Ecological Evaluation of Urban Heat Island in Chicago City, USA

The city of Chicago has experiences of Urban Heat Island (UHI) phenomena and a good example is its widely reported heat wave of 1995. This study conducted an ecological evaluation of Chicago’s UHI phenomena using LANDSAT TM of 2010, almost 15 years after the lethal heat wave and subsequently implemented various UHI mitigation efforts. The thermal characteristics of the city were assessed with a Land Surface Temperature (LST), a parameter retrieved from LANDSAT TM 6; a thermal-infrared (TIR) band (10.40 to 12.50μm), using mono-window algorithm. The ecological evaluation was made using an Urban Thermal Field Variance Index (UTFVI), which quantitatively evaluated the UHI effects on the quality of urban life. The accuracy of the model was assessed against theoretical relationships between the LST, the Normalized Difference Vegetation Index (NDVI), and Normalized Difference Built-up Index (NDBI). The LST of Chicago ranges from 18 o C in Urban Cool Islands (UCI) to 44 o C in UHI. In Chicago, although the cooling effects of Lake Michigan, downtown’s sky-high buildings, and urban parks and green spaces have worked together to suppress the concerns of UHI effects locally, still some areas experience a high UHI. In general, 25% of the city experiences ecologically bad or worse UHI effects, indicating a need for continued UHI mitigation efforts.