Using Local Climate Zones to investigate Spatio-temporal evolution of thermal environment at the urban regional level: A case study in Xi'an, China

The concept of Local Climate Zone (LCZ) classification scheme is an effective tool for quantifying the Urban Heat Island (UHI) effect. However, previous studies of the thermal environment using LCZs mainly focused on the meso- to-micro-scale or a single time, and the changes in the regional thermal environment were less considered. Thus, we selected the Xi'an urban spatial agglomeration and used remote sensing images from 2008, 2013, and 2019 to determine the spatial and temporal variations in the thermal environment for statistical analysis and contrast. The results confirmed that: (1) The proportions of low-rise types decreased significantly, and the land use for agglomerations and compacts shows an upward trend. (2) The built-up LCZs had higher land surface temperatures (LST), LCZ 10 (heavy industry) was the highest in all years. (3) The LCZs with LCZ A (dense trees), and LCZ G (water) were associated with slightly lower LSTs, and they helped to cool the city. (4) The LSTs tended to increase from natural to urban areas, before gradually decreasing with distance from the city center to rural areas. These findings may provide reference values for quantitative studies of LCZ classification maps and analyzing dynamic changes in urban surface thermal environments, thereby facilitating the UHI analysis and climate-adapted urban planning.