Diurnal and seasonal impacts of urbanization on the urban thermal environment: A case study of Beijing using MODIS data

• A contribution index was proposed to evaluate contributions of urbanization to UHI.
• Urban land as the most important contributor increases regional LST.
• The role of cropland and forest has a diurnal inter-conversion.
• The LST–NDVI relationships verify significantly the reliability of the contribution index.
• Vegetation partition is an effective approach to regulating urban thermal environment.

Beijing has experienced rapid urbanization and associated urban heat island effects and air pollution. In this study, a contribution index was proposed to explore the effect of urbanization on land surface temperature (LST) using Moderate-Resolution Imaging Spectroradiometer (MODIS)-derived data with high temporal resolution. The analysis indicated that different zones and landscapes make diurnally and seasonally different contributions to the regional thermal environment. The differences in contributions by the three main functional zones resulted from differences in their landscape compositions. The roles of landscapes in this process varied diurnally and seasonally. Urban land was the most important contributor to increases in regional LSTs. The contributions of cropland and forest varied distinctly between daytime and nighttime owing to differences in their thermal inertias. Vegetation had a notable cooling effect as the normalized vegetation difference index (NDVI) increased during summer. However, when the NDVI reached a certain value, the nighttime LST shifted markedly in other seasons. The results suggest that urban design based on vegetation partitions would be effective for regulating the thermal environment.