bluuebunny/crossref_metadata_2025_split huggingface dataset:
Economic benefits of Terminal Aerodrome Forecasts (TAFs) for Sydney Airport, Australia
Authors: Leigh R J 
Published: June 2010

AbstractThe study estimates the economic value of information contained in weather forecasts for the aviation industry known as Terminal Aerodrome Forecasts (TAFs); and estimates the economic benefits of improving the accuracy of the information. The response of an airline to a TAF, in terms of fuel load and the decision to divert the flight to another aerodrome, is modelled using a decision analytic framework. Relationships between expected direct airline cost, the value of the forecasts and TAF accuracy are derived using historical TAF verification data from 1972 to 1993 and actual airline operating costs based on 1994 economic conditions. This allows the cost savings due to improved TAF accuracy, and the value of TAFs at particular levels of accuracy and over a particular time period, to be estimated. The economic value of TAFs produced in 1993 for Sydney Airport, based on Qantas Airways Limited international routes into Sydney, was estimated at A$6.9 million. This is about 80% of the maximum potential value of ‘perfect’ forecasts. On the same basis the economic benefit of a hypothetical uniform increase in TAF accuracy of 1% was estimated at A$1.2 million per year.
Formation of dew and the drying process withincrop canopies
Authors: Jacobs Adrie F G , Nieveen Joost P 
Published: June 2010

AbstractOutdoor dew profiles within a plant canopy have been measured after dewy nights in a maize canopy and in a barley canopy. It is found that dew profiles can have a similar shape for various dew events. Clear unique dew profiles occurred when the plants are stiff, the stems as well as the leaves. This result suggests that it is likely that the similar profiles are a consequence of the more‐or‐less constant foliage area distribution of a plant canopy during a growing season. Flexible plant canopies, however, have more complex behaviour depending on the structure of the canopy and on the wind regime during the early hours. The drying process within the plant canopy has also been monitored until the free liquid water that had collected within the canopy through the night was evaporated. Initially, the drying process was faster in the upper layers of the canopy. Later, when the moisture distribution became more‐or‐less even through the whole canopy, the drying rate became approximately uniform. The amount of dew and the drying rate during the morning hours have also been estimated by making simple model simulations. For the inflexible maize canopy, the calculated total amount of dew agreed with the measured amount to within 6%. The measured drying process, however, lagged about one hour behind the calculated one. Possible causes of this difference are the dripping effect and drainage down the stems, which were not included in the calculations. These causes, however, are difficult to model, especially for a flexible canopy like a barley crop.
Pattern recognition techniques for the identification of cloud and cloud systems
Authors: Pankiewicz G S 
Published: June 2010

AbstractA wealth of often under‐used information is present in visible and infrared meteorological satellite imagery, in the form of cloud size, shape, texture and context. In an effort to provide an objective system that can identify meteorological objects over a range of scales, a study of currently available pattern recognition techniques has been undertaken. These techniques, which include supervised and unsupervised classification, image segmentation and scale context, are reviewed, together with a method for selecting the optimal image characteristics for the application of interest. This paper also considers a number of meteorological applications where these techniques can be used, such as cloud classification for operational or climatological purposes and the improvement of numerical weather prediction models. The result of the study has been the design of a synoptic‐scale object recognition system based on three layers of artificial neural networks, each operating at a different scale in a bottom‐up approach.
Synoptic situations related to spells of extreme temperatures over Argentina
Authors: Rusticucci Matilde , Vargas Walter 
Published: June 2010

AbstractThis study analyses some synoptic situations in which extreme temperatures occur. Cases of temperature‐anomaly spells from ten stations in Argentina are studied. The duration and the maximum deviation in each case are considered. The Lund correlation method or manual classification was used to analyse the synoptic situations. The cold spells in winter during the period 1971/80 occurred in three kinds of synoptic situation. Most of the days have a high‐pressure system to the west and a trough in the centre of the country, which is associated with south‐westerly winds. The coldest days have south‐easterly winds to the north (from the Atlantic), which blow around a high‐pressure system over the southern part of the country. There is a difference between this synoptic situation and the coldest synoptic situation in summer. The coldest conditions in summer take place in south‐westerlies when three or more cold fronts have passed over the area. The warmest spell in summer (January 1972) occurred with a cold front coming from the south, a low‐pressure centre in the middle of the country (between two high‐pressure systems), with a flow from the north over Argentina. In winter the warmest spells occur in similar situations, but there are also warm fronts present over the northern part of the country. Lund's method is appropriate for finding the synoptic situations connected with some special cases.
Data efficiency of meteorological and hydrological services in Bulgaria
Authors: Sharov Vladimir , Popova Maria 
Published: June 2010

AbstractIt is hard and very often not possible to demonstrate economic benefits to national economies from meteorological and hydrological activities. We propose making a relative estimate of these benefits by evaluating data efficiency. Data efficiency is a function of six parameters, each of equal weight: accuracy, availability, differentiation, timeliness, presentation and up‐date frequency. All these parameters depend on the level of data technology. Improvements in these data parameters result in a bigger volume of data and services sold. On the basis of data efficiency estimation we propose a methodology of how to create an improved strategy for up‐dating the data technology of meteorological and hydrological services. We show that the increase in usefulness of the National Meteorological Service during natural disasters and the rise in revenue from hydrometeorological services are the result of improvements in data efficiency by the new data technology. Alternatively, the increase in data efficiency could be used as good indicator of improvements in the economic benefits of meteorological and hydrological services.
Mesoscale forecasts with an atmospheric Limited Area Model
Authors: Nielsen Niels W , Sass Bent H , Jørgensen Jess 
Published: June 2010

AbstractThe prediction of mesoscale weather phenomena, such as local winds and heavy precipitation, has always been a big challenge because of their direct impact on people's lives. In recent years computer power has increased enough to make it possible to run regional numerical weather forecast models for the prediction of local weather. This paper describes examples of forecasts obtained from a nested mesoscale model currently run operationally at the Danish Meteorological Institute. The potential and problems associated with high‐resolution forecasts are discussed.
An object‐oriented technique for nowcasting heavy showers and thunderstorms
Authors: Hand W H 
Published: June 2010

AbstractAccurate forecasting of heavy showers and thunderstorms with associated hazards is vitally important for many business sectors and national utilities. In the UK a fully automated procedure is being developed in the Met. Office for the National Rivers Authority. The GANDOLF (Generating Advanced Nowcasts for Deployment in Operational Land surface Flood forecasting) system seeks to provide warnings of heavy rain and forecast accumulations in sensitive river catchments to flood hydrologists. GANDOLF will automatically choose the most appropriate nowcasting technique depending upon synoptic conditions. In a convective situation an important method available to GANDOLF is an object‐oriented nowcasting procedure. Multi‐beam, high resolution radar data and Meteosat IR satellite data are used to analyse convective cells in all stages of growth; subsequent movement and development up to 3 hours ahead is then predicted using a conceptual life‐cycle model combined with mesoscale NWP data. This paper describes the object‐oriented technique and demonstrates its usefulness in a severe convective situation with a case study.
The formation of a dynamically unstable ridge at 500 hPa as a precursor of surface cyclogenesis in the central Mediterranean
Authors: Prezerakos Nicholas G , Flocas Helena A 
Published: June 2010

AbstractAn attempt is made to find the dynamical and physical characteristics of the atmospheric circulation which contributed to the development of a great storm in the vicinity of Greece on 5 October 1989. The surface cyclogenesis could be considered as a consequence of an upper‐tropospheric minor wave which formed upstream on the eastern flank of a blocking‐type anticyclone which was centred over Britain and dominated the atmospheric circulation over western Europe. This minor wave formed three days before the initiation of the surface cyclogenesis and could be explained by the theory of ‘a dynamically unstable ridge’. As the wave moved south‐eastwards, an elongated trough formed in the upper troposphere. The southernmost part of this elongated trough was disrupted by dynamical processes, leading finally to the formation of a cut‐off low. When the area of positive relative vorticity advection due to the low became superimposed upon a shallow frontal surface lying across southern Greece in the afternoon of 4 October 1989, a deep depression developed at the surface between Crete and Athens during the next 12 hours. To further elucidate the role played by the forcing conditions at the upper levels in the surface cyclogenesis, the potential vorticity has been analysed.
Classification of ensemble forecasts by means of an artificial neural network
Authors: Eckert P , Cattani D , Ambühl J 
Published: June 2010

AbstractThe problem of clustering the members of an ensemble forecast is addressed. Fields of 500 hPa height are classified by a self‐organising Kohonen artificial neural network, for which the learning process is described. The members of the ensemble are classified according to the learned situations. An objective measure of the predictability is proposed, using the concept of information entropy. This classification technique also provides a measure for comparing forecasts with their verifying analysis.
Fog detection and fog mapping using low cost Meteosat‐WEFAX transmission
Authors: Güls I , Bendix J 
Published: June 2010

AbstractNowcasting the extent of fog and diurnal fog dynamics is important for traffic management as well as for air‐quality studies. Imagery from operational weather satellites provide a spatial database several times a day which can be used for fog monitoring given a classification scheme which is nearly operational. Unfortunately, the use of high‐resolution imagery is often expensive and time consuming, so that it is not suitable for nowcasting at local weather offices. For that reason, a method for detecting fog based on easily accessible Meteosat‐WEFAX imagery has been developed. The algorithm uses the Meteosat VIS‐channel (C‐Format) and includes illumination correction and calibration of the WEFAX signal which provides a synthetic reflectance factor. The procedure is improved by making use of an additional image of surface texture. The discrimination between fog and other surfaces has been performed by the application of a bi‐dimensional threshold test based on both images of synthetic reflectance and texture and a final snow/ice/edge correction. The resulting binary fog image has proved to be of encouraging accuracy by comparison with a classification based on NOAA‐AVHRR data as well as visibility observations. Especially in cases of fog optical depths less than 4 or a patchy fog structure, classification results should be interpreted carefully. Binary fog masks are combined into daily fog maps which clearly show diurnal fog dynamics on a European scale.
The use of potential vorticity as an operational forecast tool
Authors: Mansfield D A 
Published: June 2010

AbstractThe results from a project to evaluate the use of potential vorticity in operational forecasting are presented. An analysis of the temporal and spatial coherence of analysed and forecast potential vorticity fields showed that features with space scales downn to a few hundred kilometres could be tracked for between one and two days. Of features in these fields, 90% had a corresponding signal in the vertical motion fields, showing that they were real features having an important influence on weather‐bearing systems. A comparison between potential vorticity fields and water‐vapour imagery shows a close relationship in the region of the polar front. Examples are given showing how this can be used to detect errors in model analyses and forecasts. The use of potential vorticity as a diagnostic of model behaviour is discussed. Many authors have stressed the role of potential vorticity anomalies in major cyclogenesis. In these cases the forcing is usually clear from other diagnostics. It is suggested here that it is in highlighting areas of weaker forcing or relatively small‐scale model errors where potential vorticity is most useful to the operational forecaster.
Forecasting road‐surface temperatures for different site characteristics
Authors: Jacobs Wilfried , Raatz Wolfgang E 
Published: June 2010

AbstractIn 1992/93 the Deutscher Wetterdienst (DWD) introduced SWIS (Straßenzustands‐ und Wetterinformationssystem) as a nationwide road weather information system. In order to forecast road conditions and road‐surface temperature over a time period of 27 hours, an energy balance model is used. The course of the energy fluxes is estimated by the meteorological parameters. It is thus very important that the forecaster provides an excellent synoptic input for the energy balance model. The energy balance model is able to account for five different road site characteristics; i.e. unobstructed road sections with regular and little traffic, respectively, shaded road sections, bridges and road sections within urban influences. To evaluate the model's quality, the technique of hindcasting was employed by running the model for a day in the past (running time 0900 UTC of a given day to 1200 UTC the following day), using measured values of a specific road weather monitoring station complemented by observations from a nearby synoptic station. Preliminary results show that from 1500 UTC to 1800 UTC the mean errors are 1 to 2 K, during the remaining forecast time the mean errors are often less than 1 K; results are even better during clear sky conditions.
Improving forecasting performance by combining forecasts: The example of road‐surface temperature forecasts
Authors: Brown Barbara G , Murphy Allan H 
Published: June 2010

AbstractA recent paper by J. E. Thornes reported the results of a comparative evaluation of location‐specific, road‐surface temperature forecasts (RSTFs) formulated by two organisations, the UK Meteorological Office (MO) and Oceanroutes (OR). The present paper broadens the scope of this competition, by considering the possibility of combining the MO and OR forecasts. Combining forecasts can improve forecasting performance when one set of forecasts contains information – in this case, information about observed road‐surface temperatures – not contained in the other set of forecasts. Both simple averaging and regression modelling are examined in this study as methods of combining these RSTFs, with the former consisting of averaging the MO and OR forecasts and the latter consisting of regressing these two forecasts on the observed temperatures.The simple average forecasts outperform the MO or OR forecasts, both when these RSTFs are evaluated as forecasts of a continuous variable and when they are evaluated as forecasts of a binary (i.e. frost/no frost) variable. Combining via regression modelling leads to further modest improvements in forecasting performance (based on in‐sample results). Overall, simple averaging captures a substantial fraction of the benefits that can be realised by combining the MO and OR forecasts for this small sample of road‐surface temperature data. Several issues related to the formulation and evaluation of combined forecasts, as well as some practical implications of the results, are briefly discussed.
The formation and forecasting of condensation trails behind modern aircraft
Authors: Ferris P D 
Published: June 2010

AbstractThe formation of a condensation trail behind an aircraft gives away its presence. Despite the current use of radar for aircraft detection, contrail formation is still important to military aviation. Seeing a contrail only requires the unaided eye. The theory of contrail formation for a dry environment, using values of engine‐dependent variables appropriate to modern jet aircraft, gives values of the critical temperature for contrail formation. These form a line nearly parallel to, but colder than, the MINTRA line on a tephigram. These values though, do not allow for the effect of environmental humidity, which may be significant at the levels where aircraft fly. A new forecasting technique is proposed which involves determining the exact critical temperature value. This can be done using a suitable contrail formation graph or with a tephigram, finding the necessary correction to the MINTRA temperature. If the atmospheric temperature is colder than this critical temperature, a contrail should be forecast to form.
Monitoring of NWP models by use of satellite data
Authors: Røsting Bjørn , Sunde Jens , Midtbø Knut Helge 
Published: June 2010

AbstractThis paper describes some cases where satellite information contributes to beneficial monitoring of NWP model output. The real‐time observations and NWP parameters required for the methods used are described. Selected examples, including successful and less successful NWP developments, are used to illustrate the applicability of the methods. Key elements are the localisation and isentropic advection of potential vorticity (PV). Positive upper and middle tropospheric PV anomalies may in several weather situations be detected in the Meteosat WV imagery as dark areas in the rear of developing cyclones. This study indicates that we may have confidence in the model description of weather development when the NWP model output showing areas with high‐level potential vorticity corresponds in time and space with dry areas inferred from the WV images. However, when such correspondence is only poor, the confidence is shown to be lower. In such cases there is a need to adjust the NWP model output. Also large‐scale isentropic advection fields and cross‐sections from the NWP models are used together with the multi‐spectral AVHRR information from the NOAA polar‐orbiters. Mesoscale events related to deep convection and small‐scale wind fields in connection with polar low developments are investigated.
Calibrating the exposure of anemographs
Authors: Cook N J 
Published: June 2010

AbstractMeasurements of wind speed near the ground surface are strongly influenced by the topography surrounding the anemograph site. The influence of a change in ground level is relatively local in comparison with the influence of a change of surface roughness, which persists many kilometres downwind of the change. These exposure effects are of a similar magnitude to other effects significant in the process of engineering design, such as the shape and size of a building, and therefore need to be assessed in a similar way. In this paper, a method of exposure assessment is described which utilises contemporary engineering models to show the effect of changes of surface roughness and ground level on wind speed. Results of the method are compared with measurements of extreme wind speeds obtained from a directionally inhomogeneous anemograph site. The method is seen to account for 85% of the observed directional variance.
Visibility: An investigation based on a multivariate adaptive regression spline technique
Authors: Taliani Marco , Siani Anna Maria , Palmieri Sabino 
Published: June 2010

AbstractVisibility in the Po Valley in northern Italy is a meteorological parameter of extreme interest. In autumn and winter radiational cooling of the Valley bottom coupled with cold air drainage from surrounding mountain slopes leads to conditions favouring the formation of fog with a highly persistent character. This regime may be temporarily interrupted when vigorous northwest flow over the Alps produces descending dry currents in the lee of the range (foehn) or when an intense disturbance affects the area. A preliminary application of a statistical methodology called MARS (Multivariate Adaptive Regression Splines) to a visibility time series of Milan‐Linate Airport is carried out with the primary intent of investigating the efficiency of the technique in detecting the non‐linear dynamics of the series and the physical factors involved. Although the development of a statistical prediction scheme requires much more data in order to guarantee the stability of the model equation and reliable tests, results are interesting and indicate, beyond any doubt, the skill of MARS as a tool for making causal inferences from observables.
Case studies of cyclogenesis over South America
Authors: Gan Manoel Alonso , Rao Vadlamudi Brahmananda 
Published: June 2010

AbstractA detailed case study of cyclogenesis over South America during the period 5‐9 June 1981 is undertaken. The intensification of the cyclone occurred first in the upper troposphere. The disturbance showed several characteristics found in baroclinic disturbances, such as eastward propagation, intensification with westward vertical tilt and barotropic decay. However, the vertical tilt was confined to upper levels only and the surface temperature gradient was low. This suggests that the mechanism of development might be somewhat different than the usual cases of baroclinic instability associated with low‐level vertical inclination. Internal baroclinic instability is suggested as a plausible mechanism of development. Cases of intense cyclogenesis are also studied during the period 1979 to 1988 using the Laplacian of the sea‐level pressure criterion in the autumn, winter and spring seasons. The case which occurred on 19 September 1984 over Uruguay and southern Brazil is presented; the pressure drop was 12 hPa in 24 hours over Paraguay and South Brazil.