MAPPING MICRO-URBAN HEAT ISLANDS USING LANDSAT TM AND A GIS

Hot spots are on the rise and no I'm not talking about places where you can get the strongest Wi-Fi service connection for your laptops and smart phones.  According to a study in Dallas, Texas, micro-urban heat islands are appearing due to the lack of shade from trees in rising urban areas where buildings, parking lots and neighborhoods outnumber shade trees.  Micro-urban heat islands (MUHI) are places within urban areas that produce high levels of heat.  The shade that trees are able to provide to nearly everything help lessen the amount of  direct exposure to the sun they receive.  But when trees are cut down and buildings are built up, not only are ecosystems being destroyed but also an effective energy saving system is being eliminated.  

"In the last fifty years, the average temperature of downtown Los Angeles has increased by 2.8” (5°F). Most urban areas around the world with populations greater than 100,000 have heat islands that are 14S”C (2-8°F) warmer than rural temperatures" (Semrau, 1992).  Due to the increase of hot spots which results in an increase in temperature, more energy is having to be used to cool down areas.  The way to decrease heat areas is to increase the amounts of shade trees. 

 This study used satellite data, LANDSAT TM, to map micro-urban heat islands along with comparing urban versus rural temperature variations.  Results show that UHIs were radiative in nature, with highest temperatures in the center and cooled outward toward tree canopy.

Figure I. Display of GIS layers used to map MUHls. A, shows extracted tree canopy and water over
TM band 4; B, is color-coded thermal image from TM band 6. Blue to red represents cooler to warmer
temperatures: C, shows trees and MUHIs; D is display of TM band 4 superimposed with MUHIs

Aniello Cathy, Morgan Ken,  Busbey Arthur, and Newland Leo (1994). Mapping Micro-Urban Heat Islands Using LANDSAT TM And A GIS. Computers & Geoscience. Vol. 21, No.8.