Fig. 1: Spatial distribution of multi-year average SUHI characteristics in urban expansion areas across 31 Chinese cities from 2000 to 2018.

a SUHI_Ra during the daytime. b SUHII_Mean during the daytime. c SUHII_Max during the daytime. d SUHI_Ra during the nighttime. e SUHII_Mean during the nighttime. f SUHII_Max during the nighttime.