Relationship of surface urban heat island with air temperature and precipitation in global large cities

In the context of climate change, a systematic research of the relationship between the urban heat island (UHI) and climatic factors is needed. In this study, the relationships between surface UHI intensity (SUHII) and climate factors were investigated across 145 global large cities for the period 2003–2013, based on Moderate Resolution Imaging Spectroradiometer land surface temperature, normalized difference vegetation index, land cover, digital elevation model and meteorological observation data. The correlations of SUHII with air temperature and precipitation were examined in two ways, including individual analysis in each city and group analysis by climate type and urban size. Results indicate that the relationships between SUHII and air temperature were unstable in space, and the correlation differed significantly in macro-climatic conditions and not obviously in urban size. The sign of the correlation was affected by the difference of vegetation between urban and rural areas. In cities with greater urban and rural vegetation differences, higher temperatures would enhance SUHII. The relationships between SUHII and precipitation were relatively stable with positive correlations during the day and negative correlations at night, and it showed no obvious differences in macro-climatic conditions and in urban size, because precipitation always amplifies the difference of soil moisture between urban and rural areas. The standard deviation (STD) across time was further used to measure the stability of the SUHII. Results show that the STD had higher correlation with precipitation than air temperature, implying that the sensitivity of SUHII to precipitation was higher than that to air temperature. The STD was significantly positively correlated with precipitation, suggesting that the stability of SUHII was lower in the cities with more precipitation.