Infrared (IR) Satellite imagery: Urban Heat islands

On sunny days, IR satellite imagery can help spot developing urban heat islands, areas of enhanced heat caused by artificial surfaces (concrete, asphalt, etc.) found in cities.  These are apparent on this image by 11:15 AM in the morning. As we learned in the first lab, artificial surfaces in city streets and rooftops are designed to drain the water away as quickly as possible, whereas natural surfaces covered with greenery are designed to retain moisture. Hence solar radiation that goes into evaporating water on vegetated surfaces goes directly into heating the surface of most urban surfaces. The contrast would be particularly enhanced on a day after rain like today, when natural surfaces are saturated with moisture.