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- All Subjects: microclimate
Description
The rapid rate of urbanization coupled with continued population growth and anthropogenic activities has resulted in a myriad of urban climate related impacts across different cities around the world. Hot-arid cities are more vulnerable to induced urban heat effects due to the intense solar radiation during most of the year, leading to increased ambient air temperature and outdoor/indoor discomfort in Phoenix, Arizona. With the fast growth of the capital city of Arizona, the automobile-dependent planning of the city contributed negatively to the outdoor thermal comfort and to the people's daily social lives. One of the biggest challenges for hot-arid cities is to mitigate against the induced urban heat increase and improve the outdoor thermal. The objective of this study is to propose a pragmatic and useful framework that would improve the outdoor thermal comfort, by being able to evaluate and select minimally invasive urban heat mitigation strategies that could be applied to the existing urban settings in the hot-arid area of Phoenix. The study started with an evaluation of existing microclimate conditions by means of multiple field observations cross a North-South oriented urban block of buildings within Arizona State University’s Downtown campus in Phoenix. The collected data was evaluated and analyzed for a better understanding of the different local climates within the study area, then used to evaluate and partially validate a computational fluid dynamics model, ENVI-Met. Furthermore, three mitigation strategies were analyzed to the Urban Canopy Layer (UCL) level, an increase in the fraction of permeable materials in the ground surface, adding different configurations of high/low Leaf Area Density (LAD) trees, and replacing the trees configurations with fabric shading. All the strategies were compared and analyzed to determine the most impactful and effective mitigation strategies. The evaluated strategies have shown a substantial cooling effect from the High LAD trees scenarios. Also, the fabric shading strategies have shown a higher cooling effect than the Low LAD trees. Integrating the trees scenarios with the fabric shading had close cooling effect results in the High LAD trees scenarios. Finally, how to integrate these successful strategies into practical situations was addressed.
ContributorsAldakheelallah, Abdullah (Author) / Reddy, T Agami (Thesis advisor) / Middel, Ariane (Committee member) / Coseo, Paul (Committee member) / Arizona State University (Publisher)
Created2020
Description
Urban-induced heating is a challenge to the livability and health of city dwellers. It is a complex issue that many cities are facing, and a more urgent hazard in hot urban deserts (HUDs) than elsewhere due to already high temperatures and aridity. The challenge compounds in the absence of more localized heat mitigation understanding. In addition, over-reliance on evidence from temperate regions is disconnected from the actualities of extreme bioclimatic dynamics found in HUDs. This dissertation is an integration of a series of studies that inform urban climate relationships specific to HUDs. This three-paper dissertation demonstrates heat mitigation aspirational goals from actualities, depicts local urban thermal drivers in Kuwait, and then tests morphological sensitivity of selected thermal modulation strategies in one neighborhood in Kuwait City.
The first paper is based on a systematic literature review where evidence from morphological mitigation strategies in HUDs were critically reviewed, synthesized and integrated. Metrics, measurements, and methods were extracted to examine the applicability of the different strategies, and a content synthesis identified the levels of strategy success. Collective challenges and uncertainties were interpreted to compare aspirational goals from actualities of morphological mitigation strategies.
The second paper unpacks the relationship of urban morphological attributes in influencing thermal conditions to assess latent magnitudes of heat amelioration strategies. Mindful of the challenges presented in the first study, a 92-day summer field-measurement campaign captured system dynamics of urban thermal stimuli within sub-diurnal phenomena. A composite data set of sub-hourly air temperature measurements with sub-meter morphological attributes was built, statistically analyzed, and modeled. Morphological mediation effects were found to vary hourly with different patterns under varying weather conditions in non-linear associations. Results suggest mitigation interventions be investigated and later tested on a site- use and time-use basis.
The third paper concludes with a simulation-based study to conform on the collective findings of the earlier studies. The microclimate model ENVI-met 4.4, combined with field measurements, was used to simulate the effect of rooftop shade-sails in cooling the near ground thermal environment. Results showed significant cooling effects and thus presented a novel shading approach that challenges orthodox mitigation strategies in HUDs.
The first paper is based on a systematic literature review where evidence from morphological mitigation strategies in HUDs were critically reviewed, synthesized and integrated. Metrics, measurements, and methods were extracted to examine the applicability of the different strategies, and a content synthesis identified the levels of strategy success. Collective challenges and uncertainties were interpreted to compare aspirational goals from actualities of morphological mitigation strategies.
The second paper unpacks the relationship of urban morphological attributes in influencing thermal conditions to assess latent magnitudes of heat amelioration strategies. Mindful of the challenges presented in the first study, a 92-day summer field-measurement campaign captured system dynamics of urban thermal stimuli within sub-diurnal phenomena. A composite data set of sub-hourly air temperature measurements with sub-meter morphological attributes was built, statistically analyzed, and modeled. Morphological mediation effects were found to vary hourly with different patterns under varying weather conditions in non-linear associations. Results suggest mitigation interventions be investigated and later tested on a site- use and time-use basis.
The third paper concludes with a simulation-based study to conform on the collective findings of the earlier studies. The microclimate model ENVI-met 4.4, combined with field measurements, was used to simulate the effect of rooftop shade-sails in cooling the near ground thermal environment. Results showed significant cooling effects and thus presented a novel shading approach that challenges orthodox mitigation strategies in HUDs.
ContributorsAlKhaled, Saud R A H (Author) / Coseo, Paul (Thesis advisor) / Brazel, Anthony (Thesis advisor) / Middel, Ariane (Committee member) / Cheng, Chingwen (Committee member) / Arizona State University (Publisher)
Created2019
Description
This dissertation focuses on thermal comfort and walking as an experiential phenomenon in outdoor urban environments. The goal of the study is to provide a better understanding of the impact of psychological adaptation factors on thermal comfort. The main research questions included the impact of psychological factors on outdoor thermal comfort as well as the impact of long-term thermal perception on momentary thermal sensation. My research follows a concurrent triangulation strategy as a mixed-method approach, which consisted of a simultaneous collection and analysis of qualitative and quantitative data. Research consisted of five rounds of data collection in different locations beginning February 2018 and continuing through December 2019. During the qualitative phase, I gathered data in the form of an open-ended questionnaire but importantly, self-walking interviews where participants narrated their experience of the environment while recording one-minute long videos. The visual and audible information was first processed using thematic analysis and then further analyzed via Latent Dirichlet Allocation (LDA). During the quantitative phase, I gathered information from participants in the form of three-step survey questionnaires, that data was analyzed using T-Test regression analysis in STATA. The quantitative data helped explore and address the initial research questions, while the qualitative data helped in addressing and explaining the trends and the experiential aspects of thermal environment.
Results revealed that spatial familiarity (as a psychological adaptation factor) has a significant relationship for both overall comfort and thermal comfort within outdoor environments. Moreover, long term thermal memory influences momentary thermal sensation. The results of qualitative and quantitative data were combined, compared, and contrasted to generate new insights in the design of outdoor urban environments. The depth and breadth of the qualitative data set consisting of more than a thousand minute-long of narrated video segments along with hundreds of pages of transcribed text, demonstrated the subjective aspects of thermal comfort. This research highlights the importance of context-based and human-centric design in any evidence-based design approach for outdoor environments. The implications of the study can provide new insights not only for architects and urban designers, but also for city planners, stakeholders, public officials, and policymakers.
Results revealed that spatial familiarity (as a psychological adaptation factor) has a significant relationship for both overall comfort and thermal comfort within outdoor environments. Moreover, long term thermal memory influences momentary thermal sensation. The results of qualitative and quantitative data were combined, compared, and contrasted to generate new insights in the design of outdoor urban environments. The depth and breadth of the qualitative data set consisting of more than a thousand minute-long of narrated video segments along with hundreds of pages of transcribed text, demonstrated the subjective aspects of thermal comfort. This research highlights the importance of context-based and human-centric design in any evidence-based design approach for outdoor environments. The implications of the study can provide new insights not only for architects and urban designers, but also for city planners, stakeholders, public officials, and policymakers.
ContributorsGarshasby Moakhar, Mohsen (Author) / Hejduk, Renata (Thesis advisor) / Cheng, Chingwen (Committee member) / Coseo, Paul (Committee member) / Margolis, Eric (Committee member) / Arizona State University (Publisher)
Created2020