ASU researchers describe that the wide expanse of pavement in urban settings significantly contributes to heating the area; for instance, the nighttime temperatures in Phoenix can be up to 15 degrees warmer than the desert region next to it.

That is because during the daytime, the pavement from streets, freeways, sidewalks, and parking lots absorb and retain short-wave radiation from the sun. At night, it slowly reradiates that heat back as long-wave radiation. Researchers describe that the ?EUR??,,????'??Urban Heat Island Effect?EUR??,,????'?? not only makes the urban area hotter and unsustainable, but it contributes to health problems, electricity demand, water consumption and evaporation.

However, the researchers are promoting a new generation of paving materials that utilize new mixtures and treatments to reduce surface temperatures. Two examples include porous pavements which contain less sand, and their greater porosity allows air and water to pass through and ?EUR??,,????'??breathe?EUR??,,????'?? like natural soil. They allow trees to access more water and nutrients from the soil, growing stronger and also contributing to the cooling of the city.

Another example is rubberized asphault, which ?EUR??,,????'??reduces surface-standing water, making the roadway safer when wet. At night, the pavement cools rapidly compared with non-pervioius surfaces.

Source: The Arizona Republic