A Cool Roof
The annual mean air temperature of a city with one million or more people can be 1.8
to 5.4°F (1 to 3°C) warmer than its surroundings, and on a clear, calm night, this
temperature difference can be as much as 22°F (12°C).
Urban heat islands form as a result of reduced vegetation in urban areas, different
properties of urban materials in terms of solar reflectance, thermal emissivity and
heat capacity; and urban geometry which influences wind flow and energy absorption.
This can result in dry, exposed urban surfaces like roofs and pavements with temperatures
50 to 90°F (27 to 50°C) hotter than the surrounding air!
Given the wintertime benefits of urban heat islands, why do we care then? Learn more
about the "heat island effect" here: www.epa.gov/heat-islands/heat-island-compendium
DID YOU KNOW?
Onboard the International Space Station, the National Aeronautics and Space Administration
(MASA’s) new ECOsystem Spaceborne Thermal Radiometer Experiment on Space Station (ECOSTRESS)
measures the Earth’s surface temperatures. ECOSTRESS can help scientists identify
heat islands and study how different surfaces heat up and cool down.