Journal cover Journal topic
Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
doi:10.5194/acp-2016-953
© Author(s) 2016. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
22 Dec 2016
Review status
A revision of this discussion paper is under review for the journal Atmospheric Chemistry and Physics (ACP).
Urbanization-induced urban heat island and aerosol effects on climate extremes in the Yangtze River Delta Region of China
Shi Zhong2,1, Yun Qian1, Chun Zhao1, Ruby Leung1, Hailong Wang1, Ben Yang3,1, Jiwen Fan1, Huiping Yan4,1, Xiu-Qun Yang3, and Dongqing Liu5 1Pacific Northwest National Laboratory, Richland, WA, USA
2State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering, Center for Global Change and Water Cycle, Hohai University, Nanjing, China
3School of Atmospheric Sciences, Nanjing University, Nanjing, China
4College of Atmospheric Science, Nanjing University of Information & Technology, Nanjing, China
5Nanjing Meteorological Bureau, Nanjing, China
Abstract. The WRF-Chem model coupled with a single-layer Urban Canopy Model (UCM) is integrated for 5 years at convection-permitting scale to investigate the individual and combined impacts of urbanization-induced changes in land cover and pollutants emission on regional climate in the Yangtze River Delta (YRD) region in eastern China. Simulations with the urbanization effects reasonably reproduced the observed features of temperature and precipitation in the YRD region. Urbanization over the YRD induces an Urban Heat Island (UHI) effect, which increases the surface temperature by 0.53 °C in summer and increases the annual heat wave days at a rate of 3.7 d/yr in the major megacities in the YRD, accompanied by intensified heat stress. In winter, the near-surface air temperature increases by approximately 0.7 °C over commercial areas in the cities but decreases in the surrounding areas. Radiative effects of aerosols tend to cool the surface air by reducing net shortwave radiation at the surface. Compared to the more localized UHI effect, aerosol effects on solar radiation and temperature influence a much larger area, especially downwind of the city-cluster in the YRD.

Results also show that the UHI increases the frequency of extreme summer precipitation by strengthening the convergence and updrafts over urbanized areas in the afternoon, which favor the development of deep convection. In contrast, the radiative forcing of aerosols results in a surface cooling and upper atmospheric heating, which enhances atmospheric stability and suppresses convection. The combined effects of the UHI and aerosols on precipitation depend on synoptic conditions. Two rainfall events under two typical but different synoptic weather patterns are further analyzed and the results suggest that synoptic forcing plays a significant role in modulating the urbanization-induced land-cover and aerosol effects on individual rainfall event. Hence precipitation changes due to urbanization effects may offset each other under different synoptic conditions, resulting in little changes in mean precipitation at longer time scales.


Citation: Zhong, S., Qian, Y., Zhao, C., Leung, R., Wang, H., Yang, B., Fan, J., Yan, H., Yang, X.-Q., and Liu, D.: Urbanization-induced urban heat island and aerosol effects on climate extremes in the Yangtze River Delta Region of China, Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-953, in review, 2016.
Shi Zhong et al.
Shi Zhong et al.
Shi Zhong et al.

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Short summary
A coupled regional model is integrated for 5 years at cloud-permitting scale to quantify the impacts of urbanization-induced changes in land cover and pollutants emission on climate in the Yangtze River Delta region in eastern China. Urbanization over this region induces an Urban Heat Island effect, which increases the frequency of extreme precipitation and heat wave in summer. The results could help China government in making policies in mitigating the environmental impact of urbanization.
A coupled regional model is integrated for 5 years at cloud-permitting scale to quantify the...
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