The Urban Heat Island and Local Temperature Variations in Orlando, Florida

Abstract

Cities artificially alter local climates affecting economic and biological processes. This study examined air temperatures in Orlando's urban canopy layer using a network of twenty-nine fixed-point stations from September ∞ΩΩΩ to December ≤≠≠∞. Urban Heat Island (UHI) statistics were calculated using two stations that were representative of an urban and rural setting. Orlando's UHI develops best on calm, clear nights during dry months: its maximum magnitude exceeds ∫\C. Orlando's UHI, however, is predominantly a nocturnal phenomenon with intense heat islands sometimes occurring during warm afternoons. These events are most likely attributable to isolated thundershowers. Local temperature variations between urban and rural extremes were examined by calculating environmental indices for all stations. The range in monthly cooling degreeday totals exceeded ∞≠≠ degree days in six months of the thirty-six month study period. Heating degree totals and number of freezing hours were also highly variable. key words: urban climate, urban heat island, temperature variability, Orlandointroduction Urban climates differ significantly from conditions in the surrounding region. The higher evening and early morning temperatures of cities, commonly called the urban heat island (UHI) effect, results from differences in thermal and physical properties of construction materials, building geometry, surface roughness, factors contributing to decreased evapotranspiration, and anthropogenic heat sources (Tyson, Garstang, and Emmitt ∞Ωπ≥; Oke ∞Ω∫π). Urban heat islands have been studied in numerous cities around the world because the myriad factors leading to the existence of an UHI differ from city to city. It is important to understand heat islands in many cities to detect the impact artificially elevated temperatures have on human comfort (Palecki, Changnon, and Kunkel ≤≠≠∞), city water and energy demand (Balling and Brazel ∞Ω∫∫; Jauregui ∞ΩΩ∫; Palecki, Changnon, and Kunkel ≤≠≠∞), air pollution (Viras ≤≠≠≤), and the introduction of bias into long-term temperature records (

Historical trends in Florida temperature and precipitation

“…Various potential causes for this decrease in DTR include greenhouse warming and associated changes, increases in atmospheric aerosol concentrations, contrails, increased cloud cover at low levels, increases in precipitation, irrigation and soil moisture, stable nighttime boundary layer dynamics, the urban heat island effect, or a combination of these factors. Yow and Carbone () found that the urban heat island in Orlando, Florida, is more marked (up to 8 °C) on calm clear nights when there is less vertical and horizontal mixing and the potential for greater rural cooling rates.…”

“…Kukla and Karl () found that globally since the 1950s, daily minimum temperatures have risen three times as fast as daily maximum temperatures, resulting in a net decrease of the daily temperature range (DTR). Yow and Carbone () found that the ‘urban heat island’ in Orlando, Florida, is more marked (up to 8 °C) on calm clear nights when there is less vertical and horizontal mixing and the potential for greater rural cooling rates.…”

Urban Heat Islands: Observations, Impacts, and Adaptation

“…2006; Miyazaki et al. 2006; Runnalls and Oke 2000; Yow and Carbone 2006), mobile traverses (e.g. Bottyán et al.…”

“…Examining air temperatures in the urban canopy layer usually entails using fixed-point stations (e.g. Fortuniak et al 2006;Ji et al 2006;Miyazaki et al 2006;Runnalls and Oke 2000;Yow and Carbone 2006), mobile traverses (e.g. Bottyán et al 2005;Wong and Yu 2005), or a combination of both (e.g.…”

<b>Daily periodic temperature variation in the city of Curitiba, Paraná

“…The urban climate have been studied in numerous cities around the world because the myriad factors leading to the existence of an urban heat island differ from city to city (Yow & Carbone, 2006). The temperature conditions varied between different landscapes communities within urban area (Cui, Liu, Kuang, & Wang, 2012).…”