Journal
SUSTAINABLE CITIES AND SOCIETY
Volume 88, Issue -, Pages -Publisher
ELSEVIER
DOI: 10.1016/j.scs.2022.104254
Keywords
Urban green spaces; Cooling efficiency; Land surface temperature; Meteorological variables; Turning point; African cities
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This study focuses on the cooling efficiency (CE) of urban green spaces in major African cities. The CE, quantified as the negative ratio of land surface temperature (LST) changes to vegetation cover fraction (Fc) changes, was analyzed along with meteorological variables. The research found that the CE is influenced by temperature, dew point difference, and wind speed. Additionally, the CE shows significant changes when Fc reaches a specific threshold.
Increasing land surface temperature (LST) is one of the concerns associated with urbanization. Urban green spaces are gaining attention given its well-documented heat mitigation effects. However, the cooling efficiency (CE) of green spaces, which can be quantified as the negative ratio of LST changes to per unit change of vege-tation cover fraction (Fc), has received less attention. CE can be influenced by climate background, but the impacts remain unclear. Here we selected LST and meteorological data across 7 days of heatwaves in six major African cities and analyzed the CE and its response to meteorological variables. The mean CE generally ordered by arid (Cairo, 7.51 and Kano, 6.81), temperate (Cape Town, 9.21, Durban, 5.95 and Nairobi, 5.88), and tropical (Accra, 3.26) cities. CE showed a positive response to temperature dew point difference and wind speed. Air temperature dominated the CE in most cities, but in cities with higher wind speeds, wind speed exerted greater influences. CE in all cities experienced significant changes when the Fc reached a specific value (Fc turning point) and CE's response to meteorological variables also reversed following the threshold. The clarification of climatic impacts and Fc turning points provides climate-tailored recommendations for urban green space planning.
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