Evaluating the Climate Resiliency of Urban Trees to Mitigate Urban Heat Island in Southeastern Florida

Abstract Submission: Extreme storms and heat have the potential to challenge the urban environment. Reduction of the quantity and improvement of the quality of urban-induced stormwater runoff via Green Stormwater Infrastructure (GSI) have been well documented. However, the ancillary benefits of GSI, linked to urban trees, in mitigating the Urban Heat Island (UHI) effect have not been studied sufficiently. This is especially noted in urban regions with distinct climate types in relation to the contiguous United States, such as the southeastern Florida. Therefore, this research evaluates potential variations of urban heat index across urban trees at finer spatial and temporal resolutions in Miami, Florida. Specifically, this investigation used wireless air temperature, relative humidity, and wind sensors from shaded (i.e., trees) and unshaded (i.e., non-trees, control) locations for one year. At least three locations (i.e., two urban trees and one control) were assessed per site for a total of three study sites with distinct type of urban development (institutional and commercial): (i) Arena in Florida International University campus, Miami; (ii) Factory Town, Hialeah; and (iii) Coral Gables Public Work Department site, Miami. From continuous measurements of air temperature, relative humidity, and wind speed and direction at 5-minute time steps, this investigation determined diurnal and nocturnal variations of urban heat index across locations and sites, developing cumulative probabilities curves of those variables using the Weibull plotting position. The results of this study highlight the role of trees in mitigating the UHI effect, depending on the time of day (e.g., solar radiation) and weather conditions (e.g., cloud cover and wind characteristics).

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