No description available.

Thermal mapping, the measurement of road surface temperatures (RSTs) with an infra-red thermometer (IRT) mounted in a moving vehicle, seeks to identify a 'characteristic and repeatable' thermal fingerprint (temperature profile) for any stretch of road. A number of uses have been suggested for the process, including ice detection sensor network design and identifying stretches of road for selective gritting, with potential financial and environmental benefits due to reduced salt usage. The project 'Thermal Mapping for a Highway Gritting Network' has resulted in the most extensive survey yet undertaken. The aims were to investigate the reliability/repeatability of fingerprints and establish confidence limits. Comprehensive mapping of Sheffield roads took place during winters 1988/89- 1991/92. Significant errors (+/-3°C) in RST readings were identified after the first winter. Laboratory and road tests confirmed errors were produced due to warming/cooling of the IRT. Operating the IRT in a temperature control box eliminated these errors. Seven Sheffield routes were mapped during winters 89/90 and 90/91 with route 1 fingerprints (100) used for most of the analysis. The main factors affecting the variation in RSTs were confirmed as altitude and land-use with localised peaks occurring under bridges and by trees and tall buildings. The occurrence of cold air drainage on clear/calm (extreme') nights resulted in 'low' RSTs at relatively low altitudes. Differences were identified between what should have been identical extreme fingerprints. These were related to variations in the behaviour of cold air drainage. rom night to night and variations in wind direction/speed interacting with local relief. Confidence limits for extreme fingerprints and maps, taking into account possible errors in mapping and differences between fingerprints, were +/-20C and +/- 2.5°C respectively. With important decisions concerning gritting made when RSTs are +/-5°C confidence limits of this magnitude have important implications for thermal mapping. Future use should be restricted to sensor network design and assessment/re-design of gritting network.

Each winter, Britain spends up to £120 million spreading approximately 2 million tonnes of rock salt on our roads to keep them free of ice and snow. This thesis shows that it would be possible to significantly reduce the amount of salt spread, by improving the accuracy of the Road Danger Warnings issued to Highway Authorities. Each day in winter, the maintenance engineer receives a Road Danger Warning from his local weather centre. Unfortunately these Warnings are not very accurate because they are based on forecasts of minimum air temperature alone, rather than using road surface temperatures. During the winter of 1982/83, of 102 Road Danger Warnings issued to Hereford and Worcester County Council, only 32 were correct in predicting icy conditions on the MS motorway. This thesis presents a computer model to predict ice formation on roads up to 24 hours ahead. During the winter of 1978/79 instruments were installed in the M4 motorway to measure road surface temperature and wetness. The computer model has been tested retrospectively for 30 nights when the road surface temperature fell below 5°C. The predicted minimum road surface temperature has a root mean square error of 0.9°C. During the winters of 1982/83 and 1983/84, the model was tested in 'real time' against road surface temperatures measured automatically on the M5 and M6 motorways, giving a root mean square error of 1.5°C for 80 nights during 1.982/83, and 1.3°c for 120 nights during 1983/84. The form of the issued Road Danger Warnings has been changed from a simple sentence issued over the telephone or using telex, to a graph of predicted road surface temperature and wetness. An optimistic and a pessimistic graph is issued to give the maintenance engineer an idea of the certainty of the forecast. The thesis proposes a national network of automatic road surface monitoring sites. Each site would be linked to microcomputers in local weather centres, which would then run the prediction model and issue Road Danger Warnings accordingly. The information could then be sent to maintenance engineers using Prestel.

No description available.

No description available.

Spectral properties of global surface temperature and uncertainties of global climate sensitivity are explored in this work through the medium of Energy Balance Climate Models (EBCMs) and observational surface temperature data. In part I, a complete series of 2D time-dependent non-orthogonal eigenmodes of global surface temperature are analytically derived and their geographic patterns are presented. The amplitudes of these modes have temporal characteristics and present exponentially decaying patterns. Theoretically, if the energy balance model is forced by white noise forcing in time, the autocorrelation functions of the mode amplitudes should present the same exponentially decaying patterns. When observed surface temperature data are projected onto these theoretical modes, the autocorrelation time scales of the mode amplitudes exhibit similar exponential decaying patterns. These modes are believed to be useful for surface temperature studies and model intercomparison. In part II, an objective means of deriving the probability density function (PDF) of global climate sensitivity is investigated. The method constrains the PDF by its fit to the present climate in terms of surface temperature. We found that a wide range of parameter combinations, which corresponds to a broad range of the sensitivity, shows equally good fits to the present climate. It means that the uncertainties in global climate sensitivity are very difficult to eliminate if climate models are tuned to fit observations of surface temperature alone. The origin of the skewness of the PDF is found in very simple terms.

Spectral properties of global surface temperature and uncertainties of global climate sensitivity are explored in this work through the medium of Energy Balance Climate Models (EBCMs) and observational surface temperature data. In part I, a complete series of 2D time-dependent non-orthogonal eigenmodes of global surface temperature are analytically derived and their geographic patterns are presented. The amplitudes of these modes have temporal characteristics and present exponentially decaying patterns. Theoretically, if the energy balance model is forced by white noise forcing in time, the autocorrelation functions of the mode amplitudes should present the same exponentially decaying patterns. When observed surface temperature data are projected onto these theoretical modes, the autocorrelation time scales of the mode amplitudes exhibit similar exponential decaying patterns. These modes are believed to be useful for surface temperature studies and model intercomparison. In part II, an objective means of deriving the probability density function (PDF) of global climate sensitivity is investigated. The method constrains the PDF by its fit to the present climate in terms of surface temperature. We found that a wide range of parameter combinations, which corresponds to a broad range of the sensitivity, shows equally good fits to the present climate. It means that the uncertainties in global climate sensitivity are very difficult to eliminate if climate models are tuned to fit observations of surface temperature alone. The origin of the skewness of the PDF is found in very simple terms.

This paper presents two new schemes for interpolating missing samples in satellite diurnal temperature cycles (DTCs). The first scheme, referred to here as the cosine model, is an improvement of the model proposed in [2] and combines a cosine and exponential function for modelling the DTC. The second scheme uses the notion of a Reproducing Kernel Hilbert Space (RKHS) interpolator [1] for interpolating the missing samples. The application of RKHS interpolators to the DTC interpolation problem is novel. Results obtained by means of computer experiments are presented.

The need for improved cloud parameterisations in a road surface temperature model is demonstrated. Case studies from early 1994 are used to investigate methods of tracking cloud cover using satellite imagery and upper level geostrophic flow. Two of these studies are included in this thesis. Errors encountered in cloud tracking methods were investigated as well as relationships between cloud height and pixel brightness in satellite imagery. For the first time, a one dimensional energy balance model is developed to investigate the effects of erroneous cloud forecasts on surface temperature. The model is used to determine detailed dependency of surface freezing onset time and minimum temperature on cloud cover. Case studies from the 1995/96 winter in Devon are undertaken to determine effects of differing scenarios of cloud cover change. From each study, an algorithm for predicting road surface temperature is constructed which could be used in future occurrences of the corresponding scenario of the case study. Emphasis is strongly placed on accuracy of predictions of surface freezing onset time and minimum surface temperature. The role o f surface and upper level geostrophic flow, humidity and surface wetness in temperature prediction is also investigated. In selected case studies, mesoscale data are also analysed and compared with observations to determine feasibility of using mesoscale models to predict air temperature. Finally, the algorithms constructed from the 1995/96 studies are tested using case studies from the 1996/97 winter. This winter was significantly different from its preceding one which consequently meant that the algorithm from only one scenario of the 1995/96 winter could be tested. An algorithm is also constructed from a 1996/97 winter case study involving a completely different scenario Recommendations for future research suggest testing of existing algorithms with guidance on additional scenarios.

The release of sodium during the combustion of black liquor is a significant source of fume formation in a kraft recovery boiler, affecting efficiency in a pulp and paper mill. The fume is deposited on the surface of heat exchanger tubes in the upper furnace, causing fouling and corrosion, especially to the superheaters. This thesis reports on work done to develop improved understanding of fume formation. The mechanisms of sodium release during each stage of black liquor combustion are influenced by the surface temperature. The addition of boron to the black liquor, which debottlenecks the recausticizing plant by a reduction in lime usage, also influences the characteristics of black liquor combustion, such as combustion time and swelling. Previously, no effective measurement technique has been available to quantify sodium concentration in the plume of a burning black liquor droplet with or without boron, or to record the distribution of surface temperature through the time history of a burning droplet. This thesis reports on the adaptation of two techniques for the measurement of the release of atomic sodium and the temperature history, and their application to investigate several aspects of the release of atomic sodium during combustion of black liquor in a flat flame environment. The simultaneous employment of a planar laser-induced fluorescence (PLIF) technique with an absorption technique has been adapted to allow quantitative measurement of the release of atomic sodium. The absorption technique has been employed to correct for both fluorescence trapping due to absorption and attenuation by high concentration of the atomic sodium in the plume, and for collisional quenching by the other major gas components present in the flat flame. An independent assessment was performed using kinetic calculations, based on measured total sodium that is residual in a particle obtained at different stages in the combustion process. These independent assessments were used to provide greater insight in to the release process and to cross-check. The influence of both the initial diameter of the droplet and addition of boron to the black liquor on the temporal release and the release rate of atomic sodium during the combustion have been performed using the present PLIF technique. The second technique, two-dimensional two-colour optical pyrometry, has been adapted to measure the distribution of surface temperature and the swelling (change in surface area) of a burning black liquor droplet. The influence of surface temperature or the change in the external surface area of the droplet on the release of atomic sodium during the combustion of black liquor has been assessed through concurrent use of both adapted techniques. The highest concentration of atomic sodium was measured in the final stage of combustion that of smelt coalescence, where it is an order of magnitude greater than in the other stages combined. While the extensive release of atomic sodium at high temperature in this final combustion stage occurs in only a relatively small percentage of droplets in a kraft recovery boiler, the effect could still be significant in fume formation. This is because the extensive release is expected to occur in the very small droplets, predominantly generated by splitting or physical ejection. Small droplets will have a very short combustion time and so could remain in suspension within hot gases for sufficient time for extensive release of sodium. These measurements outcomes can be used to support the future development of sub-models for computational fluid dynamics (CFD) models in order to better understand and optimise fume formation in a kraft recovery boiler. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1474431 / Thesis (Ph.D.) - University of Adelaide, School of Mechanical Engineering, 2009