Relieved Air Pollution Enhanced Urban Heat Island Intensity in the Yangtze River Delta, China
Hao Wu；Tijian Wang；Qin'geng Wang；Nicole Riemer；Yang Cao；Chong Liu；Chaoqun Ma；Xiaodong Xie
PM_(2.5) ； Urban heat island ； WRF-Chem ； Yangtze River Delta
Aerosol and Air Quality Research
|Volume or Term/Year and Month of Publication||
19卷12期（2019 / 12 / 01）
2683 - 2696+ap1-7
The National Air Pollution Control Plan implemented by China in 2013 reduced the concentrations of air pollutants, especially PM_(2.5) (aerosol particles with an aerodynamic diameter equal to or less than 2.5 μm), between 2014 and 2017. This reduction in PM_(2.5) potentially affected the intensity of urban heat islands (UHIs), as the presence of fine particles can influence the energy balance of the earth-atmosphere system. In this study, the effect of the pollution control plan on the UHI intensity in the Yangtze River Delta, China, was investigated via observational analysis and numerical modeling. According to the observational data, the PM_(2.5) concentrations in the megacities of the Yangtze River Delta, viz., Shanghai, Nanjing, Hangzhou and Hefei, in 2017 were ~35 μg m^(-3), showing decreases of approximately 48.36%, 28.25%, 29.41% and 32.5%, respectively, compared to 2014. Furthermore, these reductions in the PM_(2.5) concentration correlated well with the strengthened diurnal intensity (increasing by up to 1 K) and the weakened nocturnal intensity (decreasing by up to 1 K) of the UHIs. Numerical simulations confirmed that this ＂seesaw effect＂ on the UHI intensity was due to the decrease in PM_(2.5) and the consequent increase in the downward surface shortwave radiation and the outgoing top-of-the-atmosphere longwave radiation. Thus, the Air Pollution Control Plan noticeably affected the UHI intensity by reducing PM_(2.5)-a factor which should be considered in future studies on urban climate and environmental planning.