Abstract
The authors compared the effect of greening on the thermal environment of some types of parking lots by measuring the following temperatures: ground surface, globe temperature, air temperature (at heights of 0.1, 0.5, 1.0, and 1.5 m), inside and outside of car body. Temperatures were measured under four different conditions: sunny asphalt pavement, tree-shaded asphalt pavement, sunny lawn, and tree-shaded lawn, on August 5-6 th, 2010 on the Tottori University campus, Tottori prefecture, Japan. During the daylight period (9:00-19:00), the mean ground surface temperature of tree-shaded lawn was 17.9°C cooler than the surface temperature of sunny asphalt. The mean globe temperature was at 8.8°C lower for shaded lawn than for sunny asphalt. Air temperatures were not decreased by any type of greening at any height. The mean daytime air temperature of a car interior was decreased 11.3°C when on asphalt shaded by trees and or on lawn shaded by trees.The daytime MRT (Mean radiant temperature) was decreased 27.4°C on tree-shaded lawn. At night (20:00-4:00), the sunny lawn was most effective for decreasing ground surface temperature as its mean temperature was 4.0°C cooler than the temperature of sunny asphalt. The globe temperature and MRT were cooler by 1.5°C, and 2.0°C respectively, compared to sunny asphalt. Greening of any type was effective at decreasing nighttime air temperature: tree-shaded lawn was 1.8°C cooler than sunny asphalt at 1.5 m height. The coolness sensed by people under tree shade in the daytime is not due to a decrease in air temperature itself, but is due to decreases in radiation temperature. At night, greening, especially lawns, creates a cooler air temperature. Therefore, we can expect mitigation of the heat island phenomenon by creation of lawn groundcovers. A combination of tree planting to create shade and lawn cover is the most effective measure for improving the thermal environment of car parking lots.
