Studying spatial-temporal changes and relationship of land cover and surface Urban Heat Island derived through remote sensing in Yerevan, Armenia

The city of Yerevan, Armenia has undergone major environmental and economic changes after the collapse of the Soviet Union. The objectives of this study were to: (i) investigate the changes of the Land Cover (LC) and Surface Urban Heat Island (SUHI) in Yerevan and analyze relations between them, (ii) study the relationships between land surface temperature (LST) and environmental factors/parameters, (iii) explore the accuracy of satellite derived LST. LC and SUHI were derived from Landsat TM/ETM+/OLI-TIRS images (years 1989, 2000, 2010 and 2018) by means of three Machine Learning algorithms and the Urban Thermal Field Variance Index (UTFVI) ecological evaluation index, respectively. The comparison between Unmanned Aerial Vehicle (UAV) and satellite LSTs showed that the overall spatial pattern of Landsat and UAV LSTs matched. It was found that the green and built-up areas were the main factors affecting LST variation in Yerevan. The results of the LC change analysis revealed an expansion of built-up areas and the reduction of green spaces. Yerevan shares almost an equal percentage of land for the excellent and the worst categories of the UTFVI. The transformations from excellent to the worst category of UTFVI were mainly related to the loss of green spaces, while the opposite transformations were associated with the gain of vegetation cover, the construction of new districts and the reduction/cessation of anthropogenic heat emission. It appeared that the urban construction had possibly led to the improvement of UTFVI index in the case of no/low anthropogenic heat emission.