Journal Article
Atmospheric Chemistry and Physics, vol. 20, iss. 11, pp. 6479-6493, 2020
Authors
Wenchao Han, Zhanqing Li, Fang Wu, Yuwei Zhang, Jianping Guo, Tianning Su, Maureen Cribb, Jiwen Fan, Tianmeng Chen, Jing Wei, Seoung-Soo Lee
Abstract
Abstract. The urban heat island intensity (UHII) is the temperature difference between
urban areas and their rural surroundings. It is commonly attributed to
changes in the underlying surface structure caused by urbanization. Air
pollution caused by aerosol particles can affect the UHII through changing
(1) the surface energy balance by the aerosol radiative effect (ARE) and (2) planetary-boundary-layer (PBL)
stability and airflow intensity by modifying thermodynamic structure, which
is referred to as the aerosol dynamic effect (ADE). By analyzing satellite data
and ground-based observations collected from 2001 to 2010 at 35 cities in
China and using the WRF-Chem model, we find that the impact of aerosols on
UHII differs considerably: reducing the UHII in summer but increasing the
UHII in winter. This seasonal contrast is proposed to be caused by the
different strengths of the ARE and ADE between summer and winter. In summer,
the ARE on UHII is dominant over the ADE, cooling down surface temperature
more strongly in urban areas than in rural areas because of much higher
aerosol loading, and offsets the urban heating, therefore weakening UHII. In
winter, however, the ADE is more dominant, because aerosols stabilize the
PBL more in the polluted condition, weakening the near-surface heat
transport over urban areas in both vertical and horizontal directions. This
means that the heat accumulated in urban areas is dispersed less effectively,
and thus the UHII is enhanced. These findings shed new light on the impact
of the interaction between urbanization-induced surface changes and air
pollution on urban climate.
