林憲德等人於1999年提出台北夏季午夜之都市熱島強度為4.5℃，至2012年簡子翔等人所提出夏季白天最大熱島強度6.18℃、午夜4.38℃，可以發現台北市的高溫化現象並未有顯著的差異，甚至還新增加了多個新興熱區。 本研究以健康新城為研究對象，以實測方式、CFD電腦模擬方法，釐清社區建築環繞下，社區內的高溫化現象，並與社區外的街道環境比較溫度差異，評估熱舒適性。研究結果顯示，建築環繞下的社區內部(社區中庭)，在日落後的確有高溫化現象，白天時則會因為各社區的遮蔽條件、綠化條件不同，而有不同程度的差別。而模擬結果亦顯示，社區開口條件、通風道配置不同，也會影響社區中庭與外部周邊街道環境之舒適性差異。 建議未來社區的建築規劃設計，除了增加綠化措施之外，尚能適度增加開放空間，增加通風性能；而公部門在訂定法定容積時，應考量都市環境因素(增加遮蔽、通風)，酌以調整已達優良的都市實質環境。 / According to Urban Heat Island’s studies by Lin et al. (1999) and Chien et al. (2012), urban heat island intensity (UHIs) of Taipei didn’t get an obvious improvement from 1999 to 2012. UHIs of Taipei was 4.5℃ in the midnight in 1999, 4.38℃ in the midnight in 2012 and 6.18℃ in the daytimes in 2012. Obviously, there are several high temperature area appeared in the years. This study tries to measure the thermal comfort between the area inside Jian-Kang community and the streets’ environment around Jian-Kang community. Furthermore, this study utilize CFD simulation that can help the study knows the reason effects thermal comfort. As the result of the study, the area inside Jian-Kang community has higher temperature after sunset. In the morning, it will have difference due to the shadow and green situation. Also, the simulation results show that the draft condition of the community will influence the thermal comfort. In the future, this study suggests some strategy to have a better urban environment. First, increase much more greening measures. Second, preserve open spaces to improve the ventilation when deciding the community’s design. Third, consider the urban environmental factors when rule the building’s height.

This dissertation contains three independent essays relating energy economics. The first essay investigates price asymmetry of diesel in South Korea by using the error correction model. Analyzing weekly market prices in the pass-through of crude oil, this model shows asymmetric price response does not exist at the upstream market but at the downstream market. Since time-variant residuals are found by the specified models for both weekly and daily retail prices at the downstream level, these models are implemented by a Generalized Autoregressive Conditional Heteroskedasticity (GARCH) process. The estimated results reveal that retail prices increase fast in the rise of crude oil prices but decrease slowly in the fall of those. Surprisingly, retail prices rarely respond to changes of crude oil prices for the first five days. Based on collusive behaviors of retailers, this price asymmetry in Korea diesel market is explained. The second essay aims to evaluate the new incentive system for biodiesel in South Korea, which keeps the blend mandate but abolishes tax credits for government revenues. To estimate changed welfare from the new policy, a multivariate stochastic simulation method is applied into time-series data for the last five years. From the simulation results, the new biodiesel policy will lead government revenues to increases with the abolishment of tax credit. However, increased prices of blended diesel will cause to decrease demands of both biodiesel and blended diesel, so consumer and producer surplus in the transport fuel market will decrease. In the third essay, the Regression - Seasonal Autoregressive Integrated Moving Average (REGSARIMA) model is employed to predict the impact of air temperature on daily peak load demand in Houston. Compared with ARIMA and Seasonal Model, a REGARIMA model provides the more accurate prediction for daily peak load demand for the short term. The estimated results reveal air temperature in the Houston areas causes an increase in electricity consumption for cooling but to save that for heating. Since the daily peak electricity consumption is significantly affected by hot air temperature, this study makes a conclusion that it is necessary to establish policies to reduce urban heat island phenomena in Houston.

A ten year analysis was conducted on the ten county Nashville metro area to determine which atmospheric thermodynamic parameters are important for thunderstorm development in North-Central Tennessee. Spatiotemporal patterns of thunderstorm activity around the city were also studied. Two case studies depicting initiation (July 10, 2009) and bifurcation (June 13, 2010) of thunderstorms were additionally discussed. The purpose of the analysis was to determine whether heat from the urban heat island (UHI) or moisture from the Gulf of Mexico was a larger factor in thunderstorm formation. A similar methodology completed by Dixon and Mote (2003) for Atlanta, Georgia was used for Nashville, Tennessee. Two land based weather stations collecting dry-bulb temperatures, twice daily radiosonde measurements, and local NEXRAD weather radar were used to determine where, when, and how thunderstorms developed around Nashville. One-sample t-test hypothesis testing of 24-hour land-surface temperature differences ahead of each event along with average daily radiosondes dry-bulb and dewpoint temperatures at five standard pressure levels were examined to determine if statistically significant mean differences (α = 0.05) were found between average study days. Atmospheric stability indices and other moisture parameters such as precipitable water (PWAT), mixing ratio, theta-e, and lapse rates were examined for average differences between average study days. Ultimately, 22 events were found (18 initiations and 4 bifurcating) over the 10-year period with the non-drought years 2005 and 2010 exhibiting the most events. The warm season month of August showed the largest distribution of events with 8 events during diurnal hours (between 2 p.m.-4 p.m. CDT). The analysis also found 12 storm centers (32%) formed within 1km of interstate highways with 77% (23) of initiation locations falling within 3 km of limited access highways. Statistical results showed that moisture, rather than heat from the UHI, were a larger component to thunderstorm formation over the city of Nashville. / Department of Geography

The urban heat island (UHI) is a phenomenon of noticeably higher temperatures in the cities as compared to their respective surrounding areas. This thesis aims at characterizing the influence of city expansion to the urban heat island phenomenon. The study is carried out in a city of Caceres in the Spanish province of the same name. A model input data is obtained with Landsat multispectral images. The analysis of satellite images shows that functional vegetation cover and water surfaces help in mitigating urban heat island effect. However, the Caceres city expansion does not influence the urban heat island intensity. A possible explanation for it is as the city expanded the ratio of vegetation to dry land remains constant in time.

Understanding climate change and variability at urban scale is essential for water resource management, land use planning, and development of adaption plans. However, there are serious challenges to meet these goals due to unavailability of observed and / or simulated high resolution spatial and temporal climate data. Recent efforts made possible the availability of high resolution climate data from non-hydrostatic regional climate model (RCM) and statistically downscaled General Circulation Models (GCMs). This study investigates trends in climate and urbanization and their impact on surface water supply for the city of Addis Ababa, Ethiopia. The methodology presented in this study focused on the observed and projected NIMRHadGEM2- AO model and Special Report on Emissions Scenarios (SRES) of B2 and A2 of HadCM3 model are also employed for rainfall, maximum temperature and minimum temperature data using for climate analysis. Water Evaluation and Planning (WEAP) modeling system was used for determination of climate and urbanization impacts on water. Land-Sat images were analyzed using Normalized Differencing Vegetation Index (NDVI). Statistical downscaling model (SDSM) was employed to investigate the major changes and intensity of the urban heat island (UHI). The result indicates monthly rainfall anomalies with respect to the baseline mean showing wet anomaly in summer (kiremt) during 2030s and 2050s, and a dry anomaly in the 2080s under A2 and B2 scenarios with exception of a wet anomaly in September over the city. The maximum temperature anomalies under Representative Concentration Pathways (RCPs) also show warming during near, mid and end terms. The mean monthly minimum temperature anomalies under A2 and B2 scenarios are warm but the anomalies are much lower than RCPs. The climate under the RCP 8.5 and high population growth (3.3 %) scenario will lead to the unmet demand of 462.77 million m3 by 2039. Future projection of urban heat island under emission pathway of A2 and B2 scenario shows that, the nocturnal UHI will be intense in winter or dry season episodes in the city. Under A2 scenario the highest urban warming will occur during October to December (2.5 ºC to 3.2 ºC). Under RCP 8.5 scenario the highest urban warming will occur during October to December (0.5 ºC to 1.0 °C) in the 2050s and 2080s. Future management and adaptation strategies are to expand water supply to meet future demand and to implement demand side water management systems of the city and UHI / Environmental Sciences / Ph. D. (Environmental Management)

Les projections climatiques prévoient une amplification du réchauffement climatique, potentiellement exacerbée en milieu urbain du fait du phénomène d’îlot de chaleur urbain. La recrudescence d’évènements extrêmes comme les canicules peut avoir des conséquences écologiques, sanitaires, et économiques dramatiques à l’échelle des villes qui concentrent la population. Parmi les mesures d’adaptation visant à améliorer le confort climatique et la demande énergétique, la climatisation et le verdissement urbain constituent deux leviers d’action aux effets parfois antagonistes. Ce travail de thèse – mené dans le cadre des trois projets de recherche CLIM2, MUSCADE et VegDUD, propose d’évaluer ces effets par des simulations du climat urbain à l’échelle de l’agglomération parisienne. La modélisation repose en particulier sur le modèle de canopée urbaine TEB qui permet de simuler les échanges de chaleur, d’eau et de quantité de mouvement entre les surfaces urbaines et l’atmosphère, et depuis peu l’énergétique des bâtiments et des indices de confort thermique dans les bâtiments et dans les rues. Afin d’améliorer la prise en compte de la végétation urbaine dans TEB, un modèle de toitures végétalisées extensives a tout d’abord été développé et évalué. Différentes pratiques d’arrosage de la végétation urbaine au sol ou sur les toits ont également été paramétrées. Les scénarios d’adaptation de la ville de Paris par la climatisation, évalués dans le cadre de CLIM2 pour la canicule 2003 par des simulations couplées de TEB avec un modèle atmosphérique, ont mis en évidence que toutes les formes de climatisation qui rejettent de la chaleur dans l’atmosphère (sèche ou humide) génèrent une augmentation de la température des rues au niveau des piétons. Ce réchauffement, proportionnel à la puissance des rejets de chaleur sensible dans l’atmosphère, est en moyenne de 0.5 à 2°C, selon le niveau de déploiement de la climatisation. Différentes stratégies de verdissement ont ensuite été mises en œuvre et évaluées toujours sur Paris, en faisant varier soit la végétation au sol (plusieurs taux et types de végétation testés), soit celle en toiture (avec ou sans arrosage), soit les deux. Ces simulations, réalisées dans la configuration générale du projet MUSCADE, i.e. en mode forcé avec une version de TEB disposant d’un générateur dynamique d’îlot de chaleur urbain, ont montré que l’augmentation de la couverture végétale au sol a un pouvoir rafraîchissant plus efficace que les toitures végétalisées, et ce d’autant plus que le taux de verdissement et que la proportion d’arbres sont importants. Les toitures végétalisées quant à elles constituent le moyen le plus efficace de réduire la consommation d’énergie, non seulement estivale mais aussi à l’échelle annuelle, essentiellement grâce à leur pouvoir isolant. / Climate projections predict an amplification of global warming, potentially exacerbated in urban areas by the urban heat island effect. More frequent extreme events such as heat waves may have severe public health, ecological, and economic consequences as cities concentrate population. Among the measures aiming at improving thermal comfort or energy demand, air conditioning and urban greening are measures that may have antagonistic effects. This PhD work is undertaken within the framework of three research projects, CLIM2, MUSCADE and VegDUD. Its objective is to evaluate the respective effects of air conditioning and urban greening based on urban climate simulations across the Paris area. The modelling relies on the Town Energy Balance (TEB) model, which simulates the exchange of heat, water and momentum between the urban surface and the atmosphere. It has been recently improved to simulate building energetics, as well as indoor and outdoor thermal comfort indices. To improve the description of urban vegetation within TEB, a green roof model has been developed and evaluated. In addition, watering practices have been implemented to model the watering of urban vegetation at ground or roof level. Within CLIM2, the air conditioning scenarios tested for adapting Paris city to the extreme temperatures of the 2003 heatwave have been evaluated based on simulations using TEB coupled with an atmospheric model. Results shows that all forms of conditioning that release waste heat (dry or wet) into the atmosphere generate a temperature increase in the streets. This warming is proportional to the power of the sensible heat releases in the atmosphere and is on average 0.5 to 2_C, depending on the level of deployment of the air conditioning. Then, the greening of Paris city has been evaluated based on simulations carried out with the general configuration of the MUSCADE project, i.e. with climate forcings and a dynamic urban heat island generator. The scenarios tested consisted in an increase in ground-base vegetation or an implementation of green roofs on compatible buildings, or the two combined, with the option of watering green roofs or not in summer. Results show that increasing the ground cover has a stronger cooling effect than implementing green roofs, and even more so when the greening rate and the proportion of trees are important. The green roofs are however the most effective way to reduce energy consumption, not only in summer but also on an annual basis, mainly due to their insulating properties.

De par ses caractéristiques, l’environnement urbain influe significativement sur le climat observé dans et à la périphérie des villes. Il est communément admis que le centre des villes présente fréquemment des températures d’air plus élevées que celles mesurées dans les zones rurales environnantes. Ce phénomène appelé îlot de chaleur urbain intéresse les enjeux relatifs à la santé publique, au confort urbain et à la demande énergétique. Ce travail de thèse propose de caractériser le phénomène d’îlot de chaleur à partir de l'association d'un zonage climatique et de mesures mobiles à haute résolution spatiale dans la canopée urbaine. Il repose sur une approche méthodologique en trois temps. Une classification climatique ("Local Climate Zones" (LCZ)) est tout d'abord appliquée à l'agglomération de Nancy. Ce découpage climatique du territoire sert de support à la réalisation de mesures embarquées effectuées en période estivale à l'aide d'un véhicule instrumenté. Celles-ci ont pour but d'observer in situ les spécificités climatiques des LCZ recensées dans l'agglomération. L'association d'une base de données de relevés météorologiques et de la classification LCZ permet de caractériser le comportement climatique du milieu urbain et de comparer le comportement de différentes typologies de quartiers en présence d'un îlot de chaleur urbain. Cette démarche propose également un cadre théorique pour le développement d'un modèle de diagnostic à partir d'indicateurs urbains et climatiques, avec la perspective de construction d'un outil de prise en compte de l'îlot de chaleur dans le processus de planification urbaine / Urban environment impacts significantly the climate observed within and around cities. In this context, city centers frequently present higher air temperatures than those measured in the rural areas nearby. This phenomenon called urban heat island impacts major issues such as public health, urban comfort and energy demand. This Ph.D. thesis proposes to characterize the urban heat island phenomenon based on the combination of a climatic zoning and high spatial density mobile measurements performed within the urban canopy layer. This study is divided into three steps. A climate classification ("Local Climate Zones" (LCZ)) is first applied to the conurbation of Nancy, France. This climatic zoning is used in order to perform mobile measurements thanks to an instrumented vehicle. These measurements target to observe the climatic patterns of the LCZ built in this conurbation. The combination of meteorological database and LCZ classification scheme allows to characterize the urban climate behavior and to compare the thermal behavior of different neighbourhood types. This approach provides a theoretical framework for the development of a diagnosis model based on urban and climatic indicators. It also brings outlooks regarding the building of a decision-support tool that aims to supply information about urban heat island adapted to the urban planners needs

<div><br></div><div>Extreme heat is one of the deadliest health hazards that is projected to increase in intensity and persistence in the near future. Temperatures are further exacerbated in the urban areas due to the Urban Heat Island (UHI) effect resulting in increased heat-related mortality and morbidity. However, the spatial distribution of urban temperatures is highly heterogeneous. As a result, metrics such as UHI Intensity that quantify the difference between the average urban and non-urban air temperatures, often fail to characterize this spatial and temporal heterogeneity. My objective in this thesis is to understand and characterize the spatio-temporal dynamics of UHI for cities across the world. This has several applications, such as targeted heat mitigation, energy load estimation, and neighborhood-level vulnerability estimation.</div><div><br></div><div>Towards this end, I have developed a novel multi-scale framework of identifying emerging heat clusters at various percentile-based thermal thresholds T_thr and refer to them collectively as <i>intra-Urban Heat Islets</i>. Using the Land Surface Temperatures from Landsat for 78 cities representative of the global diversity, I have showed that the heat islets have a fractal spatial structure. They display properties analogous to that of a percolating system as T_thr varies. At the percolation threshold, the size distribution of these islets in all cities follows a power-law, with a scaling exponent = 1.88 and an aggregated Area-Perimeter Fractal Dimension =1.33. This commonality indicates that despite the diversity in urban form and function across the world, the urban temperature patterns are different realizations with the same aggregated statistical properties. In addition, analogous to the UHI Intensity, the mean islet intensity, i.e., the difference between mean islet temperature and thermal threshold, is estimated for each islet, and their distribution follows an exponential curve. This allows for a single metric (exponential rate parameter) to serve as a comprehensive measure of thermal heterogeneity and improve upon the traditional UHI Intensity as a bulk metric.</div><div><br></div><div><br></div><div>To study the impact of urban form on the heat islet characteristics, I have introduced a novel lacunarity-based metric, which quantifies the degree of compactness of the heat islets. I have shown that while the UHIs have similar fractal structure at their respective percolation threshold, differences across cities emerge when we shift the focus to the hottest islets (T_thr = 90^th percentile). Analysis of heat islets' size distribution demonstrates the emergence of two classes where the dense cities maintain a power law, whereas the sprawling cities show an exponential deviation at higher thresholds. This indicates a significantly reduced probability of encountering large heat islets for sprawling cities. In contrast, analysis of heat islet intensity distributions indicates that while a sprawling configuration is favorable for reducing the mean Surface UHI Intensity of a city, for the same mean, it also results in higher local thermal extremes. </div><div><br></div><div>Lastly, I have examined the impact of external forcings such as heatwaves (HW) on the heat islet characteristics. As a case study, the European heatwave of 2018 is simulated using the Weather Research Forecast model with a focus on Paris. My results indicate that the UHI Intensity under this HW reduces during night time by 1^oC on average. A surface energy budget analysis reveals that this is due to drier and hotter rural background temperatures during the HW period.</div><div>To analyze the response of heat islets at every spatial scale, power spectral density analysis is done. The results show that large contiguous heat islets (city-scale) persist throughout the day during a HW, whereas the smaller islets (neighborhood-scale) display a diurnal variability that is the same as non-HW conditions. </div><div><br></div><div>In conclusion, I have presented a new viewpoint of the UHI as an archipelago of intra-urban heat islets. Along the way, I have introduced several properties that enable a seamless comparison of thermal heterogeneity across diverse cities as well as under diverse climatic conditions. This thesis is a step towards a comprehensive characterization of heat from the spatial scales of an urban block to a megalopolis.</div><div><br></div>

Indiana University-Purdue University Indianapolis (IUPUI)

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