01474099

Component

Solar reflectivity (or albedo) plays an important role in the thermal behavior of pavements and other ground surfaces, and their resultant impacts on humans and the environment. This study developed a new albedo measurement system with a dual-pyranometer and automatic data acquisition system, and used it to conduct field measurements of solar reflectivity on different pavement materials and for long-term monitoring of albedo. The albedo values were obtained for commonly used land cover materials including asphalt, concrete and block paver surfacing materials with different designs, which can help reduce the uncertainty in understanding, evaluating and modeling the thermal behavior and environmental impacts of ground surfaces with different albedos. This study found that the albedo of pavement materials is high in the early morning and late afternoon; it is low and constant over time in the mid-day. This suggests that albedo should be measured near mid-day, which is addressed in one of two standard test procedures reviewed. Clouds will negatively influence the value of measured albedo. No significant seasonal variation in albedo was found over one year. No impact of wind speed or air temperature on albedo is observed with the instrument used. An empirical relationship between the cooling effect of increased albedo on a pavement’s high temperature and solar radiation was developed. The cooling effect has a positive correlation with the peak solar radiation intensity. This empirical relationship can be used to roughly estimate the cooling effect of increased albedo or heating effect of reduced albedo on pavement for various climates and seasons with different solar radiation intensities.

This paper was sponsored by TRB committee AF000(2) Pavement Materials and the Urban Climate.

01470560

13-1116

English

20p

2013

Transportation Research Board 92nd Annual Meeting

Digital/other

Figures; References; Tables

Heat islands; Pavements; Reflectivity; Solar radiation; Thermal properties

Albedo; Cool pavements; Heat island effect

Environment; Highways; Pavements; I15: Environment; I23: Properties of Road Surfaces

Transportation Research Board Annual Meeting 2013 Paper #13-1116

TRIS, TRB, ATRI

Feb 5 2013 12:19PM