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Evaluation of the effect of urbanization on urban thermal behaviour using urban heat island indicators: the case of the CBD of Accra.

Gyasi-Addo, James Adjei

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Abstract

Various studies have shown that urban heat island (UHI) can significantly affect the local climate of the built environment. Extreme air temperatures and heat waves adversely affect people's health, their overall well-being and productivity. Tropical urban sites are constantly under the threats of the harsh urban heat island (UHI) effects – a situation which is aggravated by climate change. Several urban morphological factors can potentially modify urban climate and, consequently, the potential energy demand and supply in cities. Since independence, Ghana has experienced a significant rise in population growth, which has culminated in the urbanisation of many of its towns. The rapid growth of Accra is attributed to rural-urban migration, natural population increase, booming economic activities, political factors among others. The influx of people into urban areas has led to a high demand for more housing, commercial and other infrastructural developments. For Accra however, this drive has resulted in a sharp reduction in urban greenery. Despite the obviously warm-humid climate that is prevalent in Ghana, no UHI study had previously been carried out in the country. Due to its compactness, the central business district (CBD) of Accra was chosen for the study. Through the quantification of UHI, this study aims at evaluating the effect of urbanization on the urban thermal behaviour in the CBD of Accra, with the view to developing suitable proposals that can influence current and future strategic urban design decisions meant to mitigate the negative impacts of UHI in the city. This study employs an explanatory mixed-methods research approach. By ascertaining the presence of UHI in the city through a pilot study, the proposed research method is further improved. The quantitative study involves the collection of weather data from selected monitoring points in the city's CBD. To gain an in-depth understanding of the underlying causes of the morphological transformation the city has undergone, face-to-face semi-structured interviews with some experienced Ghanaian built environment professionals are carried out. Using a clear temperature-morphology mapping, UHI intensity dynamics within identified local climate zones are analysed. The quantitative and qualitative data sets are analysed separately and sequentially and later triangulated. This study has shown that areas in the CBD of Accra that have large expanses of hardscapes and significantly reduced greeneries have been experiencing high UHI intensities. It is also evident that areas within deep canyons experience lower daytime temperatures compared to areas within shallow canyons; for night-time temperatures however, the opposite is the case. Upon analysing the qualitative data, other major causes of the morphological transformations that have emerged include poor enforcement of development control, non-adherence to building regulations; inadequacies in the existing building regulations; architects and building designers lacking the motivation for sustainable design etc. To adequately address the identified challenges and cushion the adverse effects of urban heat in the study area, this research ultimately recommends a holistic strategic plan that encompasses suitable environmental cooling measures and policy interventions.

Citation

GYASI-ADDO, J.A. 2021. Evaluation of the effect of urbanization on urban thermal behaviour using urban heat island indicators: the case of the CBD of Accra. Robert Gordon University, PhD thesis. Hosted on OpenAIR [online]. Available from: https://doi.org/10.48526/rgu-wt-1603337

Thesis Type Thesis
Deposit Date Feb 24, 2022
Publicly Available Date Feb 24, 2022
Keywords Urban climates; Urban heat islands; Climate change; Urban planning and climate; Urban planning; Ghana
Public URL https://rgu-repository.worktribe.com/output/1603337
Publisher URL https://doi.org/10.48526/rgu-wt-1603337

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