Page "Urban heat island" Paragraph 10

Throughout the daytime, particularly when the skies are free of clouds, urban surfaces are warmed by the absorption of solar radiation.

Surfaces in the urban areas tend to warm faster than those of the surrounding rural areas.

By virtue of their high heat capacities, urban surfaces act as a giant reservoir of heat energy.

For example, concrete can hold roughly 2, 000 times as much heat as an equivalent volume of air.

As a result, the large daytime surface temperature within the UHI is easily seen via thermal remote sensing.

As is often the case with daytime heating, this warming also has the effect of generating convective winds within the urban boundary layer.

It is theorized that, due to the atmospheric mixing that results, the air temperature perturbation within the UHI is generally minimal or nonexistent during the day, though the surface temperatures can reach extremely high levels.