ANALYSIS OF URBAN HEAT ISLAND PHENOMENON IN HO CHI MINH CITY, VIETNAM

Ho Chi Minh City is one of the two largest and most modern cities in Vietnam; it has undergone rapid urbanization with many skyscrapers, residential apartments, and infrastructure. This development has resulted in vegetation decline; an increase in urban temperature, which causes Urban Heat Islands (a phenomenon that occurs when a city experiences much warmer temperatures than nearby rural areas); and impacts on outdoor manufacturing activities and residents’ quality of life. This research, therefore, aims to analyze and monitor changing trends of Urban Heat Islands in Ho Chi Minh City from 1996 to 2024 by evaluating surface spectral indices, such as the Normalized Difference Built-up Index (NDBI), Normalized Difference Vegetation Index (NDVI), and Land Surface Temperature (LST). Four sets of satellite images (showing daytime in 1996/2, 2006/4, 2015/3, and 2024/2), including Landsat 4-5 TM and Landsat 8-9 OLI/TIRS, with cloud cover of less than 10%, were collected from the United States Geological Survey (USGS, www.glovis.usgs.gov); they were then processed and analyzed using ArcGIS software. The results show that high-density urban areas (NDBI > 0.2) expanded substantially during the study period, despite a slight decrease from 74.50 km² in 1996 to 73.68 km² in 2006, before surging to 114.33 km² and 315.03 km² in 2015 and 2024, respectively. In contrast, dense vegetation areas decreased sharply from 346.95km² in 1996 to 294.34km², 132.5km², and 97.08km² during the same period. Because of an increase in urban areas and a decrease in vegetation areas, areas with surface temperature (LST) exceeding 25^oC sharply increased from 280.64km² in 1996 to 741.03km², 961.92km², 1035.98km² over the same intervals. Likewise, areas with LST over 32^oC rose significantly to 139.04 km² in 2024, compared with 0 km², 1.06 km², and 12.49 km² in 1996, 2006, and 2015, respectively. Moreover, this research also calculated the UHI index based on a relative LST anomaly, in which the UHI map in 2024 pointed out that the UHI phenomenon covered more space compared to previous years.