Surface air temperature differences of intra- and inter-local climate zones across diverse timescales and climates

The local climate zone (LCZ) scheme has been widely used in urban heat island studies in the past decade. However, the general principle of LCZ surface air temperature (SAT) differences and their climatic differences on different timescales remain largely unclear. Here we investigated both the inter- and intra-LCZ differences at four timescales across nine Chinese megacities characterized with significantly different climates, based on three-year hourly SAT measurements collected at 898 stations from 2017 to 2019. The results showed that (1) at the annual mean scale, the ΔTinter (i.e., SAT differences between various LCZ types and LCZ D): and ΔTintra (i.e., standard deviation of SAT measurements belonging to the same LCZ) were larger during the night than the day for most LCZ types; and the ΔTinter and ΔTintra for warm temperate cities were usually greater than those of subtropical cities. (2) At the seasonal scale, the ΔTinter and ΔTintra of most LCZs often peaked at winter night. The largest seasonal variation of ΔTinter was observed in mid-temperate cities. (3) At the daily scale, the day-to-day difference of ΔTinter was smaller during the day than the night and mainly ranged from −0.5 °C to 0.5 °C. By contrast, the day-to-day difference of ΔTintra was relatively large both during the day and night. (4) At the hourly scale, both the ΔTinter and ΔTintra variations throughout a diurnal cycle followed a characteristic U-shape for most LCZs. We consider these findings are helpful for better understanding the inter- and intra-LCZ thermal differences across various timescales and climates.