Diurnal cycle of the surface urban heat island at the intra-urban scale derived from ECOSTRESS observations and local climate zones

Source abstract

The surface urban heat island (SUHI) temporal variations are still not well understood, compared to its spatial features, partly due to the low temporal resolution of satellite infrared data. The ECOsystem Spaceborne Thermal Radiometer Experiment on Space Station (ECOSTRESS) provides Land Surface Temperature (LST) observations at a 70 m resolution with varying acquisition times and reduced revisit periods, thus offering new opportunities to study the SUHI dynamics. This study relies on ECOSTRESS data acquired over a five-year period (2018-2023) to explore both the day-to-day variability of the SUHI and its diurnal cycle during summer. We analyze these variations at the neighborhood scale based on the Local Climate Zones (LCZ) framework. The analysis reveals a typical LST contrast among LCZ classes with a clear distinction between built types and natural types but also within those two groups. The day-to-day variations of this pattern is assessed and it is found to be higher during daytime than at night. The drivers of these variations are shown to be distinct between day and night, with a daytime variability mostly driven by vegetation health and cover while, at night, the vegetation state and the cloud cover are the most important drivers. Continuous diurnal evolution curves of the SUHI intensity are produced and enable the observation of distinct diurnal dynamics for different LCZs. Our approach, fully based on observational data and statistical modelling, contributes to fill the lack of observations of the SUHI dynamics and could be reproduced for inter-city comparison.