Dissertations / Theses on the topic 'Climate modelling'
To see the other types of publications on this topic, follow the link: Climate modelling.
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Climate modelling.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Loptson, Claire A. "Modelling vegetation-climate interactions in past greenhouse climates." Thesis, University of Bristol, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.680126.
Full textAbstract:
The early Eocene to the Cretaceous (48-148 Ma) was a period in the Earth's history where the climate was much warmer than the present day, with no permanent ice sheets and atmospheric CO2 levels higher than the present day. Using the climate model HadCM3L coupled to a dynamic vegetation model, this thesis aims to analyse vegetation-climate interactions during these past greenhouse climates, and how the climate, vegetation and climate sensitivity of these time periods are influenced by changes in palaeogeography and CO2 . The results of these model simulations are also evaluated against climatologically-sensitive geological proxies. Past modelling studies for the early Eocene have struggled to model the shallow equator to pole temperature gradient that data suggests was present during this time. However, most models have neglected vegetation feedbacks and incorporating these may help to reduce the model-data discrepancy. In this thesis, vegetation climate interactions during the early Eocene are modelled and analysed, and the results compared to available proxy data. The model-data discrepancies for temperatures are also reduced when vegetation feedbacks were included (compared to simulations with static vegetation), although there are still differences, particularly at high latitudes. This suggests that the models are still missing important processes or the data is not being interpreted correctly. In addition, twelve consistent simulations are carried out , each representing a different stage of the Cretaceous. Each simulation has the same atmospheric CO2 level, allowing the effect of palaeogeography on climate, climate sensitivity and vegetation to be analysed. It was found that, in general, the temperature trends that occurred in the mid-Cretaceous simulations were consistent with data. However, the data record does not extend to the earliest Cretaceous, and in the late Cretaceous the results deviate from the data. The model results suggest that, in order for the model to be consistent with the data there must have been a decline in CO2 from the early to late Cretaceous, which is supported by the CO2 proxy record. More data from the early Cretaceous needs to be collected in order to carry out a more robust model-data comparison for this time period.
2
Harris, Philip P. "Modelling South American climate and climate change." Thesis, University of Reading, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.436614.
Full text
3
Glover, Robin Wallace. "Energy balance climate modelling." Thesis, University of Reading, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.308058.
Full text
4
Spain, Timothy C. "Modelling of extreme climate regimes." Thesis, University of Oxford, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.572595.
Full textAbstract:
The climate of the Neoproterozoic Snowball Earth is tested in the UKMO Unified Model, specifically the HadCM3 climate model. The model is largely left unchanged, but the boundary conditions, both external and initial, are adjusted to create experiments based on the Snowball Earth hypothesis. The model can reproduce multiple equilibrium climates, as have been seen in energy balance models of the Earth's climate. The modelled present day and Neoproterozoic versions of Earth can both reproduce both ice capped and ice covered climate states. Neither can reproduce a climate which remains ice free throughout the year, even with an equilibrated ocean or elevated levels of C02. In all cases the ice free climate reverts toward the ice capped climate after the first polar winter. The modelled Neoproterozoic ice covered climate, that is the climate of Snowball Earth, has a climate very different from the present day. These changes are mostly driven by the lower thermal inertia, latitudinal temperature differences and the changed meridional circulation that results. The weather of the modelled Snowball Earth climate is also very different, dom- inated by a strong diurnal variation due to solar heating, as opposed to the more varied weather in the present day. The model responds well to the conditions of the Snowball Earth climate, with temperatures similar to those predicted by a simple physical model. The model responds less well to high levels of C02 in the Snowball Earth climate. The ice model also allows excessive heat and moisture to escape from the ocean into the atmosphere compared to that that would be predicted from solid ice coverage of the ocean. The exit from a Snowball Earth state was also tested within the model. Neither an decrease in albedo nor an increase in CO2 is unable to increase the temperature of the climate system sufficiently to exit the Snowball Earth state.
5
Brembilla, Eleonora. "Applicability of climate-based daylight modelling." Thesis, Loughborough University, 2017. https://dspace.lboro.ac.uk/2134/28239.
Full textAbstract:
This PhD thesis evaluated the applicability of Climate-Based Daylight Modelling (CBDM) as it is presently done. The objectives stated in this thesis aimed at broadly assessing applicability by looking at multiple aspects: (i) the way CBDM is used by expert researchers and practitioners; (ii) how state-of-the-art simulation techniques compare to each other and how they are affected by uncertainty in input factors; (iii) how the simulated results compare with data measured in real occupied spaces. The answers obtained from a web-based questionnaire portrayed a variety of workflows used by different people to perform similar, if not the same, evaluations. At the same time, the inter-model comparison performed to compare the existing simulation techniques revealed significant differences in the way the sky and the sun are recreated by each technique. The results also demonstrated that some of the annual daylight metrics commonly required in building guidelines are sensitive to the choice of simulation tool, as well as other input parameters, such as climate data, orientation and material optical properties. All the analyses were carried out on four case study spaces, remodelled from existing classrooms that were the subject of a concurrent research study that monitored their interior luminous conditions. A large database of High Dynamic Range images was collected for that study, and the luminance data derived from these images could be used in this work to explore a new methodology to calibrate climate-based daylight models. The results collected and presented in this dissertation illustrate how, at the time of writing, there is not a single established common framework to follow when performing CBDM evaluations. Several different techniques coexist but each of them is characterised by a specific domain of applicability.
6
Mårtensson, Sebastian. "Ridged sea ice modelling in climate applications." Doctoral thesis, Stockholms universitet, Meteorologiska institutionen (MISU), 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-93977.
Full textAbstract:
This work aims to increase our understanding of the nature of large scale features of sea ice from a dynamics point of view.Sea ice plays an important part in the exchange of heat and humidity between sea and air and thus is an important component of the climate system. Its physical presence also directly impacts the various forms of life such as diatoms, polar bears and humans alike.The dynamics of sea ice affect both weather and climate, through the large scale drift in the Arctic from the Siberian coast towards Fram Strait, through creation of cracks in the ice called leads or polynyas, and through ridging and other mechanical deformations of ice floes.In this work, we have focused on modelling of ridged ice for a number of reasons. Direct observations of the internal ice state is very difficult to perform and in general, observations of sea ice are either sparse or of limited information density. Ridged ice can be seen as the memory of high ice stress events, giving us a view on these highly dynamic events. Ridging is of major importance for the ice thickness distribution, as the thickest ice can only be formed through mechanical processes. Further, ridged ice is of direct interest for anyone conducting shipping through seasonal or perennial ice covered seas as it can form impenetrable barriers or in extreme even cases crush a ship caught within the ice pack. To this end, a multi-category sea ice model, the HELsinki Multi category Ice model (HELMI), was implemented into the Rossby Centre Ocean model (RCO). HELMI has explicit formulations for ridged and rafted ice, as well as sub-grid scale ice thickness distribution (a feature shared with other multi category models) and an ice strength based on energetics. These features give RCO better representation of sub-grid scale physics and gives us the possibility to study the deformed ice in detail. In paper I we look at the change in behaviour in the Arctic as the ice becomes more mobile, leading to a slight increase in modelled ridged ice volume in the central Arctic, despite a general trend of a decreasing ice cover.Paper II takes us to the Baltic Sea and the possibilities of modelling ridge ice concentration with a statistical model.In Paper III we investigate how the diminishing ice cover in future scenarios affects the biological activity in the Baltic Sea.Finally Paper IV investigates how the ice stress and the internal ice force can be interpreted in terms of ice compression on the ship scale.At the time of the doctoral defence the following paper was unpublished and had a status as follows: Paper 4: Manuscript
7
Dolan, Aisling Margaret. "Modelling mid-Pliocene climate and ice sheets." Thesis, University of Leeds, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.590483.
Full textAbstract:
Given anthropogenic modification of the climate system, the future stability of Earth's major ice sheets and sea level is uncertain. One potential, lJ1ethod to investigate the behaviour of the Greenland and Antarctic ice sheets under a warmer-than-modern climate regime, is to look back at past warm periods of Earth history (for example the mid Pliocene Warm Period; 3.26 - 3.0 million years ago). The British Antarctic Survey Ice Sheet Model (BASISM) and the Hadley Centre Coupled Climate Model version 3 (HadCM3) allow the climate and ice sheets of the mid-Pliocene to be modelled, and their sensitivity to a range of uncertainties in forcing to be quantified. The ice sheets, particularly the Greenland Ice Sheet, are sensitive to changes in the Earth's orbital configuration and potential levels of atmospheric carbon dioxide (C02) during the mid-Pliocene. Exploring various orbital forcing scenarios in concert with a plausible Pliocene COz envelope (280 - 560 ppmv), enables models to generate Greenland ice sheet reconstructions that range from a 1.5% reduction from modern to an ice-free state. In contrast, on East Antarctica, significant ice sheet retreat is only simulated under warm Southern Hemisphere orbital conditions where C02 levels are at 400 ppmv or above. Maximum eustatic sea level rise corresponding to predicted ice sheet reductions is comparable with recent records suggesting mid-Pliocene sea level high-stands of 22 m greater than modern. However, ice sheet reconstructions are shown to be highly dependent on Q priori assumptions regarding the initial ice sheet configuration within the numerical modelling framework. Investigation of the dependency of ice sheet predictions on the models used, has demonstrated that results are sensitive to the modelled climatological forcing. Such dependency is most explicitly highlighted over Greenland, where Pliocene ice sheet predictions, given forcings from fifteen equivalently-configured climate models, range from no ice to a configuration that is larger than modern. These results underline the importance of considering mUltiple sources of uncertainty when predicting past ice sheets. v
8
Pope, James Owen. "Modelling Pliocene climate with perturbed physics ensembles." Thesis, University of Leeds, 2015. http://etheses.whiterose.ac.uk/10443/.
Full textAbstract:
Uncertainty in model simulations arises due to the construction of the model (structural uncertainty), the representation of sub-grid scale processes (parameter uncertainty) or the input of model boundary conditions. Perturbed physics ensembles (PPEs) produce an ensemble of simulations using a single climate model. A PPE produces different representations of climate by altering the tuning of parameterisations representing processes occurring on sub-grid scales, such as clouds and radiation. A PPE has been produced to investigate model parameter and boundary condition uncertainty for the mid-Pliocene Warm Period (3.264 to 3.025 Ma BP). Through the use of a PPE, 14 versions (13 perturbed members and the Standard version) of the UK Met Office atmosphere-ocean general circulation model HadCM3 were created. The full ensemble was re-run to assess the impact of simultaneously changing physical boundary conditions for orography, ice sheets and vegetation in combination with perturbed physics. Finally the effect of the potential range in reconstructed mid-Pliocene CO2 was investigated through a sub-ensemble of the PPE. Using data-model comparisons (DMCs), the ensemble members with higher than the Standard values of Charney sensitivity were better able to simulate the magnitude of high latitude mid-Pliocene warming. The strongest performing ensemble members for the DMCs displayed Charney sensitivities of 4.54°C, 4.62°C and 5.40°C, above the upper bound of the IPCC likely range (1.5 to 4.5°C). However, these warmer members with higher Charney sensitivities weakened the data-model comparison in the tropics. Ensemble members with lower than Standard values of Charney sensitivity, close to the lower bound of the IPCC likely range, better resolved temperature reconstructions in the tropics, but were unable to resolve high latitude warming. It is evident that the PPE is able to achieve the magnitude of mPWP warming but not the spatial distribution of the warming. The investigation into boundary condition uncertainty using the PPE reveals that the PRISM3D physical boundary conditions lead to improved simulations of the mPWP climate than the PRISM2 boundary conditions. For the range of atmospheric CO2 concentrations, the results from the sub-ensemble indicate that lower values of CO2 lead to reduced performance of the PPE members compared to the palaeo-data. The conclusion is that concentrations of CO2 below 350 ppmv for the mPWP would make simulating high latitude climates very difficult for climate models.
9
Lee, S. E. "Modelling interactions between climate and global vegetation in response to climate change." Thesis, University of Sheffield, 1997. http://etheses.whiterose.ac.uk/2063/.
Full textAbstract:
Climate change associated with increasing concentrations of the greenhouse gas, carbon dioxide(CO2), is expected to lead to an increase in global mean temperature of between 1 and 3.5 deg C by the end of the 21st century, with regional changes in rainfall and humidity. This thesis is concerned with modelling the effects of a changing climate and atmospheric C02 concentration on global vegetation. The process-based model, DOLY (Dynamic glObal phtogeographY), is used. It is able to operate using three climate variables, two soil variables and an atmospheric CO2 concentration. Its outputs are leaf area index (LAI), and net primary productivity (NPP). The LAI and NPP values predicted by DOLY were used to run a life-form model with a climate change scenario. It was found that warming led to the spread of trees into the tundra region. The DOLY model was also coupled with the Hadley Centre general circulation model to determine the feedbacks of vegetation on climate. With a global warming of 2◦C, the global feedback of vegetation on temperature was a decrease of 0.1 deg C. However at the regional scale the feedback was +/-2 ◦C, of similar magnitude to the driving temperature change. Finally, the DOLY model was run with transient climate data from the Hadley Centre. The boreal forest moved north, and the Gobi desert and the southern steppes in the former Soviet Union shrank in area. The sensitivity of the model to its soil and climate inputs have also been analysed over a range of environments and the model has been validated with reference to satellite data and experimental data. It was found to perform well. This thesis has shown that it is possible to predict current and possible future distributions of vegetation with climate change using a vegetation model.
10
Hällberg, Petter. "Permafrost Modelling and Climate Change Simulations in Northern Sweden." Thesis, Uppsala universitet, Institutionen för geovetenskaper, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-337794.
Full textAbstract:
Permafrost is an important component in Arctic environments and has been hypothesized to be diminishing due to global warming. A growing concern is that large quantities of stored organic carbon will be mobilized and released to the atmosphere as the potent greenhouse gas methane if the ground thaws. This could result in a massive positive feedback on the global climate change. To quantify this effect, the permafrost extent as well as carbon storages must be mapped. In this study, a Basal Temperature of Snow (BTS) survey is conducted in the Tarfala Valley in Northern Sweden and a model of the current permafrost extent in the region is produced. Additionally, the model explores how the permafrost extent will change under three climate change scenarios at +1°C, +2°C and +4°C. According to a statistical analysis, elevation is the only significant variable for permafrost occurrence in the Tarfala Valley. Currently, continuous permafrost (>0.8 probability) is present at elevations exceeding 1523 m a.s.l. and sporadic or patchy permafrost (<0.5 probability) dominates below 1108 m a.s.l. The permafrost in Northern Sweden is near the boundary of favorable conditions for permafrost, and the greatest decline in permafrost extent occurs during the initial warming. In the +1°C scenario, which will be reached in 20 years if current warming rate is sustained, 97.6% of the continuous permafrost in the Abisko and Tarfala area degrades. The areal extent of the zone with the lowest probability of permafrost occurrence increases from 59% to 90% in the same scenario. Under continued warming to +4°C compared to current ground temperatures, 98% of the study area will be covered by sporadic or patchy occurrences of permafrost.Permafrost är en viktig komponent i arktiska miljöer och befaras minska i utbredning på grund av den globala uppvärmningen. En farhåga är att stora mängder bundet organiskt kol ska mobiliseras och släppas ut till atmosfären som den potenta växthusgasen metan om marken värms. Detta skulle kunna innebära stor positiv återkoppling på de globalt stigande temperaturerna. För att kvantifiera den effekten är det viktigt att kartlägga permafrostens utbredning såväl som mängde bundet kol i permafrostmarker. I den här studien utförs en undersökning av bastemperaturen av snötäcket (BTS) i Tarfaladalen i norra Sverige och en modellering av permafrostens nuvarande utbredning i regionen. Vidare modelleras hur permafrostens utbredning kommer att påverkas i framtiden under tre olika klimatförändringsscenarior vid +1°C, +2°C och +4°C. Enligt en statistisk analys är altitud den enda signifikanta variabeln för permafrostförekomst i Tarfaladalen. Vid nuvarande marktemperaturer är kontinuerlig permafrost (>0.8 probabilitet) utbredd på höjder över 1523 m ö.h. och sporadisk permafrost (0.5 - 0 probabilitet) dominerar under 1108. Permafrosten i norra Sverige är nära gränsen för dess gynnsamma förhållanden och den huvudsakliga förlusten av permafrost sker redan vid en blygsam markuppvärmning. I scenariot +1°C, som inträffar redan om 20 år om nuvarande uppvärmningstakt fortsätter, degraderas 97.6% av den kontinuerliga permafrosten i Abisko och Tarfalaområdet. Utbredningen av sporadisk permafrost, det vill säga zonen med lägst sannolikhet för permafrostförekomst, ökar i det scenariot från 59% till 90%. Vid fortsatt uppvärmning till +4°C jämfört med nuvarande marktemperaturer så kommer 98% av det studerade området endast innehålla sporadiska förekomster av permafrost.
11
Betts, Richard Arthur. "Modelling the influence of the vegetated land surface on climate and climate change." Thesis, University of Reading, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.312335.
Full text
12
Islam, Muhammad Saiful. "Modelling the impact of climate change on health." Thesis, University of Westminster, 2014. https://westminsterresearch.westminster.ac.uk/item/8yqvv/modelling-the-impact-of-climate-change-on-health.
Full textAbstract:
The main objective of this thesis is to develop a robust statistical model by accounting the non-linear relationships between hospital admissions due to lower respiratory (LR) disease and factors of climate and pollution, and their delayed effects on hospital admissions. This study also evaluates whether the model fits can be improved by considering the non-linearity of the data, delayed effect of the significant factors, and thus calculate threshold levels of the significant climate and pollution factors for emergency LR hospital admissions. For the first time three unique administrative datasets were merged: Hospital Episode Statistics, Met office observational data for climate factors, and data from London Air Quality Network. The results of the final GLM, showed that daily temperature, rain, wind speed, sun hours, relative humidity, and PM10 significantly affected the LR emergency hospital admissions. Then, we developed a Distributed lag non-linear model (DLNM) model considering the significant climate and pollution factors. Time and ‘day of the week’ was incorporated as linear terms in the final model. Higher temperatures around ≥270C a quicker effect of 0-2 days lag but lower temperatures (≤00C) had delayed effects of 5-25 days lag. Humidity showed a strong immediate effect (0-3 days) of the low relative humidity at around ≤40% and a moderate effect for higher humidity (≥80%) with lag period of 0-2 days. Higher PM10 around ≥70-μg/m3 has both shorter (0-3 days) and longer lag effects (15-20 days) but the latter one is stronger comparatively. A strong effect of wind speed around ≥25 knots showed longer lag period of 8-15 days. There is a moderate effect for a shorter lag period of 0-3 days for lower wind speed (approximately 2 knots). We also notice a stronger effect of sun hours around ≥14 hours having a longer lag period of 15-20 days and moderate effect between 1-2 hours of 5-12 days lag. Similarly, higher amount of rain (≥30mm) has stronger effects, especially for the shorter lag of 0-2 days and longer lag of 7- 10 days. So far, very little research has been carried out on DLNM model in such research area and setting. This PhD research will contribute to the quantitative assessment of delayed and non-linear lag effects of climate and pollutants for the Greater London region. The methodology could easily be replicated on other disease categories and regions and not limited to LR admissions. The findings may provide useful information for the development and implementation of public health policies to reduce and prevent the impact of climate change on health problems.
13
Vadeboncoeur, Nathan Noel. "Knowing climate change : modelling, understanding, and managing risk." Thesis, University of British Columbia, 2014. http://hdl.handle.net/2429/50777.
Full textAbstract:
Climate change is a complex problem. Approaches to understanding climate change risk and preparing for its management include assessments of biophysical changes, the influence of public risk perceptions on support for policies aimed at adapting to these changes, and analysis of the governance structures charged with developing and implementing climate action plans. Climate change issues, however, are often approached from a disciplinary perspective and there are few studies examining how climate risk is viewed from multiple perspectives in a particular locale. This thesis takes a bottom-up approach to understanding climate change by focusing on how climate risk is understood on the Sunshine Coast, British Columbia, as a biophysical, social, and governance issue. It begins by surveying the available biophysical information of climate change and presents a sea level rise impact model for the Sunshine Coast. Next, it explores how public perceptions of climate risk (as distinct from climate change knowledge as scientific literacy) develop and how these affect support for climate change policies. It then examines the perspective of a local government, the Town of Gibsons, in planning for climate change adaptation. Here, it focuses on how decision- makers plan for climate change by examining their perspectives on biophysical risks and the social context within which climate issues are located. Throughout the thesis, I argue that the process of adapting to climate change (a risk management strategy) has strongly social roots and that understanding how climate change fits within the context of individual communities is, along with knowledge of biophysical hazards, an essential component of adaptation.Science, Faculty of
Resources, Environment and Sustainability (IRES), Institute for
Graduate
14
Liu, Jinliang. "Improvement in runoff parameterization for global climate modelling." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/NQ58635.pdf.
Full text
15
Berger, Marit. "Modelling the early to mid-Holocene Arctic climate." Licentiate thesis, KTH, Turbulens, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-127870.
Full textAbstract:
In the recent past it has become evident that the Earth's climate is changing, and that human activity play a significant role in these changes. One of the regions where the ongoing climate change has been most evident is in the Arctic: the surface temperature has increased twice as much in this region as compared to the global average, in addition, a significant decline in the Arctic sea-ice extent has been observed in the past decades. Climate model studies of past climates are important tools to understand the ongoing climate change and how the Earth's climate may respond to changes in the forcing. This thesis includes studies of the Arctic climate in simulations of the early and mid-Holocene, 9 000 and 6 000 years before present. Changes in the Earth's orbital parameters resulted in increased summer insolation as compared to present day, especially at high northern latitudes. Geological data imply that the surface temperatures in the early to mid Holocene were similar to those projected for the near future. In addition, the geological data implies that the Arctic sea ice cover was significantly reduced in this period. This makes the early to mid-Holocene an interesting period to study with respect to the changes observed in the region at present. Several model studies of the mid-Holocene have been performed through the Paleoclimate Modeling Intercomparison Project (PMIP1 to PMIP3). The simulations have been performed with climate models of varying complexity, from atmosphere-only models in the first phase to fully coupled models with the same resolution as used for future climate simulations in the third phase. The first part of this thesis investigates the simulated sea ice in the pre-industrial and mid-Holocene simulations included in the PMIP2 and PMIP3 ensemble. As the complexity of the models increases, the models simulate smaller extents and thinner sea ice in the Arctic; the sea-ice extent suggested by the proxy data for the mid-Holocene is however not reproduced by the majority of the models. One possible explanation for the discrepancy between the simulated and reconstructed Arctic sea ice extent is missing or inadequate representations of important processes. The representation of atmospheric aerosol direct and indirect effects in past climates is a candidate process. Previous studies of deeper time periods have concluded that the representation of the direct and indirect effects of the atmospheric aerosols can influence the simulated climates, and reduce the equator to pole temperature gradient in past warm climates, in better agreement with reconstructions. The second part of the thesis investigates the influence of aerosol on the early Holocene climate. The indirect effect of reduced aerosol concentrations as compared to the present day is found to cause an amplification of the warming, especially in the Arctic region. A better agreement with reconstructed Arctic sea ice extent is thus achieved.Under senare tid har det blivit uppenbart att jordens klimat håller på att förändras, och att mänsklig aktivitet spelar en viktig roll för dessa ändringar. Ett av de områden där den pägäende klimatfärändringen har varit tydligast är Arktis: temperaturen vid ytan har ökat dubbelt så mycket här jämfört med det globala genomsnittet. Dessutom har man observerat en betydande nedgång i havsisens utbredning i Arktis de senaste decennierna. Simuleringar gjorda med klimatmodeller av forntida klimat är viktiga verktyg för att förstå de pågående klimatförändringarna och hur jordens klimat påverkas av ändringar i klimatsystemets drivningar. Denna avhandling består av studier av det arktiska klimatet i modellsimuleringar av tidig och mid-holocen, ca. 9 000 och 6 000 år före nutid. Förändringar i jordens bana kring solen resulterade i en ökad sommar-solinstrålning jämfört med nutid, särskilt vid höga nordliga breddgrader. Geologiska data antyder att jordens temperatur vid ytan under denna period kan jämföras med dem vi förväntar för den närmaste framtiden. Vidare indikerar geologiska data att havsisen i Arktisk var kraftigt reducerad under denna period. Detta gör tidig till mid-holocen till en intressant period att studera, med avseende på de förändringar som för närvarande har observerats i området. Flera modellstudier av mitt-holocen har utförts i de olika faserna av Paleoclimate Modeling Intercomparison Project (PMIP1 till PMIP3). Simuleringarna har utförts med klimatmodeller av varierande komplexitet, från atmosfärsmodeller i den första fasen, till fullt kopplade modeller med hög rumslig upplösning i den tredje fasen. I den första delen av denna avhandling undersöks den simulerade havsisen i de förindustriella och mid-holocen simuleringar som ingår i PMIP2 och PMIP3 ensemblerna. Modellerna simulerar mindre utbredning och tunnare havsis i Arktis i den senare PMIP ensemblen, men fortfarande återskapar inte modellerna generelt den havsisutbredning som de geologiska data indikerar. En möjlig förklaring till skillnaderna mellan den simulerade och rekonstruerade havsisutsträckningen kan vara att viktiga processer i klimatsystemet saknas eller inte är tillräckligt väl beskrivna i modellerna. Beskrivningen av atmosfäriska aerosoler och dess effekter på klimatet är en möjlig kandidatprocess. Från studier av forntida varma tidsperioder har man dragit slutsatsen att beskrivningen av aerosoleffekterna påverkar det simulerade klimatet. Bland annat kan man minska temperaturgradienten mellan ekvator och polerna i tidigare varma klimat, vilket bättre överensstämmer med temperaturrekonstruktioner. Den andra delen av avhandlingen undersöker påverkan av aerosoler på klimatet under tidig holocen. Den indirekta effekten som följer av lägre aerosolkoncentrationer i tidig holocen jämfört med i dag, visar sig orsaka en förstärkning av uppvärmningen, särskilt i det arktiska områet, vilket stämmer bättre med havsisrekonstruktioner från denna period.
QC 20130910
16
Zacharioudaki, Anna. "Mathematical modelling of shoreline evolution under climate change." Thesis, University of Plymouth, 2008. http://hdl.handle.net/10026.1/473.
Full textAbstract:
This study focuses on the impact of potential changes in the wind-wave climate on shoreline change. The 'one-line' model for medium to long-term prediction of coastline evolution is employed. New analytical and numerical solutions of this important model are described. Specifically: 1) original semi-analytical solutions are derived that relax the unrealistic assumption of existing analytical work that a constant wave condition drives shoreline change and, 2) a more general form of the one-line model is solved with a novel application of the 'Method of Lines'. Model input consists of 30-year nearshore wave climate scenarios, corresponding to the 'present' (1961-1990) and the future (2071-2100). Winds from a high resolution, (12km x 12km), regional climate model, obtained offshore of the south-central coast of England at a dense temporal resolution of 3 hours, are used to develop the aforementioned wave climate scenarios, through hindcast and inshore wave transformation. A hypothetical shoreline segment is adopted as a 'benchmark' case for comparisons. Monthly and seasonal statistics of output shoreline positions are generated and assessedfo r relative changeso f 'significance' between 'present' and future. Different degrees of evidence that such changes do exist are found. This study is the first application of such high resolution climate model output to investigate climate change impact on shoreline response. Major findings include: 1) shoreline changes of 'significance' are strongly linked to 'significant' changes in future wave direction, 2) future changes appear smaller for entire seasons than for individual months, 3) shoreline position variability is often smaller in the future, 4) different climate model experiments produce diverging results; however, general trends are largely similar. The present study, at a fundamental level, offers analytical solutions of the 'oneline' model that are closer to reality and a numerical solution that is of increased effciency. At a practical level, it contributes to better understanding of the patterns of shoreline response to changing offshore wave climate through: 1) the use of fast and straightforward methods that can accommodate numerous climate scenarios without need for data reduction, and 2) the development of a methodology for using climate model output for coastal climate change impact assessment studies.
17
Ekuje, Friday T. "Bridge scour : climate change effects and modelling uncertainties." Thesis, University of Surrey, 2018. http://epubs.surrey.ac.uk/849796/.
Full textAbstract:
Scour of bridge piers and abutments has been identified as the main cause of bridge collapse around the world. Undermining of bridge foundations occurs by river sediment removal which may lead to loss of their load bearing capacity. Long-term climate change arising from global warming has the potential to further exacerbate bridge scour due to increased river flooding resulting from increased precipitation. It is important for bridge owners and managers to understand how the risk of their bridge is likely to change due to the potential effects of climate change as this will assist towards their long-term management so that the consequences arising from bridge failures/damage can be minimised as far as possible. In the UK, climate change is expected to increase the magnitude and/or frequency of precipitation, leading to increased and/or more frequent river flooding. Several recent studies on high river flows in various British rivers predict future peak discharges that capture climate change effects. These predictions supersede the older 20% and 25% allowances that have been used in the UK in the past for climate change analyses. In this research, selected climate change allowances for the UK (Environment Agency, 2016) were applied to two common bridge assessment methodologies. As part of this study, the UK highway and railway scour assessment codes were reviewed to assess their capability in capturing climate change effects on bridge scour and identify potential limitations. The main limitation of the railway code was identified as being its inability to account for changes in river discharge. The Highway Agency (2012) (BD97/12), which has been developed more recently, was suitable for adaptation to capture climate change effects on bridge scour and, as a result, has been the focus of this study. A large number of analyses were carried out as part of this study to quantify the effects of climate change on bridge scour. The generated scour data consisted of 27,000 scour depths for bridges on wide river channels, 18,000 on intermediate and 9,000 on narrow channels, each accounting for different median sediment sizes, foundation depth, pier width and angle of attack. The aim was to simulate a large number of scenarios of bridge-river configurations to identify which situations are more susceptible to climate change effects. It was found that, in some situations, climate change has the potential of shifting the scour risk ranking of bridges to a higher risk level, potentially leading to changes in their long-term risk management. The angle of attack effect on scour risk was found to be the factor that has the most significant effect on scour risk irrespective of bridge location/river channel type. Other key findings of this research are that Highway Agency (2012) the BD97/12, the scour assessment method for highway bridges over predicted scour depth. Sediment sizes and foundation depths have significant effect on bridge scour alongside the opening ratio of a bridge The availability of a large database with scour field measurements in the USA offered the opportunity to assess the accuracy of the scour model predictions in the Highway Agency (2012) BD97/12. The majority of bridge scour equations have been derived from idealised laboratory studies which may not necessarily be representative of realistic river conditions. Statistical analyses were used to quantify the deviations between code predictions and real measurements. The former were found to lead to conservative predictions. Probabilistic distributions were fitted to the data and suggested as modelling uncertainty factors to be used with the existing scour models in the codes to update their predictions to more realistic levels.
18
Thompson, Erica Lucy. "Modelling North Atlantic storms in a changing climate." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/14730.
Full textAbstract:
Quantitative projections are routinely made for the future statistics of climate variables, such as the frequency and intensity of storms in the North Atlantic. The quantification of uncertainty in these projections is particularly important if such results are to be used for decision making. This thesis addresses the design, use, and interpretation of models in climate science, using the behaviour of North Atlantic extratropical storms as a detailed case study. Results from novel statistical models and state-of-the-art dynamical models are generated and evaluated, looking at the frequency and intensity characteristics of storms in the eastern North Atlantic and the clustering characteristics of the most intense storms. It is found that statistical models are extremely limited by the shortness of the calibration data set of historical observations, and therefore have little merit other than simplicity. Dynamical models are primarily constrained by the accuracy of their dynamical assumptions, which cannot be easily quantified. Some relevant properties of dynamical systems, including structural instability, are discussed with reference to predictability in the North Atlantic and other aspects of climate science. This thesis concludes that despite the existence of "statistically significant" results from some individual models, there is little evidence that we can correctly evaluate even the sign of 21st century change of North Atlantic storm characteristics (frequency, intensity or spatial position). Although climate models do suggest that the magnitude of overall change will be small, this could still result in very large percentage changes to the tails of the distribution, given the nonlinear nature of the climate system. In order to make more confident conclusions about the tails of such distributions, much longer runs are needed than the 30 year slices requested by the CMIP experiments. In addition, formal quantification of subjective opinions about model error would benefit climate science, scientists, and decision-makers.
19
Heaphy, Liam James. "Modelling and translating future urban climate for policy." Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/modelling-and-translating-future-urban-climate-for-policy(2c2ca637-bec2-4f60-884d-5d34fa77fb26).html.
Full textAbstract:
This thesis looks at the practice of climate modelling at the urban scale in relation to projections of future climate. It responds to the question of how climate models perform in a policy context, and how these models are translated in order to have agency at the urban scale. It considers the means and circumstances through which models are constructed to selectively represent urban realities and potential realities in order to explore and reshape the built environment in response to a changing climate. This thesis is concerned with an interdisciplinary area of research and practice, while at the same time it is based on methodologies originating in science and technology studies which were later applied to architecture and planning, geography, and urban studies. Fieldwork consisted of participant-observation and interviews with three groups of practitioners: firstly, climate impacts modellers forming part of the Adaptation and Resilience in a Changing Climate (ARCC) programme; secondly, planners and adaptation policymakers in the cities of Manchester and London; and thirdly, boundary organisations such as the UK Climate Impacts Programme (UKCIP). Project and climate policy material pertinent to these projects and the case study cities were also analysed in tandem. Of particular interest was the common space shared to researchers and stakeholders where modelling results were explained, contextualised, and interrogated for policy-relevant results. This took the form of stakeholder meetings in which the limits of the models in relation to policy demands could be articulated and mediated. In considering the agency of models in relation to uncertainties, it was found that although generated in a context of applied science, models had a limited effect on policy. As such, the salience of urban climatic risk-based assessment for urban planning is restrained, because it presupposes a quantitative understanding of climate impacts that is only slowly forming due to societal and governmental pressures. This can be related both to the nature of models as sites of exploration and experimentation, and to the distribution of expertise in the climate adaptation community. Although both the research and policy communities operate partly in a common space, models and their associated tools operate at a level of sophistication that policy-makers have difficulty comprehending and integrating into planning policy beyond the level of simple guidance and messages. Adaptation in practice is constrained by a limited understanding of climate uncertainties and urban climatology, evident through the present emphasis on catch-all solutions like green infrastructure and win-win solutions rather than the empowerment of actors and a corresponding distribution of adequate resources. An analysis is provided on the means by which models and maps can shape climate adaptation at scales relevant for cities, based on considerations of how models gain agency through forms of encoded expertise like maps and the types of interaction between science and policy that they imply.
20
Karmacharya, Jagadishwor. "Climate processes over the Himalaya : the added value from high resolution regional climate modelling." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:a8cec5ba-b837-49c0-abd4-62c26d71dffd.
Full textAbstract:
The Himalaya plays a vital role in shaping the hydro-climate of South Asia and beyond, but their climate has not yet been monitored and modelled as well as some other regions. As the summer monsoon is the dominant climate system over South Asia, including the Himalaya, realistic simulation of the South Asian summer monsoon (SASM) should be a prerequisite for the satisfactory simulation of the Himalayan climate. The present research tests the assumption that higher resolution modelling will provide improved representation of the SASM, both regionally and over the Himalaya region. The first part of this research assesses the strength and stability of the temporal relationships between the monsoon rainfall indices (MRIs) and the large-scale monsoon circulation indices (MCIs), as a precursor to using such indices for model evaluation. The remainder of the thesis evaluates model performance in simulating various characteristics of SASM, mainly with regard to precipitation. In particular, the sensitivity of a regional climate model (RCM) simulation to domain size and added value of high resolution RCM simulation are evaluated. For this purpose, the Hadley Centre unified model - HadGEM is utilized in its regional and, in few instances, global configurations. The RCM simulations are performed at 0.44° and 0.11° horizontal resolutions and they are forced by the ERA interim dataset. Results show that i) the MRI-MCI relationship exhibits considerable low-frequency variability, ii) RCM simulation of SASM, particularly precipitation, shows sensitivity to domain size and simulation with a moderately sized domain that partially excludes bias prone equatorial Indian ocean outperform those with larger domains, iii) high resolution RCM simulation adds value in many aspects of SASM precipitation, including the seasonal mean, relative frequency distribution, extremes, and active and break monsoon composites, but the improvements are generally seen over the Indo-Gangetic plain rather than the Himalaya. The findings promote use of a high resolution RCM over a moderate sized domain (~ 25,000,000 sq. km) for the realistic simulation of SASM, but the study needs to be repeated with multiple realizations and different RCMs before arriving at a robust conclusion.
21
Pretis, Felix. "Econometric methods and applications in modelling non-stationary climate data." Thesis, University of Oxford, 2015. http://ora.ox.ac.uk/objects/uuid:f4c9122b-5270-4b55-a292-2cdf10ad7f2a.
Full textAbstract:
Understanding of climate change and policy responses thereto rely on accurate measurements as well as models of both socio-economic and physical processes. However, data to assess impacts and establish historical climate records are non-stationary: distributions shift over time due to shocks, measurement changes, and stochastic trends - all of which invalidate standard statistical inference. This thesis establishes econometric methods to model non-stationary climate data consistent with known physical laws, enabling joint estimation and testing, develops techniques for the automatic detection of structural breaks, and evaluates socio-economic scenarios used in long-run climate projections. Econometric cointegration analysis can be used to overcome inferential difficulties stemming from stochastic trends in time series, however, cointegration has been criticised in climate research for lacking a physical justification for its use. I show that physical two-component energy balance models of global mean climate can be mapped to a cointegrated system, making them directly testable, and thereby provide a physical justification for econometric methods in climate research. Automatic model selection with more variables than observations is introduced in modelling concentrations of atmospheric CO2, while controlling for outliers and breaks at any point in the sample using impulse indicator saturation. Without imposing the inclusion of variables a-priori, model selection results find that vegetation, temperature and other natural factors alone cannot explain the trend or the variation in CO2 growth. Industrial production components, driven by business cycles and economic shocks, are highly significant contributors. Generalizing the principle of indicator saturation, I present a methodology to detect structural breaks at any point in a time series using designed functions. Selecting over these break functions at every point in time using a general-to-specific algorithm, yields unbiased estimates of the break date and magnitude. Analytical derivations for the split-sample approach are provided under the null of no breaks and the alternative of one or more breaks. The methodology is demonstrated by detecting volcanic eruptions in a time series of Northern Hemisphere mean temperature derived from a coupled climate simulation spanning close to 1200 years. All climate models require socio-economic projections to make statements about future climate change. The large span of projected temperature changes then originates predominantly from the wide range of scenarios, rather than uncertainty in climate models themselves. For the first time, observations over two decades are available against which the first sets of socio-economic scenarios used in the Intergovernmental Panel on Climate Change reports can be assessed. The results show that the growth rate in fossil fuel CO2 emission intensity (fossil fuel CO2 emissions per GDP) over the 2000s exceeds all main scenario values, with the discrepancy being driven by underprediction of high growth rates in Asia. This underestimation of emission intensity raises concerns about achieving a world of economic prosperity in an environmentally sustainable fashion.
22
Jones, Christopher David. "Quantitative carbon cycle modelling to inform climate mitigation policy." Thesis, University of Exeter, 2017. http://hdl.handle.net/10871/27943.
Full textAbstract:
The global carbon cycle is a central part of the climate system which forms a direct link between human activity and climate change. This thesis presents my contribution to the field of research into the global carbon cycle with complex numerical models and its use to inform climate mitigation policy. Firstly, I present work I led to build, configure and apply the Hadley Centre Earth System Model, HadGEM2-ES, that successfully delivered the CMIP5 simulations. Then I present work that led to the design of the next generation of coupled carbon cycle intercomparison experiments. The aim of these experiments is to understand and quantify future centuryscale changes in land and ocean carbon storage and fluxes and their impact on climate projections. A set of ESM simulations was devised, with a common protocol, which all participating modelling centres should follow. A theoretical framework is commonly used to quantify carbon cycle feedbacks. I played an active role in its recommended use and definitions of terms. A feedback analysis I performed of future carbon cycle projections formed a central component of the IPCC’s Fifth Assessment Report. This is the first time that that the IPCC carbon cycle chapter had a section devoted to the feedbacks and future projections from coupled carbon cycle ESMs. Finally, I present three specific applications of my research and their relevance to climate mitigation policy. 1) I was the first to define the concept of committed ecosystem changes and demonstrate that ecosystems may continue to respond for many years or decades after climate is stabilised, leading to the recommendation that such committed change should be included in definitions of dangerous climate change. 2) I performed the first Earth System model analysis of the carbon emissions reductions required to follow the RCP pathways leading to the IPCC AR5 statement that, “For RCP2.6, an average 50% emission reduction is required by 2050 relative to 1990 levels”. 3) My research on carbon cycle feedbacks, especially the response of the carbon cycle to low CO2 pathways, found that models predict significant weakening, or even potential reversal, of natural carbon sinks in response to removal of CO2, which potentially hinders the effectiveness of the negative emissions. My research presented in this thesis has been influential in setting international research priorities in this field. It continues to inform global negotiations on climate mitigation policy.
23
Northrop, Paul James. "Modelling and statistical analysis of spatial-temporal rainfall fields." Thesis, University College London (University of London), 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.340891.
Full text
24
Evans, Jason Peter, and jason evans@yale edu. "Modelling Climate - Surface Hydrology Interactions in Data Sparse Areas." The Australian National University. Centre for Resource and Environmental Studies, 2000. http://thesis.anu.edu.au./public/adt-ANU20020313.032142.
Full textAbstract:
The interaction between climate and land-surface hydrology is extremely important in relation to long term water
resource planning. This is especially so in the presence of global warming and massive land use change, issues which
seem likely to have a disproportionate impact on developing countries. This thesis develops tools aimed at the study
and prediction of climate effects on land-surface hydrology (in particular streamflow), which require a minimum
amount of site specific data. This minimum data requirement allows studies to be performed in areas that are data
sparse, such as the developing world.
¶
A simple lumped dynamics-encapsulating conceptual rainfall-runoff model, which explicitly calculates the evaporative
feedback to the atmosphere, was developed. It uses the linear streamflow routing module of the rainfall-runoff model
IHACRES, with a new non-linear loss module based on the Catchment Moisture Deficit accounting scheme, and is referred
to as CMD-IHACRES. In this model, evaporation can be calculated using a number of techniques depending on the data
available, as a minimum, one to two years of precipitation, temperature and streamflow data are required. The model
was tested on catchments covering a large range of hydroclimatologies and shown to estimate streamflow well. When
tested against evaporation data the simplest technique was found to capture the medium to long term average well but
had difficulty reproducing the short-term variations.
¶
A comparison of the performance of three limited area climate models (MM5/BATS, MM5/SHEELS and RegCM2) was conducted
in order to quantify their ability to reproduce near surface variables. Components of the energy and water balance
over the land surface display considerable variation among the models, with no model performing consistently better
than the other two. However, several conclusions can be made. The MM5 longwave radiation scheme performed worse than
the scheme implemented in RegCM2. Estimates of runoff displayed the largest variations and differed from observations
by as much as 100%. The climate models exhibited greater variance than the observations for almost all the energy and
water related fluxes investigated.
¶
An investigation into improving these streamflow predictions by utilizing CMD-IHACRES was conducted. Using
CMD-IHACRES in an 'offline' mode greatly improved the streamflow estimates while the simplest evaporation technique
reproduced the evaporative time series to an accuracy comparable to that obtained from the limited area models alone.
The ability to conduct a climate change impact study using CMD-IHACRES and a stochastic weather generator is also
demonstrated. These results warrant further investigation into incorporating the rainfall-runoff model CMD-IHACRES
in a fully coupled 'online' approach.
25
Booij, Martijn Jan. "Appropriate modelling of climate change impacts on river flooding." Enschede : University of Twente [Host], 2002. http://doc.utwente.nl/58717.
Full text
26
Henderson, Browne Oliver James. "Numerical modelling of large-scale ice-sheet-climate interactions." Thesis, University of Reading, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.515704.
Full text
27
Strachan, Jane. "Understanding and modelling the climate of the Maritime Continent." Thesis, University of Reading, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.494989.
Full textAbstract:
The Maritime Continent has been identified as a region of major climatic importance on both local and global scales. It is essential that the region is sufficiently represented in GCMs in order to correctly reproduce observed regional climatology and ultimately global circulation. However, the region represents a major modelling challenge. Systematic underestimation of precipitation over the Maritime Continent region is experienced in many atmosphere-only general circulation models (AGCMs), including the Hadley Centre Global Atmospheric Model (HadGAMl). The discrepancy in rainfall leads to errors not only in the Maritime Continent region, but to systematic errors elsewhere, both in the tropics and extra-tropics.
28
Botha, Corné. "Modelling the climate in a transport container / Corné Botha." Thesis, North-West University, 2004. http://hdl.handle.net/10394/578.
Full textAbstract:
The transportation of agro-products is essential for all of us. The quality of food after
transportation is very important - none of us will buy poor quality food. In September
2002, A&FI started the three year research project QUEST(Quality and Energy efficiency
in the Storage and Transportation of Agro-materials), with the focus on the use of containers
to transport products overseas. The aim of QUEST is to find ways to reduce energy
consumption for climate conditioning during transportation of perishable goods, and to
monitor the product quality in order to minimize product losses. To achieve these goals,
predictive models that describe the climate in one box, in a layer consisting out of nine
boxes, and in a stack (few layers on top of each other) should be developed. The transport
containers used, have a cooling unit in the front and a sensor system measuring the
temperature and humidity inside the container. The goods are stored in cardboard boxes
that are stacked in piles on pallets. The climate inside the container can be controlled by
the circulation of cooled air. The main goal of this project is to develop a two-dimensional
model predicting the climate in one layer of boxes. The company A&FI already has a
model for the whole container, and wants to plug my resulting model, for one layer of
boxes, into their model.
First I model a box and a slit (space between the boxes) separately. Subsequently I
derive a network model for one layer consisting of nine boxes. The idea of the network is
to replace the temperature distribution by the averaged temperature related to each box
and slit. Such a method is strongly based on the description of heat transfer using the
analogy with electrical circuits.
My model makes it possible to determine the average temperatures at any moment of
time, i.e. , predict the climate within a layer inside a transport container. My model brings
A&FI another step closer in the process to have a global model for the whole container. I
recommend further extension of our model to a stack of boxes (to three dimensions).Thesis (M.Sc. (Applied Mathematics))--North-West University, Potchefstroom Campus, 2005.
29
Joyce, Andrew Noel. "Modelling surface climate over complex terrain for landscape ecology." Thesis, Durham University, 2000. http://etheses.dur.ac.uk/4245/.
Full textAbstract:
Climate exerts a fundamental control on ecosystem function, species diversity and distribution. Topographic variability may influence surface climate, through processes operating at a landscape- scale. To quantify and model such influences, the topography of a 72 km(^2) area of complex terrain, (including the Moor House National Nature Reserve in northern England) was analysed at 50 m resolution. A suite of topographic variables was created, including distance relative to the Pennine ridge (dist), and elevation difference between each grid cell and the lowest grid cell within a specified neighbourhood {drain). Automatic weather stations (AWS) were deployed in a series of networks to test hypothetical relationships between landscape and climate. Daily maximum air temperature, daily mean soil temperature and daily potential evapotranspiration can be modelled spatially using a daily lapse rate calculated from the difference between daily observations made at two base stations. On days with a south easterly wind direction, daily mean temperature is estimated as a function of lapse rate and dist; the spatial behaviour of temperature is consistent with a föhn mechanism. Daily minimum temperature is modelled using lapse rate and drain on days with a lapse rate of minimum temperature shallower than -2.03 x 10 C m(^-1), incorporating the effects of katabatic air flow. Daily solar radiation surfaces are estimated by a GIS routine that models interactions between slope and solar geometry and accounts for daily variations in cloudiness and daylight duration. The daily climate surfaces were tested using data measured at a range of AWS locations during different times of year. The accuracy of the daily surfaces is not seasonally-dependent. The spatial climate data are particularly well suited to landscape-scale ecology because the methods account for prevailing topoclimatic constraints and because separate climate surfaces are generated for each day, capturing the high frequency variability characteristic of upland regions.
30
Easthope, Mark Paul. "Modelling cyanobacteria in lakes : in relation to climate change." Thesis, University of Reading, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.266794.
Full text
31
Grandpré, Jean de. "Climate modelling of the ozone layer processes and interactions /." access full-text online access from Digital Dissertation Consortium, 2006. http://libweb.cityu.edu.hk/cgi-bin/er/db/ddcdiss.pl?NR19832.
Full text
32
Kaky, E. "Species distribution modelling of Egyptian plants under climate change." Thesis, University of Nottingham, 2018. http://eprints.nottingham.ac.uk/52119/.
Full textAbstract:
It is thought that climate change will have a major impact on species distributions by changing the habitat suitability for species. Species distribution modelling is a modern approach to assess the potential effect of climate change on biodiversity. We used 11 environmental variables with the MaxEnt algorithm to model the distributions of 114 Egyptian medicinal plant species under current conditions, then projecting them into three different future times (2020, 2050, and 2080) under two different climate-change emission scenarios (A2a and B2a), under two hypotheses about the capability of the species for dispersal (unlimited and no dispersal). Species richness maps for current and future times were produced. We tested the value of Egypt’s Protected Areas under climate change by estimating the species richness inside and outside under each scenario. We assessed Egyptian medicinal plants based on IUCN Red List categories and criteria, and then used the SDMs for conservation planning with and without consideration of socioeconomic factors using Zonation software. The A2 emission scenario was more harmful than B2 under all assumptions. Species richness inside Protected Areas was significantly higher than outside for all models. Based just on the records, between 75% and 90% of species could be classified as Least Concern, according to the assumptions made. Similarly, based on SDMs all species could be classified as LC at the current time, whilst in the future under climate change, up to 18% of species face the risk of extinction, depending on assumptions and based on the absolute time gap between the two future times. Based on 10 years, most species were assigned as Least Concern. Areas within PAs were no better in conservation prioritization value than area outside when socioeconomic costs (especially the Human Influence Index) were taken into account. Species distribution models appear to be extremely useful for conservation planning under climate change, particularly when only sparse data are available. Socioeconomic information adds a new dimension to conservation planning, which is actually misleading and incomplete without it.
33
Ibrahim, Abdussalam Ahmed Mohamed. "Modelling the Relationship between Climate Vegetation in the Tarhuna Region,Libya,Using Spatial Modelling Techniques." Thesis, University of Reading, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.533756.
Full textAbstract:
This research project studies the spatial and temporal relationships between climate and vegetation in the Tarhuna region of northwest Libya, in order to derive mathematical relationships describing vegetation dynamics over the study period 1981/1982-2005/2006. The study area straddles the Mediterranean and arid climate zones, and is prone to vegetation loss and land degradation due to drought and human activity. Rainfall has decreased over the period of study, leading to increased occurrence of drought and a greater risk of vegetation loss and land degradation. Rangeland and rain-fed agricultural land comprise 94% of the study area. Allowing for a two-month time lag, significant positive relationships between monthly climate and vegetation data (as measured by GIMMS NDVI archive) were found for both land cover types; the dominant control is the distribution and concentration of rainfall throughout the year. A positive relationship was found between annual rainfall and vegetation productivity. A water balance model, TVRWBM, was developed, and explained 70% of the variation of vegetation cover in the study area. By applying TVRWBM, three specific locations and time periods were identified where the model does not fit in particular years. Field investigations identified specific human activities as the cause for these anomalies. An attempt was made to use the model to predict future trends in land degradation using both statistical downscaling and GGM model predictions of future climate changes, but, although these methods can recreate temperature trend for the recorded period, they are not able to produce reliable estimates of rainfall. However, IPGG predictions suggest lower rainfall and higher temperatures for the study area in the future, so environmental pressures in the study area are likely to intensify.
34
Hutchings, Jennifer Katy. "On modelling the mass of Arctic sea ice." Thesis, University College London (University of London), 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.246736.
Full text
35
Dunn, Katherine Margaret. "Prototyping Models of Climate Change: New Approaches to Modelling Climate Change Data. 3D printed models of Climate Change research created in collaboration with Climate Scientists." Thesis, The University of Sydney, 2017. http://hdl.handle.net/2123/17623.
Full textAbstract:
Prototyping Models of Climate Change: New Approaches to Modelling Climate Change Data, identifies a gap in existing knowledge on the topic of 3D Printed, three dimensional creative visualisations of data on the impact of climate change. Communication, visualisation and dissemination of scientific research data to the general-public is a priority of science organisations. Creative visualisation projects that encourage meaningful cross-disciplinary collaboration are urgently needed, from a communication standpoint and, to act as models for agile responsive means of addressing climate change. Three-dimensional creative visualisations can give audiences alternate and more direct means of understanding information by engaging visual and haptic experience. This project contributes new knowledge in the field by way of an innovative framework and praxis for the communication and dissemination of climate change information across the disciplines of contemporary art, design and science. The focus is on projects that can effectively and affectively, communicate climate science research between the disciplines and the general-public. The research generates artefacts using 3D printing techniques. A contribution to new knowledge is the development of systems and materials for 3D printing that embody principles of sustainable fabrication. The artefacts or visualisations produced as part of the research project are made from sustainable materials that have been rigorously developed and tested. Through a series of collaborations with climate scientists, the research investigates methodologies and techniques for modelling and fabricating three-dimensional artefacts that represent climate change data. The collaborations and the research outputs are evaluated using boundary object theory. Expanding on existing boundary object categories, the research introduces new categories with parameters specifically designed to evaluate creative practice- science collaborations and their outputs.
36
Micheels, Arne. "Late miocene climate modelling with ECHAM4/ML the effects of the palaeovegetation on the Tortonian climate /." [S.l. : s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=969600089.
Full text
37
Dockerty, Trudie Lynne. "Developing a climate-space modelling approach using a GIS to estimate the impacts of climate change on nature reserves in Great Britain." Thesis, University of East Anglia, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.297467.
Full text
38
Jonsson, Andreas. "Modelling the middle atmosphere and its sensitivity to climate change." Doctoral thesis, Stockholm University, Department of Meteorology, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-769.
Full textAbstract:
The Earth's middle atmosphere at about 10-100 km has shown a substantial sensitivity to human activities. First, the ozone layer has been reduced since the the early 1980s due to man-made emissions of halogenated hydrocarbons. Second, the middle atmosphere has been identified as a region showing clear evidence of climate change due to increased emissions of greenhouse gases. While increased CO2 abundances are expected to lead to a warmer climate near the Earth's surface, observations show that the middle atmosphere has been cooling by up to 2-3 degrees per decade over the past few decades. This is partly due to CO2 increases and partly due to ozone depletion.
Predicting the future development of the middle atmosphere is problematic because of strong feedbacks between temperature and ozone. Ozone absorbs solar ultraviolet radiation and thus warms middle atmosphere, and also, ozone chemistry is temperature dependent, so that temperature changes are modulated by ozone changes.
This thesis examines the middle atmospheric response to a doubling of the atmospheric CO2 content using a coupled chemistry-climate model. The effects can be separated in the intrinsic CO2-induced radiative response, the radiative feedback through ozone changes and the response due to changes in the climate of the underlying atmosphere and surface. The results show, as expected, a substantial cooling throughout the middle atmosphere, mainly due to the radiative impact of the CO2 increase. Model simulations with and without coupled chemistry show that the ozone feedback reduces the temperature response by up to 40%. Further analyses show that the ozone changes are caused primarily by the temperature dependency of the reaction O+O2+M->O3+M. The impact of changes in the surface climate on the middle atmosphere is generally small. In particular, no noticeable change in upward propagating planetary wave flux from the lower atmosphere is found. The temperature response in the polar regions is non-robust and thus, for the model used here, polar ozone loss does not appear to be sensitive to climate change in the lower atmosphere as has been suggested recently. The large interannual variability in the polar regions suggests that simulations longer than 30 years will be necessary for further analysis of the effects in this region.
The thesis also addresses the long-standing dilemma that models tend to underestimate the ozone concentration at altitudes 40-75 km, which has important implications for climate change studies in this region. A photochemical box model is used to examine the photochemical aspects of this problem. At 40-55 km, the model reproduces satellite observations to within 10%, thus showing a substantial reduction in the ozone deficit problem. At 60-75 km, however, the model underestimates the observations by up to 35%, suggesting a significant lack of understanding of the chemistry and radiation in this region.
39
Voskamp, Alke. "Climate change, modelling and conservation of the world's terrestrial birds." Thesis, Durham University, 2017. http://etheses.dur.ac.uk/12461/.
Full textAbstract:
Global climate change is an important threat to biodiversity and is predicted to be a major driver of wildlife population extinctions throughout the current century. Across a wide range of taxa, a well-documented response to climate change has been changes in species distributions, often towards higher latitudes and altitudes. Species distribution models (SDMs) have been widely used to predict further range changes in future but their use has often focused on discrete geographical areas. Moreover, SDMs have typically been correlative, ignoring biological traits. Here, I use SDMs to project future ranges for the world’s terrestrial birds under climate change. To improve the realism of projected range changes, I incorporate biological traits, including species’ age at first breeding and natal dispersal range. I use these projections to predict large-scale patterns in the responses of terrestrial birds to climate change, and to explore the implications of these models for avian conservation. There is little consensus on the most useful predictors for SDMs, so I begin by exploring how this varies geographically. With this knowledge, I develop SDMs for the world’s terrestrial birds and project future species ranges using three different global climate models (CCSM4, GFDL-CM3, HadGEM2-ES) under a low (rcp26), a medium (rcp45) and a high (rcp85) representative concentration pathway. The projected ranges are used to identify species most at risk from climate change and to highlight global hotspots where species are projected to experience the highest range losses. I explore how the projected range changes affect global species communities and I identify areas where species communities are projected to change or novel communities will emerge. I assess how projected changes will affect the ability of the global Important Bird and Biodiversity Areas (IBAs) network to confer protection on the world’s terrestrial bird species. Additionally, I highlight - based on projected range loss and suitable habitat and climate space beyond the dispersal range - species that will be unable to track climate change and that could be candidates for Assisted Colonization (AC). Finally, I explore the divergence between global species richness (SR) patterns and phylogenetic diversity (PD) for the world’s terrestrial birds, to assess if measuring biodiversity and setting conservation targets based on SR can be expected to cover their PD as well. Identifying the global consequences of projected range changes can inform future conservation efforts and research priorities. Changes in range extent and overlap were projected for the vast majority of the world’s terrestrial birds, with one-fifth projected to experience major range losses (>75% decline in range extent projected). This has far reaching consequences for the IBA network, with an overall trend of species moving out of the IBA coverage. Furthermore 13% of the world’s terrestrial birds are projected to have severe range losses that, combined with an inability to follow suitable habitat and climate space, mean they could benefit from AC as a conservation tool. Overall, PD was found to be highly correlated to SR on a global scale; however, there are localized differences where PD is higher or lower than could be expected from SR alone. These differences suggest that considering PD could enhance conservation planning. The results demonstrate the major threat that climate change poses for the world’s terrestrial bird species across all areas of the globe, and highlight the importance of considering climate change impacts to enhance their protection.
40
Jonsson, Andreas. "Modelling the middle atmosphere and its sensitivity to climate change /." Stockholm : Department of Meteorology, Stockholm university, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-769.
Full text
41
Larson, Robert, and University of Lethbridge Faculty of Arts and Science. "Modelling climate change impacts on mountain snow hydrology, Montana-Alberta." Thesis, Lethbridge, Alta. : University of Lethbridge, Faculty of Arts and Science, 2008, 2008. http://hdl.handle.net/10133/669.
Full textAbstract:
A modelling approach focused on snow hydrology was developed and applied to project
future changes in spring streamflow volumes in the St. Mary River headwaters basin,
Montana. A spatially distributed, physically-based, hydrometeorological and snow mass
balance model was refined and used to produce snow water equivalent (SWE) and
rainfall surfaces for the study watershed. Snowmelt runoff (SR) and effective rainfall
runoff (RR) volumes were compiled for the 1961-2004 historical period. A statistical
regression model was developed linking spring streamflow volume (QS) at Babb,
Montana to the SR and RR modelled data. The modelling results indicated that SR
explained 70% of the variability in QS while RR explained another 9%.
The model was applied to climate change scenarios representing the expected range of
future change to produce annual QS for the period 2010-2099. Compared to the base
period (1961-1990), average QS change ranged from -3% to -12% for the 2020s period.
Percent changes increased to between -25% and -32% for the 2050s, and -38% and -55%
for the 2080s. Decreases in QS also accompanied substantial advances in the onset of
spring snowmelt. Whereas the spring pulse onset on average occurred on April 8 for the
base period, it occurred 36 to 50 days earlier during the 2080s. The findings suggest that
increasing precipitation will not compensate for the effects of increasing temperature in
watershed SWE and associated spring runoff generation. There are implications for
stakeholder interests related to ecosystems, the irrigation industry, and recreation.xii, 136 leaves : ill. ; 28 cm. --
42
Parkinson, Stuart D. "The application of stochastic modelling techniques to global climate change." Thesis, Lancaster University, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240453.
Full text
43
Horseman, Andrew Mark. "Modelling cirrus cloud fields for climate and atmospheric chemistry studies." Thesis, Lancaster University, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.652029.
Full textAbstract:
Cirrus clouds are thought to have a significant role in atmospheric processes: specifically; their heating/cooling contribution to the Earth's radiative balance, and the consumption of water substance due to their formation. Their presence in the upper troposphere I lower stratosphere (UTLS) also provides a surface for heterogeneous chemistry. The SLIM CAT-Cirrus model is developed to provide a tool to investigate aspects of these properties. SLIM CAT-Cirrus is based upon the existing SLIM CAT chemistry transport model and a parameterisation of the formation of cirrus ice by homogeneous nucleation. The advantages and drawbacks of the use of legacy models are discussed especially issues regarding the loss of the underlying decision-making regarding design approach, approximations, and assumptions. Techniques adopted and adapted from the software engineering and QA disciplines are used to mitigate these problems and maintain future traceabilty; this takes the form of examples of practical measures that small groups or individuals researchers can use. The difficulty in validating a complex global model in the absence of a definitive reference has been addressed by using diverse measurement data sources, and a suite of statistical merries. Model verification testing is also used to characterise processes that are difficult [0 validate. Validation of the modelled frequency of cirrus occurrence against satellite data showed an initial under-prognosis by the model. To address this a statistical scheme has been devised to reproduce some of the effects of phenomena such as gravity waves that are not resolved by the model grid. The modelled effects of the formation of cirrus on the water budget in the UTLS are comparable with measurements from the HALOE (HALogen Occultation Experiment), and are also in-line with the drying effect cirrus are thought to have on air entering the stratosphere. The radiative effects of cirrus have been represented using specific cirrus radiative parameterisations. The cirrus heating shows positive feedback into vertical transport causing meso-scale uplift of the kind thought to be responsible for part of the BrewerDobson atmospheric circulation.
44
Kocabas, Zahide. "Sensitivity of crop models to climate variations and modelling techniques." Thesis, University of Nottingham, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.358287.
Full text
45
Smith, Andrew M. "Modelling the impacts of a changing climate on flood risk." Thesis, University of Bristol, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.683693.
Full textAbstract:
In recent decades there has been a significant increase in reported flood events and flood losses. Although these losses may be attributed to improvements in reporting and increased exposure in flood prone areas, a perception now exists that flood risk is increasing as a direct result of anthropogenic global warming. In response to this perceived risk, research focused on producing projections of future flood risk has been receiving considerable attention. Indeed, climate impact studies are now being used to guide and test government policy. However, there are significant uncertainties associated with the application of climate model output in flood impact studies. Moreover, there is a disparity between current impact studies and the information required by decision makers, with studies typically focussing on changing river flows. This thesis aims to bridge this gap, cascading climate model output through to impacts at the building scale under an uncertainty framework. The overall aim is to explore the feasibility of using future flood projections as a decision making tool and ultimately to better inform decision makers. The first component of this research was focussed on investigating current climate models and exploring the suitability of their application in flood impact studies. It was found that poor model performance currently precludes their application in assessing flood risk in some regions. The results also provided recommendations for future flood impact studies; these were then used to inform the cascade modelling framework. The rest of the thesis details the development of the modelling framework, driving ensemble climate projections through hydrological, hydraulic and damage models. The modelling framework was also structured to enable uncertainty under current climate conditions to be explored. For the first time, this work presents uncertain climate projections in terms of damage at the building scale. The results reveal that there is an increase in flood magnitude under future climate conditions, however there is significant variability between projections. In fact, the results reveal that there is significant uncertainty under current climate conditions with the potential for exceptional flooding regardless of any future change. The results also emphasise the need to model damage in impact studies as the assumption of linearity between changing hazard and changing risk is invalid. The research presented here has proposed suitable methods for informing decision makers and demonstrated that there is significant scope for improvement in climate impact studies.
46
Sekerci, Firat Yadigar. "Mathematical modelling of oxygen-plankton system under the climate change." Thesis, University of Leicester, 2016. http://hdl.handle.net/2381/37971.
Full textAbstract:
Oxygen production due to phytoplankton photosynthesis is an important phenomenon keeping in mind the underlying dynamics of marine ecosystems. However, despite its crucial importance, not only for marine but also for terrestrial ecosystems, the coupled oxygen-plankton dynamics have been overlooked. This dissertation aims to provide insight into an oxygen-plankton system using mathematical modelling. We firstly develop a ‘baseline’ oxygen-phytoplankton model which is then further developed through the addition of biologically relevant factors such as plankton respiration and the predator effect of zooplankton. The properties of the model have been studied both in the nonspatial case, which corresponds to a well mixed system with a spatially uniform distribution of species, and in the spatially explicit extension, by taking into account the transport of oxygen and movement of plankton by turbulent diffusion. Since the purpose of this work is to reveal the oxygen dynamics, the effect of global warming is considered taken into consideration and modelled by various oxygen production rates and phytoplankton growth functions in Chapters 5 and 6. It is shown that sustainable oxygen production is only possible in an intermediate range of the production rate. If the oxygen production rate becomes sufficiently low or high, in the course of time, the system’s dynamics shows abrupt changes resulting in plankton extinction and oxygen depletion. We show that the spatial system’s sustainability range is larger that of the corresponding nonspatial system. We show that oxygen production by phytoplankton can stop suddenly if the water temperature exceeds a certain critical threshold. Correspondingly, this dissertation reveals the scenarios of extinction which can potentially lead to an ecological disaster.
47
Yousaf, Rehan. "Modelling heat transfer and respiration of occupants in indoor climate." Thesis, Loughborough University, 2017. https://dspace.lboro.ac.uk/2134/25472.
Full textAbstract:
Although the terms "Human Thermal Comfort" and "Indoor Air Quality (IAQ)" can be highly subjective, they still dictate the indoor climate design (HVAC design) of a building. In order to evaluate human thermal comfort and IAQ, one of three main tools are used, a) direct questioning the subjects about their thermal and air quality sensation (voting, sampling etc.), b) measuring the human thermal comfort by recording the physical parameters such as relative humidity, air and radiation temperature, air velocities and concentration gradients of pollutants or c) by using numerical simulations either including or excluding detailed thermo-physiological models. The application of the first two approaches can only take place in post commissioning and/or testing phases of the building. Use of numerical techniques can however be employed at any stage of the building design. With the rapid development in computational hard- and software technology, the costs involved in numerical studies has reduced compared to detailed tests. Employing numerical modelling to investigate human thermal comfort and IAQ however demand thorough verification and validation studies. Such studies are used to understand the limitations and application of numerical modelling of human thermal comfort and IAQ in indoor climates. This PhD research is an endeavour to verify, validate and apply, numerical simulation for modelling heat transfer and respiration of occupants in indoor climates. Along with the investigations concerning convective and radiation heat transfer between the occupants and their surroundings, the work focuses on detailed respiration modelling of sedentary human occupants. The objectives of the work have been to: verify the convective and radiation numerical models; validate them for buoyancy-driven flows due to human occupants in indoor climates; and apply these validated models for investigating human thermal comfort and IAQ in a real classroom for which field study data was available. On the basis of the detailed verification, validation and application studies, the findings are summarized as a set of guidelines for simulating human thermal comfort and IAQ in indoor climates. This PhD research involves the use of detailed human body geometries and postures. Modelling radiation and investigating the effect of geometrical posture has shown that the effective radiation area varies significantly with posture. The simulation results have shown that by using an effective radiation area factor of 0.725, estimated previously (Fanger, 1972) for a standing person, can lead to an underestimation of effective radiation area by 13% for the postures considered. Numerical modelling of convective heat transfer and respiration processes for sedentary manikins have shown that the SST turbulence model (Menter, 1994) with appropriate resolution of near wall region can simulate the local air velocity, temperature and heat transfer coefficients to a level of detail required for prediction of thermal comfort and IAQ. The present PhD work has shown that in a convection dominated environment, the detailed seated manikins give rise to an asymmetrical thermal plume as compared to the thermal plumes generated by simplified manikins or point sources. Validated simulation results obtained during the present PhD work have shown that simplified manikins can be used without significant limitations while investigating IAQ of complete indoor spaces. The use of simplified manikins however does not seem appropriate when simulating detailed respiration effects in the immediate vicinity of seated humans because of the underestimation in the amount of re-inhaled CO2 and pollutants from the surroundings. Furthermore, the results have shown that due to the simplification in geometrical form of the nostrils, the CO2 concentration is much higher near the face region (direct jet along the nostrils) as compared to a detailed geometry (sideways jet). Simulating the complete respiration cycle has shown that a pause between exhalation and inhalation has a significant effect on the amount of re-inhaled CO2. Previous results have shown the amount of re-inhaled CO2 to range between 10 - 19%. The present study has shown that by considering the pause, this amount of re-inhaled CO2 falls down to values lower than 1%. A comparison between the simplified and detailed geometry has shown that a simplified geometry can cause an underestimation in the amount of re-inhaled CO2 by more than 37% as compared to a detailed geometry. The major contribution to knowledge delivered by this PhD work is the provision of a validated seated computational thermal manikin. This PhD work follows a structured verification and validation approach for conducting CFD simulations to predict human thermal comfort and indoor air quality. The work demonstrates the application of the validated model to a classroom case with multiple occupancy and compares the measured results with the simulation results. The comparison of CFD results with measured data advocates the use of CFD and visualizes the importance of modelling thermal manikins in indoor HVAC design rather than designing the HVAC by considering empty spaces as the occupancy has a strong influence on the indoor air flow. This PhD work enables the indoor climate researchers and building designers to employ simplified thermal manikin to correctly predict the mean flow characteristics in indoor surroundings. The present work clearly demonstrates the limitation of the PIV measurement technique, the importance of using detailed CFD manikin geometry when investigating the phenomena of respiration in detail and the effect of thermal plume around the seated manikin. This computational thermal manikin used in this work is valid for a seated adult female geometry.
48
Rothwell, John R. "Modelling and control of crop production in horticultural greenhouses." Thesis, Lancaster University, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.340653.
Full text
49
Chou, Ching Ju. "The Application of Computational Fluid Dynamics to Comfort Modelling." Thesis, The University of Sydney, 2016. http://hdl.handle.net/2123/16686.
Full textAbstract:
This thesis studies thermal comfort in heating, ventilation and air-conditioning (HVAC) scenarios with computational fluid dynamics (CFD) models at domain and occupant levels. Domain level comfort modelling, where the details of the occupant are not modelled, is investigated utilising Fanger’s Predicted Mean Vote (PMV) and Predicted Percentage of Dissatisfied (PPD) comfort models. Occupant level comfort modelling, where the occupant geometry and skin temperature are required, is explored using two different models. The first model termed the thermal manikin model couples the University of California Berkeley (UCB) psychological model to a new physiological model which neglects the thermal regulation of the human body, and consists of a central core at constant temperature surrounded by a layer with thickness and corresponding thermal properties to allow the skin temperature to vary over the modelled human body. The second model based on Gagge’s two-node model, which includes thermal regulation, yet assumes the skin temperature of the occupant to be spatially uniform. The models are validated with the experimental results from the Technical University of Denmark, which provides the data of the air flow, and the Indoor Environmental Quality (IEQ) laboratory at the University of Sydney, which offered the actual votes of human subjects for a range of environmental conditions. To conclude, the prediction of the skin temperature and its spatial variation is the most important parameter to predict occupant comfort correctly. The occupant level comfort modelling approach employing the thermal manikin is found to be the superior method to evaluate thermal comfort as it can still be accurate when the environment is complex. However, the computational cost and model setup time is high. Further work employing multi-node thermal manikin models would be a fruitful area of research if the accuracy of occupant comfort prediction in complex thermal environments is of interest.
50
Kjellsson, Joakim. "Atmospheric & Oceanic Applications of Eulerian and Lagrangian Transport Modelling." Doctoral thesis, Stockholms universitet, Meteorologiska institutionen (MISU), 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-97348.
Full textAbstract:
This thesis presents several ways to understand transports of air and water masses in the atmosphere and ocean, and the transports of energy that they imply. It presents work using various kinds of observations as well as computer simulations of the atmosphere and oceans. One of the main focuses is to identify similarities and differences between models and observations, as well as between different models. The first half of the thesis applies Lagrangian methods to study flows in the atmosphere and oceans. Part of the work focuses on understanding how particles follow the currents in the Baltic Sea and how they disperse. It is suggested that the commonly used regional ocean model for the Baltic Sea, RCO, underestimates the transport and the dispersion of the particles, which can have consequences for studies of e.g. biogeochemistry as well as for operational use. A similar methodology is used to study how particles are transported between the tropics and mid-latitudes by the large-scale atmospheric circulation. It is found that the mass transport associated with northbound and southbound particles can cancel in the zonally averaged circulation, and we propose that the degree of cancellation depends on the method of averaging. The latter half of the thesis focuses on Eulerian stream functions and specifically a thermodynamic stream function that combines the zonal and meridional circulations of the atmosphere into a single circulation. The results are used to study the inter-annual variability of the intensity and thermodynamic properties of the global atmospheric circulation. A significant correlation to ENSO variability is found both in reanalysis and the EC-Earth coupled climate model. It is also shown that a set of models from the CMIP5 project show a slowdown of the atmospheric circulation as a result of global warming and associated changes in near-surface moisture content and upper-level radiative cooling.Denna avhandling presenterar olika metoder för att studera datormodeller av atmosfä- ren, haven, och klimatsystemet. Metoderna använder såväl Lagrangeska synsätt dvs att betrakta atmosfären eller haven som individuella partiklar i rörelse, som Eulerska synsätt där atmosfären och haven ses som gas eller vätska i rörelse. I artikel 1 sjö- sätts ett antal “surface drifters” i Östersjön som driver fritt med havsströmmarna och vars hastighet mäts av satelliter. Genom att modellera Lagrangeska partiklars rörelser i Östersjön och jämföra med dessa “surface drifters” kan det visas att datormodeller kan underskatta både medelhastigheten av partiklarna samt deras utbredning. I ar- tikel 2 simuleras luftmassornas rörelser mellan tropikerna och mellanbreddgraderna (∼ 45◦N/S). Ett medelvärde över all longituder tenderar att ignorera betydande mass- och energitransporter mellan tropikerna och mellanbredderna, och dessa kvantifieras i detalj i artikel 2. Artiklarna 3 och 4 presenterar en metod för att studera atmosfärens storskaliga rörelser utifrån ett termodynamiskt perspektiv där luftmassornas värme och fukt studeras. Det visas att variationer ytvattentemperatur vid ekvatorn i Stilla havet kan få atmosfären att, i ett globalt medelvärde, bli fuktigare och varmare samtidigt som masstransporter- na saktar ner. På samma sätt visas att en global uppvärmning till följd av ökade utsläpp av växthusgaser kan få atmosfären att bli varmare, fuktigare och att masstransporterna kan sakta ner.
At the time of the doctoral defence the following papers were unpublished and had a status as follows: Paper 3: In press; Paper 4: Manuscript.
BalticWay