FP simulations, when both are compared to an LES‐resolution 3‐D simulation of the same case. Copyright © 2006 Royal Meteorological Society
A low‐ozone episode during the European heatwave of August 2003
Authors: Orsolini Yvan J. , Nikulin Grigory 
Published: March 2006

AbstractAn intense low‐ozone episode (LOE) was observed over Scandinavia and the North Sea in the middle of August 2003. The LOE occurred under exceptional meteorological conditions, associated with a severe heatwave over Europe. The column ozone minimum for summer (June, July and August) 2003 was reached during the event.Using meteorological analyses, satellite ozone observations from the Total Ozone Mapping Spectrometer and the Michelson Interferometer for Passive Atmospheric Sounding aboard the Environment Satellite, we demonstrate that the LOE results from the conjunction of a deep tropospheric blocking over Europe, and a displaced Arctic pool of low‐ozone air in the stratosphere, above the anticyclone. The anticyclonic anomaly is part of a Rossby wave train that is apparent throughout the troposphere, and whose influence is felt up to 50 hPa. In the mid‐stratosphere (e.g. 30 hPa) long‐period westward propagating planetary waves dominate, with a ridge extending over northern Europe in mid‐August.We band‐pass filtered the geopotential field to isolate sub‐monthly fluctuations, and calculated three‐dimensional wave activity fluxes for quasi‐stationary, quasi‐geostrophic disturbances embedded in a zonally asymmetric basic state. Results clearly indicate that upward wave fluxes in the lower stratosphere originate from the Atlantic sector, upstream of the maturing blocking. Copyright © 2006 Royal Meteorological Society
Impact study of the 2003 North Atlantic THORPEX Regional Campaign
Authors: Fourrié Nadia , Marchal David , Rabier Florence , Chapnik Bernard , Desroziers Gerald 
Published: March 2006

AbstractAn experiment took place during autumn 2003 with the aim of testing the feasibility of an operational targeting of observations over the North Atlantic Ocean in the context of the international programme THORPEX. The purpose of this paper is to evaluate the impact of these additional observations in the French operational model ARPEGE during the last three weeks of the campaign. Results are shown for large regions over and around the North Atlantic Ocean and for specific verification areas. Over Europe, the addition of observations is slightly beneficial for the forecast, mostly in the low troposphere over wide areas and above 100 hPa. However, the impact of extra data is more significant but also more mixed for the dedicated verification areas: they are case, forecast‐range and level dependent. In addition, the information content is studied with the Degrees of Freedom for Signal (DFS) for the evaluation of the observation impact on the analysis of one case of December 2003. Firstly, the variations of the DFS have been illustrated in a simplified data assimilation system. It has been found for that case that satellite data have the most important global contribution to the overall analysis, especially the humidity sensitive infrared radiances. For the conventional data, the wind measurements of the aircraft and from the geostationary satellites are the most informative. For the targeted area, the data from aircraft and the dropsondes have the largest DFS. It has been noted that the DFS of the dropsondes located in the sensitivity maximum is larger than the other one even if there is no link between the DFS and the forecast. However, the impact of the dropsondes grows with respect to the forecast range and leads to an improvement of the forecast for this case. Copyright © 2006 Royal Meteorological Society
Laboratory investigation of positive streamer discharges from simulated ice hydrometeors
Authors: Petersen Danyal , Bailey Matthew , Hallett John , Beasley William H. 
Published: March 2006

AbstractPositive streamer discharges have been observed from ice crystals grown from the vapour under controlled temperature and air pressure corresponding to the standard atmosphere and also constant air pressure of 850 hPa. Crystals of size comparable to larger precipitation crystals were grown in a vapour diffusion chamber at various temperatures and pressures, and were subject to electric fields using an in situ electrode assembly. Results show that individual positive streamer discharges can occur at temperatures from near freezing down to at least −38°C when subject to electric fields on the order of 500kV m−1, in contrast to previous reports of continuous positive streamer discharges occurring only at temperatures warmer than −18°C for pure ice crystals. These results suggest that positive streamer discharges can occur on frozen precipitation particles at high altitudes in thunderclouds, given a sufficiently strong electric field. Such discharges may be a necessary element of the lightning‐initiation process. Copyright © 2006 Royal Meteorological Society
Vertically integrated sensible‐heat budgets for stable nocturnal boundary layers
Authors: Nakamura Reina , Mahrt L. 
Published: March 2006

AbstractThe stable nocturnal boundary layer is commonly viewed or modelled as a balance between the temperature tendency (cooling) and vertical heat‐flux divergence. Sometimes the radiative‐flux divergence is also included. This perspective has dictated the design of field experiments for investigating stable nocturnal boundary layers.Tower‐based micrometeorological data from three field campaigns are analysed to evaluate the vertically integrated sensible‐heat budget for nocturnal stable conditions. Our analysis indicates frequent occurrence of large imbalance between the temperature tendency and vertical heat‐flux divergence terms. The values of the radiative‐flux divergence are generally too small and sometimes of the wrong sign to explain the residual. An analysis of random flux errors and uncertainties in the tendency term indicate that such errors cannot explain large imbalances, suggesting the importance of advection of temperature or possibly the divergence of mesoscale fluxes. The implied role of advection is consistent with circumstantial evidence. Even weak surface heterogeneity can create significant horizontal gradients in stable boundary layers. However, it is shown that existing field data and observational strategy do not allow adequate evaluation of advection and mesoscale flux divergence terms. Copyright © 2006 Royal Meteorological Society
Seasonal forecasting of tropical storm frequency using a multi‐model ensemble
Authors: Vitart Fr'ed'eric 
Published: March 2006

AbstractThe skill of seven coupled ocean–atmosphere models to predict the frequency of tropical storms from 1987 to 2001 has been assessed using a procedure for tracking model tropical storms. The tropical storm tracker takes account of the difference of atmospheric horizontal resolution between the different models. Results indicate that the models display some skill in predicting the interannual variability of tropical storms over the Atlantic, the eastern North Pacific, the western North Pacific, the Australian basin and the South Pacific. A simple multi‐model forecast has been built by adding all the seven ensemble forecasts together after calibration. The skill of the simple multi‐model system is overall better than the skill of any individual model. Over a specific basin, combining several models leads to better forecasts than the best individual model. This indicates that the multi‐model approach could benefit the dynamical seasonal forecast of tropical storms.This conclusion is also valid for a longer time period (1959–2001). However, the individual models and the simple multi‐model display less skill in predicting the interannual variability of tropical storms in the earlier decades. Copyright © 2006 Royal Meteorological Society
Impact of flow‐dependent analysis‐error covariance norms on extratropical singular vectors
Authors: Buehner Mark , Zadra Ayrton 
Published: March 2006

AbstractFlow‐dependent analysis‐error covariances are estimated from the 128 member analysis ensembles of a pre‐operational implementation of the ensemble Kalman filter. Singular vectors are then computed with the initial‐time norm defined using the inverse of these error covariances and the final‐time norm defined by the total energy over North America. An optimization time interval of either 24 or 48 hours is used and the horizontal resolution of the singular vectors is 3°. Provided that the analysis‐error covariance estimates are accurate, these singular vectors should optimally explain the forecast error at the final time. To reduce the sampling error due to the small ensemble size, the analysis‐error covariances are spatially localized. The impact of using the analysis‐error covariance norm, with or without spatial localization, on the 20 leading singular vectors is measured relative to using the total‐energy norm. In addition, the singular vectors are also compared with sets of 20 randomly selected members of the analysis ensembles.The results are generally consistent with those of previous studies with the maximum impact from the initial‐time norm seen at the initial time. The growth is significantly reduced by using the analysis‐error covariance norm instead of total energy and the smallest growth is obtained when no covariance localization is applied. The total‐energy singular vectors are slightly more effective at explaining forecast error for most lead times than the analysis‐error covariance singular vectors. This may point to errors in the covariance estimates, the importance of model error in affecting forecast‐error evolution, or shortcomings with the tangent linear model used to compute the singular vectors. The use of a random selection of members from the analysis ensembles shows an even larger impact. In contrast with the singular vectors that continuously grow over the 72 h period examined, the total energy of the ensemble members initially decays during tangent linear model integrations. Also, the amount of forecast error explained by the ensemble members is significantly less than for all types of singular vectors. This suggests that, with respect to predicting forecast uncertainty over North America, the current approach of randomly selecting analysis ensemble members to initialize the ensemble prediction system may be improved. Copyright © 2006 Crown copyright
Subseasonal‐to‐interdecadal variability of the Australian monsoon over North Queensland
Authors: Robertson Andrew W. , Kirshner Sergey , Smyth Padhraic , Charles Stephen P. , Bates Bryson C. 
Published: March 2006

AbstractDaily rainfall occurrence and amount at 11 stations over North Queensland are examined for summers 1958–1998, using a Hidden Markov Model (HMM). Daily rainfall variability is described in terms of the occurrence of five discrete ‘weather states’, identified by the HMM. Three states are characterized respectively by very wet, moderately wet, and dry conditions at most stations; two states have enhanced rainfall along the coast and dry conditions inland. Each HMM rainfall state is associated with a distinct atmospheric circulation regime. The two wet states are accompanied by monsoonal circulation patterns with large‐scale ascent, low‐level inflow from the north‐west, and a phase reversal with height; the dry state is characterized by circulation anomalies of the opposite sense. Two of the states show significant associations with midlatitude synoptic waves.Variability of the monsoon on time‐scales from subseasonal to interdecadal is interpreted in terms of changes in the frequency of occurrence of the five HMM rainfall states. Large subseasonal variability is identified in terms of active and break phases, and a highly variable monsoon onset date. The occurrence of the very wet and dry states is somewhat modulated by the Madden–Julian oscillation. On interannual time‐scales, there are clear relationships with the El Niño–Southern Oscillation and Indian Ocean sea surface temperatures (SSTs). Interdecadal monsoonal variability is characterized by stronger monsoons during the 1970s, and weaker monsoons plus an increased prevalence of drier states in the later part of the record.Stochastic simulations of daily rainfall occurrence and amount at the 11 stations are generated by introducing predictors based on large‐scale precipitation from (a) reanalysis data, (b) an atmospheric general circulation model (GCM) run with observed SST forcing and (c) antecedent June–August Pacific SST anomalies. The reanalysis large‐scale precipitation yields relatively accurate station‐level simulations of the interannual variability of daily rainfall amount and occurrence, with rainfall intensity less well simulated. At some stations, interannual variations in 10‐day dry‐spell frequency are also simulated reasonably well. The interannual quality of the simulations is markedly degraded when the GCM simulations are used as inputs, while antecedent Pacific SST inputs yield an anomaly correlation skill comparable to that of the GCM. Copyright © 2006 Royal Meteorological Society
Sound Flanking Transmission: Assessment by a Slit Method
Authors: Martína M.A. , Tarrero A.I. , Aparicio A. , González J. , Machimbarrena M. 
Published: March 2006

The aim of this study is to understand the effect of flanking transmissions on room sound transmission. For this purpose, three tests have been carried out in-situ in three rooms with similar layout. The assessment method consisted of cutting one or two slits on the source room walls and measuring before and after cutting. Measurements of air-borne sound insulation, impact sound isolation (with impact on the source room lateral walls) and acceleration measured on the receiving room lateral walls, were made. The slit prevent transmission of wall vibration, originated by sound excitation, and thus allows us to quantify the associated flanking transmission. It is also shown that, if the slit is sealed with silicone, there is almost no change in the results, and it can be concluded that it is the difference in impedance, which prevents transmission.
Bone remodelling around a cemented polyethylene cup
Authors: Shetty N. R. , Hamer A. J. , Kerry R. M. , Stockley I. , Eastell R. , Wilkinson J. M. 
Published: March 2006

The aims of this study were to examine the repeatability of measurements of bone mineral density (BMD) around a cemented polyethylene Charnley acetabular component using dual-energy x-ray absorptiometry and to determine the longitudinal pattern of change in BMD during the first 24 months after surgery.The precision of measurements of BMD in 19 subjects ranged from 7.7% to 10.8% between regions, using a four-region-of-interest model. A longitudinal study of 27 patients demonstrated a transient decrease in net pelvic BMD during the first 12 months, which recovered to baseline at 24 months. The BMD in the region medial to the dome of the component reduced by between 7% and 10% during the first three months, but recovered to approximately baseline values by two years.Changes in BMD in the pelvis around cemented acetabular components may be measured using dual-energy x-ray absorptiometry. Bone loss after insertion of a cemented Charnley acetabular component is small, transient and occurs mainly at the medial wall of the acetabulum. After two years, bone mass returns to baseline values, with a pattern suggesting a uniform transmission of load to the acetabulum.
A Vapor–Liquid–Solid Mechanism for Growing 3C‐SiC Single‐Domain Layers on 6H‐SiC(0001)
Authors: Soueidan M. , Ferro G. 
Published: March 2006

AbstractGrowing device‐quality 3C‐SiC monocrystalline material is still an issue despite two decades of work dedicated to the subject. Using silicon as the substrate generates too many defects in the layers, owing to lattice mismatch, while it is very difficult to control the initial nucleation on an α‐SiC substrate so that 60° rotated domains are randomly formed. Herein, the elaboration of mono‐orientated 3C‐SiC layers on a 6H‐SiC(0001) on‐axis, Si face substrate using a vapor–liquid–solid mechanism is reported. This non‐conventional approach for growing monocrystalline layers involves feeding a Ge–Si melt by a propane flux at a temperature ranging from 1250 to 1550 °C. We show that, by using this technique, the 3C‐SiC material is almost always obtained on an hexagonal substrate, even if the crystal seed is oriented 8° off‐axis. Using on‐axis 6H‐SiC seeds and optimal growth conditions results in the reproducible deposition of single‐domain 3C‐SiC layers. A mechanism is proposed to clarify some aspects of this process.
Heterogeneous–homogeneous interactions in catalytic microchannel reactors
Authors: Chattopadhyay S. , Veser G. 
Published: March 2006

AbstractMicromachining of chemical reactors enables the manufacture of microchannel reactors with unsually large surface‐to‐volume ratios. This can strongly affect the coupling between heterogeneous (wall) reactions and homogeneous (gas‐phase) reactions, ultimately leading to a complete quenching of homogeneous reactions. Using a 2D boundary‐layer model coupled with detailed reaction kinetics for surface and gas‐phase reactions, we investigate the ignition behavior of hydrogen/air mixtures in a Pt‐coated microchannel. The influence of temperature, pressure, reactor diameter, and fuel‐to‐air ratio is studied. We find that a purely kinetic radical scavenging by the catalytic surface can indeed result in a complete suppression of gas‐phase reactions. However, the attainability of “intrinsic safety” in microchannel reactors is strongly dependent on a fine interplay between homogeneous and heterogeneous reaction pathways in the individual reaction system. In particular, the strong dependency of homogeneous reactions on pressure leads to a breakdown of intrinsic reactor safety at sufficiently high reactor pressure. A generalized equation for the boundary of safe reactor operation is derived for the current reaction system. © 2006 American Institute of Chemical Engineers AIChE J, 2006