bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ozone signatures of climate patterns over the Euro‐Atlantic sector in the spring
Authors: Orsolini Y. J. , Doblas‐Reyes F. J. 
Published: December 2003

AbstractThe influence of low‐frequency tropospheric dynamics upon column ozone interannual variability is estimated in the spring season over the Euro‐Atlantic sector. This dynamical variability of tropospheric origin is examined in terms of leading climate patterns, derived from an empirical orthogonal function analysis of the National Center for Environmental Prediction 500 mb geopotential height analyses. In order to fingerprint the spatial and temporal ozone signatures of these patterns, the Total Ozone Mapping Spectrometer satellite observations of column ozone during the last two decades are used. The geographical ozone signatures of these climate patterns are extracted by linear regression and their time evolution reconstructed.Geopotential anomalies associated with four leading patterns of variability (the North Atlantic Oscillation (NAO), the Scandinavian pattern, the east Atlantic pattern and the European blocking pattern) induce column ozone anomalies in the range of 5–15 Dobson Units per standard deviation of the pattern index. The impact of these combined Euro‐Atlantic climate patterns upon the regional ozone trends and interannual variability is also estimated. In order to reconstruct the regional ozone trend and variability, it proved important to incorporate several patterns, in addition to the dominant NAO. A hitherto little‐known lifting of the Arctic tropopause by the polar night jet is also shown to imprint upon the ozone signatures of some patterns. Copyright © 2003 Royal Meteorological Society
Topographically induced waves within the stable boundary layer
Authors: Brown A. R. , Athanassiadou M. , Wood N. 
Published: December 2003

AbstractResults are presented from numerical simulations of stable boundary‐layer flow over low ridges. Internal gravity waves are seen within the boundary layer when a Froude number based on the wavelength of the ridges and the magnitude of the cross‐ridge velocity component becomes sufficiently small. It is noted that this can always be achieved, even for short‐wavelength ridges, if the ridge axis is aligned so as to be closely parallel to the wind direction. The surface pressure forces are found to be highly sensitive to the presence of gravity waves, and are also affected by the presence of critical levels within the boundary layer. © Crown copyright, 2003. Royal Meteorological Society
On entrainment rates in nocturnal marine stratocumulus
Authors: Stevens Bjorn , Lenschow Donald H. , Faloona Ian , Moeng C.‐H. , Lilly D. K. , Blomquist B. , Vali G. , Bandy A. , Campos T. , Gerber H. , Haimov S. , Morley B. , Thornton D. 
Published: December 2003

AbstractThe first research flight of the second Dynamics and Chemistry of Marine Stratocumulus field study is analysed. This case attracted our interest because it showed a consistently deepening cloud layer despite macroscopic conditions which previous work has suggested should be an indication of cloud thinning or breakup. Detailed analysis of the flight data shows that despite the cloud‐top entrainment instability parameter being well beyond its critical value the cloud did indeed deepen through the night. Our best estimates show little indication of rapid changes in cloud top, while cloud base was found to be lowering at a rate of several metres per hour. This evolution, and independent measurements of trace‐gas budgets, imply an entrainment rate of 0.0039±0.001 m s−1. This is compared to entrainment rates from recently proposed parametrizations (forced by the observed forcing of the cloud layer) which range from 0.002 to 0.008 m s−1. Two of the parametrizations we test reproduce the observed entrainment rates within their stated uncertainties, although subsequent tests show that one of these rules exhibits sensitivities to changes in the environmental conditions which are difficult to justify. Large‐eddy simulation of the observed case was able to reproduce the macroscopic evolution of the layer, but in doing so had some difficulty in maintaining the observed mixing‐line structure at cloud top. A comparison of the observed and simulated turbulent structure show these to be broadly consistent, although there is an indication that the structure of the simulated turbulence differs from the observations near the flow boundaries, particularly at cloud top. Copyright © 2003 Royal Meteorological Society
Coupled chemistry–climate model simulations for the period 1980 to 2020: Ozone depletion and the start of ozone recovery
Authors: Austin John , Butchart Neal 
Published: December 2003

AbstractTwo simulations of a coupled chemistry–climate model are completed for the period 1980 to 2020, covering the recent past during which extensive satellite ozone and temperature data exist, and covering the near future when ozone levels are expected to begin to recover. In the first simulation, Rayleigh friction is used to decelerate the polar night jet. In the second simulation, a parametrized spectral gravity‐wave forcing scheme is included. This has the effect of considerably reducing the model temperature bias in the polar regions and weakening the polar night jet. In the simulations the concentrations of chlorine, bromine and the well‐mixed greenhouse gas concentrations are specified in accordance with past observations and future projected values. The calculated trends in temperature and ozone in the two runs are similar, indicating that model internal variability does not have a significant impact and suggesting that the trends arise largely from changes in external parameters. Typically, after about the year 2000, the trend in the modelled annually averaged ozone changed from a decrease to a small increase. The change was found to be statistically significant in the upper stratosphere and in the lower stratosphere over Antarctica, which are the regions most affected by halogen chemistry. Globally averaged temperature results suggest that the best place to look for future atmospheric change is in the upper stratosphere. Decadally averaged statistics are used to estimate the timing of the start of recovery of total ozone. The simulations indicate no significant further ozone loss from the current atmosphere with minima typically occurring in the years from 2000 to 2005, except in the spring Arctic where ozone values continued to decrease slowly until the end of the integrations. One major problem with the detection of the start of ozone recovery, is that the concentrations of halogens are expected to reduce only slowly from their peak value. Hence, no substantial recovery is simulated before the year 2020. The difficulty in detecting the start of ozone recovery suggests the need to continue the model simulations until the second half of this century which would also help to establish the timing of complete ozone recovery. © Crown copyright, 2003. Royal Meteorological Society
A cloud detection algorithm for high‐spectral‐resolution infrared sounders
Authors: McNally A. P. , Watts P. D. 
Published: December 2003

AbstractA method for detecting cloud contamination in radiances measured by high‐spectral‐resolution infrared sounders is presented. It seeks to identify clear channels within a measured spectrum, rather than the locations of completely clear spectra. Applied to simulated cloudy spectra, the scheme is able to detect clear channels with residual cloud contamination better than (i.e. less than) 0.2 K in many channels, and is thus considered sufficiently stringent for numerical weather‐prediction applications. The scheme has been applied to spectra measured by the Advanced InfraRed Sounder and, whilst a quantitative validation is more difficult with real data (without true clear radiances), it is found to perform well compared with coincident imagery. Copyright © 2003 Royal Meteorological Society
Summertime low‐ozone episodes at northern high latitudes
Authors: Orsolini Y. J. , Eskes H. , Hansen G. , Hoppe U.‐P. , Kylling A. , Kyrö E. , Notholt J. , Der A R. Van , Gathen P. Von Der 
Published: December 2003

AbstractA pool of low‐ozone air resides in the Arctic stratosphere in summer. Its formation and maintenance arise from a combination of chemical ozone‐destruction and transport processes. The summertime ozone destruction is induced by gas‐phase chemistry dominated by nitrogen and hydrogen catalytic cycles, which are efficient due to long summertime insolation at high latitudes. It is shown that, during events referred to as low‐ozone episodes (LOEs), column ozone can locally decrease to values comparable with the seasonal minimum. A combination is used of (i) assimilation of satellite ozone observations from the Global Ozone Monitoring Experiment, (ii) chemical trajectory modelling, and (iii) the gathering of new lidar andin situozone observations in the European Arctic in summer 2000. Hence it is shown that such LOEs involve the displacement of the pool of low‐ozone air in the middle stratosphere, which is more dynamic than previously thought and undergoes pronounced meridional excursions, in particular towards northern Europe. The thinner the ozone layer, the more ultraviolet (UV) radiation reaches the ground, where it can impact on human health and ecosystems. Erythemal UV dose enhancements of the order of 10–15% were observed in northern Norway during the LOEs in summer 2000. Copyright © 2003 Royal Meteorological Society
On the impacts of the Indian summer monsoon on ENSO in a coupled GCM
Authors: Wu Renguang , Kirtman Ben P. 
Published: December 2003

AbstractThis study explores the impacts of the Indian summer monsoon (ISM) on the El Niño–Southern Oscillation (ENSO) evolution by utilizing two coupled general‐circulation model simulations. The first simulation uses the Center for Ocean–Land–Atmosphere Studies anomaly‐coupled model and the second simulation employs a new coupling strategy, interactive ensembles, that is designed to increase the signal‐to‐noise ratio of boundary forcing. The effects of monsoon variability related and unrelated to ENSO are separated through composites in terms of both sea surface temperature (SST) over the Niño‐3.4 area (170°W–120°W,5°S–5°N) and Indian summer monsoon rainfall (IMR) anomalies. It is found that ENSO‐related monsoon variability has significant impacts on warm events. In the interactive‐ensemble simulation, a weak (strong) monsoon enhances (weakens) an ongoing warm event. The monsoon impacts are manifested in the surface zonal wind‐stress anomalies in the western central equatorial Pacific. In the anomaly‐coupled simulation, the monsoon–ENSO relationship is difficult to detect. The ongoing cold events are only weakly affected by monsoon variability. Monsoon variability that is unrelated to ENSO also induces noticeable SST anomalies in the equatorial central Pacific in the following winter. In the interactive‐ensemble model, a weak (strong) monsoon induces noticeable warm (cold) SST anomalies.The long‐term change of the ISM–ENSO relationship is also analysed. Fluctuations of the IMR–Niño‐3.4 SST correlation are larger in the anomaly‐coupled model than in the interactive‐ensemble model. No apparent relation is found between the long‐term change of the correlation and that of the monsoon and ENSO anomalies or standard deviations. In the interactive‐ensemble simulation, the IMR and concurrent El Niño‐3.4 SST standard deviations show in‐phase long‐term changes. In the anomaly‐coupled simulation, the long‐term changes of the IMR and summer Niño‐3.4 SST standard deviations have an out‐of‐phase relation. Copyright © 2003 Royal Meteorological Society
Evaluation of moisture in the Hadley Centre climate model using simulations of HIRS water‐vapour channel radiances
Authors: Allan Richard P. , Ringer M. A. , Slingo A. 
Published: December 2003

AbstractIt is important to establish that climate models can accurately simulate the observed present‐day fluctuations of water vapour. In particular, water‐vapour and cloud‐radiative feedbacks are intrinsically linked to processes governing relative‐humidity distribution and variability. To explore these issues, clear‐sky radiances, sensitive to upper‐tropospheric relative humidity, are simulated within the Hadley Centre atmospheric climate model, version HadAM3, allowing direct comparison with High Resolution Infrared Sounder (HIRS) observations. The model is forced by observed sea surface temperatures and sea‐ice fields over the period 1979–98. Evaluation of the simulated distribution and variability of water vapour is undertaken utilizing the HIRS 6.7 μm brightness temperature (T6.7) and satellite measurements of column‐integrated water vapour and clear‐sky outgoing long‐wave radiation (OLR). Modifications are made to the clear‐sky OLR and T6.7 HadAM3 diagnostics to reduce sampling inconsistencies with the observed products. Simulated T6.7 over subtropical dry zones are higher than T6.7 from observations, particularly in the southern hemisphere, and is symptomatic of an overactive circulation. The observed spatial signature of the T6.7 interannual variability is dominated by El Niño and is captured well by HadAM3. Interannual variability of the tropical ocean mean T6.7 is consistent between HadAM3 and the HIRS observations, suggesting that the small simulated decadal changes in relative humidity are realistic. © Crown copyright, 2003. Royal Meteorological Society
The effect of surface lobes on heat transfer from an ice particle
Authors: Aguirre Varela Guillermo G. , Castellano Nesvit E. , Pereyra Rodolfo G. , Avila Eldo E. 
Published: December 2003

AbstractThe convection heat‐transfer coefficient for circular cylinders, exposed to an air stream perpendicular to their axis, is dependent on the Reynolds number, Re. There is experimental evidence showing that the heat‐transfer coefficient for hail or graupel growing by accretion of supercooled water droplets is greater than that corresponding to an equivalent smooth surface. Work carried out so far indicates that surface roughness could influence this coefficient. This work presents an experimental study of the influence of lobes on the heat‐transfer process to the surroundings from metallic cylinder surfaces. The dependence of the heat‐transfer coefficient on Re was studied for $2000 < Re < 20\ 000$.Results show that the presence of lobes and lumps on a smooth surface could, in some cases, increase the heat transfer towards the surroundings by ventilation. However, results also show that this is not likely to be the effect responsible for increasing the ventilation coefficient for graupel compared with smooth surfaces. Copyright © 2003 Royal Meteorological Society
Can knowledge of the state of the stratosphere be used to improve statistical forecasts of the troposphere?
Authors: Charlton A. J. , O'Neill A. , Stephenson D. B. , Lahoz W. A. , Baldwin M. P. 
Published: December 2003

AbstractRecent analysis of the Arctic Oscillation (AO) in the stratosphere and troposphere has suggested that predictability of the state of the tropospheric AO may be obtained from the state of the stratospheric AO. However, much of this research has been of a purely qualitative nature. We present a more thorough statistical analysis of a long AO amplitude dataset which seeks to establish the magnitude of such a link.A relationship between the AO in the lower stratosphere and on the 1000 hPa surface on a 10–45 day time‐scale is revealed. The relationship accounts for ∼5% of the variance of the 1000 hPa time series at its peak value and is significant at the 5% level. Over a similar time‐scale the 1000 hPa time series accounts for ≤1% of itself and is not significant at the 5% level. Further investigation of the relationship reveals that it is only present during the winter season and in particular during February and March. It is also demonstrated that using stratospheric AO amplitude data as a predictor in a simple statistical model results in a gain of skill of ∼5% over a troposphere‐only statistical model. This gain in skill is not repeated if an unrelated time series is included as a predictor in the model. Copyright © 2003 Royal Meteorological Society
The effect of baroclinicity on the equilibrium depth of neutral and stable planetary boundary layers
Authors: Zilitinkevich Sergej S. , Esau Igor N. 
Published: December 2003

AbstractEarlier studies of the depths of the geophysical planetary boundary layers (PBLs) basically focused on the effects of the earth's rotation and density stratification. One more inherent feature of geophysical flows, namely their baroclinicity, has not been considered in that context. The present paper makes up for this deficiency. Diagnostic equations for the depths of the equilibrium, baroclinic, neutral or stable PBLs are derived and verified against data from large‐eddy simulations (LES). These latter represents the most convenient empirical‐validation tool, which allows considering separately different types of PBL: barotropic and baroclinic; truly neutral and conventionally neutral; nocturnal stable and long‐lived stable. The LES are performed using a new code specifically designed for modelling the neutral and stable PBL. Results from the comparison show an excellent correspondence between the proposed equations and LES data. Copyright © 2003 Royal Meteorological Society
Prädiktive Regelung mit Neuronalen Netzen (Predictive Control with Neural Networks)
Authors: Bollig A. 
Published: December 2003

Abstract
Dieser Beitrag beschreibt den theoretischen Hintergrund eines prädiktiven Regelungskonzepts, welches für die Regelung der Einschweißtiefe beim Laserstrahlschweißen entwickelt wurde. Durch die Regelung wird die eingebrachte Laserleistung unter Berücksichtigung der Vorschubgeschwindigkeit optimiert. Zur Modellierung des nichtlinearen Schweißprozesses wird ein Künstliches Neuronales Netz (KNN) genutzt. Der GPC-Algorithmus wird mit einem linearen Modell verwendet, welches in jedem Abtastschritt durch Linearisierung des KNN gewonnen wird. Eine Erweiterungsmöglichkeit des Trainings um lokale Modelleigenschaften wird vorgestellt.
Absatzerkennung bei autonomen mobilen Robotern (Step Detection for Autonomous Mobile Robots)
Authors: Bechtel Peter , Schatz Andreas , Dieterle Lars , Adamy Jürgen 
Published: December 2003

Abstract
In dieser Arbeit wird ein Absatzerkennungssystem für mobile Roboter vorgestellt, das die Gefahr des Absturzes an Absätzen ausschließt. Ausgehend von den allgemeinen Anforderungen wurde ein Sensorsystem, das auf einer Kombination von zwei Infrarotsensortypen basiert, und ein Fahralgorithmus zur Gefahrenvermeidung entwickelt. Die Methode ist weitgehend unabhängig vom Typ des radgetriebenen Roboters. Das System funktioniert ohne Vorwissen über das Aussehen der Absätze.
Vergleich von Modelica und Matlab anhand der Modellbildung eines Dieselmotors (Comparison of Modelica and Matlab by means of the Model of a Diesel Engine)
Authors: Richert Felix , Rückert Joachim , Schloßer Axel 
Published: December 2003

Abstract
Dieser Beitrag befasst sich mit der objektorientierten Modellbildung und Simulation eines Dieselmotors unter Modelica/Dymola, dem Vergleich mit Matlab/Simulink sowie den jeweiligen programmspezifischen Besonderheiten bei der Handhabung. Die objektorientierte Modellierungssprache Modelica bietet gegenüber der meist üblichen, signalbasierten Modellierung einen vielversprechenden Ansatz, bei dem das Simulationsprogramm die notwendigen Gleichungsmanipulationen und Strukturierung der Signale eines Modells soweit wie möglich vornimmt. Um zu untersuchen, ob dieser Anspruch auch bei komplexen Modellen erfüllt wird, ist ein in Matlab/Simulink vorhandenes Modell eines Dieselmotors nach Modelica/Dymola portiert worden.
Optimale Regelverfahren zur automatischen Bahnführung von Binnenschiffen (Automatic Track-Keeping on Waterways Using Optimal Control)
Authors: Wahl Anja , Gilles Ernst-Dieter 
Published: December 2003

Abstract
Die automatische Bahnführung von Binnenschiffen ist Inhalt des vorliegenden Beitrags. Zur Lösung der Bahnregelaufgabe werden drei unterschiedliche Regelstrategien: eine linear optimale Zustandsregelung mit Führungsgrößenaufschaltung, eine nichtlineare modellprädiktive Regelung und eine Optimalsteuerung mit unterlagerter Zustandsregelung entworfen. Diese Verfahren werden nicht nur mit Hilfe von Simulationen, sondern auch anhand der Ergebnisse von Versuchsfahrten untersucht, verglichen und bewertet. Ziel einer automatischen Streckenfahrt ist, den Schiffsführer bei seiner Routinearbeit zu entlasten und somit zu einer Erhöhung der Sicherheit des Verkehrs auf Binnenwasserstraßen beizutragen.
Flachheitsbasierte Bahnsteuerung von seilgeführten Handhabungssystemen (Flatness-Based Control of Cable Suspension Manipulators)
Authors: Maier Thomas , Woernle Christoph 
Published: December 2003

Abstract
Bei seilgeführten Handhabungssystemen wird eine Nutzlastplattform an mehreren räumlich angeordneten Seilen geführt, deren Seilwinden wie bei Kranen auf Laufkatzen angeordnet sind. Für kinematisch unbestimmte Systeme, bei denen die Lage der Nutzlastplattform durch die Längen der Seile geometrisch nicht festgelegt ist, wird auf der Grundlage der Flachheitseigenschaft eine Feedforward-Bahnsteuerung entworfen, durch welche die Nutzlastplattform pendelfrei entlang gewünschter Trajektorien im Raum geführt wird. Die Vorgehensweise wird am Beispiel eines Brückenkrans eingeführt und für die Bahnsteuerung eines experimentellen Handhabungssystems mit Lastführung durch drei Seile erweitert. Versuchsergebnisse bestätigen die Wirksamkeit des gewählten Ansatzes.
Berechnung der Bevölkerungsentwicklung mittels eines zeitvarianten diskreten Dynamikmodells (Estimation of the Populations´ Development by Means of a Timevariant, Discrete Dynamic Model)
Authors: Frederking Thilo , Laipple Bernd , Welfonder Ernst 
Published: December 2003

Abstract
Es werden die Algorithmen zur diskreten Berechnung der zeitlich sich ändernden Altersstruktur einer Bevölkerung hergeleitet und die Funktionsweise des resultierenden Dynamikmodells anhand eines Blockschaltbildes veranschaulicht. Der Test des detaillierten Bevölkerungsmodells erfolgt anhand des Vergleichs von "Messung" und "Rechnung", d. h. von statistisch erfassten und simulierten Bevölkerungsverteilungen. Betrachtet werden die unterschiedlichen Bevölkerungsentwicklungen von "Deutschland", "Indien" und "China" in der Vergangenheit und Zukunft.
Anwendung von modellbasierter prädiktiver Regelung und Methoden der hybriden Systeme zur optimalen Produktionsplanung (Using Model Predictive Control and Hybrid Systems for Optimal Scheduling of Industrial Processes)
Authors: Gallestey Eduardo , Stothert Alec , Castagnoli Dario , Ferrari-Trecate Giancarlo , Morari Manfred 
Published: December 2003

Abstract
Optimal (re)scheduling of production in industrial processes increases economic efficiency through timely and optimal use of limited resources. In this article an approach to scheduling based on the use of hybrid systems and model predictive control is presented. Modelling flexibility, acceptable computational times, and optimal disturbance rejection are the key advantages of the approach. The main ideas are illustrated with two industrial applications.
Zur Vergröberung/Verfeinerung von Petri-Netzen bei der Zuverlässigkeits-Modellbildung (On Coarsening/Refining Petri Nets for Reliability Modeling)
Authors: Schneeweiss Winfrid 
Published: December 2003

Abstract
Petri-Netze bieten unter anderem den Vorteil einer einheitlichen bildlichen Beschreibung dynamischer Systeme auf allen Systemebenen. Oft möchte man aus gut verstandenen Teilmodellen Gesamtmodelle großer, komplexer Systeme gewinnen, wobei Feinheiten unterer Systemebenen wegfallen sollen. Oder man möchte umgekehrt einen Grobentwurf sukzessive verfeinern. Hier werden Probleme, die bei dieser Vergröberung/Verfeinerung von Petri-Netzen auftreten können, analysiert. Es reicht nicht das Definieren neuer bzw. das Aufspalten “grober” Transitionen, denn auch Kanten müssen “gebündelt” bzw. aufgespalten werden. Es wird gezeigt: Entscheidend ist, dass auf jeder Systemebene eindeutige Petri-Netz-Plätze (-Stellen) für “System intakt” bzw. “System defekt” konstruiert werden.