ORIGINAL PAPER Model analysis of urbanization impacts on boundary layer meteorology under hot weather conditions: a case study of Nanjing, China Lei Chen 1,3 & Meigen Zhang 1 & Yongwei Wang 2 Received: 29 June 2014 /Accepted: 8 June 2015 /Published online: 2 July 2015 # Springer-Verlag Wien 2015 Abstract The Weather Research and Forecasting (WRF) model, configured with a single-layer urban canopy model, was employed to investigate the influence of urbanization on boundary layer meteorological parameters during a long- lasting heat wave. This study was conducted over Nanjing city, East China, from 26 July to 4 August 2010. The impacts of urban expansion and anthropogenic heat (AH) release were simulated to quantify their effects on 2-m temperature, 2-m water vapor mixing ratio, and 10-m wind speed and heat stress index. Urban sprawl increased the daily 2-m temperature in urbanized areas by around 1.6 °C and decreased the urban diurnal temperature range (DTR) by 1.24 °C. The contribution of AH release to the atmospheric warming was nearly 22 %, but AH had little influence on the DTR. The urban regional mean surface wind speed decreased by about 0.4 m s -1 , and this decrease was successfully simulated from the surface to 300 m. The influence of urbanization on 2-m water vapor mixing ratio was significant over highly urbanized areas with a decrease of 1.1–1.8 g kg -1 . With increased urbanization ratio, the duration of the inversion layer was about 4 h shorter, and the lower atmospheric layer was less stable. Urban heat island (UHI) intensity was significantly enhanced when syn- thesizing both urban sprawl and AH release and the daily mean UHI intensity increased by 0.74 °C. Urbanization in- creased the time under extreme heat stress (about 40 %) and worsened the living environment in urban areas. 1 Introduction A rapid increase of the global mean air temperature has been observed since the 1970s, the majority of which can be attrib- uted to changes in anthropogenic greenhouse gases (GHGs), aerosol loading, and land use land cover (LULC) (IPCC 2007). Future climate predictions indicate an increase in the frequency and intensity of extreme weather events, such as heat waves, with global warming (Meehl and Tebaldi 2004; Della–Marta et al. 2007). The impact on human comfort and health should not be neglected when considering severe anomalous weather scenarios (McMichael et al. 2006), espe- cially when urban areas are continuously growing through the process of urbanization. Urbanization, an extreme example of LULC change caused by human activities, is rapidly increasing globally. It increases surface roughness by forming urban canopy layers, decreases evapotranspiration by changing land cover from vegetated or natural surfaces to impervious surfaces, influences the surface energy balance by absorbing and reflecting solar radiation, and modifies thermal and dynamic characteristics by discharging additional anthropogenic heat (AH). These changes will certainly lead to modifications of the planetary boundary layer (PBL) structure in and around urban areas by perturbing the wind, temperature, moisture, and turbulence (Miao et al. 2009). This would then change local and regional weather and climate and impact the transport and distribution * Meigen Zhang mgzhang@mail.iap.ac.cn Lei Chen chenlei@mail.iap.ac.cn Yongwei Wang wyw@nuist.edu.cn 1 State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry (LAPC), Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China 2 Atmospheric Environment Center, Nanjing University of Information Science and Technology, Nanjing 210044, Jiangsu, China 3 University of Chinese Academy of Sciences, Beijing 100049, China Theor Appl Climatol (2016) 125:713–728 DOI 10.1007/s00704-015-1535-6