Search and assessment of urban heat islands on digital satellite images

Abstract

Formulation of the problem. The development of urbanization processes resulted in Urban Heat Islands (UHI) - ur-ban areas of high temperatures due to the dominance of artificial surfaces that absorb and retain heat. UHIs adversely affect the environmen-tal conditions of cities and people's health. Satellite images in the thermal infrared range of the electromagnetic spectrum allow identifying areas of the high thermal back-ground of urbanized territories for management decisions support aimed at improving urban landscapes. The aim of the work is to develop a methodology for temperature anomalies analy-sis and urban heat islands detection on digital space images from Landsat 8 satellite in the thermal infrared range of the electromagnetic spectrum. Methodology of UHI detection. The methodology proposed in the paper includes a sequence of stages of collecting, and preprocessing satellite data, generating land sur-face temperature maps, identifying temperature anomalies, comprehensive analysis of high-temperature zones based on different-time data, and identifying areas of high temperatures stable over time. Land Surface Temperature estimation. Land Surface Temperature (LST) is esti-mated from the band 10 data of space images from the Landsat 8 satellite. The initial data are subjected to atmospheric correction, after which the spectral radiation in the band is converted to brightness temperature, and then to LST (Celsius degrees). UHI mapping. On each survey date, UHIs are identified as temperature anomalies - LST map pixels with values higher than the LST mean plus standard deviation within the study area. Time series analysis of satellite images. UHI mapping is based on a time series of Landsat 8 images acquired during the warm season (when ambient temperatures are above zero) to eliminate the effect of snow and ice on the observation results. According to the time series of LST maps of different years, stable temperature anomalies are dis-tinguished - UHIs presented on all images of the time series. Conclusions. Time-stable UHIs of the urbanized territory are mapped and ana-lyzed using Landsat 8 LST data time series. The areas of the high thermal background are compared with the classes of the earth's surface. It is concluded that increasing ur-ban density contributes to the accumulation of heat and increases the ambient tem-perature. The maps of LST distribution, vegetation indices, and UHI generated in the work can be used in urban planning tasks together with traditional sources of spatial information to obtain new information on improving the city's resistance to heat waves. UHI observation data are necessary for zoning areas with different land use types, for example, increasing the amount of open space and greenery, and improving the thermal comfort of citizens.