Urban heat islands in China enhanced by haze pollution.

Chang Cao,Shoudong Liu,Mi Zhang,Natalie Schultz,Wei Xiao,Lei Zhao,Xuhui Lee

doi:10.1038/ncomms12509

Abstract

The urban heat island (UHI), the phenomenon of higher temperatures in urban land than the surrounding rural land, is commonly attributed to changes in biophysical properties of the land surface associated with urbanization. Here we provide evidence for a long-held hypothesis that the biogeochemical effect of urban aerosol or haze pollution is also a contributor to the UHI. Our results are based on satellite observations and urban climate model calculations. We find that a significant factor controlling the nighttime surface UHI across China is the urban–rural difference in the haze pollution level. The average haze contribution to the nighttime surface UHI is 0.7±0.3 K (mean±1 s.e.) for semi-arid cities, which is stronger than that in the humid climate due to a stronger longwave radiative forcing of coarser aerosols. Mitigation of haze pollution therefore provides a co-benefit of reducing heat stress on urban residents.

Highlights

The urban heat island (UHI), the phenomenon of higher temperatures in urban land than the surrounding rural land, is commonly attributed to changes in biophysical properties of the land surface associated with urbanization
We present an empirical analysis using satellite observations to show that urban haze pollution is a contributor that intensifies the UHI in China at night
The surface UHI intensity DT is the difference in surface temperature between the urban and the adjacent rural land[3], and haze pollution is measured by the aerosol optical depth (AOD)

Summary

Introduction

The urban heat island (UHI), the phenomenon of higher temperatures in urban land than the surrounding rural land, is commonly attributed to changes in biophysical properties of the land surface associated with urbanization. The surface UHI intensity DT is the difference in surface temperature between the urban and the adjacent rural land[3], and haze pollution is measured by the aerosol optical depth (AOD).

Results

Conclusion