Temporal Analysis of Heat Islands Through Surface Temperature and Vegetation Index in Recife-PE, Brazil

Abstract

Among the anthropic factors that act in the high vulnerability of heat islands formation are the relationship with population density and changes in land use. In this case study, it is highlighted that the city of Recife has a high-density population and considered the fourth Brazilian capital with the largest in the country. The general objective of this research is to analyze the variations in the vegetation index and the surface temperature to identify their influence on the formation of heat islands. Temporal multispectral images (Landsat 5-TM and Landsat 8-OLI) covering the years 1989 to 2019 are used as materials. The main results found are: (i) the year of 2019 with higher temperatures, reaching regions with 37°C; (ii) in 1989 the highest values ​​were 32°C; (iii) in terms of area, the city of Recife experienced a 34% increase of temperatures above 33°C and obtained a decrease of 44% considering milder temperatures; (iv) the vegetation cover values ​​underwent significant changes, such as the 15% growth in the exposed soil index, and the 18% reduction in the average vegetation index; (v) Spearman's correlations indicate that there is a strong inversely proportional relationship between the two parameters evaluated (temperature and vegetation index), with values ​​of -0.72 for 1989 and -0.59 for 2019. Finally, it was possible to detect the formation of heat islands, as well as freshness islands, observing an increasement of surface temperature especially where the urbanization process has intensified over time.