Exploring the multitemporal surface urban heat island effect and its driving relation in the Beijing-Tianjin-Hebei urban agglomeration

The rapid urbanization process would pose substantial disturbances to local thermal balance and induce severe surface urban heat island (SUHI) effects, which poses adverse impacts on urban ecological security and sustainable development. Therefore, it is necessary to comprehensively understand the characteristics of the SUHI effect and its potential associated factors to benefit scientific urban thermal environmental management. Hence, this study explored the seasonal SUHI effect and its potential association in the Beijing-Tianjin-Hebei (BTH) urban agglomeration based on dual indicators, such as intensity (SUHII) and footprint (FP). We found that: (1) SUHII and FP could well characterize the features of the SUHI effect from different perspectives. Both of them generally showed relatively high status in summer (than other seasons) and at nighttime (than daytime) for most case cities in the BTH region. From 2000 to 2020, both their variations showed significant city differences, as SUHII of most cities were declined but FP were still extended in some of them. (2) Urbanization poses a significant influence on the SUHI effect. Social and environmental factors played the main contributors to the variation of both SUHII and FP, but the specific key factor on both SUHII and FP varied across different seasonal and diurnal phrases. This study successfully extended the current cognation on the SUHI effect and its thermal risk by introducing the dual indicators and confirmed that urbanization is still the key to intervening in the local SUHI effect.