A Specific Study on the Impacts of PM2.5 on Urban Heat Islands with Detailed In Situ Data and Satellite Images

Abstract

Rapid urbanization often results in serious urban heat islands (UHI) and fine particulate matter (PM2.5) concentration. Previous studies found it was hard to evaluate the haze contribution to the UHI quantitatively, because of the complex properties of the atmosphere aloft and the irregular alteration of PM2.5 loads. Taking Beijing as the study site, where detailed in situ PM2.5 concentration data, canopy thermal data and MODIS land surface temperature (LST) products were all available in 2015, this study investigated the impacts of PM2.5 on both surface UHI intensity (SUHII) and canopy UHI intensity (CUHII) at daytime and night. The results reveal that the CUHII are almost unchanged throughout the year, while SUHII varies greatly in both temporal axis and spatial distribution. PM2.5 concentration has significant negative impacts on mean SUHII (r =-0.6115) and daytime SUHII (r =-0.6164), and less significant negative impact on CUHII (r =-0.51999). However, the contribution of PM2.5 concentration to nighttime SUHI is not significant. This specific study checked and improved previous works on this topic, with detailed in situ data and satellite images. The results of this work can enhance our understanding of the dynamics and driving mechanism of urban thermal environment.