Strong regulation of daily variations in nighttime surface urban heat islands by meteorological variables across global cities

Abstract

Knowledge of the day-to-day dynamics of surface urban heat island (SUHI) as well as their underlying determinants is crucial to a better design of effective heat mitigation. However, there remains a lack of a globally comprehensive investigation of the responsiveness of SUHI variations to meteorological variables. Based on the MODIS land surface temperature and auxiliary data in 2017, here we investigated 10 000+ cities worldwide to reveal day-to-day SUHI intensity (SUHII) variations (termed as SUHII_dv) in response to meteorological variables using Google Earth Engine. We found that: (a) meteorological variables related to the thermal admittance, e.g. precipitation, specific humidity (SH) and soil moisture (SM) (represented by daily temperature range in rural area, DTR_r), reveal a larger regulation on SUHII_dv than those related to the air conditions (e.g. wind speed and near-surface air temperature) over a global scale. (b) Meteorological regulations on SUHII_dv can differ greatly by background climates. The control of SH on SUHII_dv is significantly strengthened in arid zones, while that of wind speed is weakened prominently in equatorial zones. SUHII_dv is more sensitive to SM in cities with higher background temperatures. (c) All meteorological variables, except that related to SM (DTR_r), show larger impact on SUHII_dv with antecedent precipitation over the global scale. Precipitation is observed to mitigate the SUHII_dv globally, and such effects are even more pronounced in equatorial and arid zones. We consider that our findings should be helpful in enriching the knowledge of SUHI dynamics on multiple timescales.