Urban Soil: Assessing Ground Cover Impact on Surface Temperature and Thermal Comfort

Abstract

The urban population growth, together with the contemporary deindustrialization of metropolitan areas, has resulted in a large amount of available land with new possible uses. It is well known that urban green areas provide several benefits in the surrounding environment, such as the improvement of thermal comfort conditions for the population during summer heat waves. The purpose of this study is to provide useful information on thermal regimes of urban soils to urban planners to be used during an urban transformation to mitigate surface temperatures and improve human thermal comfort. Field measurements of solar radiation, surface temperature (), air temperature (), relative humidity, and wind speed were collected on four types of urban soils and pavements in the city of Florence during summer 2014. Analysis of days under calm, clear-sky condition is reported. During daytime, sun-to-shadow differences for , apparent temperature index (ATI), and were significantly positive for all surfaces. Conversely, during nighttime, differences among all surfaces were significantly negative, whereas ATI showed significantly positive differences. Moreover, was significantly negative for grass and gravel. Relative to the shaded surfaces, was higher on white gravel and grass than gray sandstone and asphalt during nighttime, whereas gray sandstone was always the warmest surface during daytime. Conversely, no differences were found during nighttime for ATI and measured over surfaces that were exposed to sun during the day, whereas showed higher values on gravel than grass and asphalt during nighttime. An exposed surface warms less if its albedo is high, leading to a significant reduction of during daytime. These results underline the importance of considering the effects of surface characteristics on surface temperature and thermal comfort. This would be fundamental for addressing urban environment issues toward the heat island mitigation considering also the impact of urban renovation on microclimate.

Modeling Tree Shade Effect on Urban Ground Surface Temperature

“…Soil temperature sensors were buried horizontally 10 mm deep. This network operated continuously from 1 June 2014 to the end of August 2014 (Brandani et al, 2015). For each surface and exposition, T s at noon was measured by an infrared thermometer (IR) (Agri-Therm II, Everest Intersciences) as the mean of five measurements collected between 12:00 and 13:00.…”

Soil in the City: Sustainably Improving Urban Soils

“…One such benefit is improvement of the thermal comfort condition of city residents during peak summer months by mitigating the urban heat island effect. The study conducted by Brandani et al (2016) provides useful information on thermal regimes of urban soils and surfaces and demonstrates that exposed surfaces became less heated if their albedo was high, which led to significant reduction in surface temperatures even under the sun's direct exposure. The authors compared four different surfaces, showing that green surfaces were always cooler than asphalt, gray sandstone, and white gravel, as indicated by lower daytime surface and air temperatures.…”

Radiosity from Individual Urban Landscape Elements Measured Using a Modified Low-Cost Temperature Sensor

“…Hence, as well as being a measure of how uncomfortable a surface may be for pedestrians, surface temperature also affects the amount of heat available for storage in the LE. Many studies of urban LE surface temperatures have been undertaken [4,13,15,[21][22][23][24][25][26][27][28]. In general, these studies found that manufactured, low albedo and dry materials were hotter than plants or than LEs that were moist or had higher albedos.…”