31 May 2017

To the Extreme: How Booming Cities Influence Climate

Researchers found that heat waves and summer storms increase under the urban heat island effect, but that pollution can suppress that effect.


When cities rapidly add people and industry, it leads to an urban heat island effect that changes land-surface properties, and causes an increase in atmospheric particle pollution. A research team led by scientists at the U.S. Department of Energy’s Pacific Northwest National Laboratory investigated the individual and combined effects of growth-induced changes in land cover and pollutants on the climate of the heavily populated Yangtze River Delta region of eastern China.


Scientists carried out three five-year cloud-permitting simulations to understand the combined urban heat island and particle pollution effects of rapid urban expansion on climate extremes in the region. The five-year simulations were a first. Researchers will use the same model framework to study how present and future city growth influences the climate in the United States and to understand how model resolution affects the results.


Researchers conducted cloud-permitting simulations with a coupled climate-chemistry-urban model to understand how the urban heat island effect and particle pollution influence the Yangtze River Delta’s climate. For the first time, scientists integrated a Weather Research and Forecasting model—interactively coupled with a chemistry/aerosol model and an urban canopy model—for five years at convection-permitting scale. Researchers ran three of these simulations with different land-surface and/or particle emission scenarios to see the separate and combined impacts of the pollution and urban heat island effect. While scientists found that the urban heat island effect increased the intensity of heat waves, as well as storms’ frequency in summer, they discovered that the pollutants tended to suppress the effect. The study also showed that the combined impacts of the urban heat island effect and pollutants on precipitation depended on synoptic (large-scale) conditions in individual rainfall events.

Yun Qian
Pacific Northwest National Laboratory
  • Regional & Global Climate Modeling
  • Atmospheric System Research
  • Water Cycle and Climate Extremes Modeling
Zhong, S., Qian, Y., Zhao, C., Leung, R. & et al. "Urbanization-induced urban heat island and aerosol effects on climate extremes in the Yangtze River Delta region of China." Atmospheric Chemistry and Physics 17, 5439-5457 (2017). [10.5194/acp-17-5439-2017].