Nanjing is one of the most important industrial cities in China,and its local land cover and environment have been modified over the past several decades.In this paper,with three scenarios(URBA,NURBA,URBNA) integrated by the WRF model,we investigate the effects of aerosol and urban expansion to boundary layer meteorology over Nanjing,China,with the aim of comparing the effects of aerosol and urban expansion during a heat wave,and discuss the feedback between them.Through the observed data validating the variable 2 m temperature and 2 m relative humidity from the model,the WRF model is capable of capturing the features of urban meteorological variables in the Nanjing region during a hot weather episode.Based on the Aerosol-Aware Thompson microphysical scheme and two types of aerosol(ice-friendly aerosol N_IFA and water-friendly aerosol N_WFA),the cooling effect caused by aerosol is apparent and dominate at daytime.The radiative forcing leads to a decrease of -0.11 ℃ in 2 m temperature and -12 W/m² in net radiation at daytime,both of which peak at 0800 LST and 1800 LST.The surface air temperature of Nanjing increases by 1.7 ℃ due to urban expansion.This in turn leads to an increase in wind speed of around 0.8 m/s,for which the increase due to heat island effect is greater than the decreased due to surface roughness.As for the 2 m temperature,the urbanization-warming effect is stronger than the aerosol-cooling effect under a hot weather episode.The latent heat flux decreases and sensible heat flux increases in the daytime,resulting in a warmer atmospheric temperature(below 1.6 km) in the daytime than in the nighttime.Urban-induced local updraft brings the aerosol to a greater height,especially in the daytime.As a result,a positive feedback may exist between the aerosol and the stability of the urban boundary layer.It is important to note that the warming effect of black carbon is not considered in this paper.