Changes in the surface urban heat island between 1986 and 2021 in the polycentric Górnośląsko-Zagłębiowska Metropolis, southern Poland

Abstract

Progressing urbanization forces urban infrastructure development and leads to an increase in artificial impervious surfaces that directly contribute to changes in surface urban heat island (SUHI) in cities. This study discusses spatial and temporal changes in the SUHI extent and intensity in the biggest Metropoly in Southern Poland in summer between 1986 and 2021. The study is based on Landsat satellite images, demographic and land cover data from 1990 to 2018 from CORINE Land Cover (CLC) classifications. The comparison of satellite images recorded in different years, on similar dates and under similar meteorological conditions revealed an increase in the SUHI extent from 0.6 to 4.3 % between 1986 and 2021 due to increase in the share of impervious areas. Moreover, regardless of changes in spatial extent, the mean land surface temperature (LST) of all types of land cover increased, which may be related to recent warming. In the research period, permanent surface heat island covered 0.85 % of the GZM, and over 50 % of its area was located only within four cities. Although the mean LST for SUHI increased, the SUHI intensity decreased due to increased LST of the cold island. The SUHI extent was more related to the inhabitant number (correlation: 0.83 to 0.98) than population density (0.39–0.58). SUHI expansion in combination with recent warming of climate is a particularly negative effect where society is ageing, like in GZM.